natural-products-in-plant-pest-management

Suppressive Effects of Compost Tea on Phytopathogens 253with sludge from distillation and tartrate recovery to produce fertilizers foragricultural use (Johnston, 2001).In general, grape-marc compost (GMC) has low nutrient status and conductivity;this compost has low water-holding capacities. It has a high contentof lignin and cellulose and a low content of water-soluble carbohydrates.There are a few reports about the disease-suppressive effects of GMC.Oka and Yermiyahu (2002) tested in pot and in vitro experiments the suppressiveeffects of GMC, on the root-knot nematode Meloidogyne javanica. Veryfew root-galls were found on tomato roots grown in soil containing 50%grape marc compost. Significant reductions in galling index were also foundin tomato plants grown in soils containing smaller concentrations of thiscompost. The water extract of GMC showed weak nematicidal activity to thejuveniles and eggs.GMC and its water extracts have been reported to suppress fungal diseasessuch as B. cinerea on tomato and pepper (Elad and Shtienberg, 1994).GMC suppressed the soilborne disease caused by R. solani and S. rolfsii(Gorodecki and Hadar, 1990; Hadar and Gorodecki, 1991). Hadar andGorodecki (1991) found an inhibitory effect of GMC on sclerotial germinationand viability, and associated this effect with high numbers of Penicilliumisolated from sclerotia. Penicillium and Aspergillus spp. have been reported tocolonize GMC; Trichoderma spp. hyperparasites of R. solani were not recoveredfrom this compost (Gorodecki and Hadar, 1990; Hadar and Gorodecki,1991). The age of the composted grape marc had a major effect on suppression;immature GMC (3 months of composting) failed to inhibit sclerotialgermination (Hadar et al., 1992). Suppression of Pythium aphanidermatum wasreported on grape marc compost, the beneficial effect of the compost wasnegated when the medium was autoclaved, and restored when compost thathad not been autoclaved was mixed with the sterile one (Hadar et al., 1992).Compost can provide natural biological control of diseases of roots aswell as the foliage of plants. Its water extracts (compost tea) has been proposedas a substitute for synthetic fungicides (Zhang et al., 1998). Most of thepapers published on the control of pathogens by means of compost tea havestudied pathogens from the aerial part of the plants, the number of trials thatuse NTC being higher. Research into the control of soilborne pathogens bymeans of compost tea has been lower, although this practice is common inecological agriculture (Scheuerell and Mahaffee, 2002a).Our research focuses on soilborne disease suppression by GMC. Thegrape marc compost was produced in the University of Sevilla. It was compostedin 40 m 3 windrows and turned each week. Composting took 5 months.During composting, the grape marc pile was fertilized with ammoniumnitrate, superphosphate, iron sulfate and magnesium sulfate. Microbiologicalanalysis of our grape marc was performed using the dilution plate technique(Wakelin et al., 1998) on different agar growth media: water agar (WA)pH11 (actynomicetes), tryptose soy agar (TSA) 1/10 (bacteria), glucose peptonemedium (GP) (yeast) and malt extract agar (MEA) (fungi). All the plateswere incubated at 25°C, and WA and TSA plates were also incubated at 40°C,for detection of thermophylic bacteria and actynomicetes. Two analyses of