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

White grubs

2. White grubs

Family: Scarabaeidae, Order: Coleoptera
Important species under the family Scarabaeidae are given sub-family wise as under

Melolonthinae:

• Brahmina coriacea
• B. crinicollis
• B. flavoserica
• Melolontha indica
• Holotrichia longipennis
• H. repitita
• H. rustica
• H. serrata
• H. conferata
• H. excise
• H. torticollis
• Rutelinae:
• Anomala dimidiata
• A. polita
• A. rugosa
• A. rufiventris
• A. communis
• A. nathani
• Dynastinae:
• Xylotrupes gideon
• Phyllognathus dionysius

Distribution: Cosmopolitan in distribution

Host range: Polyphagous, damage almost all the vegetable crops, pulses, oilseeds, cereals, millets, potato, tobacco, sorghum, groundnut, maize, soybean, chillies, ornamental plants, forest nurseries, etc

Damage:

• Both grubs and adults are damaging.
• Grubs feed on underground plant parts of various crops.
• Potato grown during summer as rainfed is prone to attack by these grubs.
• Older second instar and third instar grubs are more damaging
• Due to concealed feeding white grubs generally remain unnoticed and at harvest a large number of tubers are found infested/damaged.
• Sometimes up to 80 per cent of the crop may be lost.
• White grubs are also found to feed on the roots of horticultural/ forest nurseries and some ornamental plants.
• White grubs are serious pests of turf grass too
• Adult beetles feed on the foliage of many trees

Identification

• Freshly laid eggs are creamy white which turns dirty white before hatching.
• Full grown larvae of Brahmina coriacea are 35-38 mm in length “C” shaped.
• Beetles are of different colours

Life cycle

• Incubation period is 7-12 days.
• There are three larval instars.
• The duration of respective instars is about 20, 30 and 75 day.
• Total larval duration is about 125 days.
• Pupal period ranges from 12-20 days.
• Adult longevity ranges between 15 and 145 days.
• There is only one generation in a year

Salient features

• Beetles emerge during monsoon
• Lay eggs in soil
• Eggs are laid singly in 2-7 installments.
• Each female lays 4-40 eggs in its life span.
• The pest passes winter as grub in earthen cells.
• Pupate in cells during April – May.

Management:

• Two to three deep ploughings immediately after harvest before potato planting.
• Collect grubs from soil while ploughing the field and kill them.
• Remove weeds from bunds and super fluous plants from the vicinity of potato fields.
• Seed potatoes should be planted little deep (8-10 cm) instead of normal depth (6 cm).
• Apply only well rotten FYM
• Collect/trap adult beetles during May-June at night and kill them
• Spray host trees with chlorpyriphos (0.04%) or quinalphos (0.1%) immediately after first monsoon shower.
• Application of phorate10G (25-30Kg/ha) or carbofuran 3G (80-100Kg/ha) near plant base at the time of earthing up or drenching of ridges with chlorpyriphos 20 EC @ 2.5L/ha is effective against these pests. Drenching can be repeated after 20-25 days.
• Potato crop should be harvested immediately after required maturity i.e. by September. Crop left beyond September suffers more

Other pests

• Hadda beetles: Discussed under egg plant
• Cutworms: Discussed under cole crops
• Tomato fruit borer: Discussed under tomato
• Aphids: Myzus persicae and Aphis gossypii
• Leaf hoppers, Amrasca biguttula biguttula
• Whitefly, Bemisia tabaci
• Phytophagous mites
• Green potato bug, Nezara viridula