Texas Gourd (<i>Cucurbita texana</i>) Control with<i>Fusarium solani</i>f. sp.<i>cucurbitae</i>

Abstract

An indigenous soil-borne fungus was isolated from infected seeds and seedlings of Texas gourd [ Cucurbita texana (A.) Gray] and evaluated as a mycoherbicide. The pathogen was identified as Fusarium solani App. &amp; Wr. f. sp. cucurbitae Snyd. &amp; Hans. Only Cucurbita species were susceptible in host range tests. Ample quantities of microconidia for greenhouse and field plot inoculum were produced in shake culture on Richards' solution. Granular inoculum for field plot tests was produced in 5% (w/w) cornmeal/sand medium. In controlled-environment experiments, inoculated Texas gourd seedlings were killed over a range of air temperatures from 16 to 40 C. Optimum air temperature for disease development was 26 to 30 C. Complete kill of 4- and 8-cm-tall seedlings was achieved after 3 weeks when sprayed until runoff with a microconidial suspension containing 2.0 × 10 6 spores/ml. Texas gourd seedlings were effectively controlled in field plots (99% maximum) with liquid or granular inoculum. Soil samples from infested plots indicated that the fungus persists up to 12 months in a fine sandy loam, but after 12 months inoculum levels were insufficient to cause disease on seedlings grown under optimum conditions for disease development.