BSc Kim Xuan Loc

 Diamondback moth is a very dangerous worm that vegetable gardeners are very concerned about. Any vegetables, whether hard or soft stems, are damaged by diamondback moths (Plutella xylostella ). Especially vegetables such as kohlrabi, cabbage, leaf mustard, cauliflower, mustard greens, etc. are the vegetables most often damaged by diamondback moths

The diamondback moth has the scientific name Plutella xylostella linnaeus, belonging to the family Plutellidae and the order Lepidoptera.

MORPHOLOGICAL CHARACTERISTICS- BIOLOGY

The diamondback moth has a length of 06 - 07 mm, a wingspan of 14 - 15 mm. The forewings are brown, with a wavy band in the middle of the back, white on male moths and yellow on female moths, extending to the end of the wings. The two edges of the hind wings have very long hairy fringes. When landing ,the wings are folded along the body and upright above the body, the wing tail is slightly raised. The antenna at the head are from 3 to 3.5 mm long and always facing the front very flexibly. Each female can lay 50-200 eggs.

Flat and oval eggs,ivory white, 0.3 - 0.5 mm in diameter. Eggs are laid sporadically on the underside of leaves, near the main veins and hatch within 3 - 4 days.

The larvae are pale in color, the body is enlarged in the middle, the two ends are pointed, the body is divided into distinct segments. Larvae have 04 age levels, have a development time of about 11-15 days and if the temperature is low, it can be up to 18-20 days. The larvae are full of strength from 08 to 11 mm long and pupate right on the leaves of vegetables.

When newly pupated, the pupa is light green, about 2 days later it turns to light yellow, has a length of 05 - 07 mm and is covered with silk threads. The development time of pupae range from 5 to 10 days depending on temperature conditions. After coming out of the cocoon for 2 - 3 days, the moth lays eggs. Moth mates and lays eggs in the evening, during the day and hides on the undersides of leaves or in hidden places in vegetable fields.

HARMFUL CHARACTERISTICS:

Newly-hatched larvae crawl up the leaf surface to gnaw the epidermis forming small zigzag grooves. Larvae from the age of 02 begin to eat leaves, leaving the cuticle forming translucent marks. Adults eat the entire leaf cuticle causing holes in leaves, reducing yield and quality of vegetables. When the density of worms is high, the damaged vegetable garden is shriveled, leaving only the leaf veins. Worms often release silk to drop to the ground when being touched by other objects, so it is also called "parachute worm".

PREVENTIVE MEASURES

- After harvesting, it is necessary to clean up the remnants of the tree, remove it from the field, destroy it or compost it as fertilizer to destroy eggs, larvae etc..

- Use natural enemies, use pheromone traps to effectively kill diamondback moths in adult

- Rotating with crops that do not have the same host as rice, corn etc., should be intercropped with solanaceous plants such as eggplant, onion, garlic, etc. to scare away the adults from laying eggs.

- Vegetables should be watered with a sprinkler in the cool ate afternoon to prevent from mating of adults and wash away eggs and larvae.

- After a few crops of vegetables, a few other crops should be rotated.

- Before pulling the plant out for planting, it is recommended to spray a wave of product on the nursery or dip the seedlings in an insecticide solution to destroy the existing pests, pupae and eggs on the seedlings.

- Because diamondback moths do not usually fly high, it is possible to use a net of 02 m high can be used to surround them to prevent diamondback moths fly from the outside into the vegetable garden to lay eggs.

- Regularly check the fields, when seeing that the number of diamondback moths increases rapidly, it is necessary to spray insecticides in time.

- diamondback moths are resistant to products very quickly, so to reduce the pressure of resistance of them, farmers can alternately use products such as Saikumi 39.35SC, Sec Saigon 25EC, Sapen Alpha 5EC, Comda Gold 5WG etc .....

- Because the diamondback moths are active in the evening, we can spray SK Enspray 99EC mineral oil at this time to scare away the moths or damage the eggs.