RESUMO
The importance of fungicide seed treatments on cotton was examined using a series of standardized fungicide trials from 1993 to 2004. Fungicide seed treatments increased stands over those from seed not treated with fungicides in 119 of 211 trials. Metalaxyl increased stands compared to nontreated seed in 40 of 119 trials having significant fungicide responses, demonstrating the importance of Pythium spp. on stand establishment. Similarly, PCNB seed treatment increased stands compared to nontreated seed for 44 of 119 trials with a significant response, indicating the importance of Rhizoctonia solani in stand losses. Benefits from the use of newer seed treatment chemistries, azoxystrobin and triazoles, were demonstrated by comparison with a historic standard seed treatment, carboxin + PCNB + metalaxyl. Little to no stand improvement was found when minimal soil temperatures averaged 25°C the first 3 days after planting. Stand losses due to seedling pathogens increased dramatically as minimal soil temperatures decreased to 12°C and rainfall increased. The importance of Pythium increased dramatically as minimal soil temperature decreased and rainfall increased, while the importance of R. solani was not affected greatly by planting environment. These multi-year data support the widespread use of seed treatment fungicides for the control of the seedling disease complex on cotton.
RESUMO
Epidemics of spotted wilt, caused by tomato spotted wilt tospovirus (TSWV), were monitored in field plots of the new runner-type peanut (Arachis hypogaea) cv. UF 91108, in advanced breeding line F 84 × 9B-4-2-1-1-2-b2-B, in runner-type peanut cvs. Southern Runner and Florunner, and in Virginia-type cv. NC-V11 at two locations in 1994 and 1995. Epidemics of spotted wilt were suppressed in UF 91108 compared to the standard runner-type cv. Florunner. Final disease incidence, standardized area under the disease progress curve values, and final disease intensity ratings were lower in UF 91108 than in Florunner and were similar to those in the moderately resistant cv. Southern Runner. Results indicate that new cv. UF 91108 represents a new potential tool for management of spotted wilt in peanut production areas of the southeastern United States. UF 91108 is the first peanut cultivar in which an oil composition of approximately 65% oleic acid is combined with a moderate level of field resistance to TSWV. Epidemics of spotted wilt also were suppressed in breeding line F 84 × 9B-4-2-1-1-2-b2-B. Across the four tests, the effects of NC-V11 on epidemic development, final incidence, and spotted wilt intensity ratings were not consistent relative to the other genotypes. Use of final disease intensity ratings provided separation of the genotypes similar to use of final incidence of spotted wilt. Assessment values by these two methods were highly correlated. In three of four experiments, final disease intensity ratings were more closely correlated with pod yield than was final incidence. The new intensity rating method described in this paper requires much less time and effort than determining disease incidence and may be a practical alternative to individual plant assessment for characterization of genotype responses to TSWV.