The Eucalyptus gall wasp, Ophelimus maskelli, is a significant pest in areas throughout

the world. Heavy galling significantly weakens trees as well as causing early defoliation leading

to premature death. Eucalyptus species are grown all over the world for various uses including

fuel and paper making. The plants are especially prized in plantations for their rapid growth and

development. O. maskelli was recently discovered in southern California along with two

associated parasitoid wasps. Closterocerus chamaeleon is a known parasitoid of O. maskelli and

has been intentionally introduced in areas of Israel as well as throughout the Mediterranean for

use as a biological control agent. The second parasitoid wasp, Selitrichodes neseri, has been

intentionally introduced in South Africa as a biological control agent for another Eucalyptus gall

wasp, Leptocybe invasa. Phenologies of each species in southern California are recorded and

discussed using two different collection methods. Comparisons are made between species,

inland and coastal populations of southern California, and populations in Israel. Morphological,

molecular, and ecological data are combined in the description of a new strain of S. neseri in

southern California. Our studies discuss ecological relationships between these three wasp

species as well as provide a groundwork for further research involving the adjustment of

invasive species to a new environment.

Resource provisioning as a habitat manipulation tactic to control the melon aphid, Aphis gossypii, by the polyphagous aphid parasitoid, Aphidius colemani, was investigated in the ornamental, potted-plant nursery using the shrub Photinia x fraseri as a plant host. Floral food resources from an invasive, Conium maculatum, an ornamental, P. x fraseri, and a native, Salvia apiana considerably improved the longevity and fecundity of A. colemani in laboratory experiments. Additionally, floral nectar from P. x fraseri and honeydew from A. gossypii had a statistically similar effect on the longevity, fecundity, percent emergence, and sex ratio of A. colemani and enhanced the parasitoid more than extrafloral nectar from Cucurbita pepo. In common garden field studies, A. colemani remained for the entire seven days tested in the presences of resources while in the absence of resources, the parasitoid was detected for only 3 days. Further field studies using floral food of P. x fraseri, honeydew of A. gossypii, and a flowers x aphids treatment were conducted to determine the effects on the abundance and movement of the parasitoid in a common garden. Significantly more parasitoids were initially associated with flowers x aphids treatment 24 h post release. This was followed by a switch to the aphids treatment 1 week later. Parasitoids were found in both the treatment plots and associated crop plots (no resources) suggesting that A. colemani moves in search of resources and may be switch-foraging to maximize fitness.

Imidacloprid, a systemic insecticide commonly used in nursery systems, was detected in the xylem, nectar, pollen, and leaves of P. x fraseri treated with a full or half label rate. The concentration of imidacloprid detected in the xylem and nectar was greater than the determined LC₅₀, LC₇₅, and LC₉₀ of imidacloprid for A. colemani. Bioassay data suggested the survival of the parasitoid is negatively impacted by feeding on nectar from imidacloprid treated plants. No effect was observed when the parasitoid was exposed to leaves from imidacloprid treated plants. These findings suggest that soil-applied imidacloprid is moderately compatible with biological control due to toxicity occurring through contact with nectar from treated plants rather than direct exposure.

The red gum lerp psyllid is an insect native to Australia, where it feeds upon eucalyptus species. Since 1998 this psyllid has spread throughout California, resulting in millions of dollars in damage and control costs. To help suppress the red gum lerp psyllid, a biological control program was initiated and a psyllid-specific parasitic wasp was imported from Australia in 1999 and released in 2000. In most coastal regions this biological control agent has provided substantial control, but in some interior regions the psyllid still remains a problem. Researchers are continuing their investigations to determine if full statewide suppression will be realized eventually, or if further importation of new parasitoid species is needed.