Importance of Fungicide Seed Treatment and Environment on Seedling Diseases of Cotton.

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.

Viability and stability of biological control agents on cotton and snap bean seeds.

Cotton and snap bean were selected for a multi-year, multi-state regional (south-eastern USA) research project to evaluate the efficacy of both commercial and experimental bacterial and fungal biological control agents for the management of damping-off diseases. The goal for this portion of the project was to determine the viability and stability of biological agents after application to seed. The biological seed treatments used included: (1) Bacillaceae bacteria, (2) non-Bacillaceae bacteria, (3) the fungus Trichoderma and (4) the fungus Beauveria bassiana. Seed assays were conducted to evaluate the following application factors: short-term (< or = 3 months) stability after seed treatment; quality (i.e. isolate purity); compatibility with chemical pesticides and other biocontrol agents; application uniformity between years and plant species. For the bacterial treatments, the Bacillaceae genera (Bacillus and Paenibacillus) maintained the greatest population of bacteria per seed, the best viability over time and the best application uniformity across years and seed type. The non-Bacillaceae genera Burkholderia and Pseudomonas had the least viability and uniformity. Although Beauveria bassiana was only evaluated one year, the seed fungal populations were high and uniform. The seed fungal populations and uniformity for the Trichoderma isolates were more variable, except for the commercial product T-22. However, this product was contaminated with a Streptomyces isolate in both the years that it was evaluated. The study demonstrated that Bacillaceae can be mixed with Trichoderma isolates or with numerous pesticides to provide an integrated pest control/growth enhancement package.

Response of Rotylenchulus reniformis to Nematicide Applications on Cotton.

Field experiments were conducted to evaluate the efficacy of five nematicides for the management of Rotylenchulus reniformis and for their effects on growth, development, and yield of cotton. Treatments included 1,3-dichloropropene (1,3-D), fenamiphos, phorate, terbufos, aldicarb, and 1,3-D + aldicarb. Average R. reniformis population densities across all treatments increased from 5,284 at 10 days after planting to a final density at harvest of 15,622 nematodes/500 cm(3) soil. The 1,3-D + aldicarb combination was the only treatment with an average R. reniformis population density significantly (P