Horsegram Insect Pests

Pod borer

Biology:

• Eggs: Development of egg lasts 4-21 days depending on weather conditions. Average fecundity is about 100-300, maximum 600 eggs.
• Larva: Coloration of larvae is variable, from dirty greenish-gray to reddish; body length 15- 22 mm and larval period is about 19-40 days depending upon weather conditions.
• Pupa: Pupa is brilliant, brown, fine punctured, to 7-10 mm in length; cocoon is thick, white, and usually covered with soil particles. Pupal period is about 12-18 days. Number of generations per year reaches three, though the third generation can be facultative. Overwinters as larva.
• Adults: Body length 8-11 mm, wingspan 19-27 mm. Wings longer than abdomen, folding as roof. Forewing is yellow- or greyish-brown with characteristic light stripe along fore edge, with orange spot on basal third, and with dark fringe. Hind wings are light gray, with dark venation and dark double line near fringe; the fringe is long and light in colour. Top of abdomen with a tuft of golden-yellow hairs. Life span of adult is 20 days.

Life cycle

Damage symptoms:

• Dropping of flowers and young pods
• As the larva develops within the pod, faeces accumulate causing soft, rotten patches on the pod.
• Seeds are either partially or entirely eaten, and considerable frass and silk are present.
• Older pods marked with a brown spot where a larvae has entered

Natural enemies of pod borer:

Parasitoids:

• Egg parasitoids: Trichogrammatoidea armigera,
• Larval Parasitoids: Bracon hebetor, Phanerotoma sp., Tetrastichus sp, Phanerotoma planifrons

Nematode

Biology:

• Most species of plant parasitic nematodes have a relatively simple life cycle consisting of the egg, four larval stages and the adult male and female.
• Development of the first stage larvae occurs within the egg where the first molt occurs. Second stage larvae hatch from eggs to find and infect plant roots or in some cases foliar tissues.
• Under suitable environmental conditions, the eggs hatch and new larvae emerge to complete the life cycle within 4 to 8 weeks depending on temperature.
• Nematode development is generally most rapid within an optimal soil temperature range of 70 to 80°F.

Life cycle:

Damage symptoms:

• Infected plants in patches in the field
• Formation of galls on host root system is the primary symptom
• Roots branch profusely starting from the gall tissue causing a ‘beard root’ symptom
• Infected roots become knobby and knotty
• In severely infected plants the root system is reduced and the rootlets are almost completely absent. The roots are seriously hampered in their function of uptake and transport of water and nutrients
• Plants wilt during the hot part of day, especially under dry conditions and are often stunted
• Nematode infection predisposes plants to fungal and bacterial root pathogens

Survival and Spread:

• Primary: Cysts and egg masses in infected plant debris and soil or collateral and other hosts like Solonaceous, Malvaceous and Leguminaceous plants act as sources of inoculums.
• Secondary: Autonomous second stage juveniles that may also be water dispersed.

Favourable conditions: Loamy light soils