Effects on the feeding behaviour of Nilaparvata lugens (Stål) of sublethal concentrations of the foliarly applied nitromethylene heterocycle 2‐nitromethylene‐1, 3‐thiazinan‐3‐yl‐carbamaldehyde

Abstract

Abstract. An electrical recording technique, combined with simultaneous videofilming, was used to investigate the detailed feeding behaviour of Nilaparvata lugens (Stål) (Homoptera: Delphacidae) on rice. Phases of brief probing, of non‐feeding activities, such as walking and of sustained feeding were observed. Monitoring of electrical signals recorded during long, uninterrupted periods of contact between the insect and its host plant, revealed three pattern classes. Two clearly distinguishable wave‐like patterns represent the hopper sucking from xylem and phloem tissues. The third represents a ‘complex’ of signals believed to be associated with stylet penetration, salivation and sucking activities in non‐vascular tissues of the host plant. This recording method and simple counts of honeydew excretion activity were used to assess the effect on the feeding behaviour of N. lugens of a sublethal concentration of the nitromethylene heterocycle insecticide 2‐nitromethylene‐l, 3‐thiazinan‐3‐yl‐carbamaldehyde applied to rice. The treatment caused a general reduction in feeding activity. Analysis of the electrical trace revealed that phloem feeding was strongly inhibited. Since these effects were largely reversed on transferring hoppers from treated to untreated hosts, the test compound was considered to have an antifeedant rather than a conventional poisoning effect on the hoppers when applied at sublethal doses.