A gardener asked me about worms infesting his cucumber plant. There are a couple of possible explanations for the cucumber infestation.
One is the melon fly, which is a type of fruit fly that infests cucumber, zucchini, squashes and melons. The female fly lays eggs into the fruiting vegetable, in this case the cucumber. The eggs hatch into maggots and the white maggots bore into the cucumber.
Eventually the maggots mature, drop to the ground and form a pupa, then the adult melon fly emerges about a week later.
Another possible pest of cucumber is the pickleworm. The adult moth is brown with a 1-inch wingspan. The female lays eggs on the cucumber and the egg hatches into a caterpillar, which is mostly white with brown specks and bores a hole into the cucumber.
In some cases the female moth lays eggs into the unopened flower, especially if the flower is large like a zucchini flower. The caterpillar feeds on the pollen of the flower, reducing the available pollen for pollination.
Home gardeners can use three strategies to reduce melon fly populations:
>> Sanitation: Elimination of culled cucumber fruits will reduce the developing melon fly larvae.
>> Male annihilation: Male melon flies are caught with traps.
>> Bait sprays: Commercial bait products are used with approved insecticides on border plants such as corn, sorghum and castor bean. Bagging the young fruit soon after pollination with brown sacks may also help to reduce melon fly damage.
The more methods used, the greater the chance of reducing melon fly damage.
The pickleworm is difficult to control. If you cover the cucumber fruits and flowers to prevent the moth from laying eggs, you also prevent the bees from pollinating the flowers and would have to hand-pollinate. There are lures to be used in sticky traps to attract adult pickleworm moths. If the moths are trapped before mating, the population is reduced.
Other insects commonly attacking cucumbers are white fly, aphids, leaf miner, thrips and cutworms. Environmentally safe insecticides such as insecticidal soap and neem oil may help to control white fly and aphids while sparing the natural enemies that attack them.
Diseases commonly affecting cucumber are damping-off, nematodes, powdery mildew and mosaic viruses. Damping-off is a soil disease caused by several fungi. Nematodes are microscopic roundworms in the soil that infest roots. The addition of rotted manure or compost will help to increase the microbial activity in the soil to suppress the disease causing fungi and nematodes.
Infected soil can be heated with solarization and clear plastic tarps. Improve the soil drainage and space plants far apart enough to reduce the buildup of humidity at the soil level to reduce damping-off.
Powdery mildew can be managed with approved fungicides. Potassium bicarbonate, sulfur and some neem oil products may be effective in controlling powdery mildew. Check for products labeled for use on cucumbers.
Papaya ringspot virus-w, formerly called watermelon mosaic virus, may be a problem in certain areas. The University of Hawaii College of Tropical Agriculture and Human Resources’ cucumber varieties Lani and Milo (order at www.ctahr.hawaii.edu/seed), and certain Japanese cucumber varieties are tolerant to the virus. Zucchini yellow mosaic virus and cucumber mosaic virus may also be a problem.
These viruses are transmitted by aphids; therefore, aphid control and removal of potential weed host plants are helpful for reducing the virus diseases.
Richard Ebesu is an extension agent with the Kauai Extension Service.
