Sources of resistance to Diaprepes weevil in subfamily Aurantiodeae, rutaceae

Commercially used citrus rootstocks can all be seriously damaged by larvae of the sugar cane root weevil, Diaprepes abbreviatus (L.). Six greenhouse c hallenge experiments were used to compare the resistance of 24 selections o f citrus rootstocks and related species to this weevil by measuring root da mage, and larval growth and survival. The commercial rootstocks tested were found to be susceptible, while at least seven other species within the sub family Aurantiodeae were observed to be significantly more resistant. The s pecies Balsamocitrus dawei Stapf. was most resistant to weevil larvae, exhi bited less root damage than commonly used rootstock cultivars, and signific antly depressed larval growth and survival. The species Glycosmis pentaphyl la (Retz.) Correa, Microcitrus australis (Planch.) Swing., Eremocitrus glau ca (Lindl.) Swing., Severinia buxifolia (Poir.) Tenore, Triphasia trifolia (Burm. f.) P. Wils., and Citrus hystrix DC. suffered as much damage from th e weevil as common rootstock cultivars but significantly depressed growth o f larvae feeding on them. One new hybrid rootstock, HRS 801, also significa ntly depressed D. abbreviatus larval growth, but this effect has not yet be en verified as having significance in a long-term or field situation. Sever al strategies are discussed for developing citrus rootstocks resistant to D . abbreviatus.