Cabbage Integrated Pest Management : An Ecological Guide.

Major Cabbage Insect Pests· Other parasitoidsSeveral other species of parasitoids have been recorded on DBM. These include the larval parasitoidMicroplites plutellae, which is common in North America, and Apanteles ippeus, which is widely distributedin eastern Australia (CABI Dossier Diadegma insulare).Other parasitoids can occur naturally in certain areas and may play a role in reducing damage from DBMinfestation when (broad-spectrum) insecticides are not intensively used. In general, their levels of parasitismare relatively low.· PathogensA number of pathogens are known to kill DBM. The most common ones are the fungi Entomophthorablunckii and Entomophthora radicans. Other DBM-pathogens are Paecilomyces fumosoroseus, andZoophthora radicans . DBM caterpillars can also be killed by a granulosis virus, and a nuclear polyhedrosisvirus (NPV). Except for Bt, there are restrictions on the effectiveness of these pathogens since they needspecific conditions (temperature, humidity) to be active (Ref. www12).Commercial preparations of Bacillus thuringiensis (Bt) can effectively control DBM caterpillars as well assome other caterpillars. It should be noted here that in some areas resistance to Bt has been found. UseBt only on the basis of careful field observations. Care should be taken that Bt is not used very frequently,and that different brands are rotated. Bt kills DBM larvae slow: only after about 3 days. However, affectedlarvae stop feeding on the crop after a while. Thus, although alive, they do not damage the crop anymore.See also section 6.3.1 on Bt.· PredatorsPredators may also play a role in the control of DBM. For example, spiders,lady beetles, lacewings (Chrysopa sp.) and some beetles are reported toattack DBM. These predators tend to build up only in the later part of thecropping season. Efficiency of predators varies greatly between sites.Management and control practicesPrevention activities:· Although there seem to be differences in susceptibility to DBM attacks in different varieties ofcabbage, no resistant variety is known to date. Due to the many generations that DBM canproduce in a season, resistance may be broken down very quickly.· The adults can be monitored with pheromone traps. Pheromone-impregnated strips are also beingtested that disrupt diamondback mating.· It is preferable to plant cabbage in the rainy season when the population of DBM is deterred by therain.· Intercropping with tomato (or other crops not susceptible to DBM) may help reducing populationsof DBM. The idea of intercropping is that DBM adults will have more difficulty in finding cabbageplants when these are camouflaged between other crops. See section 3.10.1.Cabbage Ecological Guide - 200078