Handout from Ash Whitefly Information Session for Nurseries Oct 8 NWREC
Listen to my interview about ash whitefly with Mike Darcy on In the Garden [from Saturday 10-3-2015, starts at 41 minutes into the recording].
The ash whitefly, Siphoninus phillyreae (Haliday), was detected in Oregon in 2014. Late summer/fall flights of ash whiteflies have been noticed in both 2014 and 2015 in the Willamette Valley. The whitefly has a wide host range which includes many ornamentals, native plants, and fruit trees. Little is know of how impactful will be this newly detected insect in Oregon but it is not too soon to begin to monitor for the whitefly on both known (see Nguyen and Hamon, 2000; Bellows et al. 1990) and unreported hosts.
Ash whitefly was first detected in California in 1988 and has since been detected in Arizona, Florida (2010), Georgia, Nevada, New Mexico, North Carolina (1993), and South Carolina.
The adults have light yellow bodies which are covered by white wings. Ash whitefly eggs are pale waxy yellow and often surrounded by waxy deposits. Young nymphs are nearly translucent but become more opaque and covered in tufts of white wax. The puparia are covered with tufts of white wax and have tubercules or long tubes formed around the edge of their bodies topped with clear waxy droplets.
The adult female typically lives for about 30-60 days.
Female whiteflies lay eggs on the undersides of the leaves on host plants. Nymphs emerge from the eggs and settle onto the leaves where they remain and feed on the plant sap. They then pupate and later emerge as winged adults. There are four juvenile stages of the whitefly between the egg and adult stages. Both the nymph and adult stages can feed. At 77°F the whitefly can develop from egg to adult stage in 25 days (Bellows et al. 1990). The ash whitefly can develop continuously during the year although development slows with cooler temperatures. There can be several generations per year. The whiteflies tend to move from preferred deciduous summer hosts such as ash, pear, and hawthorn to evergreen overwinter hosts. All stages of the whitefly can overwinter on evergreen host plants.
The whitefly may be flying right now (September) onto evergreen hosts on which it will overwinter. Shaking or tapping branches over which whitefly are flying is one way to monitor. Another is to slowly turn over a branch, twig, or leaf and examine for whitefly adults and juvenile stages of the whitefly. Various juvenile stages (eggs, nymphs, puparia) of the whitefly on a plant indicates it is able to reproduce on the host plant. These are plants that will be more susceptible to direct damage (curling tips, stunting, defoliation) as well as indirect damage (honeydew and sooty mold) from the whitefly. While the overwintering adult stage may not directly damage a plant, it might be a shipment contaminant pest and intervention may be required if plant shipments occur while the whitefly is present.
Several biological control agents have been released in other states to manage populations of ash whitefly including a parasitic wasp Encarsia inaron (= partenopea?) and a lady beetle, Clitostethus arcuatus. The most successful agent limiting the populations of ash whitefly in California was the tiny wasp, E. inaron, which was found in emergence rates from ash whitefly nymphs at 80 to 98%. In Florida, E. inaron was also found to be effective as a parasite of ash whitefly.
Recommendations for ash whitefly management have yet to be developed specifically for Oregon nursery production. If management is required, refer to the nursery section in the PNW Insect Management Handbook for general whitefly management recommendations.
Bellows T, Paine T, Gould J, Bezark L, Ball J, Bentley W, Coviello R, Downer J, Elam P, Flaherty D, Gouveia P, Koehler C, Molinar R, O'Connell N, Perry E, Vogel G. 1992. Biological control of ash whitefly: a success in progress. Cal Ag 46(1):24-28.
Bellows T, Paine T, Arakawa K, Meisenbacher C, Leddy P, Kabashima J. 1990. Biological control sought for ash whitefly. Cal Ag 44(1):4-6. <5 October 2015>
Nguyen, Ru and Avas B. Hamon. 2000. Featured Creatures: Ash Whitefly. Florida Department of Agriculture and Consumer Services. August 2000. (18 September 2015).
Paine, T., Bellows, T. and M. Hoddle. 2009. Ash whitefly. Center for Invasive Species Research. (18 September 2015).
Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University