Identification, symptoms and nature of damage: white grub, mole cricket and ants

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White grubs:

The adult beetles are dull brown, reddish or black in colour

The larvae are “C” Shaped, white in colour with brown head and prominent thoracic legs. The grubs are generally found in the upper 5 to 10 cm layer of the soil

Identification:

Video: grubs of scarab beetles

Source: AINP on White grubs, Department of Entomology, Assam Agricultural University, Jorhat-13

Video: Adult scarab beetles

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Symptoms:

The damage becomes evident only when the entire potato plants dry up due to the grubs feeding on fibrous roots

Fig. White grub infested potato plants

Source: AINP on White grubs, Department of Entomology, Assam Agricultural University, Jorhat-13

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Nature of Damage:

Initially young grubs feed on mother tuber, roots of developing potato

plants

After tuber formation, the older second instar and third instar grubs feed

on the under ground potato tubers by making large, shallow and circular

holes into them and thus rendering them unfit for marketing

They live concealed while feeding on tubers, and the plants continues

to grow normally without any reflection of injury on aerial parts

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Fig. White grub infested potato tubers

Source: AINP on White grubs, Department of Entomology, Assam Agricultural University, Jorhat-13

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Mole cricket:

Adults are cylindrical, nearly 2.5-3.8 cm long and dull brown. Mole crickets have front legs enlarged, shovel-like and modified for digging

They fly at night, can run quickly, but are poor jumpers.

Nymphs resemble adults but are smaller and do not have fully developed wings

Identification:

Fig. Mole CricketSource: AINP on White grubs, Department of Entomology,

Assam Agricultural University, Jorhat-13

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Symptoms:

Cutting of seedlings and tunnelling in the soil

Fig. Tunneling in fallow land by mole cricket Fig. Tunneling in field after sowing

Source: http://insects.tamu.edu/extension/publications/epubs/eee_00039.cfm

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Nature of Damage:

Mole crickets can damage potato plants by feeding at night on above ground foliage or stem tissue and below ground on roots and tubers

Seedlings may be girdled at the stems near the soil surface, though some plants may be completely severed and pulled into a tunnel to be eaten

Mole cricket tunneling in the upper 25 cm of the soil dislodges plants or causes them to dry out. Reduction of plant stand is common

Fig. Potato tubers infested by mole cricketSource: AINP on White grubs, Department of Entomology,

Assam Agricultural University, Jorhat-13

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Red ant:

The red ants are reddish in colour and measures 1-1.5 cm in size

Identification:

Fig. Red ant

Source: AINP on White grubs, Department of Entomology, Assam Agricultural University, Jorhat-13

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Symptoms:

Potato tubers show minute holes on the entire surface

Fig. Potato tuber infested by red ant

Source: AINP on White grubs, Department of Entomology, Assam Agricultural University, Jorhat-13

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Nature of Damage:

This ant attacks plant parts that are mostly underground

Red ants are serious phytophagous pest of potato making galleries in tubers and their attack is characterised by presence of minute holes on the surface of tubers

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