RESPONSE OF MELOIDOGYNE SPP., HETERODERA-GLYCINES, AND RADOPHOLUS-SIMILIS TO TANNIC-ACID

Tannins, which are water-soluble polyphenols, are toxic to numerous fu ngi, bacteria, and yeasts. Our objectives were to study the efficacy o f tannic acid in control of Meloidogyne arenaria on tomato and its eff ects on the behavior of M. arenaria, M. incognita, Heterodera glycines , and Radopholus similis. Three concentrations of tannic acid, 0.1, 1. 0, and 10 g/500 cm(3) of soil, were applied preplant (powder) and at-p lant (powder and drench) into soil infested with M. arenaria. Tannic a cid at the 1.0-g rate reduced galling compared dth the untreated contr ol, regardless of methods of application. The 0.1-g rate resulted in n o reduction in galling when applied preplant but reduced galling when applied as a drench and in one of two experiments when applied at-plan t. The 10-g rate was phytotoxic to tomato seedlings except when applie d 7 days preplant. In the latter case, root galling was suppressed to very low numbers. In behavior studies on water agar, Meloidogyne secon d-stage juveniles were attracted to areas with an increasing tannic ac id gradient. Radopholus similis was repelled from the tannic acid grad ient in one of two experiments. There was no effect on H. glycines. Th e response of M. arenaria second-stage juveniles to different concentr ations of tannic acid dissolved in alginate was tested. Movement behav ior of the second-stage juveniles were observed at 1,000 and 10,000 mu g/ml of tannic acid, but not at 10 and 100 mu g/ml.