Heptachlor as a Systemic Insecticide against the Wheat Stem Sawfly, Cephus cinctus Nort.

Abstract

Granular heptachlor applied with the seed caused mortality in larvae of the wheat stem sawfly, Cephus cinctus Nort., in wheat stems. Half a pound of actual heptachlor per acre gave less control than either 1 or 2 pounds, although the latter two rates did not differ in effectiveness. Formulations with attaclay were more effective than with vermiculite.

The insecticide was most effective in the lower internodes of the stem where it caused considerable mortality of early-instar larvae but was less effective on more mature larvae.

To be effective, heptachlor evidently required light sawfly infestations restricted mainly to the lower internodes of the stems such as had occurred in 1960. In that year heptachlor gave its best control although it was no more effective than a moderately sawfly-resistant wheat. Lack of control in 1961 was related to the heavy sawfly infestations in that year. The poor control in 1962 was related to the concentration of most of the sawfly eggs in the top two internodes where the insecticide had little effect on newly-hatched larvae. Only later, when they were more mature, did the larvae reach the lower internodes.