natural-products-in-plant-pest-management

Suppressive Effects of Compost Tea on Phytopathogens 251less than 2% of 80 different batches of compost tested induced systemic resistancein radish (Raphanus sativus) against bacterial leaf spot. The effect wasdue to the activity of specific biocontrol agents in the batches of compost thatsuppressed bacterial leaf spot. They identified Trichoderma hamatum 382(Bonord.) Bainer (T 382) as the most active inducer of ISR in radish (Khan et al.,2003). Another species of the genera Trichoderma (Trichoderma harzianum RifaiT-203) was reported as an inducer of ISR in pepper (Capsicum annum) seedlingsagainst Phytophthora capsici when the seeds were previously treated with thisbiological agent (Ahmed et al., 2000). Khan et al. (2003) report how Phytophthoraroot and crown rot of cucumber caused by P. capsici was suppressed significantlyin cucumber transplants produced in a composted cow-manureamendedmix compared with those in a dark-sphagnum-peat mix. In split-rootbioassays, Trichoderma hamatum 382 (T 382) inoculated into the compostamendedpotting mix significantly reduced the severity of Phytophthora rootand crown rot of cucumber caused by P. capsici on paired roots in the peatmix. This effect did not differ significantly from that provided by a drenchwith benzothiadiazole (BTH) or mefenoxam (Subdue MAXX).12.3 Suppression of Plant Pathogens by Compost TeaThe disease-suppressive characteristic of organic tea was reported as early as1973 by Hunt et al. immobilizing the sting nematode (Belonolaimus longicaudatus).Compost tea or compost water extract can be defined as a wateryextract of compost produced through a deliberate process. The goal is toenhance populations of beneficial microbes that can then exert a biologicalcontrol over pathogens. The terminology used is not clear because there areseveral different methods used for making compost teas, those where tea isaerated during the production of the tea, and where no aeration is used andcompost is just passively steeped with little agitation. The review of Scheuerelland Mahaffee (2002a) clarified the numerous terms that have been used todescribe composts’ fermentation; many are synonymous or easy confusedwith other concepts. Terms used include compost tea, aerated compost tea,organic tea, compost extracts, watery fermented compost extract, amendedextracts, steepages and slurries. Compost tea is produced by mixing compostwith water and culturing for a defined period, either actively aerating (aeratedcompost tea; ACT) or not (non-aerated compost tea; NCT) and with orwithout additives that are intended to increase microbial population densitiesduring production (Scheuerell and Mahaffee, 2002a). These teas havebeen shown to act as a natural fungicide; they contain populations of variousbiofungicidal microbes and organic chelators Teas can be used as a foliarspray to inhibit late blight caused by Phytophthora infestans on tomatoesand potatoes, the suppressive effect of organic teas are of a living microbialnature and the sterilized or micron-filtered tea had little ability to impact onpathogens (Weltzien and Ketterer, 1986; Weltzien, 1989).There are several reports on the control of plant pathogens or plant diseaseswith organic teas including airborne and soilborne diseases; compost