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Invasion of cooler areas linked to climate change: Expert

Saturday February 29 2020


A local in Kiplekwa village, Baringo Central chases away a swarm of desert locusts that have invaded the area on February 23, 2019. PHOTO | FLORAH KOECH | NATION MEDIA GROUP 

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Is the country losing the war on locusts? Dr Muo Kasina, the chairman of the Entomological Society of Kenya, answers this and other questions.

The locust invasion has now reached nearly half of Kenya’s counties. Are the current control measures effective?

Control has had some level of success. It reduced the rate at which the   locusts bred in Kenya and therefore prevented early calamity in terms of crop destruction and pasture loss. However, control of the pest is not an immediate activity.

It requires patience and persistence. They are complicated insects which require patience and focus.

The current invasion started with the pests coming from Somali and Ethiopia on a daily basis. Such an invasion requires persistence in eliminating them.

Their migration is a marvel to behold given the distance they cover. What is the science behind their flight power?


Basically, insects cover larger distances mainly aided by wind. Desert locusts benefit from their organisational skills due to chemical communication among a swarm.

They are also difficult to study as swarms because they do not occur commonly. We try to make them live a solitary life to avoid the calamity we are facing.

Some farmers we spoke to said they saw an advance party of hoppers before a full-fledged swarm moved in. Do locusts send some to spy on new lands? If so, how do they communicate?

No. Hoppers started emerging in the past two weeks or so. Remember also that farmers are reporting the presence of locusts based on grasshoppers they observe. Therefore, we need to confirm these reports before declaring that they are desert locusts.

The present locust infestation appears to be less destructive than previous ones going by past attacks. How come?

The government initiated very early strong control mechanisms. However, let us not celebrate early, I have taken notice of adults being left to lay eggs in the hope that hoppers will be easier to manage.

The infestation also seems to defy tradition in other ways such as moving into cooler areas. What is the explanation behind this?

Cooler areas are still less infested. However, the wind movement is the main factor. Remember the cooler areas are becoming warmer due to climate change. Today we have more insect challenges in those areas as well. Even diseases transmitted by insects such as malaria are becoming more prevalent in those areas.

Experts warn that the real havoc that the locusts wreak is on the next crop, which is about to be planted. What should Kenya do to avoid or minimise this threat?

Desert locust control is not the responsibility of a single farmer. There is a need for national and county governments to keep working together and never leave the responsibility to farmers. The threat is due to a combination of the swarms coming in and new cycles developing. Do not forget that there is already a major food and feed challenge in northeastern counties where egg laying has been massive.

Adults will take three weeks to mature and lay eggs. In this period, they are pinkish in colour. When mature, they turn yellow. The eggs will hatch within two weeks. Emerged hoppers (nymphs) undergo five growth stages, growing and increasing in size, but without wings. They will take four to six weeks to become adults. Adults can stay for four months or more as they eat and lay eggs. After egg-laying, they will not live for long before dying a natural death.

What can be done to stop them from laying eggs? And in case the eggs are laid, what should be done to control the resulting larvae?

By killing adults, whether they are yellow or pink, you fully stop egg-laying. Nymphs have many ways of being controlled but they are quite complicated.

First, they are not easy to be noticed by farmers. Trained personnel should keep monitoring them. Time should be given for 100 per cent egg-hatching in an area before spraying.

Therefore, spraying can be done from the third or fourth stage onwards. In the first to third stages they feed less compared to the fourth and fifth. They can also be collected and used as feed instead of spraying. In addition, creating trenches prevents nymphs from marching to new areas.

What precautions should residents in locust-riven areas take during aerial and ground spraying?

Spraying should not be done in human settlements but in forest and field patches to minimise direct human contact. Also, people should avoid getting close to spray areas.

This is happening as residents want to see and take photos of the spray activity. Secondly, residents should use masks at times of spray and avoid getting out of their houses. Usually sprays are done early in the morning or late in the evening.

Thirdly, they should report wind strength to spray teams so that sprays can be applied when it is cool. Ground spraying poses less threats to humans.

However, it has more negative effects on the environment because of the large volumes involved.

The spray team should also be fully trained on spray volume release and their own protection. The coordinator should advise people to avoid visiting the area for three days or more after spraying.

Animals shouldn’t graze in the sprayed area during that period. The government should also advise on a first-aid strategy if people feel poisoned by the pesticides used. 

It is unsafe to eat sprayed locusts for between three and four days. A toxicological study can also be done at the University of Nairobi to determine pesticide presence in the sprayed locusts before eating. Locusts are rich in protein. The country should tap them as part of the strategic food reserve.