Insects might soon be trained to protect crops

One of the biggest contemporary challenges for humanity is to safeguard food security for current and future generations. A growing demand and a steady increase of the world population—nearly 10 billion people are expected to inhabit Earth by 2050—requires that food production per area of cultivated land will have to increase drastically. Expanding into land that is currently uncultivated is not feasible, especially considering the pressures of climate change.

 

One way to achieve higher yields will be reducing crop losses caused by pests, including insects. For instance, in cereal crops such as rice and maize, which are staple foods for a large part of the world's population, insects result in up to 15% losses.

 

Spraying chemical insecticides remains the main approach to combating insect attacks in many crops. But their future use is under scrutiny because of many concerns, not least their effects on human health. Their use also represents a large economic burden on growers, especially those in developing countries. And in any case, it is feared that insects will soon develop resistance to insecticides.

 

Curtailing their use would also be good for the planet, as insecticides are inherently unsustainable: their continuous use has resulted in massive environment pollution, which negatively affect other beneficial organisms such as bees, birds, fishes and livestock. This means that there is increasing consumer demand for residue-free food. Linked to this, the availability of insecticides for insect management is declining globally due to considerable changes in their legislation.

 

So there is an urgent need to find alternatives—preferably environmentally friendly strategies for protecting crops against insects.

 

 

Biological control, in which insect populations are reduced by using other insects (their natural enemies) is generally accepted as a sustainable and ecologically sound approach to reduce crop losses by insects.

 

These natural enemies are often highly specialized and only attack a certain number of closely related insect pests, reducing the likelihood of unforeseen knock-on effects on the rest of the local ecosystem that are commonly caused by insecticides. Natural enemies can also be introduced to control new invading insect pests. For example, European natural enemies were introduced in North America to control a new infestation of bark beetles, which carry and spread Dutch elm disease.

 

Natural enemies of insect pests include predators, pathogens (micro-organisms that include bacteria, fungi, and viruses), and parasitoids (mostly wasps or flies which lay their eggs on or in other insect, eventually killing them as the larvae grow). Parasitoids are the most effective of these three types because their numbers increase much faster than those of the predators. In addition, they are highly specialized, as they are only able to lay their eggs in a specific species and therefore have minimal effects on the rest of the ecosystem.

 

Parasitoids are very diverse and constitute of a staggering number of insect species (nearly 14% of all described insects). Many species are currently mass-reared in commercial insectaries to be released in big numbers to obtain immediate control of the pests attacking orchards or greenhouses. But their effectiveness needs to be improved. This not only demands increasing their numbers in the fields, but also enhancing their foraging success.