Cabbage Integrated Pest Management : An Ecological Guide.

Major Natural Enemies of Cabbage Insect PestsEffectivenessInsect-attacking nematodes are best suited for use against pest insects that spend some or most oftheir life cycle in the soil or in moist, protected places (like inside shoots and fruits). However, nematodesare often not effective against insects feeding on open foliage because they quickly lose effectiveness indry conditions. Nematodes can travel in the soil over considerable distances and actively seek their preyif temperature and humidity are correct.As with most biological control agents, to use insect-pathogenic nematodes effectively, it is also necessaryto understand the life-cycle of the pest insect to ensure that the most susceptible life stage is targeted.Many vegetable insect pests are susceptible to attack by nematodes but for many, the potential ofnematodes for field control still needs to be evaluated.Nematodes can be cultured in living hosts and in artificial media with little chance for contamination.Several species of nematodes are now commercially available. See “The Biopesticide Manual” andinternet sites such as www25 and www29 (chapter 12, Reference list).soil particlesNematodemovementthrough soilnematode movement through soilNematode solutions, when obtained from elsewhere, can be stored in the refrigerator for a short time afterarrival because the nematodes are in a dormant state. Before applying the nematodes, this dormancymust be broken by stirring them in room temperature (over 18 o C) water to provide oxygen. After dormancyis broken, they must be used immediately. They prefer a moist soil and are damaged by light and soshould be applied in the evening. Beneficial nematodes move faster in sandy soil than clay.ConservationGuidelines for conserving native entomopathogenic nematodes have not been well documented. In general,nematodes (both when indigenous and when applied as a spray) need protection from the drying radiationof the sun and from extremes of temperature. Although they need a moist environment to stay alive andmove around, they can form a “resting stage” to survive adverse conditions.6.4 Other natural enemies6.4.1 BirdsThe value of wild birds as insect predators is clearlydemonstrated in many situations. In some areas in India,bird perches are placed in vegetable fields to provide a restingplace where birds can lookout for food like caterpillars!Farmers in various countries have been using chickens incotton plots to eat the cotton stainers and other bugs thatBirds: insect predatorsCabbage Ecological Guide - 2000134