CLASSICAL BIOLOGICAL-CONTROL OF THE ACACIA PSYLLID, ACIZZIA UNCATOIDES (HOMOPTERA, PSYLLIDAE), AND PREDATOR-PREY-PLANT INTERACTIONS IN THE SAN-FRANCISCO BAY AREA
Sh. Dreistadt et Ks. Hagen, CLASSICAL BIOLOGICAL-CONTROL OF THE ACACIA PSYLLID, ACIZZIA UNCATOIDES (HOMOPTERA, PSYLLIDAE), AND PREDATOR-PREY-PLANT INTERACTIONS IN THE SAN-FRANCISCO BAY AREA, Biological control, 4(4), 1994, pp. 319-327
Six predaceous insect species were introduced into California to contr
ol the acacia psyllid, Acizzia uncatoides (Ferris and Klyver) (Homopte
ra: Psyllidae), a pest of Acacia and Albizia spp. planted in landscape
s. Just one of these introduced predators, Diomus pumilio Weise (Coleo
ptera: Coccinellidae), has established. Although D. pumilio was believ
ed to be responsible for providing biological control of the psyllid i
n the 1970s, no studies were conducted to document this. We found that
psyllid densities on Acacia longifolia Willdenow during 1989-1991 wer
e 2 to 20 times lower than before natural enemies were introduced. How
ever, the most abundant psyllid predator was Anthocoris nemoralis (F.)
(Hemiptera: Anthocoridae), which was not known to be established in C
alifornia prior to our study. Psyllid densities increased with increas
ed plant growth during the spring, but correlations between acacia gro
wth and psyllid density were lower or nonexistent during summer, when
psyllid and predator densities were positively correlated. Regression
analyses showed that in addition to D. pumilio and A. nemoralis, Adali
a bipunctata (L.) (Coleoptera: Coccinellidae) and Hemerobius pacificus
Banks (Neuroptera: Hemerobiidae) increase numerically with increasing
psyllid populations. Psyllid densities increased when we excluded pre
dators from psyllid-infested terminals. Our research demonstrates the
importance of documenting classical biological control efforts and may
influence projects against other exotic psyllids introduced into Cali
fornia landscapes. (C) 1994 Academic Press, Inc.