Serious new invasive pest, the citrus root weevil, has arrived in Leon County

Muhammad Haseeb
·3 min read
Citrus root weevils can cause major harm to citrus trees and other crops. Photo by Dr. Muhammad Haseeb.
Citrus root weevils can cause major harm to citrus trees and other crops. Photo by Dr. Muhammad Haseeb.

The citrus root weevil (Diaprepes abbreviatus) is a new invasive insect pest of specialty crops in Leon County. First specimens of the insect were collected at the FAMU Center for Viticulture and Small Fruit Research over the summer from satsuma mandarin trees.

Common host plants of the citrus root weevil include citrus, grapes, papayas, sweet potato, sugarcane, cotton, peanut, corn, and other plant species. The pest is known to feed on over 270 species of plants within 59 different families.

Citrus root weevils not only damage citrus, but also other crops, such as these blackberry leaves.
Citrus root weevils not only damage citrus, but also other crops, such as these blackberry leaves.

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Although the pest is native to the Caribbean basin, it was introduced to Florida in 1964 via an ornamental plant shipment from Puerto Rico.

Since then, the pest has spread over a large area of central and southern Florida and current climate vulnerabilities to production systems are causing the weevil to invade new geographical areas and potential crops.

Recently, it has been recorded in North Florida in Leon County, where it is feeding and breeding on citrus and other host plants.

Damaging crops as it spreads

The pest could reach South Georgia anytime now, where it can be problematic to numerous commercial food crops. Early economic estimates show that the pest causes about $70 million in damage annually in Florida alone and infests more than 100,000 acres of citrus.

Adult weevils notch plant leaves and tender shoots.
Adult weevils notch plant leaves and tender shoots.

Both larval and adult stages of pest can cause serious damage to host plants. In citrus, larvae feed on the roots. After infestation, the plant roots become more vulnerable to Phytophthora fungus. In citrus, even just a few larvae can cause severe damage as they feed, and adult weevils can notch the leaves and tender shoots.

Although most mature plants can tolerate this damage, a single larva can kill a young citrus plant. Citrus root weevil adults emerge from the soil around late May to early July and a second peak occurs in late August to October.

A citrus root weevil adult is less than two cm in length, with a dark black body covered by small white, orange, and/or yellow circular scales. The scales are often rubbed off on the ridges in older weevils, giving the appearance of dark brown to black stripes.

Citrus root weevil eggs are very small, oblong-oval in shape, and are laid in clusters of 30 to 265. They can be found enclosed within leaves that have been folded and glued together by the female.

Economic impact growing

A citrus root weevil adult is less than two cm long and has a dark black body and small white, orange, and/or yellow circular scales.
A citrus root weevil adult is less than two cm long and has a dark black body and small white, orange, and/or yellow circular scales.

The economic impact of damage to nursery plants and open field production is growing. No pheromones are available to monitor pest density and monitoring and sampling of larvae are difficult because larvae feed on roots below ground.

The annual seasonal abundance of weevils in citrus groves can, however, be monitored using traps to capture young adults.

To collect adult weevils, hold a white paper plate right under a branch and shake or beat the branch to dislodge the insects. The use of regular insect sweep nets for collection is also useful. Because of their size, adult weevils can also be hand-picked from host plants.

The seasonal abundance of weevils in citrus groves can be monitored using traps to capture adults.
The seasonal abundance of weevils in citrus groves can be monitored using traps to capture adults.

The presence of adults feeding on citrus can alert growers to control this serious pest, but there are very few pesticides registered for young larval control. Heavy applications of pesticides to control citrus psyllids during the last 10 years has diminished their ability to provide adequate pest control.

A few natural enemies of the citrus root weevil are known, including two egg parasitoids and certain general predators such as a predatory stink bug, the regal jumping spider, and several species of ants. Certain nematode species naturally occurring in Florida’s soil can also provide some control.

It is important for anyone growing citrus or other citrus root weevil host plants to be aware of this emerging pest and to monitor their crops for its presence.

Dr. Muhammad Haseeb is an Associate Professor of Entomology with the Center for Biological Control, College of Agriculture and Food Sciences, Florida A&M University and is a volunteer writer for UF/IFAS Extension Leon County, an Equal Opportunity Institution. For gardening questions, email the extension office at AskAMasterGardener@ifas.ufl.edu.

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This article originally appeared on Tallahassee Democrat: Beware! Invasive citrus root weevil has arrived in Tallahassee