Weevils are a type of beetle with mouths at the end of a sometimes very long head. They’re an important group of insects to be familiar with – most feed on plant material, and many are considered to be economic pests. The largest weevil in North America is the palmetto weevil (Rhynchophorus cruentatus), which is native to the US and attacks stressed and dying palm trees.

Palm Weevil larva

A palm weevil larva is quite large.

Photo Credit: ©2005 Buglady Consulting

Palm Weevil adult

An adult palm weevil can measure over an inch long.

Photo Credit: ©2005 Buglady Consulting

Palmetto weevil adults are large – about ¾ to 1¼ inches long – and vary in color from solid black to almost completely red with a variable black pattern. The larvae, or “grubs,” are legless and a creamy to yellowish color. They have dark brown heads and are very hard. Mature larvae can be large as well, measuring over an inch long with a mass of close to a quarter of an ounce!

Eggs are laid in the bases of leaves of stressed or dying palm trees. After hatching, larvae feed on the plant’s stem tissue. Mature grubs move to the outside of the stem and make a cocoon from palm fibers. Adults emerge from the cocoon and live for several weeks on or near palm trees.

Symptoms of palmetto weevil infestation usually involve an initial decline of younger leaves. As the infestation progresses, larval feeding damage and secondary rot can weaken the tree enough that the top falls over. This condition is called “popped neck.”

Early detection of weevil infestation is difficult, and insecticidal treatment – even in the early stages of infestation – is futile. The best management tactic is to cut down infested palms and destroy them before adults emerge from the tree and lay more eggs.

To prevent infestation, chose healthy trees well-adapted for the Florida climate such as sabal palmetto or royal palms. Once trees are established, follow proper fertilization and irrigation guidelines to promote healthy growth and avoid wounding the trees.

The palmetto weevil is a magnificent specimen from the insect world. It’s thought that before we began the practice of growing and transplanting palm trees, palmetto weevils were relatively rare – most likely surviving in palm trees killed by lightening strikes. It would appear that we have inadvertently increased the palmetto weevil population through our love of landscaping.