Plant Health Problems
Most melons are closely related to cucumber. See Cucurbit for a detailed discussion of the common diseases of this host.
Hop flea beetle, Psylliodes punctulata.
This insect may occasionally feed on melon. See flea beetle fact sheet.
Melon aphid, Aphis gossypii.
This aphid infests many different kinds of plants both in the field and in greenhouses, but it is particularly troublesome on cucurbits. It generally makes its appearance in scattered places in the field late in the summer and may become abundant on the undersides of the leaves. When aphids are abundant, they may cause a downward twisting or cupping of the affected leaves. Honeydew from the aphids may cause the fruit to be sticky, and aphids may also transmit viral pathogens. See aphid fact sheet.
Melonworm, Diaphania hyalinata.
On occasion, melon may be injured by slender, active greenish caterpillars with two narrow white stripes running the full length of their bodies. They feed mostly on the foliage, but may burrow into the fruit. They are rare, however, and no specific control measures have been needed.
Pickleworm, Diaphania nitidalis.
The pickleworm, which is somewhat heavier, less active and bears a row of black spots instead of the white stripe of the melon worm, may also infest melons and other cucurbits. The white, yellowish or greenish larvae have yellowish-brown heads and are about 3/5" long when mature. They burrow in the bud, blossom, vines and fruit. Control is not generally needed.
Striped cucumber beetle.
This beetle may injure young melon plants directly. It may also transmit the bacteria that cause bacterial wilt to muskmelon. Watermelon is generally not susceptible to bacterial wilt. This is the most destructive insect pest of cucumbers. The beetles hibernate under trash or in the ground, and appear upon the plants as soon as the seed germinates. The greatest injury occurs to the young plants, and the beetles feed usually on the underside of the leaves.
The beetles are ¼" or less long, with thorax and wing covers yellow, with three black longitudinal stripes that extend to the tips of the wing covers, and with a black head and abdomen. It should be distinguished from the similarly striped female western corn rootworm, which has a yellow abdomen and is not an important pest of cucurbits. Cucumbers and muskmelons are generally susceptible to this disease, although watermelons and some varieties of squash and pumpkin are not. The eggs are laid from the end of June through July on the surface of the ground or in crevices in the soil. The eggs hatch in about a week and the young larvae work their way downward along the main stem, where they burrow into it, causing much injury. A full grown larva is 1/3" long, slender and white with brown head and thorax. The adults appear again in early to mid-August. There is only one generation annually. See Cucumber Beetle fact sheet.