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The Palmetto Weevil can be found throughout Florida, as far west as southern Texas and as far north as South Carolina. It is North America's largest weevil. This pest has a taste primarily for the Cabbage Palm (sabal palmetto) although it will infest Saw Palmettos (serrenoa repens) and, occasionally, Canary Island Date Palms (phoenix canariensis), Washington Palms (washingtonia), Royal Palms (roystonea), and some coconut palms. The insect is attracted primarily to stressed or damaged trees; healthy trees rarely have weevil infestations. The Palmetto Weevil is generally lethal to cabbage palms and there is, as yet, no effective treatment. In most instances, affected trees should be cut down. In regions of weevil infestation, intensive insecticide application can prevent infestations in valuable healthy trees but, in most cases, this is not an economically viable option.
Palmetto weevils are large and not particularly attractive insects. The legless larvae are fat, yellowish and can weigh up to .25 ounces (7 grams) in the final stage. The mature insects themselves have wings, are black or red, and have a length ranging from .75 to 1.25 inches (2-3.2 cm) long. Weevils are distinguished by large mandibles which extend from the tops of their heads.
Palmetto weevils start life as eggs laid in the leaves or damaged areas of a host tree. After about three days, the eggs hatch and the grubs begin to feed on the tissue of the palm. The larvae grow by moulting and with each successive moult their appetites grow. In their final stage, the mature larvae move from deep within the tree to the outer area and spin cocoons around themselves. Weevils emerge from the cocoons after several weeks to mate. The entire cycle takes about 12 weeks. Mature insects are most noticeable in late spring and early summer.
Damage and control
By the time palmetto weevil damage is noticed, it is generally already too late to save the tree. Damage is first evident in the wilting and dying of younger leaves. As the weevils continue their work inside the tree, the entire crown may weaken and fall over.
Unfortunately, the most effective way to control palmetto weevils is to destroy the affected trees. For healthy palms, it is essential to keep the trees in good condition and, above all, to avoid wounds as these attract weevils. Great care should be taken with lawnmowers and other gardening implements to avoid damaging trees.