Spotted cucumber beetle (Diabrotica undecimpunctata)
This week’s crawly is a polka dotted critter you may not want to see in your garden. Meet the spotted cucumber beetle (Diabrotica undecimpunctata).
The good news is cuke beetles aren’t particularly pesty unless you are growing crops or have a vegetable garden with cucurbits (squash, melon, cucumber), corn, sorghum, beans, peanut, and/or sweet potato.
Spotted cuckes are native to the United States and are on of eight species of cucumber beetles found in North America.
In Oregon spotted cuckes are found almost exclusively west of the Cascades.
Fun fact: Despite their “cucumber” moniker, spotted cukes have a wide diet which includes at least 200 different plant species in 50 plant families. Even if there’s a field of one of their favored crop plants nearby, they may be just as happy chowing down in a field of flowers, leaving the corn alone.
Our yard in Trail always had spotted cukes, but my mom always managed bumper crops of several varieties of squash every year (honestly, I’d have been happy if the spotted cuckes really had wiped out all that squash. Mom really liked squash).
So, what do spotted cukes eat and how does that damage plants? For most plants, their damage will only be cosmetic. Adults first food choice is pollen, second is petals third is leaves.
If a group of adults settle on one young plant (generally one of the above crop plants) they can chow down on enough of the young leaves and stems to kill the plant. Typically you won’t find large groups gathered in a backyard setting.
When adult spotted cukes feed on flowers, they’ll leave them with a lacy look as they will chew small circles out of the petals. However, many other “pesty” plant visitors have the same MO so unless you catch a culprit in the act, it can be hard to know who to blame.
When adults chomp on pollen they are as beneficial as any other pollinator. Nature is complex.
Adult cukes are also on the menu for many carnivorous arthropods. Spiders, antlions and robber flies (just to name a few) really enjoy a good cuke meal.
Spotted cuke larvae live their young lives (40 – 60 days) underneath the soil. They dine on small underground roots and stems. You may be surprised that this does not damage the health of the plant.
Spring has sprung now so you may start seeing spotted cukes out and about now, especially on daffodils as right now those are the largest and tastiest flowers blooming.
Unlike many other beetle species who overwinter in the larval stage, here in Oregon spotted cukes hunker down in leaf litter when winter comes and hibernate. Adults will wake up on warm(ish) early spring days, then hit the snooze button when chilly, stormy weather comes back around.
In states that have truly harsh winters, spotted cukes will pack their proverbial bags and migrate south for the winter. With the wind at their backs, cukes can fly over 100 miles a day to get to warmer climes.
In late spring they’ll become fully active and start looking for love. Mom spotted cukes will lay eggs near the base of a food plant (which as we’ve learned leaves them many options). When the eggs hatch, the larvae will dig down to the roots to eat and grow.
Because spotted cukes need to hibernate, and their young have a long childhood, there is only one generation born per year – sort of their natural version of population control.
So while you may not be over the moon to spot a spotted in your garden, now you know they aren’t causing too much damage and they have a pretty interesting lifestyle.