Left: Metzneria paucipunctella adult moth.
Right: M. paucipunctella larva in spotted knapweed seedhead.
R.Richard (both)

Metzneria paucipunctella
Lepidoptera: Gelechiidae

by R.F. Lang, USDA-APHIS-PPQ, Bozeman Biocontrol Facility, Forestry Sciences Laboratory, Montana State University, Bozeman, MT 59717- 0278.

The seedhead moth, Metzneria paucipunctella, a native of Europe, was approved for release in 1971. M. paucipunctella has been released in Colorado (established), Idaho (established), Minnesota (established), Montana (established), Nebraska, Oregon (established), and Washington (established) as a part of a complex of biocontrol agents to control spotted and diffuse knapweed (Centaurea maculosaand C. diffusa).

Appearance

M. paucipunctella is a small (15 mm wing span and 6 mm body length), light brown moth with a row of black spots on each front wing. This moth closely resembles many of the commonly found "grass moths". The white larva with a brown head can easily be found in the knapweed seedheads under the flower receptacle.

Habitat

Spotted and diffuse knapweed are weed species that can be found throughout the northern tier of states and as far south as Nebraska and Virginia. These highly competitive weed species favor and establish quickly on disturbed sites and overgrazed rangeland. Both weeds will invade well established grassland communities and out compete the native vegetation. The release of M. paucipunctella is part of a program to introduce a complex of spotted and diffuse knapweed enemies to help control these weeds.

Pests Attacked

M. paucipunctella is considered host specific to spotted knapweed ( Centaurea maculosa). The moth has been recorded on diffuse knapweed ( Centaurea diffusa) in Washington. Extensive host testing in Europe found the moth host specific to C. maculosa . Eight years of sampling of over seventy European Asteraceae found M. paucipunctella exclusively in C. maculosa seedheads. The moth larvae eat the seeds in the knapweed seedhead.

Life Cycle

M. paucipunctella produces one generation per year. The adults may be found from May, in warmer climates, to July in cooler areas. Egg laying begins two to three days after the female emerges. Each female may lay 60-100 eggs. The eggs are laid on unopened flower buds and in 10-12 days the egg hatches. The larvae then climb the flower bud, which is now opening, and enter the flower to feed inside the achenes. Later the larvae will feed on all the seeds and tunnel through the receptacle. The larvae overwinter in the seedhead and pupate in a silken chamber in the early spring. Pupation lasts about three weeks and then the adults emerge.

Pesticide Susceptibility

Not yet known.

Commercial availability

In some states, M. paucipunctella adults may be obtained at no cost from state weed management agencies.

Effectiveness

M. paucipunctella reduces seed viability and destroys most of the seeds. The moth destroys all the seed in a seedhead producing nine or fewer seeds. If the number of seeds exceeds ten the moth can be expected to destroy ninety plus percent of the seed. When the moth is present with other seedhead agents, production of seeds is markedly reduced. M. paucipunctella is another agent in a biocontrol agent complex to control spotted and diffuse knapweed.

Conservation

Sites chosen for M. paucipunctella should be available without disturbance from development or pesticide use for a least ten years. M. paucipunctella does not tolerate temperatures below minus 30 C. M. paucipunctella does well in moist as well as drier sites.

References

Englert, W.D. 1971. Metzneria paucipunctella Zel. Gelechiidae, Lepidoptera): a potential insect for the biological control of Centaurea stoebe L. in Canada. Proc. Second Intl. Symp. Biol. Contr. Weeds., Rome, Italy. IIBC European Station, Delmont, Switzerland.

Harris, P. and A. Muir. 1986. Biological control of spotted knapweed by Metzneria paucipunctella (Zeller). Agriculture Canada, Ottawa. Candex: 641.613. 2 p.

Mays, W. T. and L.T. Kok. 1996. Establishment and dispersal of Urophora affinis (Diptera: Tephritidae) and Metzneria paucipunctella (Lepidoptera: Gelechiidae) in southwestern Virginia. Biol. Control 6: 299-305.

Story, J. M., K.W. Boggs, W.R. Good, P. Harris, and R.M. Nowierski. 1991. Metzneria paucipunctella Zeller (Lepidoptera: Gelechiidae), a moth introduced against spotted knapweed: its feeding strategy and impact on two introduced Urophora spp. (Diptera: Tephritidae). Can. Entomol. 123: 1001-1007.

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