Are Cabbage Caterpillars Toxic? An Introduction to Their Natural Enemies, Occurrence Patterns and Control Methods

The cabbage white butterfly, also known as the cabbage white or white butterfly, has larvae also called cabbage caterpillars. It is the most widely distributed, most damaging and frequently outbreak-forming pest in China.So are cabbage caterpillars toxic? What are their natural enemies? What are the occurrence and control methods? According to Pieridae data, cabbage caterpillars are not toxic. They are fond of feeding on cruciferous plants, especially thick-leaved crops such as cabbage, cauliflower, Chinese cabbage and radish.

What are the natural enemies of cabbage caterpillars?

1. The currently known predatory natural enemies during the egg stage of the cabbage white butterfly include flower bugs, Paederus fuscipes (rove beetles) and Cyrtorhinus chinensis (plant bugs); predatory natural enemies during the larval and pupal stages include assassin bugs, wasps and spiders.

2. Seven species of spiders, including jumping spiders, Theridion octomaculatum and Erigonidium graminicolum, together with two predatory insect species, the multicolored Asian lady beetle and the tortoise-shell lady beetle, have considerable potential for controlling cabbage white butterfly eggs and larvae. In terms of numerical response, the natural enemy most closely associated with cabbage white butterfly eggs is the tortoise-shell lady beetle, and the natural enemy most closely associated with cabbage caterpillars is the Chinese jumping spider.

What are the occurrence and control methods of cabbage caterpillars?

Cabbage caterpillars belong to the Lepidoptera family Pieridae and are a frequently occurring pest of vegetable crops. The adults are called cabbage white butterflies, cabbage whites or white butterflies, and can reproduce 8—9 generations per year, with severe generation overlap. The adults are active by day and rest at night. The larvae can move between plants to cause damage and exhibit thanatosis (playing dead), with two peak outbreaks in April—June and August—September. Cabbage caterpillars prefer cruciferous vegetables, among which they favour cabbage, cauliflower, Chinese cabbage and radish; they can also damage other plants such as lettuce and amaranth. The temperature range suitable for their growth and development is 10-34°C, with an optimum temperature of 20-25°C and a relative humidity of 70%-90%. Strengthen monitoring of the occurrence dynamics of cabbage caterpillars in vegetables, release pest and disease forecasts in a timely manner, carry out classified guidance at the appropriate time, effectively control pest and disease damage, and ensure the safe production of vegetables.

In recent years, cabbage caterpillar damage has been severe, and resistance develops rapidly during chemical control, making cabbage caterpillar control difficult. The key points of its control are timely control and alternating pesticide use. The specific control methods are as follows:

1. Keep the field clean, and promptly dispose of residual plants, old leaves and weeds after harvest to reduce pest sources. Deep ploughing and fine harrowing reduce overwintering pest sources. Rotate with solanaceous vegetables and allium vegetables or grain crops to reduce the pest population base.

2. Rotate with solanaceous vegetables and allium vegetables or grain crops to reduce the pest population base.

3. Because generation overlap in cabbage caterpillars is severe, larvae after the 3rd instar feed more heavily and have increased pesticide tolerance. Therefore, pesticide application should be carried out before the 2nd instar, applied 2—3 times in succession. The following pesticides may be used: ① 2% Shudan insecticidal and acaricidal agent at 30——50 grams per mu, diluted in 50 kg of water, or 0.2% abamectin emulsifiable concentrate at 2500——3000 times for spray treatment. Both pesticides are biological insecticides with good efficacy, are unlikely to induce resistance, are pollution-free, and can be used continuously; ② 10% Jianmie emulsifiable concentrate at 5——10 ml per mu, 10% Chujin suspension concentrate at 10 ml per mu, 5% Kungfu cypermethrin emulsifiable concentrate and 5% Laifuling emulsifiable concentrate at 2000——3000 times, or other pyrethroid emulsifiable concentrates for spray treatment. During control, attention should be paid to seizing the appropriate control period, spraying at the peak egg stage in the field and the early larval hatching stage. According to the habits of cabbage caterpillars, spraying evenly on the front and back of plant leaves in the morning or evening can effectively control cabbage caterpillar damage.