Infestation behavior of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) first instars on hard red winter wheat kernels: Preliminary observations

Abstract

The eggs of the lesser grain borer, Rhyzopertha dominica(F.) are laid loosely outside wheat kernels.  Larvae hatching from eggs (first instars) enter wheat kernels to complete immature development. Individual, sound, organic hard red winter wheat kernels (11.6% moisture [wb]) in glass vials were infested with 1, 2, 3, 4, and 5 first instars. At 2, 4, and 5 instars per kernel the percentage of kernels infested out of 50 was 26%. In treatments with three first instars the percentage of 50 kernels that were infested was 36%. Only 12% of the kernels were infested when a wheat kernel was infested with 1 first instar. The germ was the preferred site of entry for first instars (10% of the time), followed by endosperm (7.2%), and the brush portion of the kernel (6.8%). First instar density and site of entry affected insect growth as evidenced by the size of larval head capsule width.  The site of entry also influenced successful development to adulthood. Additional studies will examine the reasons why first instars prefer entering wheat kernels via the germ as opposed to the endosperm.

Keywords: Wheat, lesser grain borer, first instar, nutritional ecology