Spiders: Role in Pest Suppression and Future Directions

What is biological control?

Biological control involves the eradication or removal of weeds, insect pests, and pathogens in agroecosystems with the help of natural predators or parasites. It reduces the application of toxic chemicals to crops, which means fewer pesticide applications, minimal residues in produce, and safer food for humans.?Among the natural predators used in biological control, spiders play a key role as they are generalist predators.

Spiders Biology

Spiders belonging to the class Arachnida and their past fossils suggest that they were present on Earth approximately 380 million years ago. Spiders have 110 families, and 42751 described species. Its general body plan is divided into two parts, the cephalothorax and the abdomen. Breathing is made possible by the trachea and book lungs. This eight-leged tiny creature undergoes metamorphosis to grow in size and has a special gland that produces silk for many purposes. Antennae absent, with eight legs and six to eight eyes on the head. The female is larger in size than the male. Spiders vary in shape, size, and colour.

Spider as a Biological Control

Spiders are natural predators that act as biological predators in agroecosystems and are considered generalist predators as they can be found in litter and tree canopies, but they do not harm plants. Natural predators maintain balance among various organisms in ecosystems. The biological method of pest control helps to achieve the goal of “One Health” by reducing the negative impacts of chemical residues on soil, water, pollinators, natural enemies, plants, and humans; their abundance suppresses the population of insect pests. Approximately 10,000 species of insects act as pests to field crops, resulting in approximately 14 percent loss of crops and 20 percent loss of stored grains worldwide. Some Lepidopterans, Coleopterans, Dipterans, Hemipterans, and Orthopteran insects cause damage to leaves, fruits, and stems. Some mite species can also cause damage to field crops. Spiders also contribute to reducing vector abundance by eating adults and larvae of mosquito vectors. Some studies suggest that some species feed on whiteflies and thrips suppressing such pests. ?Common spiders found in agroecosystems are wolf, crab, jumping, funnel web, long-jawed, Sac, and Lynx spiders.

Future Perspective

Mass release of spiders can be a sustainable pest control program, but it should be made possible after considering ethical aspects such as chances of ecological imbalance and possibility of a negative impact on non-targeted species such as pollinators. Spider species that do not exhibit cannibalistic behaviour can be a potential biological way to reduce insect pests, such as tomato leaf miners and fruit flies.