When insecticides against herbivorous insects no longer work, we can always turn to spiders.
That is the lesson that emerges from recent research on new ways to combat the insect Tuta absoluta, a species popularly known as the tomato moth. This insect has developed resistance to many chemical insecticides. This is very worrying because Tuta absoluta devastates important agricultural crops, such as tomatoes and potatoes. Using more aggressive substances to combat it is not a solution because it endangers human health.
Climate change caused by humans is facilitating the spread of invasive species of herbivorous insects, such as the tomato moth, by expanding their geographical distribution zones thanks to the increase in the area with suitable environmental conditions for it.
The international team of Lena Grinsted, from the University of Portsmouth in the UK, has determined that it is feasible to use certain spiders to keep tomato moths at bay without polluting the environment or poisoning people.
Spiders of the species Cyrtophora citricola can live together without eating each other and spin large webs with which they hunt their prey.
In laboratory experiments, different types of prey, including tomato moths and ants, were introduced to spider colonies of various sizes. The researchers found that the larger spiders built larger webs and generally caught more prey, easily catching and eating tomato moths, while rarely catching the type of ants tested. That suggests they could wipe out tomato moth pests without causing serious disturbances to the local ecology.
Spiders of the species Cyrtophora citricola can make huge webs like this one. (Photo: Lena Grinsted)
Spiders that can form groups of hundreds, or even thousands, of interconnected webs can provide a large capturing surface, capable of intercepting in many cases the flight of insects. Spider colonies also provide a substrate for other spider species, further increasing the number of predators and thus potentially increasing the catching capacity of herbivorous insects within the colonies.
The study is titled “Group-Living Spider Cyrtophora citricola as a Potential Novel Biological Control Agent of the Tomato Pest Tuta absoluta”. And it has been published in the academic journal Insects. (Fountain: NCYT de Amazings)