The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

A quantitative technique has been developed to assay cotton soils for populations of Thielaviopsis basicola, a soil occurring fungus that causes the seedling disease of cotton known as Black Root Rot. The procedure utilizes a soil dilution technique with a carrot extract agar containing etridiazol, Mystatin, streptomycin sulfate, chlortetracycline, calcium carbonate and PCNB. Populations of the fungus have been monitored from April to December, 1986 in a heavily infested Pima S-6 field in cooperation with Bob Cockrill, a Coolidge grower. When field soils containing approximately 600 propagules of the fungus per gram of air dry soil were planted to Pima S-6 in the laboratory, 75-100% and 50-75% cortical decay occurred at 20 and 28 C, respectively. This seedling damage was related to subsequent reduced seedling vigor.

Application of two systemic fungicides, propiconazole (Tilt) and triadimenol (Summit), through subsurface drip irrigation resulted in a significant reduction in the number of dead plants in a Phymatotrichum-infested cotton field. The percent reductions in Tilt treatments were 72% in 1985 and 66% in 1986 and in Summit treatments were reduced 90% in 1985 and 70% in 1986.

Greenhouse techniques were developed to evaluate cotton cultivar susceptibility to Alternaria leaf spot. Results indicate that Deltapine Acala 90 is more susceptible to Alternaria leaf spot than other Gossypium hirsutum varieties tested but that it is less susceptible than the G. barbadense varieties Pima S-5 and Pima S-6.

No description available.

The effects of cotton leaf crumple disease on components of yield and on symptom expression were examined for cotton inoculated at five growth stages. As a result of virus infection, the total leaf area was reduced and significant reductions in yield were observed, regardless of plant age at time of inoculation. Yield reductions resulted from a smaller number of bolls set and/or a decrease in boll weight. Foliar symptoms were associated with plants inoculated at all five growth stages, but were observed sooner and were more severe for plants inoculated at the 2-3, 5-8, and 8-10 leaf stages than those inoculated at the 14-16 or 18-20 leaf stages.

No description available.