Effect of foliar applications of neem oil and fish emulsion on bacterial spot and yield of tomatoes and peppers

Abstract

Foliar applications of neem oil and fish emulsion, derived from neem seed and menhaden fish, respectively, were tested for their ability to reduce bacterial spot of tomato and bell pepper under both greenhouse and field conditions. Greenhouse-grown tomato and pepper plants sprayed with aqueous suspensions (0.5%, v/v) of neem oil or fish emulsion and then inoculated with Xanthomonas campestris pv. vesicatoria showed less disease symptoms than the water-treated controls. Weekly foliar sprays of neem oil and fish emulsion reduced disease severity on the foliage of inoculated field-grown tomato and pepper plants in both years of a two-year study. The disease incidence on the fruit of these plants was reduced but the effect was not always statistically significant. However, the number of lesions per pepper fruit were consistently lower with these treatments. Fish emulsion increased healthy and total fruit yield of tomatoes in 2000 and healthy fruit yield of peppers in 2001, whereas neem oil increased the yield of disease-free peppers in both years. Neem oil and fish emulsion had no observable phytotoxic effect on tomato or pepper foliage in the field. These results suggest that disease-management programs for bacterial spot may be enhanced by including foliar sprays of these products.