Occurrence and control of sesame pod borer

Sesame pod borer is one of the main pests of sesame. Mainly harmful to sesame seeds. Generally occurs in Henan, Hubei, Anhui, Jiangxi and other major sesame producing areas, generally reduce production by 10% to 20%, serious up to 30%, resulting in a significant decline in the quality of sesame. In view of the occurrence, we should seriously study the occurrence law, do a good job in the screening of control agents, and discuss its prevention and control methods.

I. occurrence regularity

The sesame pod borer has 4 generations a year in Henan, with overlapping generations and overwintering with mature larvae. Adults appeared from late July to late November, and the peak period was in the first ten days of August. Adults have phototaxis, mostly rest in the back of sesame leaves or weeds during the day, lay eggs at night, and lay eggs scattered on sesame leaves, stems, flowers, capsules and tender shoots. The egg period is 6-7 days. The larvae have the habit of migration, feed on mesophyll and like to drill into the flower heart and capsule to do harm. The larval stage is about 15 days, and the mature larvae pupate with a thin gray cocoon in the rolled leaves, in the capsule or between the stem seams, and the pupal stage is about 7 days. It takes 3738 days to complete a generation.

Second, harmful symptoms

The larvae spin silk to wrap around the flowers and leaves, feed on the mesophyll, and often feed into the flower heart, tender stem and capsule, which can eat up the seeds, the capsule turns black and falls off, and the plant is withered and yellow.

III. Morphological characteristics

The adult of sesame pod borer is 7mm long and yellowish brown, with three inconspicuous chloasma near the front and two inconspicuous black spots on the hind wing. The egg is about 0.4 mm long, oblong, milky white at first and then yellowish to pink. The larva has a body length of 16 mm, a dark brown head and a green, yellowish green, grayish yellow and reddish brown body color. The pupa is about 10 mm long, grayish green to dark green-brown, and the ends of the beak and antennae are separated from the body. IV. Prevention and control methods

1. Agricultural prevention and control

Clear the ground, roadside, field weeds and litter. Rational rotation, flood and drought rotation should be carried out in areas where conditions permit. Intensive ploughing and raking to reduce the source of overwintering insects. Irrigation at seedling stage and flowering stage to improve soil moisture.

two。 Chemical control:

(1) fumigation: during the peak period of adults in early August, 4 kg of sawdust and wheat bran were mixed with 80% dichlorvos and 150 grams of dichlorvos, 40 piles per mu, stacked evenly under sesame trees, and the efficacy could be maintained for 8 days and 10 days.

(2) spraying: the peak hatching period of larvae is 7-10 days after the peak of adult, and the control effect of spraying is the best at this time. Kill 30ml EC with 2.5% enemy per mu, 20ml EC with 20% butyl EC, or 25ml EC with 50 fenitrothion EC, add 50kg of water, dilute and spray evenly.

(3) dusting: during the peak hatching period of larvae, 1.5% dimethoate powder, 2.5% trichlorfon powder and 2% borer pine powder were sprayed evenly with a powder sprayer.