The mole cricket is a fascinating-looking insect that can be very harmful to plants grown in gardens and vegetable gardens. Often, when we find cleanly cut plants, this insect is to blame. The difficulty in biological defense is mainly due to the fact that the insect acts underground, thus managing to protect itself very well.
In this article, we will look at how to combat the mole cricket, how to recognize it, and its life cycle. We will also learn about the problems it causes to crops, how to carry out agronomic prevention, and biological defense.
The mole cricket (Gryllotalpa gryllotalpa) is an insect of the Orthoptera order, belonging to the Grillotalpidae family. Being a very polyphagous insect, meaning it can feed on many plant species and small insects, it is very common. Today it is found throughout continental Europe. It is an alien species to our ecosystem, and it is presumed to have been mistakenly imported from the USA.
How to recognize the mole cricket
This insect has a very particular appearance, so it’s not hard to recognize:
- Adults are up to 6 cm long, with a brown-blackish coloration.
- The front part is characterized by a prominent prothorax, where the robust, toothed digging legs stand out. With its strong legs, the mole cricket can dig deep tunnels in the ground.
- The Gryllotalpa gryllotalpa can fly when necessary. It indeed has both front and back wings.
- Male specimens also have so-called stridulating organs, capable of rubbing together and emitting sounds.
The damages of the mole cricket
The damage that the mole cricket does to plants is mostly due to digging deep tunnels. This insect, in fact, cleanly cuts off all the roots of the plants it encounters while searching for small insects. As mentioned, it also feeds on plant parts, but it’s the underground movement activity that causes the most damage. The presence of this insect is very common in gardens and vegetable gardens, as it encounters loose soils, moist and deep, thus easier to explore. In addition to vegetable crops, ornamental plants also suffer significant damage. Among these, bulbous plants like tulips and daffodils are particularly affected.
The mole cricket has a very long life cycle, spanning almost three solar years. It overwinters in the juvenile stage by digging deep into the ground, up to over 1 meter. In the spring, adult insects appear, which begin mating and egg-laying activities. Its burrow is called an ootheca, created 10-20 cm deep. These burrows are also visible from the outside, as they leave a small hole and stir up the soil that remains raised. In each burrow, female mole crickets can lay up to 400 eggs.
The nymphs hatch about 3 weeks after egg-laying, so at the beginning of summer. Initially, the mother feeds them; after a few days, they move away and start digging independently, searching for insects and plant parts. Thus, summer is the period when the Gryllotalpa gryllotalpa causes the most damage. The nymphs do not emerge from the ground but grow by taking refuge in burrows until the second molt that occurs in the fall. After molting, they overwinter deep in the ground. These nymphs become adults the following summer (2nd solar year). Sexual maturity, however, is reached in the spring of the 3rd solar year, thus completing only one generation in two years. Given their long cycle, different life stages of the insect can be found in the soil.
How to eliminate the mole cricket
The fight against the mole cricket is mostly carried out with soil work. The level of infestation must be assessed, and if necessary, deep plowing should be done. A winter plowing at 80-100 cm depth eliminates overwintering insects. In the spring, on the other hand, you can act by eliminating the more superficial burrows, the oothecae, which as mentioned are visible from the outside. If they can be identified, it’s easy to eliminate the eggs and thus prevent the proliferation of different generations. With a good spade, you can intervene by turning the soil. It would be good to carry out these soil probing operations before starting the organic garden in summer, with the planting of new seedlings.
Biological remedies against the Gryllotalpa gryllotalpa
- One of the remedies for the mole cricket is the presence in the garden of its natural enemies. Many birds, for example, are fond of it, but also hedgehogs and moles. Promoting an ecosystem rich in biodiversity is therefore an excellent way to naturally remedy the damages of this insect.
- Another small trick to eliminate the mole cricket is to set up homemade traps. This involves burying glass pots level with the ground; here, the insect gets trapped, unable to climb the walls. This technique is applicable, obviously, only in small gardens and vegetable gardens.
- Lastly, if you don’t want to eliminate the overwintering forms of the mole cricket by deep plowing, you can spread horse manure on the surface. The manure greatly attracts this insect, which will then be induced to emerge, exposing itself to capture.
Eliminate the mole cricket with entomopathogenic nematodes and other microorganisms
There are products allowed in organic farming with which it is possible to carry out treatments to eliminate the mole cricket. Very effective is the azadirachtin, the active ingredient of neem oil. The limitation to its use is due to the difficulty of reaching the insect by contact deep in the ground. For this reason, the use of entomopathogenic nematodes like these is more valid, which we already learned about when discussing the vine weevil. Nematodes are obligatory parasites of larvae, so they are effective only on larval stages and not on adults. They are tiny microorganisms and, when released into the soil, search for the Gryllotalpa gryllotalpa larvae. Another microorganism usable in the biological defense against the mole cricket is the beauveria bassiana. This entomopathogenic fungus can be found here.
- JSTOR, Journal of Orthoptera Research – A new species of pygmy mole cricket – “In this paper, the pygmy mole cricket Ellipes deyrupi sp. nov. is described from the northern Lake Wales Ridge of Florida”.
- JSTOR, The Florida Entomologist – Mole Cricket Phonotaxis: Effects of Intensity of Synthetic Calling Song – “Trapping flying mole crickets that land near electronic renditions of mole cricket songs is an effective means of monitoring flight”.
- JSTOR, Florida Entomological Society – Phonotaxis in Mole Crickets: Its Reproductive Significance – “The southern mole cricket, Scapteriscus acletus, is known throughout the Southeast as an important agricultural and turfgrass pest”.
- JSTOR, Florida Entomological Society – Mole Crickets and Pasture Grasses: Damage by Scapteriscus vicinus – “Two species of mole crickets are believed to be major pests of pasture grasses in Florida”.