Most Susceptible to Colonization Seasonal movements of adults in California and studies in the eastern United States indicate that the nutritional needs of GWSS may require that it feed on several different host plants to maintain viable populations. If this is true then GWSS would be expected to do best in those habitats in which there is an abundance and variety of favored hosts. Observations in southern California would tend to support this hypothesis. The same can be said for eucalyptus. In urban areas of Orange County, for example, very high numbers of adults are found feeding on the leafless twigs of backyard peach and apricot trees.
Adults are also common on oleander during the winter months.
Recommendation Nursery sites selected for survey should have a diversity of favored summer and winter hosts growing in close proximity. Nurseries which are near eucalyptus wind rows or citrus groves or commercial grape vineyards or peach, apricot, plum, almond, apple or pear orchards should be given first priority to survey. Survey Techniques and Equipment Needs Bias this survey if you can. Oleander is reported to be a winter host. Avoid nurseries that have recently received a pesticide application.