Alginate Prill Formulations ofTalaromyces flavuswith Organic Carriers for Biocontrol ofVerticillium dahliae

Abstract

Pyrophyllite clay (Pyrax), milled chitin, corn cobs, fish meal, neem cake, peanut hulls, soy fiber, and wheat bran were used to make alginate prill with or without ascospores of Talaromyces flavus. The formulations were compared for their ability to induce T. flavus to control Verticillium wilt of eggplant in the greenhouse in field soil and to increase populations of T. flavus in three field soils (two loamy sands, one silty clay). Survival of T. flavus in prill at 5 C or ambient temperature (22-24 C), as well as the carbon (C) and nitrogen (N) contents of the prill, were also determined. Two formulations (corn cobs and pyrophyllite) consistently enhanced biocontrol activity. In treatments without T. flavus, half of all plants were wilted 59 days after transplanting whereas more than half of the plants treated with T. flavus in either pyrophyllite or corn cob prill remained symptomless 90 days after transplanting. In some experiments, T. flavus in soy fiber prill delayed the median time for symptom development by about 10 days. Experiments on survival and proliferation in soils indicated that there were highly significant interactions among carrier, soil, and sampling time. These interactions indicate that the formulations performed differently in different soils. Populations of T. flavus from some prill × soil × combinations increased during the 18-wk experiment while populations from other combinations remained constant or decreased. Populations of T. flavus in two soils (Hatboro loamy sand, silty clay) amended with wheat-bran prill were greater than those with other formulations in the first 2 wk of assay in these two soils. Populations of T. flavus in the loamy sand amended with peanut hull prill were greater than those from other prill at the 8- and 12-wk samplings in this soil. Prill with pyrophyllite and corn cobs had significantly greater C/N ratios than prill with other carriers. Carriers significantly affected survival of T. flavus at 5 C and at ambient temperature. Survival at both temperatures was best in prill formulated with corn cobs, soy fiber and peanut hulls. Temperature did not alter the survival pattern during the 18-wk sampling period