Mole cricket

Identification

A large (3-5 cm) brown insect with massive, shovel-shaped front legs adapted for digging and resembling the paws of a mole. It lives underground and is active mainly at night, producing a characteristic chirping sound. Symptoms: as it tunnels shallow galleries just below the soil surface, it gnaws roots, tubers and the root collars of transplants and vegetables, which suddenly wilt and die. It also damages turf roots, leaving loosened, raised tracks across the lawn. The mole cricket is an orthopteran of the family Gryllotalpidae, a close relative of the crickets and one of the largest native orthopterans. Its body is covered in dense, velvety hairs; the short, leathery wing covers expose well-developed hind wings, thanks to which, on warm, windless nights - especially during the mating season - the insect is able to fly. The churring song is produced by the males, rubbing their wing covers together, and the funnel-shaped entrance to the burrow amplifies it further. The mole cricket prefers moist, humus-rich, light soils, often near water, compost heaps and manure piles, and is active from spring to autumn. Its life cycle is long: the mole cricket undergoes incomplete metamorphosis, so its juvenile stages are nymphs (also commonly called larvae) - the insect overwinters deep in the soil as a nymph or an adult, and in late spring (May-June) the female chews out a spherical brood chamber at a depth of about 10-30 cm, lays 200-300 eggs in it and guards them for a while. The nymphs develop slowly - reaching adulthood usually takes a year, and in a cooler climate even two years. The mole cricket is omnivorous: besides roots and tubers it also eats earthworms and insect larvae in the soil, so it is partly predatory - yet for the gardener the most damaging aspect is the burrowing feeding itself, which severs roots and undermines freshly planted seedlings. A characteristic symptom is the sudden wilting of plants along a row, following the course of the subsurface gallery, together with mounds of loose soil and winding, raised tracks across the lawn resembling miniature molehills.

Treatment

Traps are effective: smooth jars or buckets sunk flush with the surface, into which the insect falls, and in spring small heaps of manure that lure the mole crickets to nest and are later removed together with their eggs and larvae. It is worth crushing any nests and egg clusters found, applying entomopathogenic nematodes, and cultivating the soil thoroughly, which destroys the galleries and breeding chambers. The foundation of ecological control is entomopathogenic nematodes (Steinernema carpocapsae) - they are introduced into moist, warmed soil (above about 12°C), where they actively seek out the pest, penetrate its body and infect it with lethal bacteria; they work best on younger developmental stages, and their effectiveness strongly depends on the moisture and temperature of the substrate. Trapping is worth supplementing with boards or slabs laid out over the beds - the mole crickets hide beneath them during the day and can be collected from there. A freshly detected burrow can be flooded generously with water (with a little vegetable oil on the surface), which drives the insect up to the top for manual removal - this is a supplementary method, labour-intensive and practical only with individual specimens. Digging over the soil in autumn and early spring additionally destroys the brood chambers, and it is worth encouraging natural enemies (birds, hedgehogs, ground beetles). Chemical control is of limited value: ready-made granular baits with a stomach action are spread in the galleries, but the insect lives underground and is partly beneficial (it eats soil-dwelling larvae), while sprays and contact dressings barely reach it - in home gardens chemicals are rarely justified. It should also be remembered that the mole cricket is declining in many regions of Europe and appears on red lists of endangered species (including in Germany), and locally is sometimes protected - so mass, retaliatory extermination is not advisable.

How to tell it apart from look-alikes

Control — organic and chemical methods

We give active-ingredient groups and modes of action, not brand names — specific products and their approval vary by country and are sometimes withdrawn. Always check and follow the current label.