Biocontrol: Insect Projects

Biological Control of Ash Whitefly

The ash whitefly invaded California in 1988 and quickly became a serious pest of several commonly planted urban trees. Adults filled the air in some neighborhoods to such an extent that they posed a health threat due to breathing impairment. A single species of parasitic wasp was imported from Europe, the origin of the ash whitefly. Within two years of its release, this wasp greatly reduced the ash whitefly population. Today, although both insects are still present in California, they are difficult to detect in ash and ornamental pear, trees previously heavily infested by the ash whitefly. We have an ongoing monitoring program that is tracking the long-term impact of the Encarsia inaron, the wasp imported from Europe. Trees are sampled from six counties in central and northern California once a year. The number of whiteflies and parasites on leaves collected from these trees are recorded.

Click below to view photos:

  1. Adult ash whitefly, Siphoninus phillyreae, and early stage nymphs
  2. Ash whitefly nymph showing large drop of honeydew and white wax coating
  3. Heavy infestation of ash whitefly on ash tree
  4. Whitefly nymphs on ash leaves
  5. Encarsia inaron - the ash whitefly parasite (1/2)
  6. Encarsia inaron - the ash whitefly parasite (2/2)
  7. Adult parasite searching for whitefly nymphs to sting
  8. Parasitized whitefly nymphs showing exit holes where adult wasps emerge
  9. High percentage of parasitized ash whitefly