Stevens County Noxious Weed Control Board
This web site will help you identify & control noxious weeds. Conventional & biological control
(BioControl) information and photographs  are here. Maps & related information are included.

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Aplocera plagiata
St. Johnswort Inchworm
Weed(s) Attacked: St. Johnswort
SCNWCB February 2006


GENEALOGY
Original source for U.S. release was Europe. First U.S. releases made in 1989. Said to be established in Idaho, Montana, Oregon, and Washington. No work with this agent is currently underway in Stevens County.

LIFE CYCLE
This agent has two generations per year. That is, there are two cycles of "EGG/to LARVA/to ADULT" per year. Larvae are inchworms. The inchworm is not light sensitive like the Chrysolina larva and can feed during the daylight hours, although it is primarily a night feeder. It may be hard to see when it imitates a dead twig. A Female moth lays about 300 oval shaped pearl white eggs in her lifetime.
The second generation inchworm (hatched mid-August & September) overwinters in plant litter or in the soil. These overwintered inchworms becomes active again sometime in spring and can be seen into July. The adult moth can be seen in spring and summer.


EFFECT

The larva feeds on leaves and flowers.

REDISTRIBUTION
The establishment of this agent in Stevens County is unclear. New releases are said to work best at sites which are sandy, well-drained, and somewhat rocky.

COMMENTS
The inchworm tends to get fungal infections at moist soil sites. The inchworm is known to be attacked and killed by ants and wasps.

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weedboard@co.stevens.wa.us
Last Edit: March 04, 2013
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