Scientific name: Gryllotalpa orientalis (= africana) Burmeister

Common name: Mole cricket

The oriental mole cricket Gryllotalpa orientalis Burmeister   Dying young plants caused by feeding of mole crickets   Older plants that have been fed-upon by mole crickets   Oriental mole cricket

Taxonomy:

Economic importance

Mole crickets are polyphagous. They feed on the underground parts of almost all upland crops. They occasionally cause heavy damage to the roots and basal parts of rice plants growing in raised nursery beds or upland conditions. In wetland rice, infestation occurs when there is no standing water. No recorded outbreak of this pest is known.

Geographical distribution

Afghanistan, Australia, Bangladesh, Bhutan, Cambodia, India, Indonesia, Japan, Lao PDR, Malaysia, Myanmar, Nepal, Pakistan, Papua New Guinea Philippines, Thailand, and Vietnam.

Morphology

Egg
The egg is oblong to oval and gray with a shiny surface. It is 2.6 mm long and 1.7 mm broad. The eggs are deposited in a hole constructed by the adult female.

Nymph
The newly hatched nymph has a white and bluish prothorax and legs. The nymph later turns gray to black with white markings. The last nymphal stage is similar to the adult except for its short wing pads.

Adult
The adult mole cricket is brownish and very plump, measuring 25-40 mm long. It has short antennae. The enlarged front legs are modified for digging.

Symptoms

Feeding on seeds and roots results in loss of plant stand in upland rice. In older plants, tillers are also fed upon.

Biology and ecology

The eggs are laid in hardened cells constructed in the soil by the females. One cell usually contains 30-50 eggs. Egg incubation varies from 15 to 40 days. The hatching nymphs feed on roots and damage the crops in patches. The nymphs have limited migrating ability and generally suffer heavy mortality. Nymphal development takes 3-4 months. The insect has only one generation per year in the temperate region.

In flooded rice fields, mole crickets are usually seen swimming on the water. Their low population density is due to cannibalism.

Host range

The host range of G. orientalis includes the following: Allium cepa L. (onion), Brassica oleraceae L. (cabbage), Camellia sinensis (L.) O. Ktze. (tea), Helianthus annuus L. (sunflower), Hordeum sp. (barley), Nicotiana tabacum L. (tobacco), Oryza sativa L. (rice), Solanum tuberosum L. (white potato), and Triticum aestivum L. em. Thell. (wheat).

Detection and inspection

The rice field can be checked for damage symptoms by using a light trap. Cut seedlings are indicative of the insect’s feeding damage.

Management

Cultural control
Standing water can help eliminate the eggs of mole crickets on the soil. In infested areas, the rice field can be flooded for 3-4 days. Construction of a raised nursery should be avoided to reduce feeding damage on seedlings.

Biological control
Natural enemies include Chlaenius sp., Labidura sp., Larra amplipennis Smith, L. luzonensis (Rohwer), L. sanguinea Williams, Liris aurulenta (Fabricius), Motes manilae (Ashmead), M. subtessellatus (Smith), M. loboriosus (Smith), and Pheropsophus jessoensis Morawitz. Beauveria bassiana (Balsamo) Vuillemin is also recorded as an important pathogen. A mermithid, Mermis nigrescens (Dujardin), is a potential agent against this insect.

Selected references

Hahn HE. 1958. Investigation on the habits and development of Gryllotalpa africana in Braudenberg. Berr. Entomol. 8:334-365.

Pathak MD, Khan ZR. 1994. Insect pests of rice. Manila (Philippines): International Rice Research Institute. 89 p.

Reissig WH, Heinrichs EA, Litsinger JA, Moody K, Fiedler L, Mew TW, Barrion AT. 1986. Illustrated guide to integrated pest management in rice in tropical Asia. Manila (Philippines): International Rice Research Institute. 411 p.

Shepard BM, Barrion AT, Litsinger JA. 1995. Rice-feeding insects of tropical Asia. Manila (Philippines): International Rice Research Institute. 228 p.