Spring has finally made her appearance after a very long winter. Shockingly warm days this past week has made leaves seem to explode in the landscape. Along with the flush of green in the lawns and bursting leaves on the trees and perennials, is the return of two unwanted pests: the lily leaf beetle and garlic mustard.
The lily leaf beetle larva from last year spends the winter in the soil as a pupa changing into the adult beetle form sometime during the unseen underground respite. As the soil warms and the lilies poke up from the soil in the spring, the lily leaf now adult beetle comes out also. The beetles will begin to feed on lily leaves. They will also mate after which the female will lay eggs on the under side of the lily leaf. Eggs will hatch in a few days into a cream colored hump-backed grub. The grub will begin to feed on the lily leaves. Here is the gross part; when the grub poops, it will pile the excrement on its back. This is a protective measure so birds and other predators will not want to eat it! It seems to work as I find no predators eating the poop covered immature in my garden. Once the grub has grown large over a 16 to 24 day period, they drop to the ground to pupate. Adults emerge 16 to 22 days later, feeding on mostly lilies and sometimes on frittilaria, lily of the valley and a few other plants. Lily leaf beetles will only lay eggs on true lilies and larva will only feed on true lilies also. Daylilies are not true lilies and not a host for larva or adult lily leaf beetles. Control measure are handpicking all life stages or spray neem oil on the larva.
Garlic mustard is a very prolific and invasive weed. It is blooming now, showing off its many white flowers, producing incredible amounts of seed later in the season. It is believed that the European settlers brought the original plants or seeds with them here as a food or medicinal source in the 1600′s. It has become nuisance along roadsides and un-mowed areas. Garlic mustard is a biennial, producing low rosettes of leaves the first year and shooting up two to four feet with a flower stalk the second year, then the plant dies leaving a multitude of new seed to germinate in subsequent years. What makes this plant particularly obnoxious is its ability to stop growth of virtually all surrounding plants growing nearby, displacing the native plants and diverse food sources for many animals. Control can be had by continued hand removal or herbicides. Glyphosate is the recommended chemical herbicide.
- Carol Quish