control of cockchafers, wireworms, grey grubs, mole crickets ants

Biological control of chafer and wireworm larvae

Wireworm larva

Some chafer larvae (called grubs) live in the soil and proliferate by gnawing on plant roots. The damage to crops can be considerable. These worms cut the crowns of lettuce plants, causing the plant to wither and no longer receive nutrition from its roots. These pests can be attacked in the larval stage by small worms causing death by septicaemia. The nematode Heterorhabditis bacteriophora is a small microscopic worm that is a natural parasite of chafer and otiorhynchid larvae (larval and adult plant weevils).

They can be obtained from certain websites, for example here.

Pour le taupin, on peut utiliser le nématode Steinernema feltiae disponible en cliquant ici. Il existe aussi des pièges à phéromone en vente dans des magasins de jardinerie ou sites internet, par ex en cliquant ici.

Castor oil cake combined with fern slurry is said to be effective against wireworms (15 kg to 20 kg of oil cake per 100 m2). This repellent test was developed by the GRAF (Groupe de Recherche en Agriculture Biologique). Caution: castor oil cake contains ricin, which is a violent poison for mammals (and therefore humans) and must be handled with care (gloves must be used)).

The larvae of the cockchafer and the wireworm are quite easy to find during a pseudo-tillage with a fork spade. Crumbling the soil with this tool will eventually reveal these pests. This is probably the most effective physical method for a home gardener with a small plot to get rid of these very destructive larvae.

Biological control of cutworms, cockroaches and crane flies

Cutworms are larvae of noctuid moths that live in the soil and emerge at night to gnaw on the roots and collars of plants. They are very active from August until late autumn.

The mole criket belongs to the same group as the grasshoppers (order Orthoptera). The mole criket digs superficial galleries on the soil surface. It is a predator of beetle larvae, wireworms, cutworms, ants and even slugs. The mole criket is therefore not a real bio-agressors, except that it cuts through the crowns of plants in search of its prey and disrupts their roots. The damage can be significant. It should be noted that one of the most formidable enemies of the mole criket is the cat, which also has the advantage of chasing moles out of their burrows. Where a cat takes over its territory, the life expectancy of mole criket and moles collapses.

crane fly are nematoceran diptera (flies) better known by the colloquial name of ‘cousins’. Their larvae gnaw on roots.

To reduce the pressure of these troublesome little beasts, the nematode Steinernema carpocapsae can be imported. Available by clicking here.

Biological control of ants.

Ants are one of the insects that are both useful and harmful. Ants feed on weed seeds and are excellent cleaners of cultivated areas. Each species exerts a different pressure in an ecosystem conditioned by multiple factors that are not yet all known (such as their regulation by their own predators). But they do not discriminate when it comes to seedlings. Thus, rows of radish, lettuce, carrot seeds, etc. can be destroyed even if the ant nest is located outside the cultivated area.

Ants also protect aphids to feed on their sweet excrements. Some small black ants have the particularity of invading houses by colonising tiny holes and cracks. Organic methods of controlling ants, such as the use of essential oils, are generally not very effective. Pyrethrins, on the other hand, are effective, but are rapidly degraded by microflora when spread on cultivated soil. Synthetic pyrethroids with a chemical formula similar to pyrethrins are more resistant

In France, there is a preparation containing pyrethroids on the market that is still available over the counter after 1 January 2019 for private individuals: “subito anti-fourmis”. The effect of the product for domestic use in the open air (or in a well-ventilated area) is immediate and lasts several weeks. It is preferable to use it as a powder on places frequented by ants. It can also be used as a spray. In low doses, and although not specified by the manufacturer, this product is repellent. To keep ants away, I use about 80g of powder around a 100m line containing a semi.

The manufacturer’s recommended dose of 500g for a 500m line will, in principle, eradicate all species of ants: black, red, yellow, pharaoh, Argentine, etc. I have often found that ants move their nest when it is treated with pyrethroids, even when following the manufacturer’s recommended eradication rate. It is then necessary to repeat the operation to definitively destroy a nest of ants located too close to a cultivated field or a house.

Caution; like natural pyrethrins, pyrethroids are toxic insecticides. Pyrethroids can irritate the respiratory tract and are highly toxic to aquatic organisms. Although ants do not frequent rivers, pyrethroids can enter an aquatic environment through rainwater runoff. Pyrethroids and their metabolites are destroyed by the soil microflora over a period of time that varies depending on the moisture and organic matter content of the soil.

Ants can also be eliminated by treating their nests with nematodes, which can be purchased here and here.