i)
Agrotis segetum Schiff (black cut worm)
i)
Agrotis segetum Schiff (black cut worm)
ii) A. ipsilon (Hfn) (greasy cut worm)
iii) A. flammatra Schiff
iv) A. interacta Wlk.
v) A. spinnifera (Hb.)
Distribution: Cosmopolitan, present throughout world. In India cut worms are more serious in northern region than in south.
Host range: Polyphagous
Nature of damage and symptoms:
Caterpillars
are damaging.
Cut the seedling at ground level, drag the seedling into the soil. Some time replanting is required.
Cut worms usually do not eat plants beyond cutting through them, although some species climb stalks and feed on the upper parts of plants, which causes less damage.
After tuberization, they feed on tubers by making deep and irregular galleries in them, thus reducing the market value of infested tubers.
In badly infested fields, tuber damage may vary from 12-40 %.
Typical cutworm damage
Identification:
Eggs
are whitish, globular, 0.5 mm in diameter and ribbed
Caterpillars are smooth, stout, cylindrical, 40-50 mm long, blackish- brown dorsally and grayish green laterally with dark stripes.
They curl up into a tight C shape when disturbed.
Adults are dull colored moths with wing spreads of 1 to 1-3/4 inches. Hind wings are usually light in color.
Cut worm larvae in soil
Life cycle:
Moths appear soon after dusk, mate and lay eggs on ventral surface of leaves or moist soil.
Freshly ploughed fields are preferred for oviposition. Each female lays on an average 300-450 eggs in clusters of 30-50.
Incubation period is 2-13 days depending upon the weather conditions. Tiny caterpillars feed gregariously on foliage for a few days and then segregate and enter into the soil.
The caterpillars are nocturnal and feed at night. During the day these insects hide just beneath the soil close to the site of the previous night's damage (Fig 13). This pest is capable of damage sufficient to necessitate the replanting of potato. Total larval period is 10-30 days with five larval stages.
Pupate in soil and the pupal period is 10-30 days.
Total life cycle is completed in 30-68 days depending on the climatic conditions.
Figure: Life cycle of cutworms.
Management of cut worms:
Flooding of fields.
Cut worms either aestivate during summer months or hibernate during winters in the soil while completing their life cycles. Therefore, deep ploughing of potato fields during summer months in the plains exposes the immature stages to high temperature and predatory birds.
Hand
picking and destruction of early gregarious caterpillars.
Light traps installed in/around potato fields attract the adults of cut worms, and helps in mass collection and destruction of the moths.
Garlic as intercrop with potato was found to be effective in minimizing cut worm damage in potato crop at Shimla.
Natural enemies like Broscus punctatus Dist, Liogryllus bimaculatus Linn, Macrocentrus collaris Spin, Netelia ocellaris Thomson, Periscepsia carbonaria Panzer and Turanogonia chinensis Wiedemann parasitizes A. ipsilon and A. segetum and therefore should be conserved under natural field conditions.
Bacillus thuringiensis Berliner is a well-known biopesticide. Spraying the crop and ridges with this biopesticide (Bt @ 109 spores/ml) gives a good control.
Entomogenous fungus, Metarrhizium anisopliae Meld. is a best known fungal control of cut worm. Entomophilic nematode, Steinernema (Neoaplectana) sp. are also well known as dominant regulatory factors for cut worm populations from various parts of the country.
Use well rotten farm yard manure (FYM).
Soil application of Chlorpyriphos 20EC @ 2ml/lit of water at 2% plant damage.
Light trap