RESUMO
Sensitivity to mefenoxam, fresh Brassicaceae tissues, and Brassica pellets was evaluated in several isolates of Phytophthora nicotianae recovered from pepper and tomato plants. The isolates of P. nicotianae studied were classified as sensitive to mefenoxam, showing great variability among isolates in the 50 and 90% effective concentrations (EC50 and EC90, respectively). Sensitivity differentiated isolates from the two hosts of origin, being isolates from tomato plants more resistant to fungicide than those from pepper plants. This differentiation also occurred in the case of fresh Brassicaceae tissues assay. The most effective biofumigant in inhibiting mycelial growth of P. nicotianae isolates was Brassica nigra. The effectiveness of B. carinata, Sinapis alba, and B. oleracea varied depending on the dose. Isolates differed in susceptibility to compounds released by the Brassica pellets and then in the EC50 and EC90. No significant difference was found between the isolates depending on the host of origin. Greenhouse tests demonstrated the effectiveness of treatments with mefenoxam and with Brassica pellets to control P. nicotianae in pepper plants. Mefenoxam application could be a solution to the disease caused by P. nicotianae in tomato and pepper crops in this region but its use could increase resistance in populations. Biofumigation is a promising technique which can be further developed to form part of integrated pest management strategies.
RESUMO
BACKGROUND: Biofumigation with defatted seed meal of Brassicaceae in the form of pellets has several advantages over the incorporation of fresh Brassicaceae crops to control soil-borne diseases. Two field experiments were established to evaluate the effect of biofumigation with brassica pellets on the survival and infectivity of Phytophthora nicotianae Breda de Haan inoculum introduced before treatments. In the spring experiment the incorporation of additional Brassicaceae cover crop (Brassica nigra L. and Sinapis alba L.) was tested, and in the summer experiment two brassica pellet doses were applied. RESULTS: Biofumigation with brassica pellets in spring (3000 kg ha(-1) with and without plastic) or in summer (3000 kg ha(-1) with or without plastic; 6000 kg ha(-1) without plastic) had no significant effect on the survival of P. nicotianae, regardless of the incorporation of additional Brassicaceae cover crop in spring. Reduction in infectivity in spring was related to the application of plastic, especially when combined with brassica pellets and Brassicaceae crop. In summer, soil temperature was the main factor in the inactivation of the inoculum, especially when plastic was applied, and no additional inactivation was achieved with brassica pellets. CONCLUSION: In spring and summer, biofumigation with brassica pellets had no effect on the survival of P. nicotianae. Application of plastic in spring may reduce infectivity. Soil temperature is the main factor in the inactivation of inoculum in summer, especially when plastic is applied. © 2015 Society of Chemical Industry.