The effects of DDT on the behaviour and mortality of Anopheles gambiae Giles, A. funestus Giles, Mansonia uniformis (Theo.) and Culex pipiens fatigans Wied., entering experimental huts, have been studied with the assistance of gas-chromatographic techniques.Sixty to 70% of A. gambiae and 70–80% of M. uniformis were deterred from entering verandah-trap huts treated indoors with a nominal dosage of 200 μg/cm2 of DDT active ingredient. Gas chromatographic techniques indicate that the chemical basis of the deterrency was a steadily diminishing outflow of DDT from the hut, either as a dust or vapour, and the build-up of deposit on the untreated overhanging eaves to 0·02 to 0·27 μg/cm2 seven months after treatment. A. funestus was less deterred than A. gambiae and M. uniformis, but the behaviour of C. p. fatigans was almost unaffected by the DDT deposit.Overall mortalities were highest in A. funestus and M. uniformis, lower in A. gambiae and extremely low in C. p. fatigans.There was a marked irritant effect of the DDT deposit on recently blood-fed A. gambiae, some 50–70% being driven out of the treated huts. This behaviour occurred to a lesser degree in A. funestus but was absent in M. uniformis and C. p. fatigans. The chemical basis of the irritant effect was indicated to the extent that surviving mosquitoes, that left the treated hut, showed 1·5 ng/insect of DDT. Mosquitoes that died, whether indoors or after leaving the hut, picked up amounts ranging from 7 to 20 ng/insect.
Weather-damaged wheat from northern New South Wales in 1995-96 was heavily
infected with the fungus Alternaria alternata. The
mycotoxins tenuazonic acid, alternariol, and alternariol monomethyl ether were
detected at low levels which corresponded with the degree of A.
alternata infection and the geographical location.
Sorghum and undamaged wheat from the same region also showed moderate levels
of A. alternata infection and low levels of tenuazonic
acid but none of the other toxins. These mycotoxins were not found in
weather-damaged wheat from other areas of Australia where the primary
infection was by A. infectoria rather than
A. alternata.
Duplicate field trials were carried out on bulk wheat in commercial silos in Queensland and New South Wales. Laboratory bioassays on samples of treated grain at intervals over 8 or 9 months storage using malathion‐resistant strains of insects established that treatments were generally effective. Cyfluthrin (2 mg kg−1) plus piperonyl butoxide (10 mg kg−1) and cypermethrin (4 mg kg−1) plus piperonyl butoxide (10 mg kg−1) completely controlled two strains of Sitophilus oryzae L. Control of a third strain by the cypermethrin combination was incomplete after 11/2 months and neither controlled a multi‐resistant laboratory strain. Both combinations were effective against Rhyzopertha dominica F., Tribolium castaneum Herbst and Ephestia cautella Walker. No natural infestation developed in the treated grain in any silo.
Mean residues of cyfluthrin and cypermethrin after 9 months storage were 58% and 52% of the calculated application rates, respectively. Compared with overall concentrations in the wheat, residue levels were higher in bran and pollard and lower in white flour. During baking, residues decreased by up to 29%. Operators experienced respiratory irritation associated with exposure to both combinations and alternative formulations would be required for use of these materials in grain storage.
A method is described for the extraction of insecticides from treated cabbages and other vegetables and for their separation into water-soluble and petroleum-soluble groups. The further separation of members of each group from associated plant material is described for eighteen organo-phosphorus insecticides, and the quantitative separation of both groups is discussed, with particular reference to mixtures of (a) phorate with its oxygen-analogue sulphone and (b) parathion-methyl with Phosdrin.
Traditionally, structures for the storage of grain from peasant farms in tropical countries have been concerned with keeping the rain off, and the rats out. However, a major source of loss in storage, that caused by insect damage, has not been effectively controlled by traditional methods. The use of fumigants, certain safe and effective insecticides, and improvements to storage structures may provide a solution, but the existence of an adequate and well-trained advisory service is essential.
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