Is The Diaprepes Root Weevil An Emerging Blueberry Pest?

Photo by Robin Stuart

Photo by Robin Stuart

The Diaprepes root weevil (Diaprepes abbreviatus) was the most important and damaging insect pest of citrus prior to the arrival of the Asian citrus psyllid that transmits huanglongbing. The pest was introduced to Florida from the Caribbean in the 1960s. Adult D. abbreviatus feed and lay eggs on young foliage of many plant species. The hatched larvae fall to the soil where they feed on and seriously damage the plant roots. In citrus, the wounded roots are more readily infected by Phytophthora spp. Adults emerge from soil in citrus groves throughout the year, but mostly in spring and sometimes autumn.

Evil Weevils

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The economic importance of these weevils depends to some extent on the local soil habitat. In flatwoods regions and especially in poorly drained soil, weevil populations often are large and tree damage is greatest. Damage even to very young trees is common under these conditions. On the deep sandy soils of the Central Ridge, weevil populations tend to be smaller and trees often do not exhibit damage from root feeding for many years. Nevertheless, even on the Central Ridge, the wounds caused by larval feeding do not heal and the damage accumulates to eventually become evident as trees decline. The reasons weevil abundance varies among Florida’s ecoregions are poorly understood, but variable larval mortality from natural enemies such as ants and naturally occurring beneficial (entomopathogenic) nematodes has been shown to play a role.

Photo by Larry Duncan

Photo by Larry Duncan

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Despite their widespread occurrence throughout South and Central Florida, there are few reports of damage by Diaprepes root weevils to blueberries. This situation could change, because the weevil is clearly capable of severely damaging blueberry bushes in farms where damage has been detected. The extensive bedding preparation necessary for blueberry production may present pest management opportunities if soil conditions that are least favorable for weevils can be identified.

Florida citrus growers use chemical insecticides and growth regulators respectively to kill adult D. abbreviatus and prevent egg hatch. Chemical soil barriers also are available to kill neonates entering soil and adults emerging from soil. Entomopathogenic nematode products to manage larvae in soil can be effective, but are currently unavailable. Additional information about Diaprepes root weevils and weevil management can be found here.

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