LIBRARY STATE PLANT BOARD Octbber I9UU E -627 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine TESTS OF NEW INSECTICIDES AGAINST THE PEPPER WEEVIL AT ALHAMBRA, CALIFORNIA By Roy E. Campbell, Division of Truck Crop and Garden Insect Investigations During the investigations of the pepper weevil at Alhambra, Calif. , teste were made of the toxicity of many different materials, and some of the results have been reported. The purpose of this cir- cular is to assemble and make available the information obtained on the toxicity of new materials!/ in comparison with insecticides com- monly used against the pepper weevil. From a practical standpoint, cryolite was found to be the best material to use for the control of the pepper weevil, and it has been recommended for this purpose (^)£/. Therefore, in most cases cryolite will be used as a standard and the effectiveness of other materials will be compared with it. Because pep-oer fields are continually being reinfested with these weevils, materials which killed by contact were relatively ineffective. Only those which left a poisonous residue on the plants for several days were satisfactory in controlling the pepper weevil. METHODS Most of the laboratory tests were made on individual pepper plants grown in the back yard of the laboratory. Each plant was covered with a fiber-board cone which acted as a settling chamber and also pre- vented the insecticide from drifting to other plants. With the use of a precision duster (2), 1 gram of insecticide was apnlied to the plant through the top of the cone. The plant was then covered with a screen cage, and 10 weevils were put into the cage. The cage was examined at regular intervals for k or 5 days and the dead weevils were counted and removed. The mortality percentage was calculated on the basis of the dead weevils actually found, the missing ones being considered as living, but the tests were discarded whenever more than 2 weevils were missing. 17" Most of the new materials were furnished by the Division of Insecticide Investigations. W Underscored numbers in naren theses refer to Literature Cited, p. 3, -2- For testing the contact effect, the cage was put over the plant and the weevils were introduced and allowed to settle on the foliage. Then the insecticide was dusted onto the plant through the cage top, the precision duster being used. In some special tests, cut twigs of bell pepper were used instead of plants. For each twig a glass tumbler of water was covered with a thin board 6 inches square with a hole in the center. The stem of the twig was thrust through the hole and a piece of paper fitted around the top to keep the weevils from falling into the tumbler. The twigs were dusted with an undetermined quantity of insecticide by use of an atom- izer type of hand duster. The weevils were then introduced and the in- fested twig was covered with a lantern-globe cage. LABORATORY AHD FIELD TESTS, 1931 THROUGH 1939 In laboratory and field tests made during 193* &&$■ 1932. sodium fluoaluminate, potassium fluoaluminate, ammonium fluoaluminate, magnesium fluoaluminate, and barium fluosilicate were effective against the jjepper weevil, but these fluorine materials available at this time were somewhat unstable and caused slight leaf injury or. bud pruning, resulting in an actual reduction in yield (1), Oalcium arsenate, undiluted, was almost as toxic to the pepper weevil as the fluorine materials, but a little slower in action. These tests with calcium arsenate were very favorable., and a considerable quantity was used in commercial control of the pepper weevil. The commercial use of calcium arsenate, however, was followed by damage by aphids and a decided reduction in yield (U), especially when several applications were made. In laboratory tests in 193&I using 30 weevils for each material, undiluted calcium arsenate gave 70 percent mortality, wherea* none of the" following materials gave over 40 percent mortality: Dibenzothiophene k and S percent; phenothiazine 15 percent; a mixture containing 2.7 'percent of nicotine, 1.5 percent of phenothiazine, and 1.5 percent of pyridine; a mixture containing 3 percent of phenothiazine, 3 percent of pyridine,' and 3 percent of pine oil. In 1938 and 1939 field tests were made with cuprous cyanide 20 per- cent and 30 percent, and with a proprietary mixture containing 0.3 percent of pyrethrins. Infestations were low, but cuprous cyanide showed some promise. Bran baits containing H pounds of calcium arsenate and 2 to Im- pounds of molasses per 100 pounds of bran were ineffective. A spray con- taining k pounds of tartar emetic and 10 pounds of brown sugar per 100 gallons of water was also ineffective. LABORATORY TESTS, 19I40-19U2 As shown in tables 1 -and 2, most of the materials tested during I.9IK), 19Ul, and I9J42 were ineffective as compared with palcium arsenate and cryo- lite. Phenazine was toxic to the weevils but caused severe burning of the -3- pepper plants. Phenoxathiin had to be diluted with tale before it could he used at all as a duet, and at euch was relatively ineffective. Tripterygium vilfordll gare oyer 60 percent mortality, and it it worthy of further trials, especially as the 50-percent strength averaged bet- ter than the undiluted material. Two proprietary preparations contain- ing pyrethrine gare high weeril mortalities wham used in the laboratory as contact insecticides, but pyrethrum dusts bare given unsatisfactory results under field conditions, p-Amlnoazobenzene hydrochloride not only was ineffective, but was objectionable because it gave the plants a ruety color and etained the hands and clothing of the operators yel- low. p-Aainoaoe tan Hide caused definite foliage injury, especially to the growing tips. Phenazine, I-nitroeodiphenyls»iae, etyrene dibromide, and phenoxathiin were all too co&ree to be applied as dusts and had to be reground, which could not be done very satiefaeterlly with a mortar and pestle. Diaethylacridan became too moist and could not be ground at all. Hhe sample of ground Tripterygium wilfordlj was an excellent dust, being light and easy to apply. LABOBATQRT TESTS II 19U3 In 19U3 two new materials, 2-chlorofluoreae and DDT, were tested, and the results, as summarized in table 3» indicate that they may be more toxic than any material previously tested. DDT was consistent in giving 100 percent mortality within 2k hours after application, but very low mortalities were sometimes obtained within this period with 2-chloroflu- orene. Plants treated with DDT appear to be completely protected from weevil feeding. The weevils were not able to stay on the leaves or buds for more than a few eeconds at a time. The same action was observed with twigs dusted with 2-chlorofluorene, but the weevils were affected less rapidly than with the DDT. Incidentally, the DDT dust adhered to the pepper leaves and buds much better than did the 2-ohlorofluorene. LI MEATUS! CITXD (1) llmore, J. C. 1933* SoHie teste with fluorine compounds against the pepper weevil. Jour. Icon. Int. 26t 1095-1105, illus. (2) Hoy I. Campbell, and C. S. Quy 1935* * aethod of applying insecticidal duste quantitatively as a basis for cage teete of insecticldee. U. S. Dept. Agr., Bur. Int. and Plant Qiar. Circular IT-l*5t 3 PP« » illus. (Processed. ) - 19H2. The Pepper Weevil. U. S. Dept. Agr. Leaflet No. 226, 8 pp., illus. (k) and Roy I. Campbell 19^3* Aphid increase and plant injury following the use of cal- cium areenate on peppers. Jour. Icon. Int. 36 (6): 853-856. -U- Table 1.- Mortality of pepper weevils on plants treated with insecticidal dusts, 19IJO - 19^2 Materials Weevils placed on dusted foliage, 19*40 Calcium arsenate Cryolite (70$ sodium fluoaluminate) Cryolite (50$ sodium fluoaluminate) 1, 3-Diphenyl triazine 1,4-Diphenyl semicarbazide Phenothiazine (30$) Cuprous cyanide (20$) 1,3-Diphenyl triazine and bentonite (1:1) A proprietary mixture containing pyrethrins 2$ Dinitro-o-cyclohexyl phenol 2$ and dicyclohexylamine 3-35* Cuprous cyanide (30$ A proprietary material containing pyrethrum powder 15$, beta-butoxy-beta'-thiocyanodiethyl ether 1$, petroleum distillate 1$, and talc 83$ p-Aminobenzene hydrochloride Dicyclohexylamine dinitro-o-cyclohexylphenate 1.7$ and heavy oil 2$ p-Aminoacetanilide Dicylcohexylamine dinitro-o-cyclohexylphenate 1.7$ 1, H-Dinitrosopiperazine Dinitro-o-cylohexylphenol 1$ 1,^-Diphenyl semicarbazide and bentonite (1:1) Weevils placed on dusted foliage, 19^1 Phthalonitrile Phthalonitrile and talc (1:1) p-Aminoacetanilide p-Aminoacetanilide and talc (l:l) 1,4-Diphenyl semicarbazide l,ty-Diphenyl semicarbazide and talc p-Aminoazobenzene hydrochloride p-Aminoazobenzene hydrochloride and talc (l:l) None (check) : Weevils i:Mor- : used :tality Number Percent 200 90 2140 S7 270 SO 1*40 77 150 53 1*10 36 30 33 90 32 50 32 100 31 50 26 uo 25 Ik) 2k 100 23 100 22 100 20 100 10 70 9 50 6 60 32 70 23 60 12 70 17 go Ik 70 2k 50 11 70 Mo 10 -5- Table 1 - continued Materials : Weevils: Mor- : used : talitv Weevils placed on foliage before dusting, 19Hl Phthalonitrile Phthalonitrile and talc (1:1) p-Aminoacetanil ide p-Aminoacetanilide and talc (1:1) 1,4-Diphenyl semicarbazide l,l|-Diphenyl semicarbazide and talc (1:1) p-Aminoazobenzene hydrochloride p-Aminoazobenzene hydrochloride and talc (1:1) None {check) Weevils placed on dusted foliage, I9U2 Phenazinei' 2/ Phenazine and talc (l:l)— ' Cryolite (70$ sodium fluoaluminate) Cryolite (50$ sodium fluoaluminate) Cryolite (35$ sodium fluoaluminate) Tripterygium vilfordii 1' ^-Ifordii and talc (1:1) N-lIitrosodiphenylamine Phenoxathiin and talc (1{1) Styrene dibromide Node (check) 1/ Caused severe burning and complete defoliation. 2/ Caused slight burning and dropping of buds. Number Percent 70 96 60 61 80 U2 80 140 60 U2 80 55 70 33 60 33 MO 22 Uo 92 1*0 kz 196 82 212 77 151 11 180 110 67 % 20 28 50 2k lk) 10 UNIVERSITY OF FLORIDA -6- 3 1262 09230 3972 Table 2. -Mortality of pepper weevils in tests in which 10 weevils were placed on plants "before the application of insecticides and 10 weevils k to 10 days later t Tests [Mortality of j [Mortality of : Materials : con- : weevils ! [weevils placed : : ducted : dusted [on dusted : [foliage : Number - Percent 1 85 i Percent : Calcium arsenate, undiluted ! 2k . I 75 : Calcium arsenate and talc (1:1) , 10 ! ! 82 : : 83 i Cryolite and talc (70£ sodium fluoaluninate) : ' 20 : 86 ! ! Gk : Cryolite and talc (e>0$ sodium fluoaluminate) ! . 15 i : 66 i [ kl : A proprietary material containing" 15£ of pyre thrum powder, ifj of ! beta-butoxy-beta'-thiocyanodi- : i : i ethyl eth°r, IS of petroleum distillate and 83^ talc ' ! lU ! ! 87 ! ! 2k 1 A proprietary mixture containing ! i : i 2 percent of pyrethrins ! 15 ! : 88 i 25 : None (check) ! 9 ! : 10 i i 7 I .» I Table 3 --Mortality of pepper weevils placed on twigs of pepper after dust- ing with new insecticides, 19^3 Materials Strength Weevils used Mortality in 2k hours JJ 2-Chlorofluoren DDT and pyrophyllite IT Percent 20 10 10 5 3 Number 67 30 69 29 31 Percent 67 27 100 ion 100 Diluent not known