LEGUMINOUS COVER CROPS AND THEIR INTERACTIONS WITH CITRUS AND DIAPREPES ABBREVIATUS (COLEOPTERA: CURCULIONIDAE)

Abstract

Three legume species with potential as cover crops in citrus groves were studied for their effect on the developmental biology of the Diaprepes root weevil, Diaprepes abbreviatus (L.) in greenhouse studies. All 3 cover crops were hosts for the Diaprepes root weevil. Cajanus cajan (pigeon pea) was a superior host for development of D. abbreviatus compared with citrus rootstocks. C. cajan appeared to be allelopathic; the root mass of uninfested citrus was greatly reduced when grown in association with C. cajan compared with citrus grown alone. Association of citrus with C. cajan or Arachis pintoi (perennial peanut) reduced chlorophyll fluorescence, a measure of photosynthesis, compared with citrus associated with Crotalaria pallida (rattlebox) or with another citrus seedling. When grown in close association with A. pintoi, citrus produced the same amount of root mass as citrus seedlings grown alone. Infestation with larval D. abbreviatus reduced chlorophyll fluorescence of citrus by 26%. None of the 3 legume species tested reduced the feeding damage caused by D. abbreviatus to citrus. Larvae reared in pots with A. pintoi, associated with citrus or alone, gained weight at the same rate as larvae reared on the citrus rootstocks alone. Larvae recovered from pots containing C. pallida associated with citrus weighed significantly more than larvae reared on citrus alone. C. cajan appears to be particularly inappropriate as a cover crop because of its positive effect on larval growth and reduction of citrus root mass. None of the 3 legume species tested had a negative effect on D. abbreviatus or on feeding damage.