When you have submitted your report of sightings the appropriate organizations will investigate and fully trained locust officers will, if necessary, take control measures against the Desert Locust. This insect, however, often occurs in remote areas and can cause great damage before locust organizations can be informed or respond to the problem. In these instances, farmers or officials from the local plant protection departments will have to supervise and carry out local control operations to safeguard crops.
At present, the application of insecticides, often on a wide scale, is the only effective means of controlling the Desert Locust.
For locusts to be killed by an insecticide they must either swallow it or get it on the outside of their bodies. This is achieved by:
(i) putting the insecticide on or in their food, either natural vegetation or a specially prepared bait; this is poisoning by stomach action;
(ii) putting the insecticide directly on to the locusts in a form that will penetrate their skin; this is poisoning by contact action.
Insecticides can be applied in three ways: baiting, dusting and spraying.
Farmers can use backpack sprayers to spray small bands of locusts. If sprayers are not available then locusts have to be dusted or baited.
The most commonly used method of control is a form of spraying known as ultra-low-volume (ULV) in which insecticide is applied to locusts in a concentrated form. ULV spraying operations are complicated and are usually carried out by specially trained plant protection officers. ULV spraying will not be dealt with in this pocket book. The Locust Handbook, also published by the Natural Resources Institute, should be consulted for information on ULV spraying.
Suitable insecticides currently used for Desert Locust control are shown in the table on the following pages. When using any insecticide the manufacturer's instructions should always be read and followed strictly. For your information, suitable insecticides used by plant protection officers for ULV spraying are also listed in this table.
Insecticides can be dangerous. This danger should be minimized by the choice of proper formulations of insecticide, careful handling and correct use of equipment, and the use of protective clothing, especially gloves and face masks.
Insecticides can be highly poisonous. It is important to take adequate safety precautions when transporting, storing or handling them.
Always wear protective clothing: rubber gloves, overalls, face mask and respirator when mixing insecticides; and gloves, long trousers and a long sleeved shirt when applying less hazardous insecticides. These clothes can be uncomfortable in humid climates but it is important not to let insecticides enter the body through the skin, mouth or lungs.
Always read and follow the instructions on the label.
Avoid splashing or spilling liquids and causing powders to puff up or spill.
Only use insecticides when the weather is still and dry.
Never eat, smoke or drink when handling insecticides. Avoid inhaling dusts or vapours.
Keep unauthorized people, especially children, away from insecticides.
Always wash thoroughly with soap and water after handling insecticides.
Keep insecticides in a locked store which is not likely to flood and is well away from water supplies.
Keep an accurate record of insecticide usage.
Suitable dusts for killing locusts are bendiocarb and propoxur. The powdered insecticide is mixed with a suitable 'carrier', for example, chalk or talc, and sold in this ready-to-use form. Dust can be applied either by hand or by using a hand-blower.
Dust should be applied under moist conditions, either when there is high humidity, or after a heavy dew. It is most effective against night-roosting hoppers and adults, hoppers marching slowly through vegetation, and during the hatching period. It is dangerous to inhale the dust particles so care must be taken when handling the dust.
A bait is a mixture of an insecticide with an edible 'carrier'. Carrier materials readily taken by locusts include maize meal, wheat bran, maize bran, cotton seed husk and rice bran. The insecticides, bendiocarb and propoxur, are recommended for use in baits. Insecticide and bait are usually mixed in the field or at a distribution point, not by the manufacturers. Locusts eat the bait and so take in the insecticide. Bait is usually spread by hand.
The dosage required for baiting will vary considerably with the stage of development and the behaviour of the hoppers. Usually the insecticides are used in concentrations of 1 or 2% active ingredient. A mix of 10 kg of 1% bendiocarb, 25 kg of 2% propoxur or 50 kg of 1% propoxur with 200 kg of carrier gives satisfactory results. Rates of application of mixed baits are: 50-75 kg/ha for resting hoppers; 5-15 kg/ha for actively marching bands; 150-200 kg/ha for settled adults.
Hopper bands should first be tested with a small quantity of bait to see if they will stop to feed. If the hoppers are hungry, baiting should start from the front edge of the band and bait should be scattered thinly and evenly. The younger the hoppers, the less bait will be required to kill them. Baiting gives poor results during the last 2-3 days of the fifth instar and during all moulting periods. It is particularly useful for control of marching bands when there is little annual vegetation and much bare ground.
Baiting can also be used against adult locusts. It is best applied in the morning before they start to fly. Scattering bait is one of the safest methods of controlling locusts among crops.
In this method of control, liquid insecticide is broken up into fine droplets and sprayed either on to the locusts or on to the vegetation which they will eat.
To obtain the best kills at the minimum cost the suitable insecticides require special formulations and an appropriate spraying machine should be chosen.
Spraying emulsifiable concentrates with a backpack sprayer can be used to treat relatively small bands of Desert Locust. Large drops should be sprayed in a light wind or in still air. The track spacing (distance between spray runs) should be about the same as the swath width (distance from the start of spray deposit to where it reaches an insignificant level). The drops will fall in a uniform pattern over a 1 metre wide band.
Insecticides are expensive to buy and so their improper use, such as overapplication or underdosing, is costly. They can also be dangerous to man and the environment if not used correctly.