No description available.

No description available.

No description available.

Leaf drop of lettuce, caused by the fungus Sclerotinia sclerotionunb is a sporadic but potentially destructive disease in Arizona During the 1988-89 lettuce season in western Arizona, different fungicides and formulations of materials were evaluated in the field for disease control. All tested compounds provided significant disease suppression and increased yields, provided that a sufficient rate of fungicide was applied. Ronilan and Rovral, the two fungicides currently registered for use on lettuce for Sclerotinia leaf drop, were the most effective fungicides in this test, performing significantly better than the two experimental materials. The SODF formulation of Ronilan provided significantly better disease control than the SOW formulation of the same compound.

No description available.

Infection by lettuce infectious yellows vines was reduced in lettuce treated with stylet oil. There was a difference in the final infection level between treated and untreated blocks and reduced infection in early readings. Yields were slightly better in the treated blocks. It has not been determined if and under what conditions it would be feasible to use this treatment on a practical scale.

No description available.

No description available.

Bottom rot of lettuce, caused by the soil -borne fungus Rhizoctonia solani, can cause economic losses on early season lettuce harvested in November. First evidence of the disease is the appearance of brown, sunken, necrotic areas on the midribs of leaves touching the soil. Under favorable environmental conditions, the pathogen grows from leaf to leaf inside the head. If the fungus invades the leaves of the marketable head it and all similarly infected heads are left in the field resulting in economic losses. Field trials were established to evaluate the potential level of disease control obtainable by applying Ronilan or Rovral to lettuce beds immediately after thinning. No significant reduction in loss of marketable heads was observed in these trials, although there was a trend toward lower levels of bottom rot when either fungicide was in place.

A field study was conducted at Yuma in 1991 to examine the relative effectiveness of several formulations of Bacillus thuringiensis on beet armyworm and cabbage looper on seedling and pre-cupping lettuce. Several applications were made before and after thinning. Results of the study suggest that most formulations are capable of controlling small larvae. However, because of the inherent variation in beet armyworm dispersion, it was difficult to statistically attribute differences in pest levels due to insecticide efficacy.