Abstract
The brown planthopper was observed to make only infrequent attempts to probe the aerial space or distilled water behind a parafilm membrane. Most of the stylet sheaths produced in these regions were very short and did not brnch. Sucrose and aspartic acid showed little influence on the probing response despite their action as sucking stimulants.Salicylic acid was found to stimulate the stylet probing, and its optimum effect was recorded when 0.001 to 0.004 M salicylic acid was present together with 2% sucrose. In such media, the planthopper deposited a large number of branched and well extended stylet sheaths similar to those produced in rice plant tissues, indicating an enhanced stylet probing response. Other aromatic monocarboxylic acids accurring in rice plants had no effect.Salicylic acid suppressed the sucking response at the efficient concentratios at the probing stimulant. The saps obtained from rice plants and four kinds of non-host plants stimulated stylet probing of the brown planthopper.
