TOXICITY OF DIFLUBENZURON TO NYMPHS OF THE MIGRATORY GRASSHOPPER, MELANOPLUS SANGUINIPES (ORTHOPTERA: ACRIDIDAE)

Abstract

AbstractLaboratory tests showed that nymphs of the migratory grasshopper are very sensitive to diflubenzuron (Dimilin) when reared continuously on treated wheat seedlings or artificial diet and fresh lettuce. At concentrations of 10 ppm or above, diflubenzuron completely inhibited moulting of 2nd-instar nymphs. With continuous exposure on treated wheat seedlings, the LC90 values after 8, 12 and 20 days were 10.0, 2.4 and 0.8 ppm, respectively. Comparable values were obtained with the artificial diet and lettuce. However, when 2nd instars were placed on diflubenzuron-treated wheat foliage for 1 day then transferred onto untreated plants, toxicity declined markedly.Although the toxic effects of diflubenzuron were delayed, dry weight determinations on wheat seedlings indicated that nymphal feeding damage was insignificant if the plants had been sprayed with 10 ppm diflubenzuron.The implications of these findings are discussed in terms of the potential field use of diflubenzuron against stationary and mobile grasshopper nymphs.