EFFECTIVE MANAGEMENT OF DIAMOND BACKED MOTHS [DBM] LARVAE ON CAULIFLOWER, CABBAGE AND OTHER CRUCIFERS
Damage potential of DBM : Diamond back moth insect is resistant to many classes of insecticides and causes 50 to 80% loss in marketable yield among all crucifers. Larvae develop much faster (8.5 days) and pupate on cauliflower. Pupal period is shorter and adult emergence is more on cauliflower.
Stages of Diamond Backed Moth [DBM]
- The eggs of DBM are whitish yellow, very small and 0.5 mm long and each gravid female can lay up to 164 eggs under field conditions.
- Eggs are usually laid in groups on the upper surface of leaves near veins and occasionally on back side of the leaves.
- Egg period is in between two and six days.
- Neonates will be dull white with light brown head.
- Fully grown caterpillars will be light green in colour measuring about 10 mm in length.
- The larvae are actively feed for 14 and 21 days before pupation.
- The larval stage is about 4 instars, larve upto first moult live in mines formed on leaves. Other instars the larvae feed externally and have four larval instars.
- White conspicuous gonads present on dorsum of fifth abdominal segment of last instar male larvae are distinguished from the female.
- Larvae pupates in silken cocoon loosely spun by the caterpillar appears near the midrib on the upper surface of the l
- Pupa is light brown in color about 6 mm long.
- Pupal period for four days in hot and rainy season and five days in cold climates.
- Moths are greyish coloured with a wing spraed of 14 mm.
- The wing of male moths is up folded outward and towards their tips forming a row of three diamond-shaped yellow spots at the middle of the back.
- Adult longevity ranges from 6-13 days, females live shorter than males.
- 1:2 ratio of males to females.
- Mating of adults begin to at dusk on the same day of emergence; lasts one to two hours and females mate only once.
- Females start laying eggs after mating and continues for 10 days with a peak on the first day of emergence.
Chemical Control of Diamond back Moth
Protection measures to control the larvae need to be taken extra are since the vegetative coverage supports to get inside the leaves making larvae to escape. All the stages of DBM need to be considered for effective control. Mixtures of chemical insecticides, or chemicals and microbials, are often recommended for diamondback moth control. Compulsarily the wetting or spreading agents need to be added in to the insecticidal spray.
Plethora 2 mL/L + Spraywell 1 mL/L
OR Coragen 0.33 mL/L + Neemark 1 % - 1 mL/L
OR Tracer 0.375 mL/L + Nuvan 1 mL/L + Spraywell 1 mL/L
Other things to be considered for effective control of DBM on Crucifers
- Grow two rows of mustard after every 25 rows of cauliflower/ cabbage as a trap crop at the time of planting. This traps 80-90% of DBM population and other pests. One row of mustard is sown 15 days before cabbage planting and the second row 25 days after planting of cabbage. The first and last rows of plots are also mustard.
- Mustard is sprayed with Nuvan 2 mL/L as soon as it germinates.
- Installation of light traps for adult DBM @ 3 traps/acre.
- Spraying with Bacillus thuringiensis 1g/lit at 56 Days after planting (ETL 2 larvae/plant) and repeating it at 10-15 days.
K SANJEEVA REDDY,
Senior Agronomist, BigHaat.
Disclaimer: The performance of the product (s) is subject to usage as per manufacturer guidelines. Read enclosed leaflet of the product(s) carefully before use. The use of this product(s)/ information is at the discretion of user.