Cotton (Gossypium spp) has been the first large-scale, agronomic crop in the United States treated with a biological-control agent (BCA) for suppression of seedling diseases and long-term chronic diseases of the rhizosphere. The vast majority of cotton seed planted in the United States is now treated with Bacillus subtilis strain GB03, registered as Kodiak (Gustafson, Inc, Plano, TX, USA). Responses are typically a mixture of growth promotion (increased root mass) and disease suppression (Rhizoctonia and Fusarium spp). Strain GB03 shows exceptional rhizosphere competence, colonizing the rhizosphere of monocots and dicots. Though the initial success of strain GB03 has been observed in the production of cotton, other crops have shown positive yield responses following bacterization. Since B. subtilis is a spore-forming organism, it is extremely tolerant of environmental stresses, including seed-treatment pesticides, soil and seed pH, cultivar effects, edaphic factors and long-term storage. More importantly, it is readily produced with current fermentation technology. Other BCAs, such as Pseudomonas spp, do not readily adapt to large-scale production methods, and stability is a limiting factor. In order to be successful, scale-up production must provide a product with efficacy equivalent to the laboratory model. A better understanding of how fermentation and other production processes affect the efficacy and rhizosphere competence of biocontrol organisms is now required by the industry. Processes have to be carefully optimized for both maximum production and maximum efficacy. A strong collaboration and understanding between the agricultural industry and industrial microbiologists are required to continue the advance of new biologicals such as Kodiak.

A program of monitoring virus diseases with emphasis on geminiviruses including CLCuV in Sindh was initiated in late 1996. Hyderabad, Sanghar and Nawabshah districts were surveyed during September, 1996 and the districts of Ghotki, Sukkur, Khairpur and Naushehro Feroze during January, 1997. CLCuV-like symptoms showing curling, cupping upward/downward and shortening of leaves, thickening of veins and development of enations of underside of leaves were observed in cotton fields around Ubaro in district Ghotki. The presence of CLCuV was confirmed through Triple Antibody Sandwich Enzyme Linked Immunosorbent Assay (TAS-ELISA) using panel of Monoclonal Antibodies against whitefly-transmitted geminiviruses (WTGs), polymerase chain reaction (PCR) using CLCuV- specific primers and by reproducing CLCuV symptoms in cotton (cv. S-12) through whitefly inoculation under controlled conditions.

Seedling diseases of cotton (Gossypium hirsutum L.) limit production in the High Plains of Texas. Field studies were conducted from 1992 through 1995 to determine the influence of tillage (conventional or terminated wheat [Triticum aesrivum L.] conservation tillage system), seed quality, and fungicide seed treatments (specific for Rhizoctonia solani, Pythium spp., and Thielaviopsis basicola) on cotton emergence and lint yield. Seed quality positively affected plant emergence and yield in all years. Increases in plant emergence and yield were generally found with conventional rather than conservation tillage. Emergence 21 d or later was generally lower for untreated seed or Captan (C) (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide) treated seed than seed treatments that included triadimenol (Baytan 30 [B]) (Beta-(4-Chlorophenoxy)-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol) in 3 of 4 yr; carboxin-PCNB (Vitavax-PCNB [V]) (5,6-dihydro-2-methyl-N-phenyl-1,4-oxathiin-3-carboxamide-Pentachloronitrobenzene) in 2 of 3 yr and metalaxyl (Apron 2.66F [A]) (N-(2,6-dimethyl-phenyl)-N-(methoxyacetyl)alanine methyl ester) + C in one year. Yields were affected by seed treatments in 3 yr, with B being associated with higher yields every year, and lower yields associated with chloroneb (Nuflow ND [N]) (1,4-dichloro-2,5-dimethoxybenzene) + TCMTB (2-(thiocyanomethylthio) benzothizaole (1992), untreated seed (1994) and C (1995). Plants were infected most frequently with R. solani and T. basicola. The most consistent factor affecting seedling disease was seed quality. Conventional tillage and seed treatments specific for Rhizoctonia and Thielaviopsis improved seedling emergence and yield most years. Interactions between chemical seed treatments, seed quality, and tillage systems were inconsistent between years and even among different evaluation times in the same year. Research QuestionWhat are the effects of chemical seed treatments, tillage system, and seed quality, interactions as well as separate effects, on seedling emergence and cotton yield. Literature SummaryEvidence has shown that seedling disease can be higher under conservation tillage systems than conventional tillage systems. Cotton seedling emergence can be affected by seed quality and some seed treatment fungicides. However, interactions between these factors have not been studied. The impact of tillage systems on seedling emergence when seed quality varies, or with different seed treatments, is unknown. The question of whether use of new fungicides with moderate or low quality seed will adversely affect emergence is of great interest to producers. Study DescriptionThis field study was conducted from 1992 to 1995 on land that had been in either conventional tillage or conservation tillage (cotton drilled into terminated wheat) since 1986. Within each conventional or conservation tillage area, treatments consisted of three levels of seed quality and five to six fungicide seed treatments, specific for certain pathogens. Cotton emergence was monitored weekly and plots were harvested for yield. In 1994–1995, cotton roots were examined for disease symptoms, and pathogens were isolated. Applied QuestionsWere cotton emergence and yield responses from seed of different quality similar in conservation and conventional tillage treatments? Cotton emergence was positively associated with seed quality, for both conservation and conventional tillage systems. Emergence was higher in conventional tillage plots for each seed quality level than in conservation tillage plots in 2 of 4 yr. Was cotton emergence affected by new fungicide seed treatments interacting with tillage practices? Tillage did not have a consistent influence on any particular seed treatment. Were cotton emergence and yield responses negatively affected by triadimenol (Baytan 30) when combined with lower quality seed? No. Triadimenol was associated with reduced early emergence with all seed quality levels, and superior, final emergence with all seed qualities as compared with untreated seed or Captan treated seed.

Twenty-five field trials conducted over a 3-year period in five San Joaquin Valley counties included the following treatments: nontreated cotton seed; seed treated with myclobutanil for the control of Rhizoctonia solani-induced damping-off; seed treated with metalaxyl for the control of Pythium-induced damping-off; and seed treated with a combination of the two fungicides. The following parameters were measured: soil populations of Pythium spp. and R. solani at planting, soil temperature at planting, air temperatures for 5 days after planting, soil particle analysis, EC, calcium, pH, organic matter, and plant stands from each treatment. In 1993 and 1994, myclobutanil and the combination of the two fungicides resulted in improved stands in 15 of 18 fields. Metalaxyl did not increase stands in any field in 1993 to 1994. In 1995, the combination of fungicides increased stands relative to the nontreated seeds and was more effective in increasing stands than myclobutanil or metalaxyl alone. Pythium populations were much greater in 1995 than in 1993 to 1994 and may explain the increase in plant stands with the combination of fungicides and metalaxyl alone. Covariate analysis of the data indicated no relationship between stand increases from fungicide seed treatment and any of the soil parameters measured. Heat units following planting were not limiting and had no effect on stands. Populations of pathogens were not related to benefits of fungicides, with the exception of a negative correlation between stand increases from seed treatment with myclobutanil and Pythium populations. Apparently, seed protected with a fungicide active against R. solani were more susceptible to infection by Pythium spp. In general, the fungicide seed treatment active against R. solani increased stands of the cultivar Maxxa regardless of soil type and pathogen populations. Increased stands from the metalaxyl treatment occurred in 1 of the 3 years of the study.