TDOC ZTA245 .7 B873 NO-FTZl wlliol (élrollll l Wil A Four Season Approach - Texas Rolling Ploins Ilse timely land preparation and planting y Alter the Qoéovergvliintaering "x e4, \ the biological environments and physical fi B—l72l o March i995 Eliminate the late season food supply / 1Q Texas Agricultural Experiment Station ~ Edward A. Hiler, Director - The Texas A&M University System ~ College Station, Texas [Blank Page in Or@d Bulletin] ' M9" *2‘ TEXAS STATE DEPOSITORY Cultural Control of the Boll Weevil A Four Season Approach - Texas Rolling Plains J. E. Slosser‘ LIBRARY TEXAS A&M UNIVERSITY JUN 2 1 1995 TEXAS STATE DOCUMENTS ‘Professor, Texas Agricultural Experiment Station Key Words: boll weevil, Anthonomus grandis grandis Boheman, cultural control, Texas Rolling Plains, cotton, land preparation, delayed uniform planting, planting date, short season production, cotton variety, bed shape, row direction, row spacing, irrigation termination, harvest-aid chemicals, overvvin- tering habitat, habitat management, habitat destruction, habitat modification, habitat avoidance, dia- pause, suicidal emergence TABLE OF CONTENTS Page Summary ............................................................................................ .. 1 Introduction ........................................................................................ .. 1 Spring Cultural Control ....................................................................... .. 2 Prepare the land for planting ......................................................... .. 2 Utilize delayed planting ................................................................. .. 2 Use uniform planting ..................................................................... .. 3 Summary ....................................................................................... .. 4 Summer Cultural Control .................................................................... .. 4 Shorten the growing season ........................................................... .. 4 Change the microclimate ............................................................... .. 5 Row direction ........................................................................... .. 5 Bed shape ................................................................................ .. 6 Row spacing ............................................................................. .. 6 Summary ....................................................................................... .. 7 Fall Cultural Control ........................................................................... .. 7 Utilize harvest-aid chemicals ......................................................... .. 7 Role of planting date ...................................................................... .. 8 Terminate irrigations in August ..................................................... .. 8 Summary ....................................................................................... .. 9 Winter Cultural Control ....................................................................... .. 9 Eliminate the overwintering habitat ............................................... .. 9 Modify the overwintering habitat ................................................. .. l0 Avoid the overwintering habitat ................................................... .. 11 Summary ..................................................................................... .. 12 Conclusions ...................................................................................... .. 12 Acknowledgments ............................................................................. .. 12 Supporting Research Studies ............................................................ .. 13 SUMMARY Cultural control strategies to manage the boll weevil, Anthonomus grandis grandis Boheman, can be implemented during each season of the year to enhance cotton production in the Texas Rolling Plains. In the spring, the land should be prepared for planting by using a reduced tillage system and furrow diking. This system has consistently pro- vided adequate soil moisture for planting in late May. Delayed, uniform planting between late May and early June forms the basis for cultural con- trol of the boll weevil. This planting time reduces effective emergence of overwintered boll weevils, delays development of high population densities until late July, and concentrates square produc- tion in July and early August, which reduces the boll weevil population during the fall. During the summer, cultural control can be used to alter both the physical and biological environ- ments to make conditions less favorable for boll weevil population growth. The length of the growing season (biological environment) is reduced by about one week by planting in late May, as compared to planting in late April to early May. This delayed plant- ing results in lower population densities late in the season. When cotton is planted in late May, initial boll weevil populations are forced to develop during the hottest part of the summer. Planting cotton on sloped beds, in an east-west row direction, can be used to increase exposure of fallen squares to high soil temperatures (physical environment), which kill larvae inside the squares. In the fall, cultural control objectives are to eliminate squares and small bolls that allow boll weevils to build fat reserves and enter diapause. Cotton should be planted by early June and ir- rigations should be terminated by late August to reduce square production in the fall. Har- vest-aid chemicals can be used to abscise squares and small bolls by late September. This reduces the proportion of the boll weevil popu- lation that enters diapause, and fewer boll wee- vils survive the winter. During the winter, cultural control strate- gies are designed to manage the overwintering habitat. Elimination of winter habitat is one op- tion. A second option is to modify the habitat by destroying only the leaf litter where boll weevils overwinter. Elimination of leaf litter, while pre- serving the associated trees, effectively reduces overwintering boll weevil populations. A third option is to avoid planting cotton adjacent to overwintering habitat. Cultural control strategies for reducing boll weevil damage during the growing season can be used throughout the year. The recommended prac- tices are known to reduce damage and to increase yield potential, particularly in dryland cotton pro- duction. These techniques can be used by a single grower to attain boll weevil suppression on an in- dividual farm, or the strategies can be used on an areawide basis by many growers to achieve maxi- mum population suppression. INTRODUCTION Cultural control of the boll weevil, Anthonomus grandis grandis Boheman, is a topic as timely to- day as it was 100 years ago. Cultural control is the manipulation of normal farming practices to reduce pest damage, and it offers an environmentally-sound strategr for managing cotton insect pests. Addition- ally, the manipulation of some farming operations does not increase costs. Before the advent of mod- ern pest control techniques, such as using insecti- cides, cultural control offered the only hope for re- ducing the ravages of the boll weevil. In recent times, environmental concerns and pest resistance to in- secticides have again focused attention on cultural management of insect pests. Detailed research data are not reported in this review, but published technical articles on each recommended management strategr can be ob- tained by contacting the author. The recommen- dations reviewed in this report are based on 2O years of research conducted by the author from 1975 to 1994. These strategies were developed specifically for the Texas Rolling Plains. The cultural control studies were undertaken to increase our understanding of the ecological relationships between the boll weevil and its en- vironment and to enhance the value of delayed, uniform planting for boll weevil management. An historical perspective of delayed, uniform plant- ing is presented in the Acknowledgments Section of this bulletin. As studies progressed over the years, it became evident that many aspects of the seasonal ecology of the boll weevil could be ma- nipulated by planting in late May (delayed, uni- form planting). For example, the role of bed shape during the summer and the use of chemicals to terminate the crop in the fall are enhanced by a late May planting. But these studies also revealed that the type of overwintering habitat influenced boll weevil spring emergence patterns. The rea- son that delayed, uniform planting is so effective is a result of early termination of spring emer- gence from mesquite, the most abundant over- wintering habitat for boll weevils in the Rolling Plains. As the intertwined relationships between the ecology of the boll weevil and dryland cotton culture in the Rolling Plains were unravelled, it became apparent that an interrelated system of seasonal cultural control practices could be de- veloped. Each recommended cultural control strat- egy enhances efforts undertaken during the pre- ceding and succeeding seasons of the year. Many of the cultural management strategies reduce costs associated with areawide boll weevil management programs, such as fall diapause con- trol or eradication. Clearly, elimination of the boll weevil will be considerably easier if populations are reduced with cultural controls before areawide man- agement efforts begin. Eradication, once accomplish- ed, will be easier to maintain in future years by using many of the techniques outlined in this bulletin. The objectives of this report are to discuss a sequence of cultural control strategies that can be implemented throughout the year for manage- ment of the boll weevil. Cotton production in the Texas Rolling Plains serves as the focal point for the options discussed. Some of the strategies, such as delayed, uniform planting, are specific for the Texas Rolling Plains; other options, such as man- agement of the overwintering habitat, are appli- cable to many cotton producing areas. SPRING CULTURAL CONTROL Crop establishment is an important part of an in- sect control program. Timely planting is critical to managing the boll weevil in the Texas Rolling Plains. Prepare the Land for Planting To meet the target planting date, the land must have been properly prepared, including destruction of last year’s stalks, establishment of beds and per- haps furrow dikes, and application of fertilizer and herbicides. When these preparations have been made early in the year, water from spring rains can be stored in the beds (Fig. 1), and adequate soil moisture is then available for planting in late May. When planting time arrives, the grower is in a posi- tion to plant cotton rather than having to prepare the land and then planting at a later, less optimum time. Planting in late May forms the basis for boll weevil management in the Texas Rolling Plains. Utilize Delayed Planting The concept behind delayed planting is to re- duce effective emergence of the boll weevil (Fig. 2), which is that proportion of the overwintering population that emerges after squares become available for feeding and oviposition sites. Delayed planting reduces the availability of squares at the end of the boll weevil spring emergence period. Boll weevils that emerge from overwintering habi- tat before squares are present die; this is termed “suicidal emergence.” When cotton is planted in 2 late April, squares are present by mid-June (top graph, Fig. 2), but when cotton is planted in late May, squares do not appear until early July (bot- tom graph, Fig. 2). As compared with late-April planting, the late-May planting reduces effective emergence, resulting in a lower boll weevil infes- tation at the time of first squares. Figure 1. Cotton planted on beds with furrow-diking adjacent to cotton on beds without furrow-diking illustrating conserva- tion of rainfall. Chillicothe, Texas. July 1986. " a o _ e0 § Square curve for f ' '- 1O g - April planting f '. " g 2'5 Boll weevil \>- '_ -70 ‘g f, spring f 1 .. #2 g1)- emergence .' -_ -60 $3 5 .-' = ~50 2 O 1.5“ I ' a. g’ ,' ‘. -4o g '5: I " m E I: ‘i. _3o- g. wo- \ ~20 g g 0-5" Effective emergence _1o Q g (shaded) _) Z 0.0 -o 3 0 p 100 Square curve for I ‘x “ 90 2-5‘ Boll weevil May pmtmg ‘. ~eo spring ‘ \ _7O g_Q— emergence ‘ 1.0‘ I I I I I I I I I I I I I I Effective emergence (shaded) 0.5 ' 8 Number of squares per 13 row feet Number of emerging overwintered weevils 0,0 1 | I 2/28 3/31 4/30 5/31 s/ao 7/31 8/31 Date Figure 2. Comparison of effective boll weevil emergence for cotton planted in late April versus planted in late May. When dryland cotton is planted in late May, square damage is reduced about 5O percent as com- pared with damage in cotton that is planted in late April (top graph, Fig. 3). Boll weevil damage is lower in late-May cotton for two reasons: effective emer- gence is reduced and population development is hindered by high temperatures during July (refer to the Summary in Summer Cultural Control). Lint yields are reduced with each delay in planting from late April to late May to late June (middle graph, Fig. 3). However, net returns are highest when cot- ton is planted in late May (bottom graph, Fig. 3). Insecticide control costs are lowest for cotton planted in late May, and this accounts for the higher net return. Thus, when dryland cotton is planted in late May, boll weevil damage is reduced and net returns are increased. Boll weevil damage to squares is similar in irrigated cotton planted in late April and late May (top graph, Fig. 4). This is different from the case in dryland cotton; irrigation produces more luxuriant cotton plants which moderate the harsh July temperature conditions, and boll weevil populations are not suppressed during 25 ‘ 20-1 15‘ 10‘ Percent punctured squares 150‘ 100" Yield (lint lbs per acre) 8 Net returns ($ per acre) °q5$353$5e J Late June Late April Figure 3. Boll weevil damage, yield, and net returns in relation to late April, late May, and late June planting dates in dryland cotton. Chillicothe, Texas. 1986-1989. Late May July. Lint yields are reduced with each delay in planting from late April to late May to late June (middle graph, Fig. 4). However, net returns are highest when cotton is planted in late May (bot- tom graph, Fig. 4). As in the case for dryland cotton, insecticide control costs are reduced when cotton is planted in late May, which ac- counts for higher net returns. Thus, when plant- ing is delayed until late May in irrigated cotton production, net returns are increased. Use Uniform Planting Cotton can be grown successfully when planted over a 65-day period from late April to late June. In the Rolling Plains, cotton planted in late April frequently has to be replanted be- cause spring storms prevent stand establish- ment, wash the seed out of the ground, or de- stroy seedling plants. Uniform early planting could not be achieved across a broad geographi- cal area because up to 25 percent of the crop might have to be replanted in a typical year. Uniform late planting in June generally results Yield (lint lbs per acre) Percent punctured squares Net returns ($ per acre) Late dune Late ‘April Late ' May Figure 4. Boll weevil damage, yield, and net returns in relation to late April, late May, and late June planting dates in irrigated cotton. Munday, Texas. 1986 - 1989. in reduced yields and net returns because the growing season is too short. When a field is planted earlier than adjacent fields, boll weevil damage stays above the treat- ment threshold throughout the growing season, if the field is left untreated (Fig. 5). An early planted field intensifies the boll weevil problem Within a production region where growers are attempting to use a delayed, uniform planting program. The value of a uniform planting period is apparent by _ Planting Date 75 "- Early May (1 field) 6° _ - ' ' Earty June (5 fields) Percent punctured squares Treatment thresholrk 7}8 7/a2 8/‘5 8/[19 9/‘2 9/‘16 9/1210 Sample date ~\.4"*~/’ Figure 5. Boll weevil damage in a field planted in early May in relation to damage in five fields planted at a uniform time in early June. Wilbarger County, Texas. 1975. the infestation levels attained in the late-June plantings (top graphs in Figs. 3 and 4), where lev- els of square damage equal or exceed those in the late-April planting. After April- and May-planted cotton matures in August, boll weevils migrate to the immature cotton planted in late June. Then, high late-season populations develop during Sep- tember, and many diapausing adults enter over- wintering habitats. Planting between late May and early June offers the best compromise for opti- mizing boll weevil management. Summary Delayed, uniform planting between late May and early June is a strategy that reduces initial boll weevil populations that infest cotton. Delayed, uniform planting restricts population development to a short time period during July and August, thus preventing high populations during Septem- ber. This cultural management technique en- hances other cultural controls that can be imple- mented during the summer and fall months, and it reduces the importance of some overwintering habitats, particularly mesquite. SUMMER CULTURAL CONTROL During the summer, the goal of cultural con- trol is to alter the physical and biological environ- ments to make conditions less favorable for boll weevil population growth. Shorten the Growing Season The length of the growing season (biological, or biotic, environment) can be shortened by plant- ing in late May or by planting an early-maturing cotton variety. Early-maturing cottons escape high, late-season boll weevil damage, because the bolls mature and become unsuitable for food and ovi- position sites before boll weevil populations reach damaging levels. However, cotton variety and plant- ing date interact to influence rate of plant devel- opment. For example, TAMCOT CAMD-E is an early-maturing, short-season variety, while Lankart 611 is a medium maturity variety. These two varieties represent the maturity range gener- ally selected by producers in the Rolling Plains. When both varieties were planted in late April, the initial rate of square production by CAMD-E was higher than that by Lankart 6 1 1 (Fig. 6). This dem- onstrates the value of planting an early-maturing variety if planting takes place before late May. When the two varieties were planted in late May, there were more 1/ 3-grown squares in Lankart 611 than in CAMD-E during the first week of squaring (Fig. 6). These results indicate that the growth characteristics of a short-season variety are more evident when cotton is planted in late April as compared to planting in late May when soil temperatures are warmer. Both varieties pro- duced squares faster when they were planted in late May (Fig. 6). Planting in late May exerts a short- season effect on cotton development, regardless of varietal type. The time from first, 1 /3-grown squares to peak square production was 3.8 weeks for Paymaster 145 cotton planted in late April, but only 2.8 weeks for the late May planting (Fig. 7). Five insecticidal applications were required for boll weevil control in the late April planting, but only 2.3 applica- tions were required for the late May planting. Plant- ing in late May shortened the growing season by one week; this decreased the time that boll wee- vils could develop on the plants thereby reducing the number of insecticide applications. Net returns were highest in cotton planted in late May (Fig. 4), primarily because insecticide use was reduced. Change the Microclimate Temperature is one aspect of the physical, or abiotic, environment which influences mortality of boll weevil larvae and seasonal population dy- namics. During the summer, cultural control tech- niques are used to enhance the severity of the high soil temperature conditions experienced by developing larvae in fallen cotton squares. 3O Cotton Variety [EU CAMD-E E Lankart 611 25 2O 15 1O Number of squares per 1 3 row feet Late April Planting date Late May Figure 6. Average number of 1/3-grown squares in two cotton vari- eties during first week of squaring. Munday, Texas. 1986 - 1989. Time (weeks) "i Late April Planting date Late May Figure 7. Time from first, 1/3-grown squares to peak squaring in Paymaster 145 cotton. Chillicothe, Texas. 1986 - 1989. Row Direction. Boll weevil damage to squares and soft bolls is affected by row direction. Dam- age is about 28 percent higher in rows oriented north-south as compared to damage in rows ori- ented in an east-west direction (Fig. 8). This dif- ference may be caused by differential heating within the plant canopy. When rows are oriented east-west, the total plant canopy receives direct solar heating throughout the day. When plants are oriented north-south, the western half of the plant is shaded in the mornings while the east- ern half is shaded during the afternoons. Boll weevils may tend to concentrate in cotton planted in a north-south direction because day- “J ‘f Damaged squares and bolls per acre (1000’s) T“ "9 °’ O East-West Northsouth 150‘ 100‘ 50“ Yield (lbs. lint per acre) East-West North-South Row direction Figure 8. Influence of row direction on boll weevil damage and yield in cotton grown on flat beds. Chillicothe, Texas. 1981 - 1983. 5 time temperatures are cooler within the plant canopies. A 13 percent yield increase was measured in east-west row directions as compared to yields in rows oriented north-south (Fig. 8). Part of this yield increase can be attributed to reduced boll weevil damage. Bed Shape. Shaped beds increase the expo- sure of egg—punctured, fallen squares to high soil temperatures. The distance of a fallen square from the middle of the bed was 5.5 inches on flat beds, but this distance increased to 7.8 inches on sloped (shaped) beds (Fig. 9). Squares that fell from cotton grown on sloped beds rolled out from under the protective shading of the plant canopy. On flat beds only 29 percent of the fallen squares were exposed to direct solar radiation, while 52 percent of the squares were exposed when cotton was grown on sloped beds (Fig. 9). Fallen squares that are exposed to high temperatures rapidly desiccate causing thermal death of the larva inside the square. When cotton is planted in an east-west row direction, sloped beds can be used to reduce boll weevil damage in about 5O percent of the years. Sloped beds provide an effective cultural control technique in years with average temperature and rainfall conditions (years with moderate climatic dbed O-fhlhiéhfllfllflO Distance (rnches) ol square from center Flat Bed Sloped Bed 353$ Percent squares exposed to sun O FlatlBed SlopeTd Bed Shape of bed Figure 9. Effect of bed shape on exposure of fallen, boll weevil- damaged squares to sunlight. Chillicothe, Texas. 1976. 6 conditions) because furrows are exposed to direct sunlight throughout the day. In years with ex- tremely high temperatures and low rainfall, sloped beds do not enhance boll weevil mortality. Sloped beds do not reduce the amount of dam— age in north-south row directions in any year. Plants shade the furrows in mornings and after- noons, which protects the larvae in fallen squares. In two of four years, boll weevil damage to squares in rows oriented east-west was reduced an average of 28 percent in sloped beds as com- pared to amount of damage in flat beds (Fig. lO). As a result, yields were increased about 25 per- cent in the east-west rows (Fig. 10). Producers can plant on beds, or they can use a rolling cultivator after stand establishment to form a sloped bed. Row Spacing. Narrow row spacing cannot be used to reduce boll weevil damage in the Roll- ing Plains. As row spacing decreased from 4O inches to 27 inches to 20 inches, amount of boll weevil damage increased (Fig. l1). Boll weevil damage was 46 percent higher in 2O inch rows as compared to the amount of damage in 4O inch rows. Although yields were about 13 percent higher in the 2O inch rows as compared to yields in 4O inch rows, narrow rows could actually in- tensify boll weevil problems in some areas. In- 3-1 N -l r Number of damaged squares per row foot O Flatged 0 0 0 Q O O Q O 000000 0:0:0 0:0‘0 0.0.0.0:0:0 :0 000 00 0 0000.0 .0. . 0.0 0 O00 0000‘ 0‘0‘0‘0‘0‘ 0 0: 0 0‘0‘0‘0‘ 00000 00.000‘::::::::::0‘ .000‘0‘0‘0‘0‘0‘ .0.0.0.0.0 0.0000 0 ‘0000 ‘0:0:0: ::§§‘&%’ 0000 00000000 %? Q 0000 00000005 0000q£000 000000 00000‘0‘0‘ 0 00 0 ‘0‘00000 00000000‘000000000 0.0.0000“ .0 0 ‘0 0‘0‘0‘0‘0‘0‘0‘0‘0 0000000000000000000 .‘ 0 00 0i? 0000 .‘ 00 ‘:‘ 00 0 0‘0‘ ‘0 0.0.0 0. 0‘0‘ 0‘0 .000 0 :0 0 0.0 0.0 0 Yield (lbs. lint per acre) 00‘00000 0.0.0.0000 0‘: ~: 0:0‘ 0.: ‘00 0 0 0 0 0 Flatbed Shape of bed Figure 10. Influence of bed shape on boll weevil damage and yield in rows oriented east-west. Chillicothe, Texas. 1977 and 1979. ‘-¢ 4 b | nl N l .1 Q l O L O 1 per acre (1 000's) "P ‘T Damaged squares and bolls O 27 Inches 4O lnlches Flow spacing 20 lriches Figure 11. Influence of row spacing on boll weevil damage in cotton planted on flat beds. Chillicothe, Texas. 1981 - 1983. creased damage in narrow rows was associated with higher levels of square production, on a per acre basis. Apparently, boll weevils were congregating in areas with more abundant food, or perhaps they spent less time searching for squares and were able to damage more because squares were more abundant. Summary Planting date influences the timing 0f the blooming period during the summer (Fig. 12). When cotton is planted in late May, blooms are produced from mid-July to late August, and the peak blooming period occurs in late July. Tem- perature records from the Texas Agricultural Ex- periment Station at Chillicothe show that the highest daily temperatures occur during July and August at the time when cotton planted in late May is blooming. Therefore, planting in late May can be used to expose boll weevil larvae in fallen squares to the highest temperature con- ditions during the summer. When cotton is planted on sloped beds in an east-west row di- rection, cultural control is greatly enhanced because the microclimate is changed to the det- riment of the boll weevil. PLANTING DATE MAY 1 i - ' ‘.- _ - ' ‘ " " I I - - Q _ ¢ ' ' - ’ . - ‘u MAY 2a " JUN 24 Y I l l l l 1 14 2a 14 2a 14 JUL. AUG. SEP. SAMPLE DATE Figure 12. Blooming period (l) in relation to planting date and maximum air temperatures. Chillicothe, Texas. FALL CULTURAL CONTROL During the fall, a cultural control objective is to eliminate squares and small bolls; these serve as food and allow boll weevils to build fat reserves for the winter. Utilize Harvest-Aid Chemicals When cotton is planted in late May, squares formed between early July and late August con- tribute over 95 percent of the final yield. The squares and small, immature bolls present dur- ing September and October contribute little to yield and primarily serve as a food source for boll wee- vils entering diapause (Fig. 13). Low numbers of boll weevils enter diapause in late summer. Fewer than 30 percent are in diapause before the end of September, but the percentage of boll weevils entering diapause in- creases rapidly during October (Fig. l4). The potential to survive the winter is influenced by the time that diapausing boll weevils enter suit- able overwintering habitat. Boll weevils that enter Winter habitat during September have a low probability of surviving the winter, but prob- ability of survival increases when boll weevils enter winter habitat during October (Fig. l4). These data (Figs. l3 and 14) suggest that elimi- nation of the food supply by late September would greatly reduce the numbers of boll wee- vils that were capable of surviving the winter. 120' i? CD C) I 3 Squares = iquares = Boll Weevil Food Yield Number of squares per 13 row feet N h "1' °. O l I l ‘l l l I l l 1/9 1/2a a/e s/2o 9/3 9/11 10/2 10/16 11/s Time of season Figure 13. Typical square production curve for dryland cotton in the Texas Rolling Plains. Chillicothe, Texas. N O 0) £60‘ -' Sédlapause _ g 5o- Eflmurvlval E1005 g 40' Critical time Q g ao- z _ *2 2°l ' -1.o § g ‘g m... m i 9/1 9/15_ 111/1 10/15 11/1 11/15 T|me of season Figure 14. Percent of boll weevil population entering diapause and percent overwinter survival versus time of entry into habi- tat. (Data adapted from Bottrell 8i Almand 1970, Sterling & Adkisson 1974, Rummel & Carroll 1983.) The rate of diapause development and the probability of surviving the winter (Fig. 14) sug- gest that a harvest-aid chemical would be most effective when applied by late September. Ethep- hon (1.5 pts/acre) and arsenic acid (3 pts/acre) were applied to dryland cotton in the northern Rolling Plains in late September, 1990 and 1991. These two harvest-aid chemicals reduced square and boll numbers by 72 percent during October, when compared to untreated plots (Fig. 15). Boll weevil damage was reduced 94 percent in plots receiving ethephon and arsenic acid (Fig. 15). When compared to yields in untreated plots, one application of ethephon or arsenic acid in late September did not lower yields (Fig. 16). Harvest- aid chemicals are not commonly used in dryland cotton in the northern Rolling Plains, so the deci- sion to use them in late September would have to be based on their potential for boll weevil man- agement, not yield enhancement. Harvest-aid chemicals could be used effectively in an eradication program or in community dia- pause control programs to reduce overwintering boll weevil populations. This approach might re- duce the need for multiple early season and in- season insecticide applications. When used over I Squares 8i bolls (1990 8* 1991) W Weevil damage (1991) Number of squares and bolls per 13 row feet O -* N G b 0| O *1 G Arsenic Acid Cotton termination treatment Untreated Ethephon Figure 15. Effect of chemical terminaton on availability of squares and bolls and on boll weevil damage during October. Chillicothe, Texas. 500' 450' 4°°_ 350' 300' 25°_ 150' 100' 50' Yield (lbs. lint per acre) Arsenic Acid Chemical termination treatment Untreated Ethephon Figure 16. Effect of chemical termination of cotton during late September on yield. Chillicothe, Texas. 1990-1991. a large geographic area, harvest-aid chemicals could reduce total control costs and other adverse aspects associated with using insecticides. Role of Planting Date It is very important to limit the availability of 1 /3-grown squares during late summer and early fall. Planting cotton in late May restricts the pri- mary period of 1/ 3-grown square production to July and August, but when cotton is planted in late June, 1 /3-grown squares are produced in high numbers during August and September (Fig. 17). When high numbers of squares are present in fields during September, as occurs when cotton is planted in late June, boll weevil population num- bers become very high during the fall (Fig. 17). Planting between late May and early June is a cultural strategy that can be used to reduce num- bers of late season squares and bolls, thereby lim- iting boll weevil population growth during the fall. Terminate Irrigations in August Large numbers of diapausing boll weevils of- ten develop in irrigated cotton fields in Septem- ber and October. For example, there can be three times as many squares and small bolls in irri- gated fields during the fall as compared to num- bers in dryland fields (compare the dryland and irrigated fields in Wilbarger County in Fig. 18). Excessive numbers of squares and bolls in irri- gated fields allow development of high populations of diapausing boll weevils. Management of irrigated fields during the sum- mer is necessaiy to reduce boll weevil problems the following year. Irrigation termination in Au- gust is an effective cultural technique for reduc- ing pest populations and their food supply during the fall. This cultural strategy has effectively elimi- nated overwintering populations of pink boll- worms, Pectino-phora gossypiella (Saunders), in Planting date _ __ LateApril c 14° __ Late May g __ LateJune 9 120- l.‘ ‘:\_ 9* \ \ - - / / g a, 10o A Q m- a 5 g g3 6°“ g \- 4 w- '9 4° Q Q. i5 20* .0 g 0 r I l | T T z 6/18 7/2 7/16 7/30 8/13 8/27 9/10 6- l, Planting date _ I '; 5 ~ _ __ Late Apnl _ ‘\ 3 late May I ‘ 318; 4- __ LateJune . \ g ‘i _ c! ‘L _ a g Q 3 I ~0- l’) O t _ | .0 \ , \\ , g 1 \\ / / Z \/ ‘ZE 0 6/18 7/2 7/‘16 7/80 8/13 8/87 9/‘10 Time of year Figure 17. Influence of three planting dates on timing of square production (top) and on boll weevil population development f (bottom) in dryland cotton. Chillicothe,Texas. Arizona. A similar technique holds promise for managing boll weevils in irrigated fields in the Texas Rolling Plains. For example, some irrigated fields in Knox County, Texas, which had irriga- tions terminated during August, had numbers of =85 30" f!) 32-: $ g 2o- ? 5 a t ‘~”‘ 0 § g 1o- B "-6 E .0 5“ = l Z o Dryland Irrigated Irrigated Wllbarger County Wilbarger County Knox County Water management Figure 18. Average number of squares and soft bolls during September and October in dryland and irrigated fields. 1984. squares and bolls similar to those in dryland fields in Wilbarger County (Fig. 18). Summary The primary cultural control objective during the fall is to eliminate the food supply of boll weevils as they prepare for overwintering. Harvest-aid chemi- cals show promise for this purpose, especially when applied by late September. Planting cotton between late May and early June is another way to effec- tively reduce numbers of squares and bolls during September and October. A management option in irrigated fields is to terminate irrigations in August; this significantly reduces numbers of squares and bolls during the fall. It is important to eliminate squares and small bolls by late summer because successful overwintering is dependent upon avail- ability of a food supply during the early fall. WINTER CULTURAL CONTROL Cultural control objectives during the winter months are designed to deprive the boll weevil of suitable overwintering habitats. Eliminate the Overwintering Habitat There are many types of suitable overwin- tering habitats for boll weevils in the Rolling Plains region including shelterbelts, sand shin- nery oak, mottes of western soapberry or hack- berry trees, overgrown vegetation around aban- doned farmsteads, dense mesquite pastures, and fence rows overgrown with woody vegeta- tion. These favorable overwintering sites can be small in total area, but they can harbor large numbers of boll weevils. The economic costs associated with boll weevil survival in shelterbelts, one type of winter habitat which ‘is generally small in area, were estimated at $54.78 per acre in the adjacent 40-acre cotton field. Some of the habitats could be destroyed. In an experiment in Arkansas, a five acre wooded area within a 600—acre cotton field was destroyed, and no boll weevil infestation occurred the follow- ing year. In this example, the five acres of woods were converted to five acres of cotton, a place where boll weevils do not typically overwinter. Examples of habitat that could be eliminated in the Texas Rolling Plains include western soapberry and sand shinnery oak mottes in and adjacent to cotton fields, old abandoned farm sites that have become overgrown with vegetation, and mesquite- infested rangeland adjacent to cotton. Sand shinnery oak occurs on about 570 thou- sand acres of rangeland in the western and south- ern Rolling Plains of Texas. This oak shrub pro- vides one of the best overwintering habitats for boll weevils. Tebuthiuron herbicide was used to convert shinnery-infested rangeland to a more desirable grass-dominated rangeland. The herbicide did not immediately kill the shinnery oak shrubs, so the leaf litter where boll weevils overwinter was not im- mediately affected. Survival in untreated plots and tebuthiuron-treated plots was similar the first two winters following treatment. However, overwinter survival was reduced 67 percent during the third winter in the tebuthiuron plots (Fig. 19). It took two years following herbicide treatment for the litter layer to decompose or blow away sufficiently to reduce winter survival of the boll weevil. Herbicide applications are expensive, so their long-term effects are important. In 1982, two years posttreatment, grass and forb production totaled 360 lbs. per acre in untreated plots and 2670 lbs. per acre in tebuthiuron-treated plots. In 1990, which was ten years posttreatment, total grass and forb production in untreated plots was 360 lbs. per acre while that in the tebuthiuron-treated plots was 890 lbs. per acre (Fig. 20). In 1982 and 1990 there was a 642 percent increase and a 147 percent increase, respectively, in grasses and forbs I Untreated E38 Tebuthiuron Percent boll weevil survival o - r0 o: b 01 o ~1 m Year 2 Year 3 Posttreatment Figure 19. Survival of overwintering boll weevils in sand shinnery oak treated with tebuthiuron herbicide in 1980. Kent County, Texas. Year 1 3,000 2,500 I Untreated ‘ 2,000 E221 Tebuthiuron Grass and forbs (lbs. per acre) 1,500 1 ,ooo 50o o Year 2 Year 1 O Posttreatment Figure 20. Grass and forb production in sand shinnery oak treated with tebuthiuron herbicide in 1980. Kent County, Texas. l0 in the tebuthiuron-treated plots. Plots had been deferred from grazing for three years at the time of the 1982 measurements, but the plots had been grazed by cattle for seven years at the time of the 1990 measurements. These data demonstrate that sand shinnery oak can be converted to a more desirable, long term grass and forage resource for cattle, and at the same time the leaf litter habitat of overwintering boll weevils can be eliminated. Destruction of trees and brush can reduce both plant and animal diversity. Vegetation should be altered only when there will be no undesirable side effects, such as elimination of wildlife habitat. Modify the Overwintering Habitat Modification of habitat through elimination of leaf litter, where the boll weevils overwinter, is a more desirable approach than complete destruction of the habitat. For example, seven tree rows were e1irr1i- nated in an existing ten-row shelterbelt. Distance between the remaining three tree rows was increased from 10 feet to 20 feet. The interior, lower limbs of the trees were pruned high enough to allow pas- sage of a tractor, and the leaf litter could then be destroyed by annual disking. (Fig. 21 shows the shelterbelt and leaf litter before tree row removal, and Fig. 22 shows the shelterbelt after thinning.) The three remaining tree rows still provided an ef- fective windbreak. Figure 21. Unmanaged shelterbelt with dense tree planting and abundant leaf litter accumulation. Foard County, Texas. 1977. U- Figure 22. Managed shelterbelt with selective tree row removal and lower limb pruning which allows disking to destroy leaf litter. Foard County, Texas. 1981. There were four primary benefits to shelter- belt management using selective tree row re- moval and disking. First, there was an 84 per- cent reduction in leaf litter. Therefore, the shelterbelt could not harbor as many overwin- tering boll weevils because most of the micro- habitat (leaf litter) was destroyed. Second, win- ter temperatures averaged 5.4 °F colder than those in unmanaged plots, and freezing tempera- tures occurred in managed plots but not in unmanaged plots. Percent overwinter survival was reduced 63 percent in the managed area because of the colder environment. Third, tem- peratures during the spring averaged 2.2 °F warmer in the managed plots as compared to temperatures in unmanaged areas. As a result of the warmer temperatures, spring emergence terminated from one week to one month earlier in managed plots. Therefore, most spring emer- gence was suicidal; these boll weevils died be- fore 1 /3-grown squares were available as feed- ing and oviposition sites. And fourth, fewer mi- grating boll weevils selected the managed area during the fall, which resulted in a 7O percent reduction of the overwintering population as compared to that in unmanaged plots. Sand shinnery oak mottes are small thickets of tall hybrid oak trees that are intermingled with "\the low shinnery brush. Mottes are important be- cause cooler litter temperatures during the spring, as compared to temperatures in low brush, delay spring emergence so that some boll weevils emerge after 1 /3-grown squares become available. These mottes function to increase effective emergence. Cattle often seek shelter from summer heat in mottes, and if this activity is encouraged, the ani- mals can destroy upto 85 percent of the leaf litter where boll weevils overwinter. In this case the motte is preserved, but the litter is destroyed. As another example, boll weevils can overwinter in Conservation Reserve Program grass plantings. Periodic fires, which would not permanently in- jure the plantings, could be used to eliminate the grass residues where boll weevils overwinter. These examples show that in selected instances, habi- tats can be modified without destroying them. Avoid the Overwintering Habitat When practical, producers should plant cot- ton as far from favorable overwintering habitat as possible; this reduces the probability of the field becoming infested during the growing season. Cotton fields within several hundred yards of good winter habitat are the ones most likely to be in- fested during the growing season. When cotton is planted in late May, 1/ S-grown squares become available for oviposition in late June - early July. Although boll weevils can sur- vive the winter in mesquite, most of these survivors can be avoided by using delayed, uniform planting. For example, in the southern Rolling Plains, the date of last emergence from mesquite litter was June 4, which was 19 days earlier than date of last emer- gence from pecan litter. In the northern Rolling Plains, date of last emergence from mesquite litter was May 3 1 , which was 34 days earlier than date of last emergence from sand shinnery oak litter (Fig. 23). Although mesquite is not one of the best overwintering habitats, it occupies about 9.6 mil- lion acres in the Rolling Plains. Mesquite actually may be the most important overwintering habitat in the region, but delayed, uniform planting de- creases the importance of this habitat. Producers often have some fields that are adjacent to winter habitat and some fields that are isolated from habitat. An alternative in this case is to plant the isolated fields first, in ac- cordance with delayed uniform planting recom- mendations, and then plant the fields that are closer to favorable winter habitat last. A later planting date for fields adjacent to winter habi- tat will reduce the level of infestation during the growing season. ll 2 Meoqulte litter Broedled litter Tom Green County - Southem Rolling Plains June 4 Q’V...'."QQ’.Q'Q'Q"Q‘QQQQQQ’."QQQQQQQQQQQQQQQQQ.QQ‘ fofofofofofofofoTofofofoYofofofofofofofoYofofofofofofofofof0YoYofof0fofofofofofofofofofofofofofofofofofofol J u n 9 23 Hardeman County - Northern Rolling Plains February March April May June July Spring-summer emergence period Figure 23. Date of last emerging boll weevils from mesquite and broadleaf litter in the southern and northern Texas Rolling Plains. 1986 - 1988. Summary The overwintering habitats of the boll weevil can be destroyed, modified or avoided. Destruc- tion completely eliminates the trees and associ- ated leaf litter, and the area is then planted to a crop or it becomes grass-dominated rangeland or some other vegetation type unsuitable for over- wintering boll weevils. The objective of habitat modification is to eliminate the leaf litter while leaving the associated deciduous, broadleaf trees intact. This is the most desirable goal for manag- ing shelterbelts because the windbreak function of the tree plantings must be maintained. Cattle can be used to trample leaf litter in shady groves of trees; this destroys the leaf litter but not the trees. Overwinter habitats can be avoided. The delayed, uniform planting strategy generally al- lows cotton to avoid boll weevils that overwinter in mesquite. If practical, cotton can be planted as far as possible from winter habitat; this allows the crop to escape those boll weevils that do sur- vive the winter. CONCLUSIONS Delayed, uniform planting between late May and early June is a cultural control system that enhances boll weevil management throughout the year. This strategr reduces effective emergence of adults in the spring, increases mortality of larvae in fallen squares during the summer, limits the food supply for diapausing boH weevils during the fall, and enables the cotton crop to avoid those weevils that overwinter in mesquite. Utilization of a short growing season, harvest-aid chemicals, ir- rigation termination in August, and overwinter habitat management are additional cultural man- agement strategies that effectively reduce popula- tion densities and crop damage. Cultural control can be utilized in all seasons of the year to reduce boll weevil damage during the growing season. ACKNOWLEDGMENTS There is an important history associated with the development of delayed, uniform planting for boll weevil management in the Texas Rolling Plains. Many people have contributed to the success of this program, but Emory P. Boring, III, with the Texas Agricultural Extension Service at Vernon, has been the key person involved in the implementation of this highly successful Extension program. The value of delayed, uniform planting was first reported by D. R. Rummel (1965) when he noted that develop- ment of boll weevil populations was slower at Afton as compared with populations at Spur. He attrib- uted the lower boll weevil populations at Afton to the later planting there, and these observations and subsequent discussions in grower meetings formed the basis for delayed planting in the Rolling Plains. In the early 1970s, E. P. Boring, III began recom- mending the use of delayed, uniform planting in 12 the Rolling Plains. His recommendation was to plant cotton throughout the region after rr1id—May (Bor- ing, 1973). This program was subsequently adopted by most cotton producers throughout the Rolling Plains and is recognized by many as being a pri- mary component in the economical management of the boll weevil in dryland cotton. The first research to support delayed, uniform planting was presented by J. E. Slosser (1978). He compared boll weevil damage and population development in an April- planted field with that in early June-planted fields, and he reported that damage and populations were higher and yields were lower in the April-planted field. T. W. Fuchs, Extension Entomologist in the southern Rolling Plains, developed a delayed plant- ing program for that area in the 1980s. Again, this program is recognized as being highly successful. However, producers in the southern area consider e W W ,.\ several factors before selecting a specific planting date (Fuchs and England 1989). Lastly, an eco- nomic analysis by S. M. Masud and others (1985) showed that net returns in dryland cotton were increased $21.37 per acre in response to delayed, uniform planting. All of these efforts have collec- tively built confidence in and have led to broad acceptance of delayed, uniform planting in the Texas Rolling Plains. The author extends special thanks to long-time technician, Rex Price, for his help with many of the studies referenced herein. Other valuable co-work- ers include P. W. Jacoby, L. E. Clark, D. G. Bordovsky, H. T. Wiedemarm, L. J . Meinke, G. J. Puterka, R. Montandon, G. B. Idol, B. T. Cross and C. H. Meadors with the Texas Agricultural Experi- ment Station; E. P. Boring, III, T. W. Fuchs, C. W. Neeb, S. J . Bevers, James Lee, A. A. England, R. R. Minzenmayer, Bruce Griffith, and Mark Geeslin with the Texas Agricultural Extension Service; and R. J. Fewin and J. R. Bryson with the Texas Forest Ser- vice. M. K. Berry, Vernon, Ben Spradling, Spur, and Donnie Reed, Big Spring, provided land for the management studies with shelterbelts and sand shinnery oak. Other research sites for comparing boll weevil survival in mesquite litter and broadleaf litter were provided by F. D. Bradshaw, Bill Bond, Gene Evans, Jerry Stringer, Dale VonTongeln, and C. L. Wall (northern Rolling Plains) and George Ahlschwede, Erwin Weierhausen, and Gary Haltrnan (southern Rolling Plains). All other research was conducted at the Texas Agricultural Experiment Station farms located at Chillicothe and Munday. Appreciation goes to Weldon Williams, Gene Obenhaus, and Tom Angerer, farm foreman at these locations, for their assistance and patience. Some financial support for research on over- winter habitat management was provided by grants from Cotton Incorporated (Research Agreement 79-440), Howard County Cotton Pro- ducers Association, and Martin County Insect Control Association. SUPPORTING RESEARCH STUDIES The following scientific studies provide sup- porting data for the boll weevil cultural control guidelines presented in this paper. Adkisson, P. L., J. W. Davis, W. L. Owen, and D. R. Rummel. 1965. Evaluation of the 1964 diapause boll weevil program on the High Plains of Texas. Tex. Agric. Exp. Sta., Dept. Entomol. Tech. Rep. 1. Bevers, S. J. and J. E. Slosser. 1992. Assessing cost effectiveness of planting dates and insecticide chemicals in Texas dryland cotton production . J. Prod. Agric . 5: 374- 377. Boring, E. P., III. 1972. Studies on overwintering habi- tat, spring movement, and population dynamics of the boll weevil in the Rolling Plains area of Texas. M.S. thesis, Texas A&M Univ., College Station. Boring, E. P., III. 1973. Uniform planting and early sea- son boll weevil control. Tex. Agric. Ext. Ser. News Release. April, 1973. Boring, E. P., III, J. E. Slosser, and R. J. Fewin. 1985. Windbreak management to reduce overwintering boll weevil habitat. Tex. Agric. Ext. Ser. Leaf. 2 135. Boring, E. P., III, J. F. Leser, T. W. Fuchs, and C. T. Allen. 1989-1990. Management of cotton insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas. Tex. Agric. Ext. Ser. Bull. 1209. Bottrell, D. G. and L. K. Almand. 1970. Evaluation of the 1968 reproductive-diapause boll weevil control '\ program of the Texas High Plains. Tex. Agric. Exp. Sta. Prog. Rep. 2766. Bottrell, D. G., J. R. White, D. S. Moody, and D. D. Hardee. 1972. Overwintering habitats of the boll weevil in the Rolling Plains of Texas. Environ. Entomol. 1: 633-638. Carroll, S. C., D. R. Rummel, and E. Segarra. 1993. Overwintering by the boll weevil (Coleoptera: Curculionidae) in Conservation Reserve Program grasses on the Texas High Plains. J. Econ. Ento- mol. 86: 382-393. Clark, L.E. 1987. Weather data from Chillicothe. Chillicothe Field Day Report, Sept. 24, 1987. Clark, L. E., H. T. Wiedemann. C. J. Gerard and J. R. Martin. 1991. A reduced tillage system with fur- row diking for cotton production. Trans. Amer. Soc. Agric. Eng. 34: 1597-1603. V DeMichele, D. W., G. L. Curry, P. J. H. Sharpe, and C. S. Barfield. 1976. Cotton bud drying: a theoreti- cal model. Environ. Entomol. 8: 1011-1016. Finley, M. D. 1978. Fisher-Jones Pest Management Report. Tex. Agric. Ext. Ser., February, 1978. Fuchs, T. W. and A. England. 1989. Winter habitat sam- pling for overwintering boll weevils as a component of an integrated pest management program. South- west. Entomol. 14: 265-269 Helms, D. 1980. Revision and reversion: changing cul- tural control practices for the cotton boll weevil. Agric. History. 54: 108-125. Henneberry, T. J., T. Meng, W. D. Hutchison, L. A. Bariola, and B. Deeter. 1988. Effects of ethephon 13 on boll weevil (Coleoptera: Curculionidae) popula- tion development, cotton fruiting, and boll open- ing. J. Econ. Entomol. 81: 628-633. Hinds, W. E. 1915. Chain drag for boll weevil control. Ala. Agric. Exp. Sta. Bull. No. 78. Isely, D. 1930. Control of the boll weevil in winter. Ark. Agric. Exp. Sta. Bull. 257: 54-56. Jacoby, P. W., J . E. Slosser, and C. H. Meadors. 1983. Vegetational responses following control of sand shinnery oak with tebuthiuron. J . Range Manage. 36: 510-512. Masud, S. M., R. D. Lacewell, E. P. Boring, III and T. W. Fuchs. 1985. Economic implications of a regional uniform planting date cotton production system: Texas Rolling Plains. J . Econ. Entomol. 78: 535-54 1. Montandon, R., J. E. Slosser, and L. E. Clark. 1994. Late-season termination effects on cotton fruiting, yield, and boll weevil (Coleoptera: Curculionidae) damage in Texas dryland cotton. J . Econ. Entomol. 87: 1647-1652. Rummel, D. R. 1965. Results of in-season control below caprock. In: Minutes of a meeting, Plains Cotton Growers Technical Advisory, Steering and Area-wide Boll Weevil Committees. Lubbock, Tex., Aug. 3, 1965. Rummel, D. R. and P. L. Adkisson. 1970. Distribution of boll weevil-infested cotton fields in relation to overwintering habitat in the High and Rolling Plains of Texas. J. Econ. Entomol. 63: 1906-1909. Rummel, D. R. and S. C. Carroll. 1983. Winter survival and effective emergence of boll weevil cohorts en- tering winter habitat at different times. Southwest. Entomol. 8: 101-106. Rummel, D. R. and S. C. Carroll. 1985. Longevity of overwintered boll weevils (Coleoptera: Curcu- lionidae) following emergence in spring and early summer. Environ. Entomol. 14: 127-130. Slosser, J . E. 1978. The influence of planting date on boll weevil management. Southwest. Entomol. 3: 241-246. Slosser, J. E. 1981. Cultural control of the boll weevil: influence of bed shape. J . Econ. Entomol. 74: 561-565. Slosser, J . E. 1993. Influence of planting date and in- secticide treatment on insect pest abundance and damage in dryland cotton. J. Econ. Entomol. 4: 86: 1213-1222. Slosser, J . E. and E. P. Boring, III. 1980. Shelterbelts and boll weevils: a control strategr based on man- agement of overwintering habitat. Environ. Ento- mol. 9: 1-6. Slosser, J . E. and T. W. Fuchs. 1 991. Over-winter survival of boll weevils (Coleoptera: Curculionidae) in the Texas Rolling Plains. Environ. Entomol. 20: 877-881. Slosser, J . E., J . R. Price, and P. W. Jacoby. 1984. Ef- fect of two shinnery oak habitats on winter sur- 14 vival and on spring and early summer emergence -. of the boll weevil. Southwest. Entomol. 9: 240-244. w Slosser, J. E., P. W. Jacoby, and J . R. Price. 1985. Man- agement of sand shinnery oak for control of the boll weevil (Coleoptera: Curculionidae) in the Texas Roll- ing Plains. J . Econ. Entomol. 78: 383-389. Slosser, J. E., G. J. Puterka, and J. R. Price. 1986. Cultural control of the boll weevil (Coleoptera: Curculionidae): effects of narrow-row spacing and row direction. J . Econ. Entomol. 79: 378-383. Slosser, J . E., D. G. Bordovsky, and S. J . Bevers. 1994. Damage and costs associated with insect manage- A ment options in irrigated cotton. J . Econ. Entomol. 87: 436-445. Slosser, J. E., P. W. Jacoby, D. G. Foster, and C. W. Neeb. 1982. Management potential of sand shin- nery oak to reduce overwintering habitat of boll weevils. Tex. Agric. Exp. Sta. Misc. Pub. 1515. Slosser, J . E., R. J . Fewin, J . R. Price, L. J . Meinke, and J. R. Bryson. 1984. Potential of shelter- belt management for boll weevil (Coleoptera: Curculionidae) control in the Texas Rolling Plains. J. Econ. Entomol. 77: 377-385. Slosser, J. E., E. P. Boring, III, J. R. Price, and G. J. Puterka. 1987. Influence of field margins on den- sities of cotton fruit and on boll weevils and their damage during late season. Southwest. Entomol. 12: 253-258. Sterling, W. L. and P. L. Adkisson. 1974. Seasonal incidence of diapause and reproduction in boll weevils inhabiting the High and Rolling Plains of Texas. Tex. Agric. Exp. Sta. Misc. Pub. 1145. Summy, K. R. and E. G. King. 1992. Cultural control of cotton insect pests in the United States. Crop Prot. 11: 307-319. Walker, J . K. 1984. The boll weevil in Texas and the cultural strategr. Southwest. Entomol. 9: 444-463. Walker, J. K., Jr. and G. A. Niles. 1971. Population dynamics of the boll weevil and modified cotton types. Tex. Agric. Exp. Sta. Bull. 1109. Watson, T. F., F. M. Carasso, D. T. Langston, E. B. Jack- son, and D. G. Fullerton. 1978. Pink bollworm sup- pression through crop termination. J. Econ. Entomol. 71: 638-641. Wade, L. J . and D. R. Rummel. 1978. Boll weevil im- migration into winter habitat and subsequent spring and summer emergence. J . Econ. Entomol. 71: 173-178. Wiedemarm, H. T., J . E. Slosser, and B. T. Cross. 1979. Tree uprooting with a low-energy grubber for shelterbelt thinning. Trans. Am. Soc. Agric. Eng. 22: 1275-1278. White, J . R. and D. R. Rummel. 1978. Emergence pro- file of overwintered boll weevils and entry into cot- ton. Environ. Entomol. 7: 7-14. W ‘~5- [Bhmk Page in Original Bulletin] ' 7 J A , ‘ ‘a Y‘ H r " :3?’ ‘ ‘ " VP‘ J . 2.45 1 , / — , ,4 "J Texas Agricultural Experiment Station The Texas A8