Keeping cabbage caterpillars under control
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CTA. 1998. Keeping cabbage caterpillars under control. Spore 73. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/48976
Internet URL: http://spore.cta.int/images/stories/pdf/old/spore73.pdf
The green caterpillar of the Large Cabbage Worm Pieris rapae, with its narrow orange or yellow dorsal stripe, emerges from the soil for two to four weeks in order to feed on the leaves of many different species of cabbages. It then returns...
The green caterpillar of the Large Cabbage Worm Pieris rapae, with its narrow orange or yellow dorsal stripe, emerges from the soil for two to four weeks in order to feed on the leaves of many different species of cabbages. It then returns underground to reappear 15 days later as a white butterfly. An understanding of this life-cycle shows how the pest can be controlled without the use of chemicals. The first step is to practice crop rotation by alternating carrots or maize, for example, with cabbages. The caterpillars are then starved of their food source. By turning over the soil around the cabbage plants several times, both at the beginning and at the end of the season, the caterpillars are desiccated through exposure to air. If some escape they can be retrieved manually and destroyed. The butterflies can be controlled by using a sticky, yellow trap placed in the middle of the crop, or they can be discouraged by cultivating plants that have a strong and, to the butterflies, unpleasant, odour (onion, garlic, sage, mint, cinnamon). Other non-chemical means of control include the use of a garlic concoction made with crushed garlic cloves (five cloves to four litres of water) or by macerating neem seeds (two handfuls of crushed seed to ten litres of water over 12 hours) or even by scattering a mixture of one part salt to two parts flour on the plants after rain. The caterpillars gorge themselves on this mixture and become so bloated that they die. Another strong ally is a small wasp which lays its eggs among those of the Large Cabbage Worm and on which the young wasps feed. Wasps can be attracted by planting, for example, mint or parsley, but insecticides must be avoided because the wasps are particularly sensitive to them. However, with this array of weapons ranged against the pest, chemicals should be unnecessary. Daniel Eldridge DCFRN P O Box 12 Toronto CANADA M5G 2C2
SubjectsCROP PRODUCTION AND PROTECTION;
- CTA Spore (English)