The Synthetic and botanical insecticides are relatively safer for environment and beneficial insects. The study was conducted in Rahim Yar Khan during the cotton cropping season 2014 to evaluate the comparative efficacy of two Synthetic insecticides i.e. Nitenpyram (Jasper 10% SL) and Pyriproxyfen (Bruce 10.8% EC) and two botanical extracts of Calotropic procera and Azadirachta indica, against sucking insect pest complex of cotton and their natural enemies. Upon reaching economic thresholds, the recommended field doses of all the insecticides were applied on cotton cultivar MNH-886. Data against sucking pests and their natural enemies was recorded 24 hours prior to insecticidal application and then 24, 48, 72 and 96 hours after insecticidal application. Results revealed that Nitenpyram was much toxic against sucking pests followed by Pyriproxyfen as compared to two botanical extracts. On the other hand, the synthetic insecticides did not prove safer for natural enemies as compared to botanical extracts. It was concluded that as an Integrated Pest Management (IPM) strategy, botanical extracts can be used at low infestation levels so that ecosystem service of biological control may be sustained.

The ultra-violet photolysis of DDT and the pyrethrins was investigated with selected wavebands in the middle and near ultra-violet. Severe decomposition is caused by light strongly absorbed by both insecticides at zroo-zqoo A. DDT is not affected by other parts of the spectrum, but the pyrethrins are slowly decomposed by radiation between 2400 A and the visible region. probably by a light-catalysed oxidation rather than direct photolysis. DDT, like the pyrethrins, undergoes rapid photolysis in strong sunlight, suggesting that traces of light of the waveband 2200--2qoo A may penetrate to the earth's surface.

Both p, p′DDT and a sample of commerical DDT have been compared with γ BHC as insecticides acting in the vapour phase. Both the direct fumigant action of the insecticides and the toxicity of the vapours sorbed on to stored products have been examined. After storage in atmosphere saturated with the vapours for six months, wheat retained sufficient of all three insecticides to control adults of Calandra graria (L.) and inhibit the develpment of larval Sitotroga ceraalella (Ol.). This control and inhibition was complete for BHC, and stronger for commercial than for p, p′DDT. Similar results were obtained when the insecticides sorbed on flour were tested using the eggs or larvae of Tribolium confusum Duv., or when fumigated groundnut kernels were tested against T. confusum, but such groundnut produced little toxic action against Oryzaephilus surinamensis (L.).

Mercury is not a new addition to the list of preservatives for stored grain. It has insecticidal properties that are well known to the peasants who insert a drop of mercury in an excavated soap-nut {Sapindus detergens) or cowdung ball which is then placed in the stored grain to protect it against the ravages of insect pests. This method of application was considered dangerous, in the case of grain meant for consumption, because the cowdung balls are porous and with a slight jerk mercury droplets get mixed with the grain. A little mishandling in the case of soap-nuts also causes the mercury to escape into the grain heap, thus affecting the health of the consumer adversely. These facts were first recorded by Kunhi Kannan (1920) who initiated the study of the insecticidal properties of mercury on scientific lines by experimenting with Bruchid beetles and silkworms and found that the eggs of these insects, when exposed to mercury vapour, did not hatch but turned black. Larson in the United States (1922) tested mercury vapour against Bruchus quadrimaculatus, F., a pest of cowpeas, and confirmed these observations. Dutt and Puri (1929) carried out investigations at Pusa and recommended the use of mercury in the form of mercury-tin amalgam because it was easy to handle and its vapour pressure being low did not render the grain unfit for seed purposes or human consumption (60 maunds* of grains treated in this manner were used by a family without any untoward effect). The amalgam was prepared by rubbing together 2 parts of tin and 3 parts of mercury into a homogenous mass of paste-like consistency. This mass was then squeezed through a piece of linen, thus removing the free droplets of mercury and eliminating the possibility of mercury becoming mixed with the grain. The amalgam was flattened to expose a greater effective surface and half an ounce was sufficient to keep 14 seers* of wheat free from the attack of Sitophilus oryzae, L. Rahman (1942) recommended mercury at the rate of 3-4 tolas* per maund of wheat. He suggested that mercury carried in twill or long-cloth bags measuring 2x2 ins. at the rate of 1 tola of mercury per bag, should be distributed evenly in layers throughout the bin, with a depth of 8 to 12 ins. of wheat between two successive layers. These bags come out easily when the grain is removed through the exit hole and he was of the opinion that this type of application had no deleterious effect on the germination of the seed or its eating quality. The author on the other hand feels that bags are not safe to use because a little mishandling will cause the mercury to escape and render the grain unsafe for consumption.The Government Entomologist, Punjab, in his Annual Report for the year 1938-39 stated that the use of mercury in bins to control Khapra, Trogoderma granarium, Everts, completely checked the attack when it was uniformly distributed in the grain, but, if only the top and bottom portions were treated, the attack continued although at a slower rate than in the control bins. In view of these differe...