Kaolin as a possible treatment against lepidopteran larvae and mites in organic fruit production

Summary

Few control methods are available in Norwegian organic fruit production that can prevent damage by early
and late larvae. Also phytophagous mites are difficult to control without harming the beneficial mites. Processed
kaolin function by coating trees and thus creating a physical barrier to infestation, impeding movement,
feeding and egg-laying. Kaolin may reduce feeding and movement of over-wintering tortricide larvae
and other larvae that hatch early in spring and have a repellent effect against egg-laying tortricide females in
summer. Kaolin may also have a control effect against mites as it clings to the body and reduce feeding. Trials
with kaolin were conducted in 2003, 2004 and 2005 in plum and apple orchards. Results show that kaolin
reduces the population of rust mite, however it also affected the number of beneficial mites. The effect
against early and late larvae was more variable. Treatments with kaolin resulted in a small reduction in early
larvae and damage in some fields and years, however no clear effect against late larvae was found. The effect
of kaolin will be discussed in relation to population size and number of treatments.