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This article examines the effects of insecticides on greenhouse whitefly. In trials on a commercial cucumber nursery in Kent, England in 1971, malathion high-volume sprays gave good control of whitefly adults and young scales. Malathion applied at ultra-low volume or as an aerosol was less effective. Malathion dust controlled only adults. Nicotine and petroleum oil were ineffective. In laboratory and glasshouse experiments in 1972, 16 chemicals as sprays, dips, drenches, smokes or fumigants were tested against each stage of a malathion-susceptible and a malathion-resistant whitefly population cultured on French beans.

Tests were made to select insecticides which would kill adult seed wasps in crowns of cone-bearing Douglas fir trees. In the laboratory, gamma BHC, malathion and diazinon were found to be active against females. In further tests, on males and females, gamma BHC and malathion were active when the insects were allowed contact with treated surfaces; fenitrothion was less active. The effectiveness of gamma BHC was partly due to fumigant action whereas malathion and fenitrothion had no fumigant effect. In separate field experiments between 1962 and 1966 in Kent and Herefordshire, gamma BHC and fenitrothion gave no control but malathion gave good control. In 1968, trees in Kent to which malathion was applied three times at 10-day intervals during June had about 13 per cent infestation of potentially sound seed, when assessed in September, compared with about 45 per cent infestation on unsprayed trees. Malathion plus gamma BHC did not further reduce infestation. [ABSTRACT FROM AUTHOR]

Observations made in England between 1965 and 1970 showed that larvae of Acleris comariana (Zell.), Clepsis spectrana (Treits.), Lozotaenia forsterana (F.), Cnephasia interjectana (Haw.), Cacoecimorpha pronubana (Hübn.) and Argyroploce lacunana (Den. & Schiff.) occur on strawberry. Of the pesticides tested primarily against Acleris comariana, azinphos-methyl, fenitrothion, malathion, methidathion, mevinphos, parathion and trichlorphon gave very good control of second generation larvae when applied at 200 gal/acre (2,245 1./ha). DDT and TDE gave relatively poor control. When applied against first generation larvae in the spring at 100 gal/acre (1,123 1./ha), azinphos-methyl, fenitrothion, metkidathion and trichlorphon were less effective though the number of larvae was reduced by over 50 per cent. DDT, phosalone and phosmet also killed over 50 per cent of first generation larvae, but dichlorvos and Dupont 1642 did not; malathion gave variable results. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the control of the weevil Apion dichroum Bedel in wild white clover grown for seed using a spray of malathion. The experimental area was approximately 12 acres (4.9 ha) and the design was six blocks each of two plots, one being sprayed and the other unsprayed. The changes with time in the density of flower heads vulnerable to weevil attack and of those suitable for harvesting were recorded. The experiment suggested a useful increase in yield—18 or more lb per acre (20 or more kg per ha)—as a result of the treatment, but there was no conclusive evidence of any increase. An increase of 4 lb per acre (4.5 kg per ha) would cover the cost of spraying. There was no evidence that spraying reduced the activity of bees. Data from two independent sampling methods show that the weevil population in the treated plots was always less than 10 per cent of that in the untreated ones during the whole period in which the crop was vulnerable to weevil attack. [ABSTRACT FROM AUTHOR]

Single sprays of DDT, malathion, azinphos-methyl and vamidothion were applied to apple trees at petal fall in 1967 and 1968 for the control of Lygocoris pabulinus in a commercial orchard in the west of England. The degree of control was assessed by sampling the number of capsids and newly damaged twigs in each treatment after spraying. Control on all sprayed trees was virtually complete in 1967. In the following year DDT, azinphos-methyl and vamidothion gave 74, 67 and 81 per cent control respectively, whereas no L. pabulinus was found on malathiontreated trees and only 0.2 per cent of the twigs assessed for damage showed recent feeding punctures. It was concluded that vamidothion and azinphos-methyl gave as good control of this species as DDT and that malathion gave better control. [ABSTRACT FROM AUTHOR]