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Award of Merit Article

Rose Curculio

by Nanette Londeree, Consulting Rosarian

Have you ever seen these critters in your rose garden, or worse yet, do you have any of these symptoms - roses with petals that resemble Swiss cheese; young buds that have dried up, or stems that are broken just below the bud? Well, you are not seeing lady beetles without spots. What you are seeing are the real bad guys of the rose garden. Meet the Rose curculio or rose weevil (Merhynchites bicolor). These destructive beetles are about inch long, bright red to dull black , and have the very characteristic narrow, black, curved snout with a set of antennae midway up. They are chewing insects, with biting mouthparts on the end of their long snouts. These weevils feed on all types of roses, especially shrub roses. Left unchecked, they can do serious damage to your roses.

Rose Curculio
The reproductive cycle begins when females lay eggs in hips and flower buds in late May and June. The legless larvae (up to 1/4 inch in length) emerge from the buds and feed on the reproductive parts of the flower, seeds and to some extent petals. Buds damaged by larvae will often be deformed or may not open at all. They drop to the ground to pupate in soil over the winter and the single annual generation emerge as adults in late spring to early summer. They crawl up to feed on flower buds. When few buds are present, adults may feed on the tips of new rose shoots, causing the terminals to die. They can also gouge bud stems, causing the bud to wilt and then die. Feeding on the stem below the bud can cause it to bend over.

Rose Curculio Damage
This time of the year, the most common indication of curculios is the holes in buds that then fail to open, or open with petals riddled with holes. If you see one and try to remove it, they may just drop from the bush and play dead, though the little beast will soon "revive" and crawl back up the plant.

Rose Curculio Damage
Serious infestation can prevent almost all bloom. You can reduce current populations by handpicking - gently shake canes over a bucket or tray of water or other liquid to collect fallen adults and dispose of them. To reduce future generations, remove spent blooms and hips, and any damaged blooms. If you spray, you can use a contact (insecticidal soap, neem oil) or ingested (Orthene) insecticide during the active season, in late May and June, though this is not effective for the larvae within the buds.

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Last Modified: 08/06/2013