Are pesticides sprayed on desert locusts killing useful insects?

Bees, ladybugs, lacewings, dragonflies and earthworms at risk

On January 10, thick clouds of locusts blackened the skies of East Africa from Ethiopia and Somalia into Kenya.

Interestingly, the government attempted to rebel the ravaging insects using teargas and live bullets.

Many said it was unheard of and by all standards and an absurdity. This compelled the government to change tack, resorting to aerial spraying.

However, conservationists are worried the insecticides being used might have a devastating effect on other useful insects, such as bees and wildlife.

Bees, the lovely little ladybugs, green lacewings, beautifully daring dragonflies and squirmy old earthworms are some of the useful insects they are concerned about.

Each of these insects has a role to play in the ecosystem. Ladybugs eat pesky aphids, whiteflies and other insects that destroy plants. In fact, a ladybug can eat up to 5,000 aphids in its lifetime.

Lacewings are also great hunters of pests, such as aphids, thrips, mealybugs, small caterpillars, mites and whiteflies, eating them both as larvae and adults.

Dragonflies are like ladybugs in that many insect haters still appreciate their beauty. They are also easy to love because they prey on pesky flying insects, including mosquitoes, flies, moths, whiteflies and fruit flies.

They also eat the larvae of these creatures, stopping them before they can cause damage.

The squirmy old earthworms are incredibly beneficial. They help to improve the soil as their excrement enriches the soil and controls its pH. They are also critical in giving the soil water and air.

Bees are perfectly adapted to pollinate, helping plants grow, breed and produce food. They do so by transferring pollen between flowering plants and so keep the cycle of life turning. The vast majority of plants we need for food rely on pollination, especially by bees.

A global review published last year concluded 40 per cent of insect species are at risk of extinction in the next few decades.

A 2019 UN report warned that biodiversity ‘indispensable to food security, sustainable development and the supply of many vital ecosystem services’ is in decline, risking ‘severe production losses or livelihood disruption’.

Pollinators maintain the reproductive success of wildflowers and the yields of crops we eat. Sadly, as this report shows, many pollinator species are struggling.

The main pressures faced by bees the world over include the devastating changes to climate, loss and fragmentation of vital habitats, and threats from pesticides and pollution.

Their collapse in population is set to have big economic impacts. The tiny bee has also been useful in other aspects.

This is because, over and above providing honey, it defends an impoverished farmer against the advance of enormous and hungry elephants in the Tsavo East National Park.

But will the ongoing battle against desert locust affect some of these useful insects?

FAO: Swarms of 40km x 60km are ravaging crops in Kenya. 1km2 can eat the same food as 35,000 people so this swarm can eat the same amount of food as 84 million people.

FAO: Swarms of 40km x 60km are ravaging crops in Kenya. 1km2 can eat the same food as 35,000 people so this swarm can eat the same amount of food as 84 million people.

Earth Worms

Earth Worms

Earth Worms

Beekeeping

Beekeeping

Beekeeping

Dragonfly

Dragonfly

Lacewings

Lacewings

NO CAUSE FOR ALARM?

Views vary on the potential impact of the aerial spraying on these useful insects.

Dr Muo Kasina, chairman of the Entomological Society of Kenya told the Star there is no cause for alarm.

“The current model of application and formulation of pesticides being used has minimal negative effects,” Kasina said.

He said ultra-low volume oil-based formulations and atomisation of the molecules are being used.

“It is difficult to control locust plagues using other means. The first approach is to suppress their population with pesticides, then follow with bio-control and use various methods for hopper bands,” Kasina said.

Another locust expert, Dr Christian Kooyman, said the locust situation is pretty serious this year.

This, he said, is not only in Kenya but in the whole Horn of Africa, the Arabian Peninsula and up to Southern Asia. 

Dr Kooyman is retired, but he is one of the world’s experts on locusts and worked on their control for many years.

He worked at ICIPE and was involved in the development of a bio-pesticide for locusts that is very effective against the hoppers.

Dr Kooyman said there is a biological pesticide by the name Novacrid. The pesticide, however, works too slowly to stop the swarms from flying for another 10 days.

Dr Kooyman said when faced with swarms of flying locusts, there is no real alternative to spraying chemicals. He said it is very effective against the hoppers, the non-flying locust larvae, because they do not go far before dying.

"I would recommend the use of that product in Kenya," he said. 

Dr Kooyman said the government has no choice but to spray chemicals. "We can only hope that they choose the ones that are least damaging," he said.

"Of course, where they spray, the other insects will suffer, including bees and other pollinators. And that is a great pity." 

Dr Kooyman said it is obvious the government was not prepared when the first swarms entered the country.

"It had not heeded the warnings issued by the FAO. I guess they did not expect this level of invasions," he said.

Dr Kooyman said after the 1940s, when the last major invasion occurred, only a few swarms entered Kenya every 10 years or so.

He suggests the affected countries in the Horn stockpile suitable pesticides for future locust outbreaks with an agreement that they can be quickly moved to whichever countries need them the most.

"One of the products should, of course, be the biological one for eliminating hopper bands," he said.

Desert locusts may be nymphs, also called hoppers, or they may be winged adults.

They may be in solitarious phase (dull-coloured and living individually) or in the gregarious phase (contrasting colouration and tending to gather in groups).

Gregarious groups of nymphs are called hopper bands and large groups of adults are called swarms.

WATER-BASED SPRAYING 

FAO said water-based spraying is common in conventional agricultural crop protection.

It usually involves applying hundreds of litres of insecticide-water mixture per hectare.

The insecticide formulation, that is, the mixture supplied by the manufacturer, is usually an emulsifiable concentrate (EC), but may also be a wettable powder or other type of formulation.

Water-based spraying is, however, rarely carried out on a large scale against desert locusts because the work rate (number of hectares treated per hour) is low and the large volumes of clean water are difficult to find in most desert locust habitats.

Ultra-low volume (ULV) spraying is another technique, using much smaller volumes of spray liquid. It was initially developed in the 1950s for use against the desert locust and is now the most efficient and commonly used method.

It is defined as applying between 0.5-5.0 litres of spray liquid per hectare, although between 0.5 and 1.0 l/ha is preferred for ULV locust control.

This small quantity of concentrated insecticide is not mixed with water or any other liquid; the special formulation, known as a ULV (or UL) formulation, is usually supplied ready to spray.

The spraying of settled swarms means spraying the locusts that are roosting on vegetation, usually either in the morning before take-off or in the late afternoon, when the swarms have settled again.

Settled swarms are usually sprayed by aircraft but vehicle-mounted airblast sprayers are sometimes used, occasionally at night.

The advantage of spraying swarms is that there are many millions of locusts gathered in one place; they are composed of locusts from many bands or smaller swarmlets, so the problem of finding many individual targets is reduced.

Swarms are also sometimes sprayed while laying eggs, although they usually disperse before laying and are not such a dense target.

Swarms can also be sprayed from aircraft while they are either milling (some of them making short flights around the roost site in the morning or evening) or in full flight.

The best time for spraying is usually in the morning between 8am and 11am and in the afternoon after 4pm.

FAO recommends that, for efficacy, spraying should not happen during windy, rainy and sunny days.