Formulations of Fusarium oxysporum f.sp. erythroxyli for biocontrol of Erythroxylum coca var. coca

Formulations of Fusarium oxysporum Schlechtend:Fr. f.sp. erythroxyli isolate EN-4, pathogenic to Erythroxylum coca var, coca (coca) were evaluated in greenhouse and field studies to determine their relative ability to enhance pathogen populations in the soil or cause disease in coca. The formulations rice-alginate prill, Pesta, and CG were most thoroughly tested and are products of three formulation processes. The formulations were applied in the greenhouse and field at 33.6 kg ha(-1). Ail the formulations tested enhanced the population of EN-4 in the soil during greenhouse (> 6 wk) and field (> 7 mo) experiments. EN-4 was present in the upper 1 cm of formulation-treated soil at > 200-fold higher populations than established below a depth of 7 to 10 cm in both greenhouse and field experiments. This population distribution was maintained throughout the 7-mo sampling period for field experiments. The enhanced soil populations of EN-4 were associated with an increase in root colonization by the pathogen EN-4 in the field 5 to 7 mo after treatment. The formulated F. oxysporum began to have a significant effect on plant death 100 to 200 d after application in two of three field experiments, based on repeated measures analysis. The various formulations rested tended to establish similar pathogen populations in soil and subsequently caused similar levels of disease. The primary factors influencing formulation performance may be environmental, since inoculum production is dependent on sporulation of the formulation, which, although rapid, may continue over several weeks subsequent to application.