Question: I have several cucumber, pumpkin, and squash plants that have discolored leaves and distorted leaves. I see no insect damage and have sprayed for powdery mildew. The plants have adequate nutrition and are watered regularly. What's wrong with my plants?

Answer: Your curcurbits (squash and melon family) have been infected with a virus. There are several different viruses that infect this family of plants. They include: cucumber mosaic virus (CVM), squash leaf curl virus (SLCV), squash mosaic virus (SQMV), watermelon mosaic virus (WMV), and zucchini yellow mosaic virus (ZYMV). Each of these pathogens usually have several strains. Sometimes and infected plant may have more than one virus causing symptoms. Therefore, it makes an exact diagnosis difficult without laboratory work.

Plants will have mottled leaves that is patches of green and yellow, often in varying hues mixed in the leaf. Whole plants and leaves are usually smaller than normal and many times deformed and fragmented. Cucumber, melon, and squash fruit are also small stunted and colored unusually. The fruits at times will have warts and be bumpy.

Viruses cannot survive outside of living organisms. They may be contained in the seed when planted, which occurs with SQMV. Insects serve as vectors (transmittance agents) for many viruses. Sucking insects like aphids and white flies and chewing insects such as cucumber beetles and grasshoppers transmit virus particles from infected plants to healthy ones.

Control: Some virus resistant varieties are available, their use is advisable. Control of host plants like weeds serve as stores of viruses as well as infected crop plants. Destroy these plants as soon as symptoms appear. Control insects which transmit viruses from one plant to another. I know of no chemical or natural cures for viruses in plants. The plant many times will live in a weakened state much like what happens to humans when we get a viral flu or cold.

Question: What can I do about cicadas? They are so loud some years.

Answer: Periodic cicadas are distributed widely throughout the United States. The annual cicadas are present in summer, but the periodic species have long life cycles. A mature annual species is over two inches long with a brown-black body, ornamented with clear wings that have green veins. Eyes are red to brown and quite large. There are six species of periodic cicadas in the United States. Three with a 17 year life cycle and three with a 13 year life cycle. When all life cycle coincide the male mating sounds can be deafening. Damage is caused by egg laying or ovipostiting females in twigs and branches of trees and shrubs. Branches having a diameter slightly larger than a pencil are preferred. A series of wounds are made in which eggs are laid. Weakened branches can break off or become permanently scarred and abnormal. Over 500 eggs can be deposited by one female. Nymphal cicadas hatch and then drop to the ground, burrow into the soil, and feed on root sap. Depending on the species they will remain in soil for 17 or 13 years. At the end of this time they emerge from the ground through soil tubes they construct that are nearly half an inch wide and a quarter inch high above the ground. Great numbers emerge at the same time, starting at dusk. They crawl up tree trunks or other objects, expand their wings, and begin their short adult life. The familiar song or call is made only by the males and is produced by a pair of drum like organs on the basal segments of the abdomen. These "love calls" can become very loud. Mating occurs and then egg laying beings, completing the life cycle.

Control: Winter pruning and destruction of damaged limbs or twigs that contain eggs may decrease the population. Where feasible, valuable plants may be protected by covering them with shade cloth, cheesecloth, or hardware cloth. Natural enemies include birds, fungal diseases, and the cicada killer wasp, which kills some adults. Other predatory insects and mites may attack the eggs.

Reference: Insect Pests of Farm, Garden, and Orchard 1987, Davidson and Lyons. John Wiley and Sons, New York. Pp. 373-376