BEHAVIOR AND SURVIVAL IN CORN PLANTS IN OSTRINIA-NUBILALIS (LEPIDOPTERA, PYRALIDAE) LARVAE WHEN INFECTED WITH NOSEMA-PYRAUSTA (MICROSPORA, NOSEMATIDAE) AND PARASITIZED BY MACROCENTRUS-GRANDII (HYMENOPTERA, BRACONIDAE)
Db. Orr et al., BEHAVIOR AND SURVIVAL IN CORN PLANTS IN OSTRINIA-NUBILALIS (LEPIDOPTERA, PYRALIDAE) LARVAE WHEN INFECTED WITH NOSEMA-PYRAUSTA (MICROSPORA, NOSEMATIDAE) AND PARASITIZED BY MACROCENTRUS-GRANDII (HYMENOPTERA, BRACONIDAE), Environmental entomology, 23(4), 1994, pp. 1020-1024
To clarify the interaction among the European corn borer, Ostrinia nub
ilalis, the parasitic wasp, Macrocentrus grandii, and the entomopathog
en Nosema pyrausta, we examined behavior and survival in corn stems of
O. nubilalis larvae infected with N. pyrausta and parasitized by M. g
randii. Fifty-four percent of heavily infected, parasitize O. nubilali
s larvae emigrated from their tunnels before emergence of parasitoid l
arvae and did not reestablish on corn plants. One-third as many heavil
y infected host larvae as noninfected larvae remained in tunnels until
parasitoid larval emergence. The tunnels bored by infected, parasitiz
ed O. nubilalis larvae did not differ in length from those of noninfec
ted parasitized larvae, suggesting that emigration behavioral changes
occur after feeding. Parasitoid larval and pupal mortalities were grea
ter in infected O. nubilalis hosts than in noninfected hosts. Greater
than 46% of heavily infected M. grandii broods wandered instead of rem
aining clustered around host carcasses and pupating. This behavior acc
ounted for almost almost-equal-to 40% of the observed mortality in inf
ected parasitoids. Wandering was attributed to decreased production of
cocoons by hosts, causing parasitoid larvae to search for suitable su
bstrates on which to spin their own cocoons. Percentage emergence of M
. grandii adults from com stalks was significantly lower in N. pyraust
a-infected treatments, but the sex ratio of the parasitoid was unaffec
ted by the level of host infection. The mean number of M. grandii adul
ts per brood was reduced from 39.8 in the noninfected treatment to 10.
5 in heavily infected larvae.