Control of Phytophthora nicotianae with Mefenoxam, Fresh Brassica Tissues, and Brassica Pellets

Abstract

Morales-Rodríguez, C, Palo, C, Palo, E., and Rodríguez-Molina, M. C. 2014. Control of Phytophthora nicotianae with mefenoxam, fresh Brassica dssues, and Brassica pellets. Plant Dis. 98;[77][78][79][80][81][82][83] Sensitivity to mefenoxam, fresh Brassicaceae dssues, 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 (ECjo and EC90, respecdvely). Sensitivity differendated 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. olerácea varied depending on the dose. Isolates differed in susceptibility to compounds released by the Brassica pellets and then in the EC50 and Edjo. 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 populadons. Biofumigation is a promising technique which can be further developed to form part of integrated pest management strategies.Phytophthora nicotianae Breda de Haan (= P. parasitica Dastur) is one of the most widespread and destructive soilbome plant pathogens. This oomycete is also known as a worldwide pathogen on tomato and pepper plants, causing disease in many countries (12), Soil fumigation with toxic volatile compounds is a usual practice to control this pathogen. Currently, many of the compounds used in this control, such as methyl bromide, 1,3-dichIoropropene, or chloropicrin, are not included in Annex I (Directive 91/414/CEE). Since its first introducfion in 1977, metalaxyl and its more recent isomer mefenoxam have been used widely and intensively to control of diseases caused by oomycetes in numerous crops, including ornamentals (9,12), and it is one of the few products currently allowed in this region. Development of resistance to metalaxyl and mefenoxam has been frequently detected in several Phytophthora spp. and oomycetes (17,27,42). Information on fitness of mefenoxam-resistant and -sensitive populations in P. nicotianae is particularly important because of its central role in population dynamics and in making antiresistance strategies (16). To detect shifts in metalaxyl sensitivity within a given Phytophthora sp., the natural range of sensitivity needs to be determined. Inhibifion of mycelial growth in vitro has been used as the primary method for detennining metalaxyl sensitiv...

Microbiota Characterization of Compost Using Omics Approaches Opens New Perspectives for Phytophthora Root Rot Control

“…nicotianae causes root- and collar- rot in pepper plants ( Capsicum annuum L.) and has become a major disease during the last years [ 3 – 5 ]. Management of this disease is based on soil fumigation using compounds such as methyl bromide, 1,3-dichloropropene, chloropicrin, metalaxyl and mefenoxam [ 6 ]. The banned use of most of these products and their inability to totally control the disease, have prompted the exploration and identification of new approaches.…”

Efficacy of Biofumigation with Brassica carinata Commercial Pellets (BioFence) to Control Vegetative and Reproductive Structures of Phytophthora cinnamomi

“…In pellets, the GSL-myrosinase system is not compartmentalized and ITC are formed when water is added to the treated soil. A previous study with P. nicotianae showed that 320 g of fresh B carinata tissue only slightly inhibited (40%) the culture diameter in contrast to 40 mg of BioFence pellets, which had a fungicidal effect (Morales-Rodríguez et al 2014).…”

“…In vitro inhibition tests. Trials were conducted using BioFence pellets (4 mm in diameter and 3 to 7 mm in length) according to the protocol described by Morales-Rodríguez et al (2014). For use, the pellet was crumbled with a mortar and pestle.…”