Occurrence and integrated control of Chilo suppressalis

Since 1990s, eggplant has developed rapidly in Jingning County. At present, the planting area of the whole county has exceeded 1300 hectares, and the annual total output is more than 51,000 tons. At the same time, the yellow spot borer of eggplant showed a tendency of aggravation in this county, which affected the development of eggplant production. Therefore, the occurrence regularity and integrated control techniques of this pest were studied preliminarily.

1. Occurrence and damage characteristics

Eggplant yellow spot borer, also known as eggplant borer, is a lepidoptera moth family. The larvae bore and damaged eggplant buds, stamens, ovaries, tender stems, tender shoots and fruits, causing branches to wither, flowers to drop, fruits to drop, affecting yield. Although the damage to eggplant fruit in early summer is relatively light, the tender buds are seriously damaged, resulting in reduced production; in autumn, the eggplant fruit is eaten more often, and there are often 35 larvae in one eggplant fruit. The damaged surface of the eggplant fruit has holes, and the accumulation of insect dung in the fruit seriously affects the edible and commodity value. This insect often causes "ten eggplant nine borers", and the insect fruit rate is as high as 50%~85%. The insect fruit rate in general years is also 25%~35%.

The yellow spot borer has 4~5 generations a year in this county, and the generations overlap. The larvae damage period of early, middle and late maturing eggplant is generally from the middle of May to the end of October. The first generation mainly damages summer shoots and eggplant fruits from the middle of May to June. The larvae of the second, third and fourth generations are the most serious from July to September, especially the third generation damages Kandelia candel most severely in the middle and late August.

2 Habits of life

The yellow spot borer overwinters in this county as mature larvae in residual branches, withered leaves, weed rhizosphere and soil surface cracks. The overwintering larvae pupate in March of the following year and emerge from early May to early June. Adult nocturnal activity, phototaxis weak, with tender sex. The eggs are scattered on the back of tender leaves, flower buds, tender eggplant fruits and tender leaf stalks of the upper middle part of the eggplant plant (eggs: milky white at the beginning of production, gray black before hatching, shaped like dumplings, with 2~5 serrations on the ridge). The first-hatched larvae mostly eat flower buds, stamens, ovaries, heart leaves, tender shoots and tender leaf stalks directly at the bottom of egg shells, causing flower buds and ovaries to fall off (larvae: young larvae are yellow-white, most of them are pink when mature, each node has 6 black-brown hair spots and 2 tubercles, and the mature larvae are 15~18mm in length); the third-instar larvae eat fruits. After the fruits are damaged, holes appear on the surface of the fruits. The accumulation of insect dung in the fruits often causes decay, and the upper part of the tender shoots dies after being damaged. After the larvae are mature, they climb out of the damaged eggplant fruit and spin silk near the branches, rolled leaves, fruit stalks or the upper middle leaf edge of the eggplant plant to form pupae (pupa: light brown, 8~9mm in length, tough pupa cocoon, with two layers inside and outside, cocoon shape is long cylindrical, grayish brown, about 35mm in length, about 5mm in width, with ventilation opening at the bottom, yellow spot borer pupating in cocoon); they can also spin silk and fall to the ground, litter, weeds and soil cracks to form cocoons and pupate.

It can adapt to a wide range of temperatures, 17~35℃ can grow and develop, the optimal environmental temperature is 20~28℃, and the appropriate relative humidity is 80%~90%. According to observation, the whole generation duration of the 2nd ~ 4th generation is 32~51 days, including egg stage 5~7 days, larva stage 10 ~15 days, pupa stage 10~15 days and adult stage 7~12 days.

3 Reasons for serious problems in recent years

① Suitable climate in recent years, warmer winter, eggplant yellow spot borer winter favorable, winter survival rate is higher. May to September is the season of high temperature and humidity, suitable for the occurrence of yellow spot borer, is the peak period of the occurrence of the insect.

(2) Sufficient food The main hosts of the yellow spot borer are eggplant, solanum nigrum, potato, beans and other crops. The planting area is expanded, the early, middle and late maturing varieties are mixed obviously, the sowing and fruiting differences are large in different altitude areas, and the food is abundant, which is beneficial to its occurrence. The plants with irregular growth, shade and high humidity in the same field were more serious.

(3) Natural enemies decreased. The natural enemies of yellow spot borer were cocoon wasp, parasitoid wasp and birds. The parasitism rate of parasitoid wasps on larvae and pupae of yellow spot moth was more than 50%. However, unreasonable drug use often causes excessive killing of natural enemies and promotes the occurrence of yellow spot borer.

4 Integrated control techniques

① Strengthen field management to remove fallen flowers in time, prune tender shoots of damaged plants, remove damaged fruits in time, and take them out of the field for centralized deep burial or burning treatment to reduce insect sources.

(2) To trap and kill adults. In the large area of eggplant and bean vegetables, black light lamp and frequency-vibrating insecticidal lamp were set up from May to October to trap and kill adults.

(3) The pesticide control should be selected in the representative field, and the dynamics of the growth and decline of the yellow spot borer should be investigated regularly. Select high efficiency, low toxicity and low residue chemicals. 5% Regent 1000 times solution or 20% Ludefu 1500 times solution or 0.36% Matrine 1000 times solution or 15% DuPont 4000 times solution or 2.5% Caixi 1000 times solution or 48% Lesben 1500 times solution can be used alternately, and the safety interval of pesticides should be strictly controlled. When spraying medicine, it must be sprayed evenly on the buds, ovaries, leaf backs, leaves and stems of plants. The amount of liquid sprayed should be wet and dripping.