Skip to main content
ARS Home » Research » Publications at this Location » Publication #174221
Title: PHENOLOGY AND DEMOGRAPHY OF HOMALODISCA COAGULATA IN SOUTHERN CALIFORNIA CITRUS AND IMPLICATIONS FOR MANAGEMENT

Author
item Castle, Steven
item Naranjo, Steven
item BI, J - U CA, RIVERSIDE
item BYRNE, FRANK - U CA, RIVERSIDE
item TOSCANO, NICK - U CA, RIVERSIDE

Submitted to: Entomological Research Bulletin of
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2005
Publication Date: 12/1/2005
Citation: Castle, S.J., Naranjo, S.E., Bi, J.L., Byrne, F.J., Toscano, N.C. 2005. Phenology and demography of homalodisca coagulata in southern California citrus and implications for management. Bulletin of Entomological Research 95:621-634.

Interpretive Summary: Effective pest management is often realized through timely control actions initiated at a critical point in the growth and development of pest populations. For glassy-winged sharpshooter, an invasive species in California responsible for the recent epidemic of Pierces's disease in southern California vineyards, little was known about its population dynamics in its new habitat where it was first identified in California in 1989. By developing a better understanding of its seasonal occurrence, effective management strategies might be identified to help suppress populations of GWSS. Sampling conducted in citrus orchards in Riverside, CA showed that GWSS has discrete populations in southern California as they increase from very low levels in late winter to relatively high levels by early summer. Egg laying and development of immatures occurs through the spring in citrus orchards with new adults emerging beginning in late June. By defining seasonal patterns in GWSS populations, control strategies can be more effectively applied during the spring when immature populations are most vulnerable to various control actions.

Technical Abstract: Populations of Homalodisca coagulata (Say) were sampled from citrus orchards in southern California to characterize and quantify seasonal occurrences of nymphs and adults with the goal of identifying management opportunities. Higher densities of H. coagulata in 2001 contributed to a complete seasonal profile that began in early spring with the emergence of first instar nymphs and their progression through 5 nymphal instars. Collection of nymphs ceased by mid-August without a 2nd generation produced in citrus. Adult emergence began in mid-June with peak adult densities attained in mid-August. A persistent and significant male bias was observed in the adult sex ratio from the time of first emergence through mid-October in oranges; the same trend was present in lemons, but with more variability. Adult densities gradually declined through the winter months into the following spring before rapidly increasing again in June as the 2002 spring generation of nymphs began emerging as adults. The seasonal timing of nymphs and adults in 2002 was nearly identical to that observed the previous year. Phenology data from both years were incorporated into a stochastic, temperature dependent model that predicts the occurrences of H. coagulata stages through time. Applications of imidacloprid early in the spring generation of nymphs proved very effective at reducing nymphs and sustaining lower densities of adults through summer.