7/2/2013 - By Matthew Shultz

This month I wanted to discuss an insect pest that causes damage both as a larvae and an adult.. the weevil. Not many insect nursery pests cause damage both during both lifestages, so the weevil is unique in that sense. This is also the reason why weevils can be such a problem in the production setting and landscape. In most areas the Black Vine Weevil is the most common weevil pest but other species include Arborvitae weevil, Fuller Rose weevil, and in the northeastern US the Two-banded Japanese Weevil.

The Black Vine Weevil overwinters in the soil as a larvae, and in the spring comes out of dormancy and starts to feed on the roots of many broadleaf evergreen plants including Rhododendron, Yew, Hemlock, and Euonymous. Arborvitae weevils feed on Arbs as well as some cedars, the Fuller Rose Weevil obviously feeds on Roses and other deciduous ornamentals and fruit trees, and the Two-banded Japanese Weevil feeds on azaleas, hollies and some deciduous material too. Once the larvae has grown and is ready to pupate, usually early summer depending on the species, it will emerge as an adult. The adults of most species are flightless or are clumsy fliers at best.

Weevil adults are easily identified because all have a trunk like appendage as their mouthpiece, much like an elephant. This mouth part is used for chewing and adults can “notch” out large portions of leaf material which is a dead giveaway to their presence. Holes typically start from the leaf margin and continue in towards the leaf mid-vein. In some weevil species like the Black Vine weevil the females produce eggs without the need for a male. The easiest way to control the Black Vine weevil is by targeting the larvae while they are active in the soil in early spring. Use beneficial nematodes to target the larvae in the soil. Soil applications of insecticides like Orthene, Mavrik, or Duraguard can help too. Adults are very difficult to control!

Black Vine Weevil on Spinach – Photo taken by Matthew Shultz

Weevil – Photo by Matthew Shultz