845 I A/aaemfiea I956 GREENE U GS and J0me Uzi/oer Pest: of Imall Grain: in cooperation with the TEXAS TECHNOLOGICAL COLLEGE and the U. S. DEPARTMENT OF AGRICULTURE TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS, DIRECTOR, COLLEGE STATION,.TEXAS y SUMMARY Information is given in this bulletin on the biology, distinguishing characteristics and contr of greenbugs. mites and false wireworms. all important pests of small grains in Texas. ' The greenbug. probably Mediterranean in origin. has been a pest oi small grains in the Unit c States since 1882. with several severe outbreaks occurring since that time. Greenbugs preyed upon by a number of insect enemies. among which are lady beetles. nabids. lace flies and syrphid flies. They also are parasitized by a tiny wasp. Greenbugs can reprodu well at temperatures between 40° and 80° F. whereas most of their insect enemies reprodu slowly at temperatures below 65°. Thus. long periods of cool weather permit the greenbug. increase rapidly. * Cultural practices which will promote the development of vigorous plants are encourag At present. the use oi insecticides is the best means oi controlling established infestati of greenbugs. Oi the many insecticides tested. parathion and methyl parathion were the m profitable. Gamma BHC was effective under ideal weather conditions. but it performed in erratic manner under less favorable conditions.» TEPP also gave good control. Applications were made when 5O greenbugs per row foot were found on ‘small wheat.‘ plants were large. spraying began with populations oi 100 per foot oi drill row. Days temperatures oi at least 50° F. and with winds oi less than l0 miles per hour were . for application. In irrigated wheat. treatments made as soon as‘possible after the water ~ l applied insured the best kill. w » Since the use oi chemicals against the greenbug is not always dependable and is expe =1 _ it is necessary to seek a more satisfactory control. One of the most promising methods is I development of varieties of small grains that are resistant to this aphid. Research along ; line is now being carried on at the Denton and Amarillo stations. " Chemical control against the brown wheat mite. the wheat curl mite and a white mite is = practical. The only importance of the wheat curl mite is that it transmits the virus causing wh_ streak-mosaic. Heavy rains greatly reduce brown wheat mite populations and border irrigati has given control for about 3 weeks. Several of the phosphorous compounds have given g { control of the winter grain mite. A suitable rotation may be used to lower mite populati Mites are much more abundant on continuously cropped grain. False wireworrns damage germinating wheat and sorghum. Their greatest injury is ca A during dry fall seasons since they usually increase during dry years. Clean culture accumulated soil moisture associated with summer fallowing reduce injury. Aldrin. diel heptachlor and lindane applied as seed treatment have given effective control of false wirewoé i on sorghum. ACKNOWLEDGMENTS _ The work reported in this bulletin was done cooperatively by the Texas Agricultural E - Q ment Station. Texas Technological College and U. S. Department of Agriculture. Thanks _v due to the many grain farmers. chemical companies and aerial applicators who cooper ‘ in these investigations. Funds for the Texas Technological College ‘program were furnished a the Texas Technological College Foundation. W eenbugr and Some Other Pests of Small Grains N. E. DANIELS, H. L. CHADA, DONALD ASHDOWN and E. A. CLEVELAND* GROWTH OF THE SMALL GRAIN INDUSTRY in Texas, i d other parts of the grain belt was made possible by l vements in many phases of production. The develop- of machinery capable of tilling, seeding and harvest- rger acreages enabled farmers to increase greatly the -- of seeded acres. In the development and expansion Qricultural crops, man frequently increases his insect ems. Before the settlement of a country, native s live on wild plants. As new plants are introduced grown in greater abundance, native pests and those entally brought in from foreign countries, finding the acceptable food, may multiply rapidly to injurious rs. easures for the control of these pests may be divided plseveral categories, among which are natural, cultural _ chemical control. Whatever the method and its iveness, the cost of control should be a deciding r as to its practical use. It is evi-dent that no cial profit to an individual will be gained by pting control when the cost is greater than the pble loss would be without the control measure. 1 e applying a costly control, a farmer should consider op potential and prospective returns. mall grains in Texas are subject to attack from several t. The most important of these are greenbugs, mites false wireworms. 7f lthough sorghum is not a small grain, it shares some rtant insect problems. ‘ GREENBUG HISTORY AND BIOLOGY The greenbug, Toxoptera graminum (Rond.), is a ~ reserved for the most important of several kinds of ds which commonly infest small grains in Texas. This » , green plant louse has caused periodical crop failures. The greenbug is an unusual pest in many ways. It is lly most abundant in winter and spring, long before other pests appear. It is small, nearly the same green a as the leaf and to all but the trained observer, its nce goes undetected until yellow or brown spots w in the field. These spots indicate areas in which plants have died as a result of greenbug feeding Vi; re 4). These aphids are approximately 1/16 inch in pectively, assistant entomologist, Texas Agricultural Experi- -| Station, USDA Southwestern Great Plains Field Station, hland, Texas; entomologist, Entomology Research Branch, licultural Research Service, U. S. Department of Agriculture, - ton, Texas; and director of Greenbug Research and formerly 'stant entomologist, PanTech Farms, Texas Technological i ege, Panhandle, Texas. length and when full grown have a dark green stripe down the back. Both wingless and winged forms occur (Figure 1). All of the wingless forms, and most of the winged forms, are females and give birth to living young. Most females begin reproduction in 6 to 30 days after birth and continue to produce two or three aphids a day for 2O to 3O days. Many generations may be produced in a year under favorable conditions. Male greenbugs have not been observed under Texas conditions. Although several eggs have been recovered from greenbug-infested wheat in the greenhouse, they have not hatched, and there is little evidence that eggs are either deposited or hatched under field conditions in Texas. It appears from studies in the field that greenbugs either oversummer as active aphids in the area, or migrate from areas to the north or south. The distribution pattern of greenbugs in the Panhandle in 1953 and 1954 indicated fall migration from the north, while the localized fall infestations in the 1955-56 season strongly. suggested local over-summering. Greenbugs are most likely to become abundant when a cool summer is followed by a mild winter and a late, cool spring. They can reproduce at 40° F., and at a much more rapid rate at temperatures between 55° and 80°. If the temperature goes as low as 0° or as high as 105°, some greenbugs will be killed, although those in the field become “hardened” to extreme temperatures. Winged forms are most numerous in the field during drouth and windy periods. They reproduce less efficiently than wingless forms, but they fly and are readily blown many miles to establish new colonies. CONTENTS Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Acknowledgments . . . . . . . . . . . . . . . . . . . . . 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 Greenbug . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 History and Biology . . . . . . . . . . . . . . . . . . 3 Natural Control . . . . . . . . . . . . . . . . . . . . . . 4 Predaceous . . . . . . . . . . . . . . . . . . . . . .. 4 Parasitic . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Cultural Control . . . . . . . . . . . . . . . . . . . . . 5 Insecticidal Control . . . . . . . . . . . . . . . . . . 6 Precautions . . . . . . . . . . . . . . . . . . . . . . . . . 9 Resistance . . . . . . . . . . . . . . . . . . . . . . . . .. 9 Mites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Brown Wheat Mite . . . . . . . . . . . . . . . . . . . 10 A White Mite . . . . . . . . . . . . . . . . . . . . . . . . ll Wheat Curl Mite . . . . . . . . . . . . . . . . . . . . . 11 Winter Grain Mite . . . . . . . . . . . . . . . . . . .11 False Wireworms . . . . . . . . . . . . . . . . . . . . . . 12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 1. Wingless and winged forms oi the greenbug. Courtesy Department oi Entomology, University of Kansas. The greenbug is not new to Texas, or to the rest of the country. It was first described in Italy in 1852 (17) and first recorded in the United States-from Virginia in 1882. The earliest recorded outbreak in Texas was reported by ]. L. Fooks from Era, Cooke county, on January 26, 1890. A letter by H. K. Jones of Valley View, Texas, dated 1901, indicated that an infestation "about ten years previously killed about all the wheat in the country” (25). This and other correspondence indicate that Collin, Cooke, Denton, Grayson and Wilbarger coun- ties were damaged by this infestation. Another major outbreak occurred in 1901, beginning near Waco and spreading northward into Oklahoma. Another came in 1903, but was again confined to counties in North Central Texas. A major and very extensive outbreak occurred in 1906-7. This outbreak apparently started in Central Texas and spread northeast to within 60 miles of Chicago, Illinois. By the end of the crop season, it had reached Eastern Colorado, North and South Carolina and Wash- ington, D. C. This was the greatest infestation known from a geographical standpoint, and over 50 million bushels of small grains were destroyed (22). An outbreak in 1916 covered only North Central Texas counties; major damage occurred in Oklahoma and Kansas (18). Texas was again hit by greenbugs in 1933 in a minor infestation which extended into Oklahoma. In 1926, an infestation which centered in Minnesota was believed to have originated from migrations of green- bugs which overwintered in Oklahoma and Kansas, al- though some greenbugs were observed near St. Paul, Minne- sota, in 1925. This infestation was somewhat unique in that it centered in Minnesota and extended into Wiscon- sin, North Dakota, Ohio and Iowa. Outbreaks in Oklahoma occurred each year from 1934 through 1939. The outbreak of 1939 centered in Northeast- ern Oklahoma and caused a half-million dollar loss to the small grains crop. 4 A major outbreak occurred in 1942, involvi small grain acreages in Texas and Southern (2). Almost total crop losses occurred on oats = in the principal growing areas, and on wheat in - area from south of Temple, west to Abilen Dallas and Denton, and extending some dist, of. Lawton, Oklahoma. Over 61 million" bushe were lost. i‘, Record losses again occurred in 1949-50anci- The latter was the most damaging infestation, have occurred in the Panhandle. A It is obvious that damaging infestations of I bug do not occur every year, at regular int i any predictable pattern. é -._ ._._~i..- no» o-I-fa NATURAL CONTROL Greenbugs are preyed upon by a number; enemies, among which are lady beetles, nabids a flies. They are also parasitized by a tiny wasp. temperatures are below 65° F., most greenb reproduce slowly or hardly at all. Long peri weather thus permit the greenbug to increase -. numbers, while its natural enemies increase , This relationship between the greenbug and and the effect of the weather upon them, is- sponsible for greater greenbug abundance winters followed by .cool springs. ‘r Predaceous Chief among the predaceous insects are: beetles, Coccinellidae, chiefly Hippodamia , (Guer.), small, orange, spotted beetles w- grain fields. These are well known as adul immature, dark slug-like grubs from which the develop are not so well recognized. Clusters Q yellow eggs, from which these grubs hatch, f attached to the wheat leaves when lady f numerous. Both adults and larvae of these p e-_, on the greenbugs and in some years aid mate trolling them. Much publicity has been given, of these beetles for greenbug control durii years. This practice, however, is not reco m, cording to Fenton and Dahms (14), the r-l not an effective control for the greenbug in “At an average rate of consumption, at favor i, tures, it would require one gallon of beetles { prevent greenbug increase in a moderately infi they reported. Also, if natural conditions -_ able for lady beetle development at the " release, the beetles would, in many cases, W the field. Economically this type of contro unreasonable. " Included in the greenbug predators are ; bugs or nabids, chiefly Nabis ferur (Linn.),_f gray or brown elongated insects about 5/16 i y These insects search the wheat plants for gr other aphids, piercing them with their beaks ‘ the blood. They have. been found consistently the winter, but always in the adult stage. - have been observed moving about and feedi p atures below 50° F., at least 10-12° below -j lady beetles are active. Because they do not ~ I tiply until March or April, they constitute a p ins. When caged with greenbugs, a single nabid has g- as many as 84 of them in a. 24-hour period. j rphid flies, Syrp/Jidae sp., are classed in the group ireenbug enemies. Medium-size flies, with yellow A on the body, they are found sometimes hovering d greenbug-infested plants. They dart from place ace with great speed. ‘The larvae or immature stage se flies feed on the aphids and are found on the plants .. midst of the greenbug colonies. They are slug- and vary in color from green to brown, gray or ed. They lack legs and head, but possess pointed with which they pick and-suck all the body contents fr a greenbug and discard its empty skin. Syrphid k are valuable in aphid colonies since they destroy ‘bugs rapidly for considerable periods of time. ti. this class of feedersis the immature stage of a te, green, gauzy-winged insect called the lacewing iC/Jryropa sp. The larva of this insect is predaceous, ling about over the plants in search of greenbugs, 'ng them with its long jaws and sucking their blood. (.116 1 reenbug populations are held in check sometimes by All wasp, A p/aidiur tritici (Cress), which usually is , twhen greenbugs are abundant. This wasp deposits egg within the aphid’s body. The egg hatches into a y so small that it can feed inside the greenbug. When larva is full grown, the skin of the dead aphid turns (n, remains fastened to a leaf and the wasp passes a g g stage inside. A few days later the adult parasite ges by cutting a circular lid in the back of the aphid. -.- the parasite is active, many brown greenbug . ies may be found attached to wheat leaves. These _~- are of less value against the greenbug in the Pan- i e than in other areas of Texas. CULTURAL CONTROL A Most early efforts at control were modifications of i ral practices, such as plowing under volunteer grain, h drags, plowing, soil-packing devices and even ing were used without marked success (25). i reenbug infestations may start in volunteer grain. , exact whereabouts of the insect during the summer is ionable. The aphids app-ear on the grain in the fall, possibly migrating by flight into fields of fall- p» grain. Two other oversummering possibilities are a eggs and summer host plants. Greenbug eggs have p observed in the greenhouse during April at the 2 land station (10) but never in the field. Attempts to (e infested plants other than small grain which might tain the greenbugs in Texas during the summer have i unsuccessful. It is known, however, that the green- feeds on a number of grasses, such as orchardgrass, barley, western wheatgrass, crested wheatgrass and grass. Although theie is some evidence that destroying ted volunteer hosts by plowing, fallowing or other ral measures may help to control greenbugs, data are sufficiently complete to warrant such recommendations. Grazing of wheat during greenbug infestations has in cases decreased greenbug populations considerably. i ; an expansive,lbiotic force in reducing greenbug pop-i s ment of planting dates, variety and crop selection. ~ Figure 2. Area in background sprayed with parathion at the rate of 0.5 pound per acre for greenbug control. Un- sprayed check in foreground. However, if grazing is continued in March, grain yields may be reduced in proportion’ to the lateness of grazing and the earliness of the wheat variety. Usually where small grain fields are heavily infested over an area or a general outbreak is occurring, greenbug populations will increase in a grazed field after removal of the livestock. In such cases, chemical control may become necessary a few days after the cattle are removed. However, if the weather is warm and a good predator population is present, insecti- cidal application may be unnecessary. Cultural measures that will stimulate the gtowth of small grain plants and keep them in a vigorous condition will, in many cases, enable them to withstand more green- bug damage than unhealthy plants. Greenhouse studies conducted at the Amarillo station indicated that wheat grown in soil following alfalfa was more tolerant to green- bugs and supported greater populations than wheat grown in soil following wheat (11). These results were associated with high nitrogen levels in the soil and increased plant vigor (Figure 5). Large plants frequently survive high infestations of greenbugs while smaller plants are kille-d. An infestation of 500 greenbugs per linear foot of drill row in small wheat may be more severe than a population of 1,500 er linear foot in large wheat. The smaller wheat would no doubt have more insects per gram of foliage. Foliage clippings were taken along with greenbug counts for a comparison of infestation between two fields in the Dimmitt area under different cropping practices during March 1956. The plots in the fields were 1/20 acre and TABLE 1. EFFECTS OF CROPPING PRACTICES ON PLANT DEVELOPMENT AND ON GREENBUG INFESTA- TION IN WHEAT. DIMMITT. 1956 Height Foliage Number of Greenbugs Field of plants. weight. greenbugs per gram inches grams per foot of foliage Summer {allowed 6-8 31 1.572 51 Continuously ' cropped 3-4 7 620 89 / . . ' No chemical materials for economic greenbug i‘ A i‘ " were found until new organic insecticides becamea following World War II. Severe greenbug outb. 1950 and 1951 afforded an opportunity to devel‘ factory chemical control measures. Dahms conducted extensive insecticidal tests i‘ From this work, a very acceptable control i‘ developed, and over 21/2 million acres of smal were sprayed, chiefly with parathion (1). Para .2 to .5 pound per acre was superior to BHC, linda ‘4 or TEPP, and emulsifiable concentrates were i’ satisfactory formulations for use in sprays with ei or ground application (8). Owen et a1. in 1950 and 1951 (19, 20) f0 i parathion spray at .3 to .5 pound per acre gave control. Gamma BHC dust at .5 to .6 pound i‘ gave good control, but sprays were much less , Laboratory and field tests conducted by Hanna et indicated that parathion was more toxic to green‘ Figure 3. Left, wheat treated with parathion. Right. BHC; They.poi_“ted_ out thf? nflfssit)’ f0!’ Warm '. wheat treated with_ BHC. Middle, check plot where weeds tures at application time, and found that greenbu 1.».- replaced wheat “killed out" by the greenbuq- leaves Of the plants were more readily elimi“ _ _ _ insecticides than those among dead leaves at the ~C the sampling unit was 1 foot of drill row. The results are ShOWII in Table 1- _ Experiments for chemical control of greenb i been conducted on the High Plains since 1950. _’ INSECTICIDAL CQNTRQL insecticides, mainly phosphorus compounds, w _ _ _ against the greenbug both in 1955 and 1956 Apparently the first chemical control was obtained with Expmiments I and H were conducted at Huff . kerosene emulsions at 8 to 1O percent strength. Whale oil applications being made April 14, 1955, Ex‘ soap solutions also gave excellent control of greenbugs in consisted of five treatments; replicated four ti {g bluegrass lawns in Washington, D. C., in 1907 (25). plot was 1/10 acre in size. Yields were increasedi TABLE 2. GREENBUG REDUCTION AND WHEAT YIELDS FOLLOWING INSECTICIDAL TREATMENTS IN IRRIGA P‘, AT HEREFORD AND DIMMITT. 1955-56 Pounds iléieflgfitugfs _ d. Ne; piercentitnaortalitlyr. r Treatment per drill row in ica e ays a er app ica ion acre ' h) 4 8 14 28 36 initial count EXPERIMENT I Malathion a 1.1 210 -— 86 70 — — — Parathion .3 186 — 86 82 — — — Methyl parathion .3 158 — 90 76 -— — — Demeton .3 177 — 93 77 — — — Meta-Systox .3 229 — 91 76 — — — Check — 208 — 196‘ 71‘ — — — Difference in yield required for significance Thimet (Am. Cyanamid 3911) .6 75 — 85 9'0 — — — Am. Cyanamid 12008 .6 102 - 63 69 — — — Guthion (Bayer 17147) ‘.6 ‘ 167 — 38 56 -— — — Parathion .6 120 — 92 96 - — — Check z L7 — 147‘ 82‘ — — — Diiierence in yield required ior significance Parathion .5 1.300 77 — 94 94 97 97 Methyl parathion .5 1.235 68 — 93 ' 94 98 92 Demeton .5 1.212 85 — 95 93 9 95 Check — 980 956‘ — 1.636‘ 1.786‘ 1.118‘ 385‘ EXPERIMENT IV . Gamma BHC .5 540 96 — 91 -- — — TEPP .6 530 87 — 77 "— — — Parathion .5 520 99 — 93 — — — Check — 628 540‘ — 83‘ — — — ‘Number of greenbugs per foot of drill row. 6 by all materials except malathion. In experiment e plot. size was 1/40 acre and there were four es. Yields were increased significantly by parathion e experimental materials, Am. Cyanamid 3911 and “Cyanamid 12008. The chemical 3911 was a little i than 12008, but parathion was superior to both at e dosage level. Experiment III was conducted at itt. It consisted of three treatments replicated four i The plot size was 1/ 2O acre. Spraying was done rch 28, 1956, when the temperature was 58° F. pplication of parathion, methyl parathion or demeton y increased the yield. The greatest increase resulted the application of demeton. Experiment IV, also v ed at Dimmitt, consisted of three treatments eted four times. Each plot was 1/ 20 acre in size. ing was done on April 25, when the temperature 0° F. While yield data were not obtained, parathion ‘Tbetter control than gamma BHC or TEPP. __"e results of spraying for greenbug control with 'on are shown in Figure 2. HANDLE LOCATIONS Additional tests with insecticides were made, usually in single plots, at several other locations in the Pan- handle. Results of these experiments are presented in Table 5. Experiment I consisted of four treatments on dryland wheat, with each plot 1/ 100 acre in size. Applications were made with a ground sprayer when the temperature was 29° F. Within 8 hours, the temperature rose to 60°. In experiment II, the spray was applied with power equip- ment that delivered 12 gallons of liquid per acre. The temperature was 55° and the wind velocities 1O to 20 mph. Each plot was 40 feet in width and duplicated. The wheat on the check plots died and was replaced mostly by weed growth (Figure 5). Yields were calculated from samples harvested at random within each plot. Experiment III was with a series of organic phosphorus compounds. Materials were applied in 40-foot swaths with a Cub airplane when the air was calm or nearly so and the temperature was 74° F. The wheat had been 3. AVERAGE PERCENTAGE GREENBUG REDUCTION FOLLOWING INSECTICIDAL TREATMENTS IN SEVERAL PAN- Number of P d Percent bYielgdl. ,. . greenbugs per - - 01111 S - 11S e S i - ent Location Date ioot of drill Insectrcide per acre reitirgson “wheat row, initial count per acre GROUND SPRAYER 2 days 10 days Gruver 1-6-53 12 Parathion .5 80 100 Demeton .5 95 I00 Metacide .5 95 100 Chlorthion .5 100 IOU Check — 33 55 5 days v28 days Hereford 4-4-55 250 Parathion .5 97 96 19.8 Metacide .5 98 96 23.1 Malathion .75 93 91 16.0 Check — 25 — 0.3 AIRPLANE 6 days 23 days Hereford 4-28-54 480 Chlorthion spray .5 97 99 Demeton .5 83 98 Methyl parathion .5 99 99 Malathion .5 97 98 Metacide .5 99 95 Parathion .5 98 98 Check — 65 79 6 days 23 days Hereford 4-28-54 85 Parathion spray .25 87 92 Parathion 5 96 95 Check — 4U 79 2 days 1U days Summerfield 4-22-56 250 Parathion dust .5 — — 38.5 Check -’ _ _ 28.0 4 days Hereford 4-24-56 300 Parathion dust .5 97 -— 49.8 Check — 75 — 44.5 Black —- 350 Gamma BHC dust 1.25 — — 33.6 v V; Check —. — -— 19.2 i Hereford i: — 275 Gamma BHC dust 1.0 — —- 37.4 » "Methyl parathion spray .5 — — 34.3 Black — 400 Gamma BHC spray 1.25 — — 78.0 5 days 2O days Hereford 4-16-56 250 Metacide spray _ .5 7U 62 15.8 4-27-56 BHC spray 1.25 -— — - Figure 4. “Greenbug spot" in barley showing discolor- ation caused by greenbug feeding. heavily grazed, was irrigated and in the boot stage. Plot size was 2 acres. Experiment IV compared two rates of parathion applied to dryland wheat the same day under ideal conditions. Plots were 1O acres in size and showed con- siderable greenbug damage before spray application. Ex- periment V evaluated the effectiveness in terms of in- creased yield of late airplane applications of parathion dust to wheat in the bo-ot to early-head stage. Half the field was left untreated as a check. The wheat was irrigated just before spraying. Experiment VI was similar to experiment V with the wheat in a less advanced stage. Figure 5. Wheat plants fertilized at the rate of 60 pounds of nitrogen per acre (left) and plants receiving no nitrogen (right) after 5 weeks of greenbug infestation. USDA Southwestern Great Plains Field Station. 1955. 8 The results of experiment VII indicated on the yields, that BHC dust is effective under certain c I for greenbug control. I Tests VII, IX and X were conducted to evaluat} chemicals for the control of greenbugs on a sizable y under practical field conditions. Test VIII compar dust with a methyl parathion spra . The plots were when the wheat was in the pre-lioot stage. Goodf was obtained with both compounds. The results”. IX indicate the high yield which can result when .5 cation is applied properly under ideal conditions. X, the conditions during applications were unf resulting in poor control and low yields. Results of the experiments reported herein that parathion or methyl parathion were effectiv rate of .25 to .5 pound of the insecticide per North Central Texas, .25 pound per acre us effective control. However, in the Panhandle, .5 acre was needed unless spray conditions were exc, good. Application of gamma BHC dust at a rated 1.25 pounds per acre or TEPP at .6 pound per i spray also gave good control. Chlorthion and although safer to use, were not as effective as ~»~ or methyl parathion for greenbug control. Good control was obtained when the insectici. applied with ground equipment or by airplan were most effectivewhen the air was calm. D spring in the Panhandle, high wind velocities constant that it is difficult to select a day suit spraying. . , Factors to be considered in determiningwh secticidal treatment of small grains for greenbugf will be practical are: I , Parathion or methyl most effective at tem, of 50° F. or above at application and for 5i thereafter. TEPP and fective only when tem are above 75°. Temperature: O to 1O mph for airpl cation. Ground equipm 15 mph. Higher dosage when windy. a I Wind velocities Low infestations more r fall, winter and early? Time of year when plants are small. Do not spray if soil’. potential and outlook adequate to produce 10 per acre. Soil moisture potential (dryland ) Critical damage caused numbers of aphids on plants. Tillered plants more greenbugs than I plants. Size of wheat plant: If possible, irrigate no? Iwigatio” before spraying. Treatment justified if there are 5O per foot on small plants or early in, season, at least 100 per foot on large plants. ber bf greenbugs per foot If predators and parasites com- bined equal 1/10 to 1/25 the number of greenbugs, delay spraying. atom and parasites PRECAUTIONS Insecticides are poisonous. Handle them with care. ow the directions and heed all precautions on the q‘ 'ner label. i-Parathion and methyl parathion are extremely poison- l They should be applied only by a person thoroughly iar with their hazards who will assume full re- isibility for safe use and comply with all the pre- “ons on the label. In applying insecticides, try to keep them off your I and away from your eyes, nose and mouth. When have finished the job, wash all exposed surfaces of body with soap and water. Change your clothing. D0 not pasture animals in grain fields for 2 weeks the fields have been treated with parathion, methyl gthion or Chlorthion. Do not pasture animals in fields A ed with malathion for 7 days after application. Small , s treated with TEPP should not be grazed for 5 days 1i application. If BHC is applied, do not feed the 1 ed crop to dairy animals or animals being furnished ‘slaughter. VBHC should not be used for greenbug ol in areas where vegetable crops will follow in the tion, since residues in the soil may cause off-flavor. RESISTANCE iControls that have been developed for the greenbug I knot always practical. In areas where yields are low use of low fertility, drouth or winter-killing, costs of , icicles are ineffective at temperatures below 50° F., n greenbugs are feeding and reproducing. Control by ites or predators or by cultural means is no-t de- Cable. Consequently, new methods of control must sought. The development of greenbug-resistant small I varieties offers a promising approach. Differences in response of plant varieties to insect have been recorded for over 100 years. About 100 l: species have shown resistance to more than 100 insects i). Resistance to aphids in plants has been repo-rted e frequently than that to any other insect group. ‘dley (25) was one of the first to observe differences ‘esponse of plants to the greenbug. He found it more icult to irear greenbugs on Mindum durum than on ral common winter iwheat varieties. He reported that yVernal emmer less ‘than 1O percent of the aphids I red and that no second generation developed. Fenton I Fisher (15) noticed differences in susceptibility to ck among oat varieties. Walton (24) observed a erence in the reaction of barley varieties to greenbug ‘ck. The reaction of several hundred varieties of wheat, t and barley under field conditions in Texas and ' ici-dal control may be too high. Most of the available . Figure 6. Reaction oi barley varieties to greenbug attack. From leit to right in order of increasing resistance are Cordova, Ward. Reno. Kearney and Dicktoo. Oklahoma was studied by Atkins and Dahms (2). They reported resistance in some wheat and barley strains, but none in oats. Dahms, Johnston, Schlehuber and Wood (9) reported on the reaction of several hundred varieties and hybrids of small grains which were tested for resistance under greenhouse, field and insectary conditions. Many of the barley varieties showed a high degree of resistance, and it was indicated that the resistance was inherited. One variety that occurred as a mixture in Triticum durum, Dickinson No. 485, C. I. 5707, showed a high degree of resistance and several others were more resistant than those commonly grown in the hard red winter wheat area. None of the oat varieties showed marked resistance although some variation was observed. Chatters and Schlehuber (7) studied the feeding habits of the greenbug on small grains. They concluded that discolora- tion and tissue breakdown are caused by the injection into the plant of toxic saliva by. the aphid, and that resistance and susceptibility are expressions of physiological differences. Studies on the resistance of small grains to the green- bug in Texas were initiated at Denton and Bushland in Figure 7. Summer-iallowed wheat (left) and continuous wheat (right) under drouth conditions. F allowed wheat had 15 to 40 brown wheat mites per foot of row. while the con- tinuous wheat had 360 to 480 mites. USDA Southwestern Great Plains Field Station. 1953. ~ 9 Figure 8. Small grains being tested for greenbug resist- ance in the insectary, Denton Experiment Station. 1952. These involve insectary, greenhouse and field tests. Differences in susceptibility to greenbug attack among small grain varieties can be shown under each condition. Figure 6 shows differences in reactions of barley varieties at the Bushland station. Plants 3 to 4 inches tall were subjected to uniform greenbug infestation for 5 weeks. In the insectary and greenhouse at Denton, varieties from the world collection of small grain maintained by the U. S. Department of Agriculture and local varieties and strains of small grains are tested for greenbug resistance by ex- posing them to uniform infestations (Figure 8). They then are rated for their reaction to greenbugs, the ratings being based on the percentage of total leaf area damaged. Those that have a high degree of resistance are referred to the plantbreeder for crossing with adapted varieties or strains in an attempt to produce a well adapted, good quality, highly resistant variety. Selections of each of the field-planted generations of the crosses are again tested for resistance in the insectary. Only those which are as resistant or more so than the resistant parent are saved for further development. Varieties and hybrids which have shown resistance under insectary or greenhouse testing are planted in greenbug nurseries in the field at several locations to study their reaction to natural greenbug in- festations. Since the initiation of these studies, it has been possible to supply plant breeders with definitely resistant parents, whereas, previously, little was known regarding the reaction of the parents in the crosses. To date, 7,688 varieties of wheat, oats and barley have been tested for resistance at Denton. No outstanding resistance was found among 332 domestic and Oriental wheat varieties tested. Some 350 third-generation lines of three wheat crosses involving Dickinson Selection, the most resistant wheat observed to date, have been tested. Many of the selections in each cross show considerably more resistance than the common wheats; therefore, the resistance of Dickinson Selection has been transferred by cross breeding. A total of 2,609 barley varieties and hybrids have been tested for resistance. These include 115 miscellaneous l0 varieties among which Omugi and Kearney are resistant. Plant breeders are having success in conc g resistance in new lines. i A total. of 5,100 oat varieties have been teste? resistance was found among 102 domestic varieties, ‘f showing the most, but the degree o-f resistance is n, Among the 4,998 oat varieties tested from the c0 only 77 are 1O percent or more resistant than A the resistant check. Only 7 are 2O percent o} resistant than Andrew. The most resistant variety is No. 77 from Canada. It shows 33 percent more i than Andrew. Many of the more resistant oat vari from the Mediterranean countries, especially Tur Yugoslavia, and this area may serve as a source off resistance in oats. Progress has been made by the entomologist i‘: breeder in the development of small grain varieti. are resistant to the greenbug. However, until they; available for farmers’ use, current chemical if commendations should be followed. 1 MITES BROWN WHEAT MITE The brown wheat mite, Petrobia latent (Mil _ pest of small grains. Damage by this mite 0c J during dry weather and in some respects rese l“ caused by drouth. A mottling of leaves occurs, observed from a distance, ayellowing or bronzie < may be noted. Infested leaves first show a silvery later turn brown. When this stage is reached, hub‘ mites can be seen on the leaves and on the f; the base of the plants. The mite has a rounded, i dark brown or blackish body about the size of a newsprint, with short hairs on the back. The p pale yellow, with the fore legs characteristicall; than the other three pairs. It can be identified“ hand lens in the field (Figure 9). This species if spin webs as do some spider mites. i‘ Brown wheat mites pass the summer as s - "f? white eggs. The egg is coated with a white waxy and one en-d is flattened in a circular cap somew than the egg itself. Large numbers of these e found at the base of the plants in the soil, a r debris and clods. To hatch, the eggs must be i with free moisture. Hatching begins in the fall as there is a small amount of free moisture. Y‘ are bright red and have three pairs of legs, buté; as they feed, most of them become brownish- TABLE 4. EFFECT OF BORDER IRRIGATION WHEAT MITE POPULATIONS. BUS i TION. 1955 Average number oi mites per toot of row t u Du e Irrigated 52g‘??? iApfil 23 and April 23 March 3U ll3 6 April 6 147 l2 April 21 164 51 April 29 l0 ll ges each have four pairs of legs; some of them have 'sh bodies and some resemble the adults in color. hatching, the mites reach the adult stage in 9 to- 1O Egg laying begins 1 or 2 days later. Winter eggs, uring the fall, winter and early spring, are brick a d spherical. They hatch in 6 or 7 days under pile conditions. Each adult lays 7O to 9O eggs in a * period. According to Baker and Pritchard (5), I, are unknown and the eggs hatch without fertilization. l g the late spring, certain adults begin to lay summer , and will lay about 3O .during a 3-week period. An p does not produce both summer and winter eggs. eavy rains reduce greatly the brown wheat mite tions. Replicated plot experiments at the Amarillo have shown that irrigation lowers populations. effect of border irrigation on the brown wheat mite is I in Table 4. Border irrigation is similar to flooding i field ditches, except that small levees or border I confine the water to a limited area as it moves across ield. Although mite populations were low, control border irrigation was good for about 3 weeks. On 25, after flooding of the plots (irrigated and 'ously nonirrigated), overall mite populations were ‘ ed to approximately equal levels. Complete flooding border irrigation is better than flooding by g gated furrows to lower mite populations. When ir- (‘on is done by flooding listed furrows, the water a does not cover the tops of the ridges, and the is rbed mites may migrate and become as numerous in on the plants in the furrows as on the ridges. grown wheat mite populations usually are much lower mmer-fallowed wheat than on continuously cropped g (Figure 7). If the lan-d is fallowed following a E crop and summer eggshatch from stubble or residue e fall, the young mites will die from lack of food. ntrolling this pest with chemicals is difficult.) Tests ,_ shown that .5 pound of parathion per acre gave écontrol of the mite, but did not increase the yield of . t. It is believed that chemical control of the brown c is not practical (16). A WHITE MITE A white mite, Oligonyc/aur pratenrir (Banks), is a pest mall grains in some parts of Texas. It differs from Bother mites discussed here since it spins fine webbing the plants. The mites are whitish or yellowish, and t half the size of the brown wheat mite. Feeding toms are similar to those of the brown wheat mite. "ng the fall when the wheat is small, the mites locate A all colonies on the leaves. During the winter, after plants have tillered and temperatures are lower, they r mainly in the crown of the plants near the soil ace. Infested plants can be detected by the presence of u in the crowns and usually an abnormal number of d leaves. ~ The mites generally remain at the plant bases ,5 May, and then moye to the upper leaves. Sometimes, heads will becomq, infested as they emerge from the Controlling this pest with chemicals is not practical. WHEAT CURL IVIITE iThe wheat curl mite, Aceria tulipae (Keif.), which in ew instances has been found on the High Plains of Figure 9. Drawing of an adult brown wheat mite. greatly enlarged. Cour- tesy of the Division of Agricultural Sciences. University of California. = < 1'. ‘ ~..;»*‘"; Texas, is responsible for transmitting the virus wheat streak-mosaic. Transmitting mosaic is the only reason fo-r the importance of this mite. Other damage done by it is slight and consists of curling and folding of the leaves causing "trapped leaves.” Aphids also cause this condition, but do not transmit the virus. The wheat curl mite is white, spindle-shaped, with only four legs on the front of the body. These mites are so small that they are barely visible when magnified 1O times. They usually are found on the upper leaf surface of the plant and in the whorl. Eggs are laid in the grooves of the wheat leaf. The mites pass the summer between wheat crops on volunteer wheat and various grasses. They may be present on wheat without transmitting the mosaic. So far, no practical chemical con- trol for this mite has been developed. WINTER GRAIN IVIITE The winter grain mite, Pent/mleur major (Duges), causes considerable damage to fall-sown small grains, particularly in North Central and Central Texas. Banks (4) established the first record of this m-ite in the United States from Washington, D. C. It was reported damaging i barley in Arizona in 1911 (unpublished manuscript by T. Scott Wilson). A county agent reported seeing this mite and its damage to small grains in Dallas county as early as 1919. Essig (12) and Campbell (5) discussed its damage to peas in California. Because of its economic damage to small grains, research on its biology and con- trol was undertaken at the Denton station in 1952. Small grains and grasses are the favored hosts of this mite, but it also feeds on legumes, weeds and vegetables. Heavily infested fields have a grayish or silvery appearance which is caused by the removal of chlorophyll and plant juices by the feeding mites (Figure 10). The plants die under heavy infestation. Loss in small grains is the reduced amount of forage during the winter and the reduced yields of grain in spring and summer. The first-generation mites hatch in the fall, usually around November 1, from eggs which oversummered on grain stubble, straw or debris in the field. The dark brown to black mites (Figure 11) are about 1/ 25 inch in length and have four pairs of legs. The legs and mouth- parts are reddish-orange. There usually is a reddish- l1 Figure l0. Winter grain mite damage. Field on left was in oats for 6 years continuously. Field on right was in clover the previous year. Denton. 1954. orange spot on the back which surrounds the anus. The second generation develops in early January from eggs deposited by first-generation mites. Second-generation mites deposit the eggs that oversummer. When hot weather sets in, usually around April 15, all mites disappear from the fiel-ds. Cool and moist conditions are necessary for mite development. Mites feed on the leaves mainly at night or on cloudy days; on bright days they hide under foliage on the moist soil surface. If the soil is dry, they burrow into it until they reach moisture. Light, loose soils are preferred. Both cultural and chemical control recommendations for the winter grain mite have been developed as a result of research conducted at the Denton station. Fields planted to small grains continuously for 5 or more years usually were heavily infested and damaged. In fields where the previous crop was other " than a small grain, such as cotto-n, corn, clover or sorghum, mites were either absent or very scarce, and there was no damage. Therefore, a Figure ll. Winter grain mite adult. greatly enlarged. 12 change from continuous cropping of small grai rotation involving other crops at least every 2 years greatly the damage caused by the winter grai Several of the phosphorus compounds gave satisfact trol of the mite at relatively low dosages (6). Par .25 poundor malathion at .5 to .75 pound per acre t’ in a spray gave adequate control of the winter gr‘ in small grains. at t. FALSE WIREWORMS Several species of false wireworms, Eleod f frequently cause damage to germinating wheat and ~ in the small grain growing areas. Sorghum ship important insect problem. False wireworms at prairie insects that originally fed on roots and ger seed of wild plants, chiefly grasses. They attack? crops, including newly sown wheat and sorghum The adult false wireworm or beetle hibernates areas, along fence rows and in crevices. The whit eggs, covered with a sticky substance, are J the spring and early summer. They are laid singlj soil .5 to 3 inches deep. In 1O to 14 days, the g, into yellow, hard-shelled cylindrical worms that tu j as they become older. Some of them become asj 1.5 inches as they pass through several instars, -. period of about a year. They are not full gro the year following egg deposition. Pupation place and lasts about 2O days. Newly emerged a pear during the summer and feed on seed and r tered through the soil until cold weather forces hibernation. t " The larvae cause the greatest injury during seasons. They usually increase during dry year wheat is seeded or “dusted in” in the fall and li weeks before rainfall starts germination, During: period, the larvae eat the germ of the kernels. The content often varies within a field, resulting i, infestations. False wireworms injure young see cutting them off just ~ below the soil surface, damage is not so common as damage to the worms also damage sorghum seed sown in F or early summer, especially if there is little e They usually feed in the top 6 inches of the soil to the surface only when it becomes wet. ” Clean culture and accumulated soil moisture with summer fallowing reduce the amount of cropping system of continuous wheat favors the 1'? ment. Fallowed fields are less attractive to‘ adults and will tend to starve the larvae. f TABLE s. EFFECT ON PLANT STAND or son TREATMENTS wrm INSECTICIDE POWDERS TO CONTROL "mt: F WORM, BUSHLAND STATION. 1954 Ounces of actual Numbo toxicant per 100 per pounds of seed Insecticide Aldrin 50% 2 Lindane 25% '2 Heptachlor 25% 2 Dieldrin 75% 1 BHC 3 Check — trol on sorghum was possible with some of the 'cides. Seed treatment tests have been conducted at A ari-llo station and PanTech Farms during the past i ars. Lindane, aldrin an-d heptachlor at 2 ounces of toxicant per 100 pounds of sorghum seed gave ctory control in the summer of 1954, as shown in {*1 ‘Q Table 5. Dieldrin at 1 ounce did not give as good control as the other chemicals, but in other tests, a 2-ounce dosage did give excellent control. BHC was the least effective. Germination was not affected by aldrin, lindane, haptachlor or dieldrin in these tests. However, germination was re- duced in the BHC-treated plots. 13 __, .. (1) (Z) (5) (4) (5) (6) (7) (8) (9) (10) <11) <12) REFERENCES Ashdown, D. A., R. G. Dahms; W. O. Ridgeway and C. F. Stiles. 1953. Hazards in the use 0f parathion for greenbug control. jour. Econ. Ent. 45: 82-84. Atkins, I. M., and R. GQDahms. 1945. Reaction of small grain varieties to greenbug attack. U. S. Dept. Agr. Tech. Bul. 901: 30 pp. Baker, E. W., and A. E. Pritchard. 1953. A guide to the spider mites‘ of cotton. Hilgardia 22: 203-234. Banks, N. 1902. New genera and species af acarians. Canad. Ent. 34: 172. Campbell, Roy E. 1941. Further notes on the blue oat or pea mite, Penfihaleus major (Duges), in California. Bul. Calif. Dept. Agr. 30; 312-314. Chada, Harvey L. 1956. Biology of the winter grain mite and its control in small grains. ]our. Econ. Ent. 49: 515-520. Chatters, R. M., and A. M. Schlehuber. 1951. Mechanics of feeding of the greenbug (Toxoptem graminum Ron-d.) on Hordeum, Avena, and Triticum. Okla. Agr. Exp. Sta. Tech. Bul. No. T-40: 18 pp. Dahms, R. G. 1951. Insecticide formulations and equipment used for greenbug control. ]our. Econ. Ent. 44: 954-57. Dahms, R. G., T. H. Johnston, A. M. Schlehuber and E. A. Wood, Jr. 1955. Resistance of small grain verieties and hybrids to greenbug attack. Okla. Agr. Expt. Sta. Tech. Bul. No. T-55: 61 PP- Daniels, N. E. 1956. Greenbug eggs below the thirty-fifth parallel. jour. Econ. Ent. 49:567. Daniels, N. E., and K_. B. Porter, 1956. Greenbug damage to winter wheat as affected by preceding crop. jour. Econ. Ent. 49:600-602. Essig, E. O. 1939. The blue oat or pea mite, Penthaleus major (Duges), in California. Bul Calif. Dept. Agr. 28: 507-508. (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) Fenton, F. A., and E. H. Fisher. 1.940. , greenbug outbreak in Oklahoma. Jour. Ent. 33: 628-38. Fenton, F. A., and R. G. Dahms. 1951. 1 at controlling the greenbhg by the importat release of ladybeetles in‘ Oklahoma. Oklaf Sci. Proc. 32: 1-2. ‘ Hanna, R. L., C. Gaines and R. Wii 1951. Results of tests for greenbug contro Econ. Ent. 44: 347-350. ;- Henderson, C. F., and E. W. Tilton. 1955. with acaricides against the brown whe ]our. Econ. Ent. 48: 157-161. '5 Hunter, S. Kansas Univ. Bul. 9: 1-163. Kelly, E. O. G. 1917. The greenbug (T graminum Rond.) outbreak of 1916. ]our.§ Ent. 10: 233-248. i Owen, W. L., ]r., R. L. Hanna and ]. C.- 1951. Greenbug control. Tex. Agr. Exp. 1_ gress Report 1234. - Owen, W. L. ]r., R. L. Hanna and C. I 1952. Insecticidal control of greenbuj Agr. Exp. Sta. Progress Report 1438. Painter, R. H. 1951.; Insect resistance ' plants. 488 pp. The Macmillan Co. Ruggles, A. G., and F. M. Wadley. 192‘ greenbug in Minnesota. Jour. Econ. -_ 521-327. L Wadley, F. M. 1931. Ecology of T.‘ graminum, especially as to factors aff- 11' portance in the Northern United States. ' Amer. Ann. 24: 325-395. Walton, R. R. 1944. Greenbug injury oni varieties at Woodward, Oklahoma in Okla. Acad. Sci. Proc. 31: 130-134. Webster, F. M., an-d ]. Phillips. 191 spring grain aphis or “greenbug." U. S.j_ Agr. Bur. Ent. Bul. N0. 110: 153 pp. ' 1909. The greenbug and its ' ' [Blank Page in Original Bulletin] State-wide ljtiesearc The Texas Agricultural Experiment Stati is the public agricultural research age oi the State oi Texas. and is one of Location of field research units in Texas main- t'dbthT A'ltlE't i $11,150,, .,‘,’,., §.,,,,°,’,‘§?,,, “$3,222; "‘°‘"““°“ pert-e ei the Texas MM College Svet IN THE MAIN STATION, with headquarters at College Station, are 16 subject-matter departments, 2 J departments, 3 regulatory services and the administrative staff. Located out in the major agricultur of Texas are 21 substations and 9 field laboratories. In addition, there are 14 cooperating stations by other agencies. Cooperating agencies include the Texas Forest Service, Game and Fish Commi Texas, Texas Prison System, U. S. Department of Agriculture, University of Texas, Texas Technologi lege and the King Ranch. Some experiments are conducted on farms and ranches and in rural homes? RESEARCH BY THE TEXAS STATION is organized by programs and projects. A program of research; sents a coordinated effort to solve the many problems relating to a common objective or situation. search project represents the procedures for attacking a specific problem within a program. THE TEXAS STATION is conducting about 350 active research projects, grouped in 25 programs w clude all phases of agriculture in Texas. Among these are: conservation and improvement of soil servation and use of water in agriculture; grasses and legumes for pastures, ranges, hay, conservati improvement of soils; grain crops; cotton and other fiber crops; vegetable crops; citrus and other s f cal fruits, fruits and nuts; oil seed crops—other than cotton; ornamental plants—including turf; b i weeds; insects; plant diseases; beef cattle; dairy cattle; sheep and goats; swine; chickens and turk.‘ mal disease and parasites; fish and game on farms and ranches; farm and ranch engineering; f g ranch business; marketing agricultural products; rural home economics; and rural agricultural eco Two additional programs are maintenance and upkeep, and central services. RESEARCH RESULTS are carried to Texas farm and ranch owners and homemakers by specialists and , agents of the Texas Agricultural Extension Service.