Diatomaceous earth (DE) is almost pure amorphous silicon dioxide, made up of fossilised diatoms; it acts as an insecticide by absorption of epicuticular lipids and fatty acids, leading to desiccation in arthropods. Numerous DE formulations have been attempted for the management of stored-product pests with good results. DE is persistent in its action, poses few or no pest resistance problems, and it leaves no residue. The efficacy of DE is affected by factors such as: its provenance, temperature, humidity and characteristics of target pests and substrate. Application of DE at currently recommended doses causes changes in bulk density of the grain; however, the use of enhanced DE formulations provides control at much lower doses. Therefore, new formulations of DEs usually include other low toxicity insecticides.

Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) is a major pest of several economically important crops with worldwide distribution. Use of insecticides is the principal strategy for its management, which has subsequently led to insecticide resistance and control failures. Functional response of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) at larval and adult stages was evaluated in this study, using S. litura eggs as the prey at various temperatures varying between 15 and 35 °C. Based on logistic model findings, linear parameters of various predatory stages of H. axyridis at various temperatures were significantly negative, which indicate a type II functional response. The theoretical maximum number (T/T_h) of eggs consumed increased with increasing temperature across all predatory stages. According to the random predator equation, the coefficients of attack rate increased and that of handling time decreased as the temperature increased. The 4th instar and adult stages were superior candidates for biocontrol of the target prey, typically at higher temperatures. The maximum attack rate (0.546 ± 0.058 h⁻¹) and lowest handling time (0.189 ± 0.004 h) were exhibited by the females at 30 and 35 °C, respectively, whereas these parameters were inferior for early instars. These findings clearly depict that the 4th instar and adult predators are efficient egg consumers and can serve as potential suppressors of S. litura field populations. The limitations of the predictions formulated by functional response trials are also discussed.

Aphis pomi De Geer, the green apple aphid, is an economic pest of apple and other rosaceae throughout the world. In the present study, functional responses of the syrphids Episyrphus balteatus De Geer, Eristalis tenax (L.), Eristalis interruptus (Poda), and Sphaerophoria scripta (L.), to A. pomi were studied under laboratory conditions to determine their relative predatory potential. The second- and third-instar larvae of the predators were exposed to increasing densities of similar-sized A. pomi nymphs in Petri dishes. Ep. balteatus was found to possess the highest consumption rate followed by Er. tenax , Er. interruptus , and S. scripta . All predator species and stages exhibited a Type II functional response. The coefficients of attack rate and handling time showed an insignificant variation between species and preying stages, suggesting equal potential of the four syrphid species to regulate A. pomi colonies.