Abstract
Gregarious desert locusts constitute very destructive agricultural pests. They aggregate and form collectively moving swarms that devastate vegetation and reduce crop production. To combat gregarious locusts, a bio-pesticide formulation that contains linseed oil as the main component was described recently. Since linseed oil is rich in fatty acids, some of which function as necromones that indicate injury or death in various insect species, we investigated the influence of linseed oil on the aggregation behaviour of sexually mature gregarious desert locusts. For this reason, we performed a series of aggregation experiments with six individuals of the same sex and brushed the wings of one individual (target individual) with linseed oil. The time the oil brushed target males spent close to any other individual was reduced in 76% of trials (average reduction of 18%), whereas the time target females spent in groups with members of the same sex did not alter. These results suggest that linseed oil may act as a bioactive agent that has the potential to disrupt swarm formation.
Highlights
Desert locusts (Schistocerca gregaria Forsskål, 1775) are considered to be among the most serious agricultural pests because of their polyphagous feeding behaviour, rapid reproduction rates and quick migration patterns [1,2]
If the duration of group formation changed after the application of linseed oil or after sham operation by more than 10% (2.5 min), we considered this as a change in aggregation time
Brushing the wings of the target individuals with linseed oil did not change the average distance covered by the target locusts, which suggests that the reduced group formation time observed in males is not caused by an overall reduction in the activity of the target locust
Summary
Desert locusts (Schistocerca gregaria Forsskål, 1775) are considered to be among the most serious agricultural pests because of their polyphagous feeding behaviour, rapid reproduction rates and quick migration patterns [1,2]. If the population density increases, even over a short time period, the behavioural transition to the gregarious phase is evoked [5,6]. This is the case, for example, after rainfalls that end long periods of drought, resulting in nymphs hatching from eggs laid in burrows in the ground [7]. A small swarm of locusts contains thousands of individuals that spread out over several hundred square metres, but large swarms contain up to 80 million individuals per square kilometre Since such swarms can cover a distance of 100 km per day [1], farmers regard gregarious locusts as one of the most destructive plagues on earth
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