Submitted to: Florida Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/5/2009
Publication Date: 3/2/2009
Citation: Duncan, L.W., Stuart, R.J., Gmitter, F.G., Lapointe, S.L. 2009. Use of landscape fabric to manage Diaprepes root weevil in citrus groves. Florida Entomologist 92:74-79. Interpretive Summary: Experiments were conducted at two sites in Florida to determine whether landscape fabric, used as soil mulch, can reduce damage to citrus trees by Diaprepes abbreviatus. The mulches were intended to prevent newly hatched weevil larvae from entering the soil to feed on roots and to prevent teneral adult weevils from exiting the soil to initiate egg-laying. The weight of aboveground parts of trees at a site heavily infested by D. abbreviatus on the east coast was 70% larger (P = 0.05) for trees grown for 3 yr on mulched compared to unmulched soil. At a site on the Central Ridge with low weevil population density, average trunk diameter of mulched trees was 31% greater (P < 0.02) than trees in bare soil. The number of adult weevils captured in traps designed to catch weevils emerging from soil was reduced by more than 99% when traps were installed next to trees on mulch compared to bare soil. Mulching did not affect the amount of feeding damage to roots at the east coast site, suggesting that mulched trees tolerated the damage better than trees in bare soil. Small plot size and relatively narrow fabric dimensions at the east coast site may have facilitated the entry of neonate larvae into soil.
Technical Abstract: The tropical root weevil, Diaprepes abbreviatus, is a major pest of citrus and other crops through the Caribbean and the southern parts of Florida, Texas and California. The larvae hatch from eggs laid by the female weevils on leaves. The newly hatched larvae fall to the ground where they burrow into the soil and begin feeding on plant roots. When development is complete, the larvae pupate in the soil and the emergent adults must burrow their way out of the soil. We tested two types of landscape fabrics as barriers laid underneath the canopy of citrus trees at two locations to prevent the neonates from moving into the soil, and to prevent adults from emerging. Fewer weevils were trapped emerging from plots with landscape cloth. Although feeding on roots by larvae did not appear to be reduced by landscape cloth, the trees grew larger when provided with landscape cloth. It was difficult to demonstrate the effect of a barrier on larvae, but results were sufficiently encouraging to justify further research into this approach.