Location: Tropical Crops and Germplasm Research
Title: Interactions of a Rhabditis sp. on the virulence of Heterorhabditis and Steinernema in Puerto Rico Authors
Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 2011
Publication Date: September 1, 2011
Citation: Garcia, J., Jenkins, D.A., Chavarria, J.A., Shapiro Ilan, D.I., Goenaga, R.J. 2011. Interactions of a Rhabditis sp. on the virulence of Heterorhabditis and Steinernema in Puerto Rico. Florida Entomologist. 94(3):704-705. Interpretive Summary: Surveys of various agricultural soils revealed the presence of a Rhabditis species nematode. Nematodes may be used to control pests that spend some time in the soil. The prevalence of this nematode in Puerto Rican soils could hinder or help biological control of soil-borne pests in fruit orchards. We compared the mortality caused by the Rhabditis sp. to the mortality of two other nematodes typically used to control soil-borne pests, as well as the mortality caused by the Rhabditis sp. in combination with the two biocontrol agents. Rhabditis sp. did not appear to cause mortality to the target organisms and did not affect the virulence of the two biological control agents, either by increasing or decreasing the mortality. However, Rhabditis sp. did emerge from some cadavers of target organisms that were killed by other nematodes, indicating that it is an opportunistic feeder on insect cadavers.
Technical Abstract: Rhabditis sp. nematodes were recovered from Galleria melonella cadavers exposed to soil collected from three regions of Puerto Rico. This nematode was then assayed for virulence to last instar larvae of Diaprepes abbreviatus, both alone and in conjunction with the entomopathogenic nematode species, Steinernema glaseri and Heterorhabditis bacteriophora. Applied at low doses (10 infective juveniles per cm2) we did not detect a significant difference between the mortality in the Rhabditis sp. treatment and the control treatment. However, cadavers from soil that had been treated with the Rhabditis sp. yielded Rhabditis sp. nematodes, indicating that it is an opportunistic invader of cadavers. When applied with either S. glaseri or H. bacteriophora at low doses, Rhabditis sp. nematodes had no detectable impact on the virulence of the other nematodes, either in total mortality caused or in the speed of the mortality. Because S. glaseri is so much larger than the Rhabditis sp., it was easy to distinguish which nematode emerged from cadavers exposed to both, and in several cases Rhabditis sp. nematodes were detected emerging from cadavers, demonstrating its opportunistic nature.