Researchers are asking farmers and growers with a wireworm problem to get in touch to help them develop new control methods.
Wireworms, or click beetle larvae, are a major pest of cereals and root vegetables, and seed treatments and other contact insecticides are traditionally used to protect crops from feeding damage.
However, these pesticides are being phased out in Europe, and it is doubtful if a new soil insecticide could ever become available for wireworm management.
Wireworm control
In response to this, Rothamsted Research’s Dr. Jozsef Vuts and Dr. Gareth Thomas are investigating alternative methods of control.
Dr Vuts said: “Plants are constantly releasing chemicals into the air or the soil, and pest species have evolved to tune into these as a way of finding food. We can use that to our advantage by creating traps that lure the wireworms by emitting these very same ‘smells’.
“These traps are non-toxic and provide an environmentally benign alternative for soil pest management.
“The main aim of our project is to develop wireworm management strategies based on attractive soil traps.”
It is anticipated that blends of these attractant chemicals, applied as slow-release formulations for instance, will help create pest monitoring and management systems for wireworms, circumventing the issues connected with insecticides.
Wireworms
This work also has great significance within the history of Rothamsted, as in 1919 some of the first papers from its then newly-formed Entomology Department were on the chemical control of wireworms.
Wireworms became a problem after World War I, as large areas of grassland were being dug up for potatoes – but back then the limited pest control options available to farmers included using arsenic or cyanide.
However, it is now hoped that the Rothamsted work will beneficially impact international plant and insect science by providing a better understanding of below ground ‘chemical ecology’.
Dr. Thomas explained:
“It will also create a model for controlling soil pests in general towards other more sustainable solutions – such as breeding of crop plants with chemical traits that either don’t attract, or even repel, pests.”
Young wireworms are initially white and about 1.5mm long. Young larvae need live vegetable material to survive and grow, and are likely to die of starvation within 30 days in the absence of food, as they are unable to survive on soil organic matter.
As they grow, their colour darkens to a shiny golden brown typical of all wireworms. They mature very slowly, passing through one to three instars each year.
Potato growers
According to Teagasc, if potatoes are to be sown in an infected field, growers should choose a variety that can be harvested in mid-August or earlier.
A recommended insecticide should be applied at planting with checks made on the progress of damage from mid-August onwards.
Growers should lift crops at the earliest opportunity, if damage is staring to occur.
The life cycle of most common wireworms takes three to four years under favourable conditions. Wireworms spend the winter in the soil either as partially grown larvae or as new adults in overwintering cells.
Adults work their way to the soil surface in the spring when soil temperatures rise. These adults eat little if anything, and cause no economic damage.