|Culbreath, Albert - UNIV OF GA|
Submitted to: International Congress of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2008
Publication Date: June 13, 2008
Repository URL: http://www.ifns.org
Citation: Timper, P.; Culbreath A.K. 2008. Influence of fungicides on a nematode-suppressive soil. Presented at the 5th International Congress of Nematology. Pg. 302 Technical Abstract: We identified a field in Georgia, USA that was moderately suppressive to Meloidogyne spp. In the greenhouse, reproduction of both M. incognita on cotton and M. arenaria on peanut was greater in microwave-heated soil than in natural soil from this field suggesting that nematode suppression was caused by a heat-sensitive organism. Because fungi antagonistic to nematodes are common in soils and are frequently associated with suppressive soils, we hypothesized that fungicides would reduce the activity of these fungi and allow greater nematode reproduction. To test this hypothesis, we collected soil from the suppressive field and placed it in 6 liter pots. Peanut was planted and 2 weeks later inoculated with 3,000 eggs of M. arenaria. Starting 5 weeks after planting (WAP), the peanuts were sprayed with one of four fungicide treatments: 1) five applications of chlorothalonil, 2) four applications of tebuconazole, and 3) two applications each of flutolanil, and 4) azoxystrobin. These fungicides are commonly sprayed on peanut at the rates and frequencies used. There were eight replications of each treatment and control (no fungicide). The number of eggs/g root was determined 15 WAP. In both trials of the experiment, azoxystrobin was the only fungicide that led to an increase (P = 0.0004) in nematode densities relative to the control; nematode densities in the other fungicide treatments were not different from the control. The number of eggs/g root was 20,391 in control pots and 44,315 in azoxystrobin-treated pots, a two-fold increase in nematode reproduction. Further research is underway to determine whether azoxystrobin has a similar effect on nematode densities in heat-treated soil.