Authors: Gugulotu Laxman
Division of Entomology, ICAR-Indian Agricultural Research Institute, New Delhi-110012
Corresponding author: email@example.com
The diamondback moth (DBM), Plutella xylostella (Linnaeus) (Plutellidae: Lepidoptera), is the major destructive pest on cruciferous crops such as cauliflower, cabbage, and mustard, and causes significant economic losses to farmers . Most often growers depend on insecticides to control DBM which leads to development of resistance, residues problems and destruction of nontarget organisms.
Distribution : The diamondback moth is probably of European origin but is now found throughout the world. In India, DBM was reported in 1914 on cruciferous vegetables and is now the most devastating pest of cole crops in the states of Punjab, Haryana, Himachal Pradesh, Delhi, Uttar Pradesh, Bihar, Tamil Nadu, Maharashtra and Karnataka
Egg: Diamondback moth eggs are oval and flattened. Eggs are yellow or pale green in color. Female moths laid eggs soon after mating, and the oviposition period extended upto four days, during which the female laid about 11-188 eggs. The incubation period was 5-6 days under the control of temperatures
Larva: The diamondback moth has four instars. Average and range of development time is about 4.5, 4, 4 and 5 days, respectively. The larval body form tapers at both ends, and a pair of prolegs protrudes from the posterior end, forming a distinctive "V". There are five pairs of prolegs
Pupa: Pupation occurs in a loose silk cocoon, usually formed on the lower or outer leaves. In cauliflower and broccoli, pupation may occur in the florets. The duration of the pupal period varied from 4 to 15 days depending on the temperature
Adult: The adult is a small, slender, grayish-brown moth with pronounced antennae and marked with a broad cream or light brown band along the back. The band is sometimes constricted to form one or more light-colored diamonds on the back. Females deposit eggs for about 10 days.
Host Plants : Diamondback moth attacks only plants in the family Cruciferae. Virtually all cruciferous vegetable crops are eaten, including broccoli, Brussels sprouts, cabbage, Chinese cabbage, cauliflower, collard, kale, kohlrabi, mustard, radish, turnip, and watercress. Among these cabbage and cauliflower are the most preferred host plants. Several cruciferous weeds are important hosts, especially early in the season before cultivated crops are available.
Nature of damage : Initially, the first instar larvae act as leaf miner. The larvae emerge from their mines feed on the lower surface of the leaf. Their chewing results in irregular patches of damage, and the upper leaf epidermis is often left intact. The presence of larvae in florets can result in complete rejection of produce. Injury to leaves is not usually serious, except when the wrapper or cap leaves of cabbage are injured.
Symptoms of damage
- Holes on leaves
- Withered appearance of affected leaves
- Skeletonised leaves
- Stunted growth
- Installation of light traps for adult DBM @ 3 traps/acre.
- Check fields during the seedling stage, at thinning, and just before heading. Also, record diamondback larvae numbers when you make your twice-weekly samples for other caterpillar pests
- In cabbage fields, regularly monitor wrapper leaves for damage after heading
- Pheromone traps can be used to monitor adult populations
- Varieties with leaf wax is the major component of the resistance
- Glossy varieties, lacking the normal waxy bloom are somewhat resistant to DBM because larvae spend more time in searching rather than feeding.
- Removal and destruction of plant remnants, stubbles, debris after harvest and ploughing the field
- Adjusting the time of planting
- crop rotation of crucifers with cucurbits, beans, peas, tomato, and melons could suppress DBM population substantially
- Rainfall has been identified as a major mortality factor for young larvae, so it is not surprising that crucifer crops with overhead sprinkle irrigation tend to have fewer diamondback moth larvae
- Planting preferred host as trap crop. E.g: Surrounding cabbage crops with two or more rows of more preferred hosts such as collard and mustard can delay or prevent the dispersal of diamondback moth into cabbage crops.
- Tomatoes and onion intercropped with cabbage significantly reduces the DBM
- Release of egg parasitoid Trichogramma chilonis at 0.5 lakh/ha 3-4 times at weekly interval on 35 days after planting (DAP) after noticing the moth activity.
- Release of larval parasitoid, Cotesia plutellae @ 50,000/ha
- Ground beetles, true bugs, syrphid fly larvae, and spiders are the predators of DBM.
- Spary application of Bacillus thuringensis, granulosis virus and entomopathogenic fungi, Beauveria bassiana,Paecilomyces fumosoroseus and Metarhizium anisopliae will suppress the DBM
- Spray NSKE 5% for killing the eggs
Under severe infestation spray application of spinosad or dichorovos or fenvelrate or cypermethrin or deltamethrin will suppress the pest
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About Author / Additional Info:
Pursuing Ph D in Entomology in Indian Agricultural Research Institute