Rose Curculios

by Nanette Londeree, Master Rosarian

SIGNS

Adult insect 0.25 inch in length, bright lacquer red flight wing covers and thorax, and a black head with a long black snout
Adult feeding on the buds and petals of roses, and other plants in the rose family (blackberries, raspberries)
Legless, small (less than a quarter inch), whitish larvae

SYMPTOMS

Ragged rose blossoms
Holes in flower buds; deformed flower buds; buds that may not open at all
New growth (terminals) die
Gouges in bud stems, causing the bud to wilt and then die
Rose stems with “bent neck” – damage to the stem below the bud, causing it to bend over
Damage to the reproductive parts of the flower

CAUSE

The rose curculio or rose weevil, in the family Merhynchites bicolor; they go through a complete metamorphosis

OPTIMAL CONDITIONS

Mid-spring to summer, roses with new growth, especially yellow or light colored flowers
Eggs are laid in bites made by the female in developing flowers in late May and June
Larvae (grubs) fall to the soil and pupate the following spring
A single annual generation emerge as adults in late spring to early summer

TREATMENT

Prevention:

Avoid yellow and white roses apparently preferred by the beetle
Prune out and remove finished flowers to remove larvae, which can help reduce future problems

Elimination:

Handpick adults; when bothered, adults fall from the plant, so gently shake flowers over a bucket or tray of soapy water to collect fallen adults
Destroy damaged flowers, buds and stems
Broad-spectrum synthetic pesticide, such as carbaryl (Sevin) or acephate (Orthene) can be applied when adults are seen if infestations are severe

GOOD GUY / BAD GUY?

For most Rosarians, a real bad guy that can do a lot of damage to rose blooms if not kept under control

Photo of the Rose Curculios at the top of the page is by Baldo Villegas from the extraordinary website: http://members.tripod.com/buggyrose/irosepests.htm

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