LIBRARY • 16.6 Nicotine bentonite (dry-mix 1:5) 3 lb. 22.6 Cryolite (90 percent) 3 lb. 14.4 DDT 1/2 lb. plus pyrophyllite 1 lb. 11.4 £/ Seven different nicotine bentonite programs were included in these tests. Detailed information on all of the programs is not given, but the range in results is indicated. -3- Tests at Poughkeepsie , N. Y. (6 cover sprays) Worms per 100 apples Standard lead arsenate 3 lb» 12*3 Nicotine bentonite, tank-mixed, containing nicotine sulfate l/2 pt. (U sprays following 2 of lead arsenate) 9*0 DDT (microniied with equal weight of pyrophyllite) 1 lb. 2.7 2 lb. 0.5 Check(un sprayed) 165.2 At Vincennes ^ ounces of DDT with half the usual concentration of lead arsenate or nicotine bentonite reduced the number of wormy apples to less than half of that resulting from standard lead arsenate or nicotine bentonite alone and as good results as DDT, 1 pound per 100 gallons, without any other insecticide. It is of interest to note that destructive increases in mite populations did not occur in the plots in which such low dosages of DDT were used, whereas they did occur in most plots in which higher ones were used. In the Kearneysville experiments, the four applications of DDT gave almost perfect control of first-brood worms, and a continuation of the applications during the second-brood period presumably would have prod- duced exceptionally clean fruit. At Foughkeepsle a 5 percent DDT-pyrophyllite dust was more effective than a 20 percent lead arsenate or a phenothlazine dust, or 20 percent lead arsenate dusts combined with oil, nicotine bentonite, or lime, and gave better control than the grower's spray schedule, which included lead arsenate, fixed nicotine, and oil. Both here and at Vincennes DDT dusts were not so efficient as the sprays. In a large-scale test in a heavily Infested 8-acre block of apple trees at Vincennes, 10 cover sprays of DDT (prepared as a paste containing DDT 1 part (by weight), pyrophyllite 1 part, and water 2 parts),used at the rate of 1 pound per 100 gallons in 5 eprays and }/k pound per 100 in the others, were applied. On an average 23 worms per 100 apples were found in this area as compared with 68 in adjacent blocks receiving 11 cover and 2 top-off sprays of tank-mixed nicotine bentonite, the most effective spray mixture previously available for that locality. Since residues of DDT on apples may later be found objectionable, exploratory work with residue removal is being undertaken. Preliminary tests at Vincennes have indicated that such residues may be difficult to remove by either brush machines or flotation- type washers. Soaps, oils, wetting agents, and strong alkaline solutions had little effect, and none removed as much as half the residue. Similar teats at Yakima confirmed -4- the results reported from Vincennes. A maximum of approximately 60 percent of the DDT spray residue was removed by using 2 percent of oil in water followed by a wash in a wetting agent to remove residual oil. Japanese Beetle DDT has given outstanding control of adult Japanese beetles. In laboratory tests at Moorestown, N. J., as little as 1/16 pound of DDT in 100 gallons of water was as effective as 6 pounds of lead arsenate. In combination with most fungicides it was slightly less effective. In field tests, many of which were in cooperation with the New Jersey Agricultural Experiment Station, one to three sprays of DDT (micronited with equal parts of pyrophyllite, and with glue as a wetting agent) at the rate of 1 pound per 100 gallons gave almost complete control of the beetles on peaches, early apples, grapes, blueberries, and a miscellaneous group of ornamental and shade trees and shrubs. Applications after the first spray were neces- sary largely to protect new growth. DDT applied in spray or in dust form has also been found very effective in soil treatments against the grubs of the Japanese beetle. Tests with 28 different soils, which hero been in progress for more than a year, in- dicate that 25 pounds of DDT (in various formulations) per acre are more effective against third-ins tar larvae than 1,000 pounds of lead arsenate, and that the effectiveness of the DDT in the soil has not changed during the period of the tests. Large-scale tests in turf, with dosages of 25 and 35 pounds por acre, are now under way. Some of the soil tests, which resulted in plant injury, are discussed elsewhere. A more detailed report on this work will appear in the E series of the Bureau. Leafhoppers Observations and the results of preliminary experiments indicate that DDT may control some species of leafhoppers effectively. At "Yakima the DDT formulas used for control of the codling moth also appeared to control apple leafhoppers (chiefly Typhi ocyba spp.). On August 28 the average number of leaf hopper nymphs per 100 leaves was 0.6 on trees sprayed with DDT. 25.3 on trees sprayed with lead arsenate plus oil emulsion, and 7^»3 00 trees sprayed with nicotine bentonite. In codling moth field plots at Vincennes various DDT sprays gave complete control of several species of apple leaf- hoppers. Promising results in the control of the grape leafhopper were obtained in preliminary tests with DDT in Ohio, 1.5 pounds of DDT (dissolved in a mixture of benzene and kerosene, which was then emulsified) per 100 gallons, and in New Jersey (same formula as used in tests against Japanese beetle adults). Apple Aphid e At Vincennes, early in April 1?UU, it was noted that trees sprayed with DDT in several formulations in 19^3 had very low or no aphid popula- tions, although adjacent trees were heavily infested. In 19HU DDT was slow in eliminating aphids (all three species common on apple) already present, but they disappeared by mid-season. The apple-grain and the rosy apple aphids disappeared earlier from the trees treated with DDT than -5- they did froa the untreated trees. In the fall aerial colonies of the woolly apple aphid were common on trees in lead arsenate plots, hut absent froa trees in DDT or nicotine plots. At Takiaa it has been noted that woolly aphid* hare becoae mxch aore coaaon in soae apple trees sprayed with DDT (DDT 1 part plus pyrophyllite 2 parts) than in adjacent treee sprayed with lead arsenate. Here it is possible that DDT aay be interfering with the activity of the Aphe linns parasite, which hae been effective in holding the woolly aphid in check in the Pacific Horthwest. Tests aade on the woolly apple aphid at Takiaa in October, with DDT sprays that had been used for the codling aoth during the sunaer, resulted in alaost no control whatever. It was only by dissolving ths DDT in a petroleum oil derivative, and using an eaulsion of this solution with a wetting agent, that anything approaching satisfactory control of this aphid was obtained. It is recognised that the chief difficulty here aay be the inability to wet the insects thoroughly. Oriental Fruit Moth Injury to peaches by the oriental fruit aoth was reduced considerably in field plots sprayed with DDT (Japanese beetle formulation) , 1 pound per 100 gallons, in an experiment conducted in cooperation with the Hew Jersey Agricultural Experiment Station. Two applications, one each Just before the appearance of both second- and third-brood larvae, were aore effective than one application aade prior to appearance of the second brood. The DDT eprays reduced the activity of parasites, but did not eliminate them. At Mo ores town DDT sprays were found to be auch aore toxic to adults of Macrocentrus ancyllvorus Hoh. than of the oriental fruit aoth, and the residues were toxic to them for a auch longer period. Grape Berry Moth In saall-scale tests at Sandusky, Ohio, 1 1/2 pounds of DDT (in a mixture of bensene and keroeene that was eaulslfled) per 100 gallons did not kill the eggs of the grape berry aoth on berries; it was about 50 percent effective 20 days after application in control of larvae trying to enter grape berries; and In a Latin-square field teet it wae aore effective when used In three or four applications than lead arsenate used in four applications. In a large-block field test, however, one application of DDT did not hold up so well ae one application of lead arsenate. In a field teet of DDT (Japanese beetle formulation), 1 pound per 100 gallons, on Hiagara grapes in Hew Jersey, 15. 6 percent of the berries were injured in the DDT plot, and Hi. 7 percent in the lead arsenate plot, but on Jersey Muscat grapes DDT was no more effective than the standard lead arsenate treataeat. Hose Chafer The results of a cage test at Sandusky indicate that DDT aay oontrol the rose chafer effectively. Grape foliage and clusters were sprayed on June 5 vith DDT (saae formulation as used on grape berry aoth at Sandusky), -6- 1 1/2 pounds per 100 gallons, and then placed in two cages; 25 beetles were introduced into each cage on June 5» 8, 13, and 17 . All of the beetles were knocked down in less than 2k hours and were dead in less than 48 hours. Scale Insects In general, scale insects have been little affected by DDT. Ho benefit appeared to result from the addition of DDT to oil sprays against the Florida red scale and fig scale. The addition of DDT improved the immediate kill of Parlatoria chinensis Marlatt, but had no residual effect on crawlers. There was little or no immediate effeot against the Cali- fornia red scale, but the residual value against crawlers was considerable in cool weather as compared with that in hot weather. Plum Curculio Against the plum curculio, DDT appears much less effective than lead arsenate. Tests at Beltsville with DDT-pyrophyllite (1:1), applied with various fungicides at the rate of 1 1/2 pounds of DDT per 100 gallons, indicated little control of curculio on apple and peach. At Fort Valley, Ga. , k pounds of DDT (with wetting agent) per 100 gallons seemed to be about equal to the standard 2 pounds of lead arsenate for control of the curculio on peach. Orchard Mites At the dosages required for codling moth control, DDT apparently is not toxic to the Pacific mite, the European red mite, and the citrus red mite. In fact, the use of this chemical has in several cases caused an increase in mite population, apparently by eliminating or reducing the numbers of natural enemies of the mites. If DDT is used for the control of orchard insects, it is likely that some adjustment of spray programs will be necessary to provide for the control of mites in areas where they are present. Other Insects Preliminary laboratory or very limited field tests have been made with DDT in various formulations on many other insects. Favorable results have been obtained in the control of the pistol casebearer on apple, the grubs of the Asiatic garden beetle, an annual white grub. Cyclocephala boreal is Arrow, in the soil, certain sucking bugs that cause distortion of peaches, the hickory shuckworm, the pecan weevil, chestnut weevils, the citrus thrips, the little fire ant on citrus trees in Florida, ante and saw-toothed beetles in raisin storages in California, the grape bud beetle (Glyptoscells squamulata Crotch) , and the grape rootworm. With the apple maggot, the cherry frultfly, the pecan nut casebearer, and newly hatched crawlers of the Comstock mealybug results have been promising enough to warrant further teste. -7- In small-scale field and laboratory tests at Poughkeepsie, pear psyllas vers not controlled during the dormant season with 2 pounds of DDT plus 2 ounoes of sodium lauryl sulfate per 100 gallons. Unfarorable results were also obtained in similar tests against the summer-brood nymphs with 1 1/2 pounds of DDT aieronized vlth pyrophyllite (1:1) and with several other formulations . ITRCf 0? DDT ON TRIES AND PLAHT8 Most of the trees and plants on which DDT has been used hare not shown evidence of injury. On eome apple trees, however , there has bean soae yellowing and dropping of foliage, but an inoreaee in mite abuniance has been largely, if not wholly , responsible. In experiments with soil treatments for Japanese beetle grubs, 25 pounds of DDT per acre definitely retarded the growth of bush beans, lima beans, soybeans, hollyhock, onions, spinach, and tomatoes. Some of the bean leares became yellow, and tomato plants were somewhat distorted. Higher strengths caused some growth retardation in beets, carrots, muskmelons, and potatoee. Tests are under way at Beltsville in which excessive quantities of DDT have been applied to the soil under apple and peach trees, to simulate the accumulation that might occur over a period of years if DDT should come into general use. Thus far no injury has become evident. imcT or ddt on huxticial iisicts General observations have Indicated that DDT is very toxie to many forms of Insect life, and that its application to fruit trees brings down a tremendous number of beneficial insects. Cage tests have shown that DDT is extremely toxie te many hymenopteroue parasites, Including Macrocentrus ancyllvorus of the oriental fruit moth and Pseudaphycus ep. of the Constock mealybug. There are also numerous indications that DDT is fatal to many of the lady beetles that normally control aphido. mealybugs, and mites. DDT MATERIALS AFD TOBKULATIOSS lither technical-grade DDT or DDT mixed with pyrophyllite in various proportions was used in most of the teats conducted during lykk. DDT-oil preparations were used in a few tests. The DDT dust preparations were ordinarily ueed ae received or, when lees concentrated mixtures were de- sired, were further diluted with pyrophyllite. The technical grade of DDT could not be used satisfactorily as received, and epecial treatment was neceeeary to prooess it for use as a powder, a paete, or ae an emulsion. In some cases it was merely mixed with water containing a email amount of wetting agent. In others it was ground with water In a pebble mill; diluted with pyrophyllite, and mlcronised or ground dry or with water in a ball mill; diluted with pyre phyl lite or kaolin and ground in a Mikropulverlser; or dissolved in a suitable solrent, such as mineral oil, kerosene, or bensene, and then emulsified. -8- Some of the formulations that were prepared and used were as follows (when not otherwise specified, proportions are "by weight): (1) A micronised 1:1 nixture of DDT with pyrophyllite (2) A *K):60 DDT-water paste prepared by grinding in a pebble Bill (3) A 1:2 DDT-pyrophyllite mixture ground in a ball mill (k) A 1:9 DDT-pyr6phyllite mixture ground in a ball mill (5) A 1:1:2 DDT-pyrophyllite-water paste prepared by grinding in a ball mill (6) A 1:1 DDT-pyrophyllite mixture ground in a Mikropulveriser (7) A 1:1 DDT-kaolin mixture ground in a Mikropulveriser (8) 0.5 pound of DDT dissolved in 1 pint of bensene and emulsified with 0.5 ounce of B-195& (a phthalic glyceral alkyl resin) (9) A stock emulsion prepared by dissolving 1.5 pounds of DDT in 58.8 ounces of benzene (tech.), adding 5*2 ounces of kerosene and 6.0 ounces of B-I956, shaking, and adding water to make 1 gallon (10) 1 pound of DDT dissolved in 1 quart of bensene or xylene and emulsified with casein and ammonia just prior to use (11) A 5 percent DDT-ethylene dichloride solution emulsified with IN-181-P (sodium alkyl sulfates, principally lauryl) A satisfactory spray mixture was prepared as follows: DDT 1 lb. ) ) micronlsed together Pyrophyllite 1 lb. ) Fish glue solution 1 pt. (1 lb. liquid glue per gal.) Summer oil emulsion 1 qt. Water to make 100 gal. The DDT-pyrophyllite mixture and the glue solution were placed in a pail and worked into a stiff paste with a small quantity of water. More water was then added, with constant stirring, until a thin paste was obtained. While the spray tank was being filled with water this paste was poured into it through a screen. When the tank was about three-fourths full, the summer oil was added and the tank was then filled to capacity. -9- At Moorestown the 10 percent DDT powder wai not sufficiently free- flowing to be used in a Sandy spreader for soil treating. Howerer, a suitable, but not altogether satisfactory, material was prepared by diluting the 10-percent material with sand until the DDT content was 2.5 percent. A suitable 10 percent DDT free- flowing mixture was prepared by adding 78 percent of talc and 2 percent of tricalciua phosphate to the 1:1 mioronlied DDT-pyrophyllite mixture. Despite the work done on the preparation of DDT for use in sprays and as dusts, further improrement is needed in methods of formulation and application. The most immediate need is for a practical, wet table DDT preparation which can be used in the tank of standard orchard spray equip- ment without preliminary preparation. Experience appears to Indicate that the material should be in powder form and contain the absolute minimum of diluents and wetting agents. Aqueous emulsions also appear to hold some promise. UNIVERSITY OF FLORIDA 3 1262 09230 3865