Desert locust (Schistocerca gregaria Forsk) infestation in relation to meteorology and sunspot cycles in India during 1945-1980

Abstract

To know the role of meteorological systems of synoptic scale in outbreaks of desert locust (Schistocerca gregaria Forsk) at various phases of its life cycle in western India, data on locust situation and synoptic disturbances during period from 1945 to 1980 were analysed.

The analysis of the fortnightly data of the infestation of egg layings, hoppers, scattered adults and swarms for seven stations shows that the chronological orders of these activities follow the spatial progress of the normal monsoon onset with pre-monsoon rains. However, the highest swarm activity was found in the first fortnight of August.

Simple linear correlation technique was used to know the degree of association of various meteorological disturbances with locust activity at different stages for a station with good record of data set. The egg-laying activity was parallel with rainfall and slight decrease in rainfall between peaks did not affect the activity- Hopper emergence peaks were seen generally after a month of rainfall. Scattered adults activity showed no good association with rainfall. The swarms intensity was highest during first fortnight of August and September. The main meteorological systems causing rainfall were western disturbances, depressions over Arabian Sea and a few depressions developed over land.

It was also found that a negative correlation exists between swarm infestation and sunspot number.