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 challenge experiments were used to compare the resistance of 24 selections of citrus rootstocks and related species to this weevil by measuring root damage, and larval growth and survival. The commercial rootstocks tested were found to be susceptible, while at least seven other species within the subfamily Aurantiodeae were observed to be significantly more resistant. The species Balsamocitrus dawei Stapf. was most resistant to weevil larvae, exhibited less root damage than commonly used rootstock cultivars, and significantly depressed larval growth and survival. The species Glycosmis pentaphylla (Retz.) Correa, Microcitrus australis (Planch.) Swing., Eremocitrus glauca (Lindl.) Swing., Severinia buxifolia (Poir.) Tenore, Triphasia trifolia (Burm. f.) P. Wils., and Citrus hystrix DC. suffered as much damage from the weevil as common rootstock cultivars but significantly depressed growth of larvae feeding on them. One new hybrid rootstock, HRS 801, also significantly depressed D. abbreviatus larval growth, but this effect has not yet been verified as having significance in a long-term or field situation. Several strategies are discussed for developing citrus rootstocks resistant to D. abbreviatus.