Cucumber Beetles

by Nanette Londeree, Master Rosarian

SIGNS

Shiny, greenish-yellow six legged insect, about 0.25 inch long, with black heads and long antennae
Striped or spotted adults, depending upon species
Whitish, slender larvae with three pairs of short legs; the head and tip of the abdomen are darker 

SYMPTOMS

Shoots and blossoms that exhibit damage
Scars on soft fruit
Appearance of mosaic virus or wilts in cucurbits

CAUSE

Western spotted cucumber beetle, Diabrotica undecimpunctata
Western striped cucumber beetle, Acalymma trivittata

OPTIMAL CONDITIONS

Over winter as adults in weedy areas
Move into planted fields and gardens as soon as plants start to come up
Several generations a year
Before cucurbits are available, subsist on the pollen and petals of many plants
Pests of many plants including cucumbers and their relatives (squashes, gourds, and melons), beans, peas, corn and blossoms of several wild and cultivated plants; potatoes, beets, tomatoes, eggplants, and cabbage, roses and dahlias

TREATMENT

Prevention:

Maintain good garden sanitation
Dust diatomaceous earth around the base of plants to kill larvae emerging to eat and also create a barrier to egg laying
Knock, shake, or hand pick beetles off plants and out of flowers
For most vegetable gardens, place protective cloth over emerging plants and remove it when plants are old enough to tolerate damage
Maintain a diverse garden that includes general predators and parasites; birds, parasitic wasps, soldier beetles, and tachinid flies

Elimination:

Pyrethrum and rotenone sprays
Pesticides such as Adios® that combine cucurbitacins as a feeding stimulant with a small amount of the pesticide carbaryl (Sevin ™

GOOD GUY / BAD GUY?

A very bad guy in the food garden as they girdle stems by gnawing on the tender shoots of seedlings, feed on blossoms and leave scars on the fruit; larvae injure plants by feeding on roots and tunneling through stems, and transmit deadly diseases – mosaic and bacterial wilts
It is more of a nuisance pest of roses

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