Combating desert Locust

Combating desert Locustplague – Pakistan scenario

Dr. Tasneem Ahmad

Desert locust swarms are reportedly entering Pakistan from three sides including Iran, Oman, India and Afghanistan, in addition to local breeding in spring breeding areas of Baluchistan. It appears to be a new trend adopted by the desert locust, using of Afghanistan for attacking our green crops of Pakistan. However, in the past, it is interesting to note that a different locust species probably Moroccan locust (not desert locust) rarely entered Pakistan’s northern areas from Central States including Uzbekistan, Tajikistan, Kazakhstan, Kirghizstan etc. Hence it is necessary to identify the species of the current swarms of the locust because if this is not normal desert locust then we need to adopt control strategies based on the invading species.

FAO locust watch has given its latest report of our region on 27 May 2020. The region is categorized as SOUTH-WEST ASIA including Afghanistan, India, Iran and Pakistan. The report indicates that these swarms are forming in the spring breeding areas and also migrating east to the Indo-Pakistan border ahead of the monsoon rains. These immature adult groups and swarms that arrived in Rajasthan from the west continued to move east in the eastern portion of the state and to the central states of Madhya Pradesh and Maharashtra excluding at least one swarm had reached to the northeast of Bhopal on 26 May. Much of these movements were associated with strong westerly winds from Cyclone Amphan in the Bay of Bengal. With forecast that several successive waves of invasions can be expected until July in Rajasthan with eastward surges across northern India as far as Bihar and Orissa followed by westward movements and a return to Rajasthan on the changing winds associated with the monsoon. These movements will cease as swarms begin to breed and become less mobile. Similarly, adults are forming groups and small swarms in Baluchistan and the Indus Valley with forecast that these infestations will move to the summer breeding areas along the Indo-Pakistan border from Cholistan to Tharparkar. Situation in Iran is not different where adults are forming groups and small swarms along the southern coast and parts of Sistan-Baluchistan as vegetation is drying out. These infestations too will move east to the Indo-Pakistan summer breeding areas. Yesterday (Ist June) Indian locust organization has reported that a locust swarm covered a distance of nearly 1000 Km from Rajasthan to Prayagraj in UP.

Our national position is no different from above existing in Iran and India. Hopper bands, adults and swarms are moving from breeding areas to agricultural/cropped areas of Multan and Dera Ghazi Khan Divisions in Punjab. Day before yesterday, the Minister for National Food Security and Research, informed that sixty-one districts are under attack of locust. Additionally, breeding is reported in Thal desert which has immediately invaded adjoining cropped areas up to Jauharabad/Khushab district.

Even with superiority in the region by having and maintaining a technical department with conspicuous aerial wing consisting of aircrafts exclusively meant to fight the locust plague, the unskilled, none technical and inexperienced approach of the departmental personnel responsible for surveying and control of desert locust, the menace has become challenge in Pakistan. As I already pointed out in my earlier article, collective effort is needed to annihilate this scourge. It is heartening that provincial governments especially Punjab, MNFSR and NDMA is taking a leading role is commendable. However, again it is apprised that technicalities involved in locust control may be taken as seriously as SOPs involved in controlling COVID-19. Experts with experience in locust surveying and control may be taken on board at all stages of control measures as well as proper safety be provided to the operators, applicators, pilots, staff and farmers at large when operating in cropped areas. Most of all priority should be given to the environment safety and food security. Sanity must be prevailed at all stages of fighting the desert locust that food safety is not compromised.

The desert locust control methods can be summarized as:  i) mechanical method- digging trenches, beating and burning, ii) baiting – scattering locust food impregnated with locusticides, iii) dusting-using dust formulation of locusticides, and iv) spraying liquid insecticides (chemical, biological and insect growth regulators). Fighting desert locust is a complete science as well as technology. We have to take into account the stage of locust (nymph, hopper stage or adults) present, area of occurrence (desert or cropped area), density of population and environmental conditions. Selection of appropriate pesticides, their formulations, dosages, toxicity and timing of spraying are the most important factors to be considered to ensure the safety of the operators as well as food. Selection of appropriate spraying machinery for the powders, water based, EC, WP with big volumes requiring clean water should be made. Finally, ULV (ultra-low volume) is the most popular treatment because this is effective and needs no water which makes it easy to carry and transport. Application techniques are again a technology leading to the effective droplet size of the spray must be noticed, will be shared in next article. Selection of poison or locusticide is very important for obtaining maximum mortality of the locust. This is not very simple and easy as is being perceived. Selection of an appropriate poison that can cause maximum mortality with minimum effect on the environment is the actual test of the field entomologist. Keeping in view available resources, the entomologist has to decide whether the poison should be contact, stomach, systemic or a fumigant. This will be based on the biology, feeding and movement of the locust and prevailing climatic conditions.  

Similarly, judicious use of locusticides is very important. It is to keep in mind that these are poisons and should be applied rationally according to recommended and calculated dosages. It neither should be over dosed or under dosed because underdosing will not kill this locust whereas over dosing will be expensive and detrimental to the non- target organisms. Poor and inappropriate selection of pesticides can lead to the poisoning of the environment, undesirable residues in edibles, and hazardous effects on environment may lead to damage to animals, vegetation and human beings.

Additionally, underdosing may result in development of resistance in the locust and other pests against these pesticides. Reportedly, a pesticide, Malathion ULV is successively being used in agricultural crops (effectively used against house hold pests and mosquito control) and also in deserts against the locust. Its repeated use may have developed resistance in locust which may result in reduced mortality against locust. It is suggested that Malathion may not be made marathon and some other selections with different modes of action be selected for effective control of locust menace.

At last it is emphasized that for effective control of desert locust in schedule deserts of Pakistan, where Federal Government still has its mandate to survey and control this scourge, there is dire need to apply some persistent locusticide that will give residual control effectively against the nymphs, hoppers and even fledglings. This strategy should result in breaking the life cycle of desert locust and ensure effective control for some time.

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