This study was initiated (1963) to obtain bionomical knowledge of Empoasca solana DeLong, the southern garden leafhopper, which could help improve integrated control measures on cotton. The following subjects were investigated in the field: relationship of populations on cotton to those on other crops in the area; seasonal occurrence and abundance; damage to cotton; association of parasites and predators with E. solana; seasonal occurrence and abundance of the parasites; effects of various control measures upon E. solana and the parasites. Laboratory investigations supplemented the field studies, with particular emphasis being placed upon the development of E. solana under controlled environmental conditions, the differentiation of all species of Empoasca found in California cotton fields, and the establishment of the types of injury inflicted upon cotton by the three species most commonly found on this crop in California.

It was found that populations of E. solana overwinter in sugar beet fields in California’s southern desert valleys. High population levels are reached in late spring on sugar beets, and the populations move into adjacent cotton fields as sugar beets become unattractive to the leafhoppers. Population levels in cotton fields generally peak in early and mid-summer.

The symptoms of feeding by E. solana on cotton include chlorosis and reddening of lower leaves of the plant. As a result of heavy feeding, young bolls and squares are shed and older bolls become soft and spongy. Yields are thus drastically affected.

Three hymenopterous parasites were found to attack the egg of E. solana. They are: Abella subflava Girault, Aphelinoidea plutella Girault (Trichogrammatidae), and Anagrus giraulti Crawford (Mymaridae). Only giraulti exhibits an increase in numbers with an increase in the numbers of E. solana.

Under controlled environmental conditions, E. solana exhibits its maximum reproductive capacity at 80° F. The developmental period is shorter at 90° F than at 80° F, but the number of eggs produced at 90° F is also drastically reduced.

Six species of Empoasca occur on cotton in California. These are E. abrupta DeLong, E. arida DeLong, E. fabae (Harris), E. filamenta DeLong, E. mexara Ross and Moore, and E. solana DeLong. E. abrupta, E. mexara and E. solana occur on cotton primarily in the southern desert valleys while E. arida, E. fabae, and E. filamenta occur on cotton primarily in the San Joaquin Valley. E. abrupta and E. solana are found on cotton in both areas. These species are differentiated on the basis of various morphological characters associated with the male genitalia.

Of these species E. abrupta, E. arida, and E. filamenta are primarily mesophyll feeders, while E. fabae and E. solana feed primarily upon phloem tissues. Species causing the most damage, and thus of greatest economic importance on cotton in California, are E. fabae and E. solana, both primarily phloem-feeders.