‘We can make powerful nature-inspired ‘pesticides’ sans poison’

ISLAMABAD: While no one enjoys seeing carefully nurtured crops destroyed by hordes of hungry insects, the most common way to prevent it – the use of insecticides – is causing massive ecological problems.

Some are wreaking havoc on bee populations globally, killing birds and piling onto the challenges already faced by endangered species. Thankfully, insecticides are generally only in our food at low levels, but they do harm humans who are highly exposed to them too, like the workers growing our crops. They also destroy predatory insect populations, which just makes the problem of crop pests worse in the long term - with fewer pest enemies around to keep their numbers in check, reported international media.

One alternative that researchers and farmers have been putting to the test is the use of predatory insects to control the problematic plant eaters. However, this approach, known as biological control, has its own challenges.

The predators are also very reliant on environmental conditions – temperature and day length can alter their behaviour so they may only be effective during certain seasons. This, along with the fact that some pests are invasive and have no native predators means some pesticides may still need to be used, which can then also impact the predators.

In a series of trials the researchers let collard-snacking aphids (Myzus persicae) choose between the scent of leaves with predatory ladybugs (Harmonia axyridis) on them or the smell of leaves with no ladybug. They found exposure to the ladybug scent impacted the aphids' plant choices and even reduced their reproductive rate.