Apart from the worldwide COVID-19 pandemic fear & economic losses, there is a warning of locust swarm in South Asia by FAO this year. Locust are the collection of species of short-horned grasshoppers in the family Acrididae which have swarming phase. Generally, they are solitary but under certain circumstances they become gregarious and change their habit. During the suitable condition of drought which is followed by quick vegetative growth cause huge serotonin release in their brain that triggers dramatic set of changes: they start breeding, becoming gregariously and migratory.
Guaiacol is one of the main components of the pheromones that cause locust swarming.
Locust that are attacking currently in Pakistan & India are the desert locust (Schistocerca gregaria). Swarming behavior of locust is due to abundant population or over-crowding at the gregarious phase where they tend to bound together. They travel up to 150 km per day eating every bite of greenery in the path. They will breed up to 40 to 80 million locust per square kilometer area during active breeding in a swarm.
Desert locust upsurges:
- 1915 Ottoman Syria locust infestation
- 2003-2005 desert locust upsurge (WestAfrica)
- 2019-20 East Africa & Asia infestation
African countries like Ethopia & Somalia are witnessing one of the worst locust attacks in the last 25 years. The cyclonic storms Mekunu & Luban that had struck Oman & Yemen respectively in 2018. These turned large desert tracts into lakes, accessing locust breeding that continued through 2019. Locust swarms attack crop in East Africa which reached peak population from November and built up in southern Iran & finally in Pakistan since the beginning of 2020 with the heavy rain in East Africa in March-April enabling breeding.
It consists of three stages, the egg, the nymph known as hopper & winged adult. After copulation, sperm is transferred from the tip of male abdomen to the tip of female`s where it is stored. Female seeks suitable soil to lay the eggs which are surrounded by foam which hardens into membrane. Incubation period is two weeks or longer depending upon temperature. Newly hatched nymphs soon begin to feed which passes through 5 moultings and become winged adult. They pass through gregarious & solitary phase.
Gregarious phase locust bunch together and in the latter instars develop bold coloring whereas in solitary phase individual do not form bunch and develop green background color.
It is believed that desert locust feed almost equivalent to its body weight i.e. 2 gram/day in green vegetation. As, they are polyphagous nearly all crop & non-crop plants are eaten including pearl millet, maize, pasture grass, vegetables & many more. Desert locust plague occurred in different time period from 20th century.
Locust plague certainly lead to food insecurity causing famine & starvation among people. Currently some of the African countries are facing this issue & is coming in the Asia & Indian sub-continent including Nepal.
Can you imagine how much crop loss will be there, if a swarm of 80 million locust prevails in specific area for 1 week?
Locust are difficult to control; however, different methods of control technique can be applied to control & manage locust in the governmental scale. An individual is foolish enough to control locust swarm however every individual must support in controlling this deadly pest. Government should be active & more initiative in this issue. Early warning & preventive control is principle method for controlling locust swarm.
- Adoption of the necessary monitoring & control activities by the governmental departments & concerned ministry.
- Best method of controlling locust is by applying small concentrated doses of contact or stomach poison (In Bait) insecticides by the vehicle-mounted and aerial sprayers at ultra-low volume (ULV) rate of application.
- Natural enemies like predatory beetle larvae, birds & reptiles will control if present in small number in solitary phase. So, their rearing is beneficial.
- Mechanical methods include digging trenches, and burying hopper bands.
- Making noise, burning tires or other woods & violent methods are other scary methods to force away the locust swarm.
- Bio-pesticides include fungi, bacteria, neem extract & pheromones which is equivalent to conventional chemical method. However, they take longer to kill insects. Green Muscles & NOVACRID are based on Metarhizium acridum which is entomopathogenic fungus widely used in controlling locust.
Keywords: desert locust gregarious solitary swarm
References: wikipedia, Indiantimes