Finlayson, D. G.

Noble, M. D.

English

Journal of the Entomological Society of British Columbia

PROC. E NTOMOL. Soc. BRIT. CoLUMBIA, VOL. 61 (1964 ), DEC. I, 1964 11 THE EFFECT OF DOSAGE OF ORGANOPHOSPHATE INSECTICIDES ON THE EMERGENCE OF RADISH SEEDLINGS AND ON DAMAGE BY CABBAGE MAGGOTS I D. G. FINLAYSON AND M. D. NOBLE Introduction With the development of a strain of cabbage maggot (Hylemya bras-sicae [Bouche]) resistant to the cyclodiene group of the organochlor-ine insecticides in the Pacific North-west, it once again became virtually impossible to grow marketable root and stem brassicas on Vancouver Island and in the lower Fraser Val-ley. Work by Howitt and Cole (1962) and by Finlayson and Noble (1964) indicated that maggots attacking root crops might be controlled with several organophosphates. However, reduced numbers of emergent seed-lings when granular formulations were applied in the furrow indicated that further work was needed. This paper reports on the effects of vari-ous rates of several organophosphate insecticides in three soil types on emergence of seedlings and preven-tion of damage in radish by resistant strains of cabbage maggots. Materials and Methods The insecticides were in granular formulations as follows : Diazinon O,O-diethyl O-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothi()ate; 5% on walnut shell ; F,isons (Canada) Ltd., Toronto, Ont. Guthion . . . O.O-dimethyl S·(4-oxo-1,2,3,benzotriazin-3(4H)-ylmethyl phosphorodithioate; 10%; Chemagro Corp., Kansas City, Mo. Heptachlor 1,4,5,6,7 ,8,8-heptachioro.3a,4, 7,7 a ·tetrahydro-4, 7· methanoindene; 5%; Velsicol Chemical Corp., Chicago, Ill. Nemacide (V·C 13) O,O-diethyl O·2,4-dichlorophenyl phosphorothioate; 5%; Pennsalt Chemicals Corp., Tacoma, Wash. Zinophos O,O-diethyl 0-2·pyrazinyl phosphorothioote; 10%; American Cyanamid Co., Princeton, N.J. The Early Scarlet Globe variety of radish was used. The investigation was conducted at three sites: at Essondale in muck soil ; at Victoria in peat soil; and at the University Farm in Vancouver in sandy soil. The design, a split-plot latin square, consisted of five insec-ticides applied at four rates, 0, 7. 14, and 28 g of toxicant per 1,000 feet of row, replicated five times. A plot consisted of four 20-foot rows, each row treated at one of the above rates. The insecticides were applied with three grams of seed (approxi-mately 300) sown with a V-belt seeder. The seedlings were counted I Contribution No. 77, Research Station, Re· search Branch, Canada Department of Agrlcul· ture, 6660 N.W. Marine Drlve, Vancouver 8, B.C. about 15 days after planting. At harvest random samples of 50 radishes per sub-plot were collected, washed, and inspected for maggot tunnels. A radish was considered damaged if there was any blemish caused by maggots. Percentage dam-age was calculated in terms of the number of radishes damaged. Results and Discussion Counts of emergent seedlings and percentage damage by root maggots are given in Table 1. Only Zinophos caused an appreciable reduction in emergence and this was more evi-dent in light sandy loam than in organic soils. There was no maggot damage in any treatment nor in the untreated checks at Vancouver and Essondale. At Victoria damage rang-12 PRO(, . E'iTOMOL. Soc. BRIT. COU; MBI A. VOL. 61 (1964), DEC. 1, 1964 I I I TABLE I.-Materials and rate of application, average number of seedlings, and percen-tage damage by root maggots in radish in British Columbia, 1962. Toxicant in g Emergent seedlings per 20 row·feet Percentage Granular per 1000 row· Essondale Victoria Vancouver damage insecticide feet (muck) (peat) (sandy) Victoria 0 245 250 229 79 Diazinon 7 232 252 223 60 5% 14 248 257 222 24 28 252 253 212 31 ! 0 218 249 230 82 7 245 223 Gutmon 211 14 202 10% 28 233 0 225 7 210 Heptachlor 14 218 5% 28 208 0 211 Nemacide 7 222 5% 14 223 28 216 0 249 7 225 Zinophos 14 218 10% 28 225 Difference necessary for significance, P=.05 N.S.D. ed from 4% in plots treated with 28 g of Zinophos to an average of 93% in treatments with heptachlor and 87% in untreated plots. Howitt and Cole (1962) reported that cabbage maggots resistant to ryclodiene insecticides in Washing-ton State appeared to be resistant also to organophosphates. Maggots of the strain at Victoria were sus-ceptible however, especially to Zino-phos. All treatments with organo-phosphate insecticides reduced the amount of damage. With the excep-tion of a slight reversal at the 14 and 28 g rates with diazinon, the percentage damage decreased as the dosage increased. Zinophos was the most effective insecticide. At 7 g per 1,000 rOw-feet only 12% damage was recorded, and this was very minor. Unfortunately, Zinophos caused some reduction in the numbers of emergent seedlings in the light soil. In peat and muck soils there was no appreciable re-duction. At Victoria at the 28 grate 56 262 236 48 237 220 36 248 225 92 257 232 93 260 232 93 262 214 92 246 239 96 244 233 75 234 220 69 238 221 55 257 227 87 237 152 12 230 119 9 199 61 4 N.S.D. 14 13 emergent seedlings were reduced 20%. The reduction was not signifi-cant. At Vancouver on the light soil even at 7 g per 1,000 feet of row approximately 30% fewer radishes emerged; at 14 g about 50%; and at 28 g the emergence was only 27% of the numbers recorded for the un-treated plots. Summary At Vancouver, Victoria, and Es-sondale, furrow treatments with granular formulations of diazinon, Guthion, heptachlor, Nemacide, and Zinophos were applied at 0, 7, 14, and 28 g toxicant per 1,000 row-feet. No maggot damage was recorded at Vancouver and Essondale. At Vic-toria damage ranged from 4% in plots treated with Zinophos at 28 g to 93% for heptachlor treatments and 87% for untreated checks. Only Zinophos caused any appreciable reduction in the numbers of emerg-ent seedlings. This was more evident in light sandy soil at Vancouver than in organic soils at Victoria and PROl'. E:I"TOMOr.. SoC'. BRIT. CoLUMRIA, VOL. 61 (1964). DEC. 1, 1964 13 Essondale. At Vancouver the average number of seedlings per 20 row-feet at 0, 7, 14, and 28 g of Zinophos was 227, 152, 118, and 61 respectively. Acknowledgements Grateful acknowledgment is made for assistance from our colleagues, H. R. Mac-Carthy and A. T. S. Wilkinson, and for technical assistance by N. J. Filmer. References Finlayson, D. G., and M. D. Noble. 1964. The efficacy of organocarbamate, organoch-lorine, and organophosphate insecticides against turnip maggots and resistant cabbage maggots in rutabaga in British Columbia. Proc. Entomol. Soc. Brit. Columbia 61:3-10. Howitt, A. J., and S. G. Cole. 1962. Chemical control of Hylemya brassicae in the Pa-cific Northwest. J. Econ. Entomol. 55:33-::18. EXPERIMENTS AGAINST CARROT RUST FLY (Psi. IDS,. (F')) RESISTANT TO CYCLODIENE ORGANOCHLORINE INSECTICIDES' D. G. FINLAYSON, H . G. FULTON, ANDM. D. NOBLE In July, 1961 reports from the Provincial Government's Colony Farm at Essondale, near Vancouver, to the effect that aldrin was no longer protecting carrots from dam-age by carrot maggots (Psila rosae [F.l), led to an investigation to de-termine: if strains of flies resistant to cyclodiene insecticides were pres-ent, and if suitable control measures could be developed. The first spring seeding of carrots at Essondale was destroyed because the damage was so severe. Although recommended chemicals had been applied it soon became evident that the second crop also was hea vily infested. Random samples in mid-August showed that at least 50% of the carrots were damaged. Collec-tions of pupae were made at this time by sifting the soil for three inches on each side of the row to a depth of about six inches. Forty-five feet of row yielded more than 750 puparia plus an additional 1,200 from the maggots in the infested carrots. Samples of these puparia were shipped to the Entomological Laboratory at Chatham, Ont. , for screening against I Contribution No. 78, Research Station, Re-search Branch, Canada Department of Agricul-ture, 6660 N .W. Marine Drive, Vancouver 8, B.C. various insecticides. The results of these tests (Niemczyk and Harris, 1962) showed that the flies were highly resistant to aldrin but very susceptible to diazinon. The toxicity of malathion was about mid-way between the other two. Based on results obtained during investigations to find effective insec-ticides against resistant strains of onion maggots (Finlayson, 1959 and Howitt, 1958) ; cabbage maggots (Finlayson and Noble, 1964a and b and Howitt and Cole, 1962); and carrot maggots (Howitt and Cole, 1959); experiments were designed to test the effective insecticides against the second generation of carrot rust fly at Essondale. This paper reports on the experiments in 1961, 1962, and 1963. A temporary method was developed for preventing damage and the effects are shown of several dosages of chemicals on seedling emergence in various soil types. In the lower Fraser Valley commercial carrots are usually grown in muck soil . Materials and Methods The pesticides used in the investi-gation are listed in Table 1 and are identified chemically in accordance with Billings (1963) and Kenaga 

The effect of dosage of organophosphate insecticides on the emergence of radish seedlings and on damage by cabbage maggots

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The effect of dosage of organophosphate insecticides on the emergence of radish seedlings and on damage by cabbage maggots

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