LIBRARY, A & M COLLEGE, CAMPUS. A217-103l-12M-L180 TEXAS AGRICULTURAL EXPERIMENT STATION A. B. CONNER, DIRECTOR College Station, Brazos County, Texas BULLETIN NO. 435 NOVEMBER, 1931 DIVISION OF ENTOMOLOGY The Control 0f Fire Ants in the Lower Rio Grande Valley AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. O. WALTON, President DIAIIUJN ADMINISTRATION: A. B CoNNER, M. S., Director R. E. KARPER, M. S., Vice-Director CLARIGE MixsoN, B. A., S 1V1. P. HoLLEMAN, JR., Chief J. K. FRANcKLow. Assistant Chief Clerk CHEsTER HIGGs, Executive Assistant HQWARD BERRY, B. S., Technical Assistant CHEMISTRY: . S. FRAPS, Ph. D., Chief; State Chemist . E. AsBURY, M. S., C emist . F. FUDGE, Ph. D., Chemist . C. CARLYLE, M. S., Assistant Chemist . H. WALKER, Assistant Chemist ELMA GRAHAM, Assistant Chemist . L. OGIER, B. S., Assistant Chemist . J. STERGEs, B. S., Assistant Chemist ANNE F. DEMQTTIER, Asst. Chemist _ AY TREIGHLER, M. S., Assistant Chemist . L. SCHWARTZ, B. S., Assistant Chemist . M. PoUNDERs, B. S., Assistant Chemist HORTICULTURE: S. H. YARNELL, Sc. D., Chief **L. R. HAWTHORN, M. S., Horticulturist H. REED, M. S., Horticulturist J. F. Wo0D, B. S., Horticulturist L. E. BR0oKs, B. S., Horticulturist RANGE ANIMAL HUSBANDRY: J. M. JoNEs, A. M., Chief B. L.WARWICK, Ph.D., Breeding Investigations S. P. DAvIs, Wool Grader nww;>aw QQ2::oU s::wQ<2 n0 Uibfimfl‘ . . . . . . . . . . .23.? ucofiom oQQ .Q5.~Qnm QQmQQm . . . diam QQmQQw QQQ-mm QQQ UwNSmISw EQQQ2QQ2Q QQQQQQo w» . . . .Q5.Q%m QmmQQQ 5.2mm QQQ QQQQQQEQQQ 532mg QuQQQQo Q . . . 255$ QwwQQQ 202mm QQQ wuflflflfiaw EQQEQQQI QQQQQQQo wQQ . . . dab? QQmQQQ QQo2Qm QQQ 3x222; EQQEQQQQ QQQQQQQo m . . . JQQQEQQ QQwQQQ 202mm QQQ QQQQQEQQQ QQQQQEQQS QQQQQQQQ Km . . . 255$ QmwQQQ QQo2ww QQQ QQQQQQEQQQ EQQEQQQQ QQQQQQQQ w. . . . AQQQEQQ QQmQQQ 5.2mm QQQ QQQQQEQQQ 522223 QQQQQQQQ NQ. .. 225$ QwwQQQ 5.2mm QQQ QQQEEQQQ 522222 QQQQQQQQ fin QQQQQQQQQ QQAQQQQQ Z QQQQQSQU mcobm Ammfi JQQQQ PG QQo QQuQbo cam 95mm QmmQQQ 2o 5.2mm QQQ QQQQQQEQQQ QQQQQEQQQQQ we QQSwQQQQQm wiwgwflvwr? .m QEQQP THE CONTROL OF FIRE ANTS IN THE LOWER RIO GRANDE VALLEY 9 for the purposeat hand. The containers should be large enough to hold sufiicient bait to kill out a single colony. Sponges cut to fit the bait boxes were used to enable the ants to readily obtain the syrup. The bait used in this test was made of the following ingredients: sugar, 12 pounds; honey, 2 pounds; water, 11 pints; thallium sulphate, ~51; pound. Tests in 1931- In view of the exceptional results obtained during the fall of 1930, it was deemed advisable to conduct further tests in order to determine the weakest solution of poison it would be possible to use and obtain satisfactory results. Table 3 shows the results of these tests. It will be noted that some control was obtained with as little as one ounce of thallium sulphate per gallon of syrup. All nests were dug out eight days after the treat- ment. The stock syrup was made as follows: sugar, 5 pounds; honey, 4 pound; water, 43%; pints. This made one gallon of solution, to which was added poison of various strengths. The syrup was poured on sponges which had been placed in one-half-pint ice cream contain- ers. This type of container was Fig. 4.——Type of_ poison bait box used in the Superigr t0 thg Smaller bQXeS, as, later tests with thallium sulphate baits. . frequent refilling was unnecessary. A small opening was cut in the side of the container (Fig. 4.) This type of container was waterproof and durable and proved to be very satisfactory. In order to determine the effectiveness of thallium sulphate baits during the summer season, tests of three strengths of poison were con- ducted during August. The summarized results of these tests are pre- sented in Table 4. Table 4. Eifect of difierent strengths of thallium sulphate baits on fire ants during the summer, 1931. Strong Colonies Medium Colonies Weak Colonies Total Treatment Number A Number Number Number Number Number exter- Number exter- Number exter- t colonies colonies treated minated treated minated treated minated treated exter- minated 1% ounces thallium sulphate per I gallon sugar syrup................ 7 4 9 8 10 10 26 22 Per cent control . . . . . . . . . . . . . . 57.2 . 88.9 _ 100 84,6 2 ounces thallium sulphate per gallon j I gallon sugar syrup................ 8 5 8 J 6 10 10 26 21 Per cent control . . . . . . . . . . . . . . 62.5 75.0 100 80.8 2V2 ounces thallium sulphate per l I gallon sugar syrup . . . . . . . . . . . . . . . . 4 3 2 2 4 4 10 l 9 Per cent control . . . . . . . . . . . . . . 75.0 100 100 90,0 It will be noted in Table 4 that the control with all three strengths of poisoned bait was very satisfactory. The bait boxes were placed at the nests on August 14 and were removed on August .19, or slightly 10 BULLETIN NO. 435, TEXAS AGRICULTURAL EXPERIMENT STATION more than four days. All nests were dug out August 20 to determine ;. the condition of the colony. A recheck one week later confirmed the results as given in Table 4. The trees used in this test were in an orchard which had been pre- viously treated for fire ants by the owner. A proprietary thallium- sulphate-syrup mixture had been used but did not give satisfactory i‘ control. There were several factors which influenced the effectiveness of this treatment. The small quantity of poisoned syrup used, the ex- cessive amount of absorptive material, and the small openings in the containers contributed to the poor results obtained. In view of the fact that liquid syrups with thallium sulphate were giving excellent results in fire-ant control, but were subject to a cer- tain amount of evaporation, sugar candies were made up, utilizing various strengths of thallium sulphate. All the baits gave a certain degree of control. The bait of the weakest strength, which contained 2% grams of thallium sulphate per unit, gave the highest degree of kill. The candy used in these tests was made as follows: sugar, 4 cups; water, 1 cup; vinegar, 1 teaspoonful. The ants did not take to the candies as readily as to the syrup, and a longer time was necessary before any control was noticeable. RECOMMENDATIONS It is apparent that success in controlling fire ants, feeding upon citrus trees, depends upon several factors. Frequent inspections of the grove are necessary, regardless of treatment used. If thallium sulphate syrup is used, suitable containers are a necessity. The entrance of the ants into the boxes should be facilitated by making a large opening in the container (Fig. 4). Sufficient bait should be placed in the con- tainer so that there is no interruption to the feeding of the ants. It is necessary that the boxes be placed so that the ants may have no difficulty in carrying large quantities of the syrup into the nest. At certain times and under certain conditions it will be noted that the ants may prefer their natural food to the poisoned syrup. Presence -of scale insects or aphids upon the trees or other plants will necessitate control measures for them before the ants can be satisfactorily con- trolled. Under other conditions, when the ants refuse to eat the syrup, calcium cyanide should be used. Fire-ant nests in the tree rows or away from the trunks of the trees should be treated with calcium cyanide. It has been noted that while the Weaker solutions of poisoned syrup will effect control in a period of time, the stronger solutions will give quicker results. However, as the poison is the most costly ingredient, the cost increases in proportion to the amount of thallium sulphate used. Fire ants, when feeding in boxes, will carry small particles of dirt into the box and deposit them around the opening, both inside and out. This does not affect the to-xicity of the material but facilitates the feeding of the ants and should cause the grower no concern. By the judicious use of a combination treatment of calcium cyanide and thallium sulphate syrup, the average grove may be practically rid THE CONTROL OF FIRE ANTS IN THE LOWER RIO GRANDE VALLEY 11 of fire ant colonies and subsequent injury. Reinfestations will occur and frequent inspections and treatment are necessary. Preparation of Thallium Sulphate Bait and Its Use The formula suggested for preparation of the bait is as follows: Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4% pints Thallium sulphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ounces Sugar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 pounds Honey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . é pound Dissolve the thallium sulphate in the four and one-half pints of water. This may be boiled to accomplish the purpose. Use precau- tions against breathing the fumes during the process. After the poison is in solution, add the sugar and honey and stir until the sugar is dis- solved. Add enough water to bring the total to one gallon. Cut a piece of sponge to fit the container to be used and soak the sponge thoroughly in water, squeeze the sponge dry, place in the con- tainer, and pour at least four tablespoonfuls of the poisoned bait over it. The bait is then ready for use. Non-resinous excelsior may be used instead of the sponge and is to be preferred because of its cheapness. Place the box containing the po-isoned bait in the center of the nest and tap lightly with the finger until the ants emerge and climb up the bait box. Where the nest is very large, two bait boxes should be used. After the ants are killed, the trunk of the tree should be scraped free of mud and gum and painted with Bordeaux paste. The Bordeaux paste should be prepared with dry Bordeaux and water, being mixed to the consistency of house paint. The boxes may be refilled and used again. Dirt which has been plastered over the opening should be removed. CAUTION- Thallium sulphate* is very poisonous and is without taste, smell, or other warning property. The preparation of syrups containing this material should ‘be entrusted only to persons who un- derstand its dangerous qualities and will exercise extreme care in handling it. As the fumes of thallium sulphate are poisonous when breathed, do not prepare the poison bait indoors. The poison may be absorbed through the skin, and rubber gloves should be used in all handling of this material Do not place this bait where children, irre- sponsible persons, or domestic animals will have access to it. ANTIDOTE- Call a physician. Induce vomiting by inserting finger in the throat or by the use of emetics, such as mustard or salt in warm Water. After the stomach has been emptied, the patient should take Epsom or Glauber salts; milk of magnesia is also recommended. Calcium Cyanide Dust and Its Use Calcium cyanide, when it comes into contact with moisture, gives as fumes which are deadly to life. Therefore, it is necessary to use precautions against breathing the gas. *J. C. Munch and J. Silver. The Pharmacology of Thallium and Its Use in Rodent Control. U. S. D. A. Tech. Bul. 2381931. 12 BULLETIN NO. 435, TEXAS AGRICULTURAL EXPERIMENT STATION Fire ants may be effectively controlled by this material (Table 1). When applying calcium cyanide near the trees, always use a dust gun. The nests of ants should be thoroughly disturbed with a bar of some kind (Fig. 1), and as the ants rush out, the dust should be applied as a light covering over the surface of the soil. Where the nests are some distance from the tree, the material should be stirred into the nest and covered with soil. Where the nest is located near the tree, the cyanide should not be covered but should be allowed to remain exposed to the air. Use great care to avoid getting any quantity of the material on the trunk of the tree, particularly if it has been pre- viously painted with Bordeaux mixture. CAUTION- The fumes from calcium cyanide are very poisonous when breathed and all precautions must be used to prevent any quan- tity from being taken into the lungs. This poison should be kept from the hands of careless or irresponsibe persons. y - ACKNOWLEDGMENTS Thanks are due Mr. W. H. Friend, Superintendent of the Valley Substation, for his many helpful suggestions and criticisms during the progress of the work and to the various growers who co-operated to the extent of allowing the use of their orchards for the greater part of this experimental work. SUMMARY 1. The fire ant, Solenopsis geminata (Fabn) causes severe injury to young citrus trees in the Lower Rio Grande Valley of Texas. 2. Calcium cyanide dust applied to the nests will give a good meas- ure of control; however, there is some danger to the tree where nests are close to- the base, and when the mate-rial is in the hands of inex- perienced or careless operators. 3. Poisoned baits, utilizing arsenicals as the active poison ingredi- ent, were ineffective in fire-ant control under the conditions of these tests. 4. Crude carbolic acid, creosote, and creolin compounds are not rec- ommended for use in protecting citrus trees from ants. 5. Poisoned bait, incorporating thallium sulphate as the active poison, was very eflicient in control of the fire ant under the conditions of these experiments. 6. The per cent of poison in the syrup suggested in this publica- tion is the lowest which should be used to obtain satisfactory control. Extermination may be hastened by increasing the percentage of poison in the mixture. '7. After the ants have been killed, the wounded areas of the trees should be cleaned and Bordeaux paint applied. '8. Thallium sulphate is a deadly poison, and great care should be exercised in handling it. Do.not place the bait where children or ani- mals will have access to it. i