Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 1995
Publication Date: N/A
Interpretive Summary: The root lesion nematode, Pratylenchus penetrans, has a worldwide distribution and is the most economically important plant-parasitic nematode in the Northeastern USA. This nematode lives within plant roots where it can cause severe damage to plants. In potato production, root lesion nematodes can cause up to 45% loss in potato yields. Until recently, damaging populations of root lesion nematode were held in check by the use of chemical pesticides. Because of environmental and human health hazards associated with the use of these pesticides, many of them were withdrawn from the market. A result of declining pesticide usage has been a resurgence of potato production problems associated with an increase in population densities or root lesion nematode. Research on environmentally safe means of controlling root lesion nematodes has centered on host-plant resistance and microbial antagonists. We have been examining the effectiveness of a fungal pathogen, Hirsutella rhossiliensis, in controlling the root lesion nematode. In this study, we determined whether non pest nematodes that are abundant around potato roots could serve as an alternative hosts for the fungus. We hypothesized that the fungus would infect these non pest nematodes and produce more infectious unites (conidia) which could then infect and kill the root lesion nematode. We found that the non pest nematodes did not increase the amount of fungus because they were somewhat resistant to infection.
Technical Abstract: The fungus Hirsutella rhossiliensis is an obligate pathogen with a broad host range among nematodes. Our objective was to determine the influence of the bacterial-feeding nematode Teratorhabditis dentifera on the abundance of the fungus and the plant-parasitic nematode Pratylenchus penetrans. The experiments were conducted in a growth chamber with pots containing pasteurized soil and potato plants. In the first experiment, the amont of H. rhossiliensis conidia was compared periodically over 70 days in soil with and without T. dentifera. The nematode reached high densities (3000-4000/100 cm3 soil) by day 70, but did not affect the abundance of conidia. In the second experiment, a two-way factorial design was used to determine the effect of H. rhossiliensis and T. dentifera on numbers of P. penetrans. In one trial, fungal abundance was higher in soil containing T. dentifera. Accordingly, suppression of P. penetrans by H. rhossiliensis was also greater in the presence of T. dentifera. The nematode by itself had no effect on P. penetrans. When the experiment was repeated, T. dentifera had no effect on abundance of the fungus or P. penetrans. In the first and second experiment, many T. dentifera were dauer juveniles, which acquired conidia but did not become infected. To test whether this life stage could deplete the pool of conidia in soil, different proportions of dauers juveniles with (resistant) and without (susceptible) a sheath were added to H. rhossiliensis-infected soil. The amount of conidia in the soil decreased with an increasing proportion of resistant nematodes.