Locust is the member of class Insecta, having order orthoptera and family Acrididae. These are winged insects in their adult phase and can fly up to 150 km in daylight. These insects have two phases; solitary and gregarious. Mostly these insects live in solitary form but due to some micro and macro environmental changed like drought or rapid vegetation growth, serotonin hormone produced in their brains triggers certain changes in locust brains, so they breed rapidly and form gregarious form which acts as a migratory phase. When a certain level of population builds up of wingless nymph (Immature stage of insect) later become a swarm of winged adults. Then these swarms move rapidly and damage the crops around where the swarm settles.
These insects appear without any warning in previously uninfested areas and rapidly consume the green pastures and crops.
In Pakistan, locust appeared in April 2019 in different areas of Sindh and Baluchistan. It migrated from Sindh and Baluchistan to different parts of the country like south Punjab then passed into the desert area of India adjacent to Bahawalpur, Bahawal Nagar and Hasalpur in July 2019. The swarms settle in different areas of Punjab because these insects can only fly in daylight and after dusk, the swarms settle on trees like Kikar, Karir, wheat, and Canola crop and on the desert. They lay their eggs there. When the winter season starts, the swarm flighted from those desert areas towards Baluchistan by crossing Hasilpur, Vehari, Burewala, Mian Channu, Khanewal, Kabirwala, D.I. Khan because of its habit to live in sandy moist soils. Its swarms were about 8-10 km long and 3-5 km wide.
Now a day when the temperature is rising, eggs hatch in desert areas where the previous swarm settled, the nymphs feed in desert areas of Cholistan then form small swarms of adults and damaging the wheat and canola crops in Bahawalpur Division. Their habit is to fly downwind so the swarms scattered in different areas of Punjab like Lodhran, Multan, Khanewal, Sahiwal, Toba Tek Singh, Faisalabad, Khushab, Bakhar and Layyah districts.
Now when the locust scattered in different areas of Punjab and Sindh, different management strategies are being carried out to control this insect pest in which Much of our focus in on chemical control. Different types of chemical insecticides like Lambda-cyhalothrin, Chlorpyriphos, Bifenthrin, etc. are being sprayed in the desert as well as crop areas to combat this pest and because of non-resistance of this insect against these pesticides, these insects killed in minute time. But these chemicals have a bad impact on humans, animals, and the environment. They are many persistent in the environment and can kill non- targeted mammals.
The dose rate prescribed by the department is a 5% solution of pesticides. So, it means that 5 liters of pesticides are mixed with 95 liters of water and spray on the field where locust infestation is observed. Normally the pesticides recommended for locust control are already been in use on different crops for controlling different insect pests. Like lambda, cyhalothrin is recommended on the cotton crop but the dose rate is 250 ml per 120 liters of water. Likewise, Bifenthrin is recommended in cotton and other crops @ 250 ml /120 liters of water. So, the dose rates of these pesticides on locust and other insect pests are not comparable. We are already facing resistance and cross-resistance problems of insecticides. There will be serious threats to our environment by spraying these insecticides on these dose rates. The killed locust is when feeding out by natural predators like crows or by mammals like dogs, they are also dying. The residues are affecting the drinking water in populated areas where spray activities are being carried out. The labor which is sparing these chemicals is affecting by skin burning and respiratory problems.
Control Measure
A basic prerequisite in controlling this insect pest is a national survey and training of the staff which is involved. The pesticides are applied when and where absolutely needed.
Special care should be taken to avoid using chemical pesticides in ecologically or economically sensitive areas. Nature reserves and other protected areas should be off-limits for large scale locust control. Water bodies and honey beekeeping areas should be avoided or if essential, low-risk insecticides or biological insecticides should be sprayed.
Use of New Technologies to combat Locust
- Barrier treatment
- Bait Application
- Use of Biological insecticides
Barrier treatment
In this method, only a small portion of the infested area is sprayed. A small no of trees and cultivated crops are sprayed with effective pesticides on which locust can feed. In this method money and environment, both can be saved.
Bait Application
In this method, bait is prepared for the nymphal stage of Locust and insecticide is mixed in this bait. When the eggs hatch and nymphs come out from the soil, they need to feed for development and growth, so when these nymphs feed on treated baits, they killed.
Use of Biological insecticides
The use of biological insecticides is another option for controlling the locust. The biological pesticides like Beauveria bassiana and Metarhizium anisopliae have been in the international market and commercially produces. These are basically soil inhibiting fungus and attacks on most insects to feed. They attach with the bodies of insects, develop its hypha which penetrates in the insect body, suck the hemolymph insides then produce further conidia by killing the insect. A commercial formulation of Metarhizium anisopliae “Muscle” has been tested against locust for several years in Africa and found to be very effective. A similar product, Green Guard is being used on Desert Locust in Australia. Because of their slow mode of action, these are most effective in the preventive control system, where crops are not directly threatened and can be used in sensitive ecosystems such as national parks and nature conservative areas.
The government should import these bio pesticides and provide stakeholders for the control of Desert Locust.
The writer is an Agriculture Officer, Pest Warning & Quality Control of Pesticides Punjab. He can be reached at [email protected]