Insect Pests of Vegetable, Ornamental and Spice Crops (2+1)

Polu beetle

1. Polu beetle, Longitarsus nigripennis (Chrysomelidae: Coleoptera)

Damage:

• Grubs bore and feed on the contents of tender berries making them hollow
• The external indication of infestation is the presence of dark, drying berries possessing characteristic circular hole in the midst of green healthy berries
• A single grub can destroy 3-4 berries
• The extent of damage caused by polu beetle goes up to 40 per cent in certain endemic areas

Identification

• Polu beetle is small, shining and brownish black flea beetle with stout legs
• Grubs are pale yellow

Life cycle

• The adult beetle lays eggs in small shallow depressions made on the rind of tender pepper berries
• A single grub can destroy 3-4 berries.
• Fully grown grubs drop to soil, construct oval shaped earthen cocoons and pupate in them
• Total life cycle of the pest is completed in 40-50 days
• There are four generation between July and January.
• Egg laying stops by December when pepper berries mature.
• Pest is active from July to Jan-Feb but the maximum population is during November
• The high yielding cultivars suffer more heavily
• TMB V and ‘Shimoga’ were particularly free from pollu beetle infestation.

Management:

• Cultural operations like raking of soil and regulation of shade by standards.
• Tilling the soil at the base of the vine at regular intervals
• Soil application of insecticides is also affective in controlling the grubs falling to ground for pupation.
• Spraying of vines with quinalphos (0.05%) twice a year during July and October control the pest effectively.

2. Top shoot borer, Cydia (Laspeyresia) hemidoxa (Eucosmidae: Lepidoptera)

Damage

• The caterpillars damage terminal shoots by boring into them
• Drying of terminal portions of the vines.

Salient features:

• Adults are yellow coloured moths
• The incidence is more during August to December, when tender shoots are available
• Pest takes about a month to complete its life cycle

Management

• Spraying vines with dimethoate or phosphamidon at 0.05% is effective
• Parasitoids like Apanteles sp. (Braconidae), Euderus sp. (Eulophidae) and Goniozus sp. (Bethylidae) have been reported to attack the caterpillars in nature

3. Gall forming thrips, Liothrips (Gynaikothrips) karnyi (Thripidae: Thysanoptera)

Salient features:

• It is a persistent pest in almost all the pepper growing areas of India
• The thrips make marginal galls on leaves within which they live in colonies
• Rasp and suck the sap
• Leaf tissue become thick
• Under server infestation whole leaf presents crinkled or mall formed appearance
• Proliferation of cells
• Leaves become brittle

Management

• Spraying of vines with malathion (0.1%) or dimethoate (0.05%) or quinalphos (0.54%) is effective
• An anthocorid bug and some predaceous mites have also been reported