Cabbage Integrated Pest Management : An Ecological Guide.

Ecology of Insect Pests and Natural EnemiesUsing botanicals is a normal practice under many traditional agricultural systems. A well-known andwidely used botanical is neem, which can control some insects in vegetables. In Vietnam, vegetablefarmers have utilized several botanical pesticides, including extracts from Derris roots, tobacco leavesand seeds of Milletia, which they claim to be effective.However, in addition to pest insects, some natural enemies may be killed by botanicals!A few commonly used botanicals will be briefly described below.Neem, derived from the neem tree (Azadiracta indica) of arid tropical regions,contains many active compounds that act as feeding deterrents and as growthregulators. The main active ingredient is azadiractin, which is said to be effectiveon 200 types of insects, mites and nematodes. These include caterpillars,thrips and whiteflies. It has low toxicity to mammals.Both seeds and leaves are used to extract the oil or juices. A neemsolution looses its effectiveness when exposed to direct sunlight and iseffective for only eight hours after preparation. It is most effective underhumid conditions or when the plants and insects are damp.High concentrations can cause burning of plant leaves! Also, naturalenemies such as Cotesia sp. can be negatively affected by neemapplications (Loke et al, 1992).Neem seed kernel extract: the recipeIn Ghana, Africa, neem seed kernel extract is used against insect pests on various vegetable crops.It has been tried on cabbage in a TOTs and FFSs and had a very good effect on diamondback moth(Plutella xylostella), probably due to the repelling action of neem.Here is their recipe:Pound or grind 30 g neem kernels (that is the seed of which the seed coat has been removed) andmix it in one liter of water. Leave that overnight. Next morning, strain or sieve it and use it immediatelyfor spraying. It should not be further diluted. Of course any neem preparation and spray applicationshould only be done after a previous AESA has shown the need for a neem application (pers. comm.Dr. J.Vos, 2000).Nicotine, derived from tobacco, is extremely toxic and fast acting on mostanimals, including livestock such as cows and chicken. It can kill people. Thenicotine of half a cigarette is enough to kill a full-grown man! In parts of WestAfrica, the tobacco plant is intercropped with maize because it is said to lowernumbers of borer insects on the maize. Nicotine kills insects by contact, and ifinhaled or eaten. The most common use is to control soft-bodied insects suchas aphids, mites and caterpillars.An additional danger of using tobacco leaf extract is that this extract may containa virus disease called Tobacco Mosaic Virus, or TMV. This virus disease affectsa wide range of plants, mainly solanaceous crops. When spraying tobaccoextract, chances are that you actually apply TMV!65 Cabbage Ecological Guide - 2000