Impact of Steinernema riobravis (Rhabditida: Steinernematidae) on the control of Helicoverpa zea (Lepidoptera: Noctuidae) in corn
1995
Cabanillas, H.E. | Raulston, J.R.
The efficacy of using an endemic entomopathogenic nematode, Steinernema riobravis Cabanillas, Poinar & Raulston, to suppress prepupal and pupal populations of corn earworm, Helicoverpa zea (Boddie), in the soil was evaluated. The optimum timing of nematode soil application in relation to larval exit from the corn ear, the effects of nematode concentration, introduction method, and persistence on control of corn earworm were determined. Better parasitism resulted when S. riobravis infective juveniles were applied on the subsurface + surface (81%) than when they were applied on the soil surface alone (45%), in the greenhouse. Striking results were obtained with 2 billion nematodes per ha applied when 10% of the corn earworms had exited the ear to pupate or when 50% of the corn earworms had developed to large larvae. This resulted in 95 and 100% parasitism, respectively. A low rate of parasitism (22%) was observed in plots that received nematodes when 40% of the corn earworm had developed to medium size larvae. Parasitism in all plots that received nematodes was higher than the 11% natural parasitism observed in control plots. S. riobravis persisted (22%) in this sandy clay loam soil during the 75-d period field evaluations. These findings show the potential of using S. riobravis for soil application in source areas where the corn acts as nursery crop to suppress the build-up of corn earworm adult populations.
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