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.

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.

The Epistle of Sālim Ibn Dhakwān Patricia Crone Fritz Zimmermann Oxford Oxford University Press 2001 407 Hardback£65.00 0–19–815265–5