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653These insects prey on Toadflax1. Brachypterolus pulicarius

2. Calophasia lunula

3. Eteobalea serratella

4. Gymnetron antirrhini

5. Gymnetron linariae

6. Mecinus janthinus

Dalmatian Toadflax Linaria dalamatica

Statewide Noxious Weed Awareness and Education Campaign

Montana State UniversityLand Resources and Environmental Sciencesin cooperation withUnited States Department of AgricultureAnimal and Plant Health Inspection ServicePlant Protection Quarantine

Some are beneficial . . . biological noxious weed control can be elusive and long term

The flower-feeding beetle Brachypterolus pulicarius was brought to North America by accident in 1919, probably in a shipment of toadflax. The beetle adult eats the tips of toadflax shoots, and the larvae feed on pollen, flower parts, and seeds. Feeding on yellow toadflax can reduce the number of seeds by 80 to 90%. Although seed reduction is huge, scientists consider this ineffective because it does not reduce plant populations.

Two root-boring moths Eteobalea interme-diella and E. serratella lay their eggs on toadflax, and their larvae then feed on the root crown. This really damages the roots and weakens the whole plant. As the plant dies off, the top of the root easily breaks off, and the plant can’t grow any more. The toadflax moth Calophasia lunula lays its eggs on toadflax. The eggs hatch within 11 days, and the little gray-black larvae start feeding on the plant’s leaves and flowers. The larvae grow into inch-long caterpillars with black and bright yellow stripes running the length of their bodies. If enough caterpillars feed on a stand of toadflax, they can strip off most of the leaves and flowers. This weakens the plants and reduces the number of seeds produced.

Seed capsule and root-galling weevils Gymnetron antirrhini and G. linariae were released in Montana from Eurasia in 1996. The Dalmatian toadflax-adapted strain of G. antirrhini was first released in Montana in 1996. The yellow toadflax strain is estab-lished in Idaho, Montana, Oregon, Washington, and Wyoming. These insects are generally available where yellow toadflax infestations occur. The only definitive record of Gymnetron linariae establishment in the United States is at a solitary Dalmatian toadflax site in Wyoming. A small release of the Dalmatian toadflax-adapted strain occurred in Wyoming in 1998.

Mecinus janthinus, toadflax stem weevil, was first introduced into Montana in 1996 and is established in Colorado, Idaho, Montana, Washington, and Oregon. Adult stem weevils attack both Dalmatian and yellow toadflax leaves and stems. Larvae mine the stems. In Europe, adult feeding on the leaves and stems apparently has a limited effect under field conditions. However, mining of the stems by the larvae causes premature wilting of shoots and suppresses flower formation, particularly under conditions of high weevil

density and cases of multiple attacks. Effects of the weevil on the plant reportedly are enhanced under drought stress. A small release of the Dalmatian toadflax-adapted strain of Gymnetron linariae occurred in Wyoming in 1998. As of 2003, this was the only definitive record of G.linariae establishment in the United States.

This insect preys on SaltcedarDiorhabda elongata

Saltcedar Tamarix ramosissima

Statewide Noxious Weed Awareness and Education Campaign

Montana State UniversityLand Resources and Environmental Sciencesin cooperation withUnited States Department of AgricultureAnimal and Plant Health Inspection ServicePlant Protection Quarantine

Some are beneficial . . . biological noxious weed control agents

Most weed plants are weed-size, not tree-size. One of the largest noxious weeds in the United States is saltcedar, a shrub or tree that can grow to be thirty feet tall. Imagine a weed as tall as a three-story house!

Scientists are experimenting with an insect that eats saltcedar, called the saltcedar leaf beetle Diorhabda elongata. The saltcedar leaf beetles were brought to the United States in 2001 from Asia, just like the saltcedar. An adult beetle lays up to 200 eggs on a saltcedar plant. When they hatch, the larvae eat the leaves. Together, adult beetles and larvae can strip all the leaves off a saltcedar plant. When a swarm of beetles eats a stand of saltcedar bare, they’ll fly a few hundred yards to the next saltcedar dining table.

Saltcedar grows along streams and rivers, around springs, and along the shores of lakes and reservoirs. A stand of saltcedar can suck the ground dry, using 200 or more gallons of water every day. That’s enough in a growing season to create a swimming pool the size of a city block and 9 feet deep!

That kind of thirst reduces streams to a trickle, or even drinks them dry. Saltcedar clogs river channels and reduces the size of spring floods. Floods are part of the natural ebb and flow of many rivers, and many native plants depend on floods. Cottonwood trees and willows, for example, will grow only where floods scour mud off the gravel and cobblestones.

Once saltcedar takes over an area, it keeps other plants out by oozing salt from its leaves. The leaves dip and fall to the ground, making the surrounding soil too salty for most plants. Soon, birds, animals, and even insects are driven away to look elsewhere for food.

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34These insects prey on Purple Loosestrife1. Galerucella calmariensis

2. Galerucella pusilla

3. Nanophyes marmoratus

4. Hylobius transversovittatus

Purple Loosestrife Lythrum salicaria

Statewide Noxious Weed Awareness and Education Campaign

Montana State UniversityLand Resources and Environmental Sciencesin cooperation withUnited States Department of AgricultureAnimal and Plant Health Inspection ServicePlant Protection Quarantine

Some are beneficial . . . biological noxious weed control agents are host specificResearchers study insects that feed on

particular plants. Plants that insects feed on exclusively are called the insect’s “host” plant. For example, purple loosestrife is a host plant for loosestrife beetles. The black-margined and golden purple loosestrife beetles, Galerucella calmariensis and G. pusilla were introduced into the United States from northern Germany in 1992. More golden beetles were released than its look-alike and highly mobile black-margined beetle. The adult black-margined beetle feeds on loosestrife leaves and buds while the golden beetle skeletonizes and defoliates loosestrife so severely that the plant turns brown.

Hylobius transversovittatus root weevils deplete loosestrife root storage reserves during the growing season and and Nanophyes mamoratus seed weevils tolerate a wide range of climates and landscapes where they easily find purple loosestrife. Depleted root storage reserves limit looses-trife’s ability to recuperate after the beetles defoliate the leaves. Although more damage is done by the other insects, scientists believe the seed weevil may play an important role after loosestrife abundance declines and other insects become less effective.

Why is it not bad when these insects damage purple loosestrife?

Purple loosestrife, once established, changes how riparian systems function. These insects were introduced to control purple loosestrife spread. Researchers introduced these insects because they attack purple loosestrife without significant impacts on other plants or endangered species. A lot of testing and research goes into selecting biological control agents. A technical advisory group (TAG) helps with communications between groups responsible for environnmental and potential risk to endangered species.

Once the public have an opportunity to comment and the responsible regulatory agencies have together found no significant impact on anything besides the target plant, in this case purple loosestrife, a permit is issued and insects can be placed in quaran-tine. Quarantine laboratories confirm insect identity, get rid of parasites, and check for and eliminate diseases before insects insects are released into the field.

Although purple loosestrife is the targeted plant, the black-margined loosestrife beetle

also feeds on two native plants, Swamp loosestrife Decodon verticillatus and Winged loosestrife Lythrum alatum, and two introduced plants, Lesser loosestrife Lythrum hyssopifolia and the tree Crape Myrtle Lagerstroemia indica. The black-margined beetle was permitted because it does not reproduce on these host plants.

This pathogen feeds on Yellow StarthistlePuccinia jaceae

Yellow Starthistle Centaurea solstitialis

Statewide Noxious Weed Awareness and Education Campaign

Montana State UniversityLand Resources and Environmental Sciencesin cooperation withUnited States Department of AgricultureAnimal and Plant Health Inspection ServicePlant Protection Quarantine

Some are beneficial . . . biological noxious weed control insects and pathogens

Some biological control agents are not insects, they are plant pathogens. Pathogens such as bacteria, fungus, and virus cause diseases. You have probably heard of whirling disease detected in fish when they swim in a circular fashion. Whirling disease in fish is caused by a virus pathogen that affects the nervous system. Puccinia jaceae is a yellow starthistle rust fungus that scientists are studying to see if it causes damage to yellow starthistle. The rust fungus is found in southern Eurasia and the Mediterranean basin while its original source is Turkey.

The rust has five spore stages that are all completed on a single host plant. With ideal weather conditions spores can germinate, spread by wind, and infect new plants. You may recognize a mass of spores on an infected leaf where it will be dark to reddish-brown and powdery in appearance. The fungus attacks yellow starthistle foliage and green stems and scientists expect it to reduce plant vigor. The fungus was first introduced in California and recovered from its first generation. Scientists redistribute the fungus by vacuuming spores from infected leaves, suspending in water with a wetting agent, and then spraying on foliage prior to an extended dew period.

While scientists learn more about fungus, weevils with well-developed snouts and chewing parts at its tip chew deep into yellow starthistle.

Yellow starthistle bud weevil Bangasternus orientalis and hairy weevil Eustenopus villosus were introduced from northern Greece. Yellow starthistle reproduces by seeds. The bud weevil and hairy weevil are most effective in the larval stage where they cause damage to yellow starthistle seed heads. Both weevils are established in California, Idaho, Oregon, and Washington.

When biological control agents are introduced to damage a specific host plant, they rarely destroy the entire plant population. Once plant populations reduce in size, insects and pathogens must find host plants in other locations. Biological control is not promoted for yellow starthistle in Montana where early detection and rapid response to eradicate small patches is the strategy.

These insects prey on Spotted Knapweed1. Agapeta zoegana

2. Cyphocleonus achates

3. Urophora affinis

4. Spenoptera jugoslavica

5. Larinus minutus

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Spotted Knapweed Centaurea biebersteinii also known as C. maculosa

Statewide Noxious Weed Awareness and Education Campaign

Montana State UniversityLand Resources and Environmental Sciencesin cooperation withUnited States Department of AgricultureAnimal and Plant Health Inspection ServicePlant Protection Quarantine

Some are beneficial . . . biological noxious weed control moths, beetles, and flies

The sulfur knapweed moth Agapeta zoegana is also known as the yellow-winged knapweed root moth. First introduced to Montana from Europe and western Asia in 1984, it feeds on spotted knapweed roots. If you want to see if you have the moth in knapweed patches near you, take a black-light and suspend it over a white sheet in early evening in early August. Mostly male moths will be attracted to the light. You can identify them by their brilliant yellow color.

Cyphocleonus achates root weevil feeds on both spotted and diffuse knapweed. The larvae mine and gall the central vascular root tissue. Adults feed on the leaves. First introduced to Montana from Europe in 1988, the root weevil is established in California, Colorado, Idaho, Montana, New Mexico, Oregon, Utah, Washington, and Wyoming. This weevil prefers hot, dry, well-drained sites with low, scattered vegetation in temperate areas. The bronze knapweed root borer Sphenoptera jugoslavica larvae attack the center of the knapweed root, which becomes swollen. The root borer was first introduced in 1980 and is established in nine northwestern states. It is readily available in Oregon and Washington.

The lesser knapweed flower weevil Larinus minutus was introduced into Montana, Washington, and Wyoming from Greece in 1991. The adult feeds on foliage and the larvae feed inside the seedheads. Defoliation by adults can be severe in sites with high weevil populations, Although somewhat smaller, more reddish tibia, and covered with more grayish hairs, Larinus minutus is hard to distinguish from L. obtusus, the blunt knap-weed flower weevil. The blunt knapweed flower weevil is larger, darker, and has dark reddish-black tibia.

The banded gall fly Urophora affinis was introduced into Montana and Oregon in 1973. It is established throughout most of diffuse and spotted knapweed-infested areas of the United States. It does not disperse as rapidly as the other introduced seed head gall fly U. quadrifasciata, but has been the more persistent colonizer and is the dominant species at most North American sites where both flies coexist. The seedhead moth and weevils often destroy Urophora species when they occur in the same seed head.

These insects prey on Leafy Spurge1. Apthona flava

2. Apthona nigriscutis

3. Apthona lacertosa

4. Oberea erythrocephala

5. Spurgia esulae

6. Hyles euphoribiae

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Leafy Spurge Euphorbia esula

Statewide Noxious Weed Awareness and Education Campaign

Montana State UniversityLand Resources and Environmental Sciencesin cooperation withUnited States Department of AgricultureAnimal and Plant Health Inspection ServicePlant Protection Quarantine

Some are beneficial . . . biological noxious weed control needs many points of attack

Leafy spurge flea beetles were introduced into Montana and North Dakota from Europe between 1985 and 1993. Copper or amber Aphthona flava, black dot A. nigriscutis, and brown-legged A. lacertosa flea beetles are established in nineteen states. Flea beetles feed on leafy spurge fine roots and foliage.

Red-headed leafy spurge stem borers Oberea erythrocephala are native to Italy and Switzerland. First introduced into Montana 1982 they are established in seven states. Their heads are red, with small black eyes and two antennae nearly as long as the body. Some people call them the “longhorn beetle” because of their prominent antennae.

The adult red-headed stem borer feeds on leafy spurge leaves, but not enough to really damage the plant. Instead, what kills the plant is how the female lays her eggs. She chews all the way around the stem, sometimes twice or more, before laying eggs. The chewing “girdles” the plant, killing the shoot above. She then bores a hole into the stem above the girdle and lays an egg inside. Larvae feeding in the stem also help kill the plant.

Leafy spurge tip gall midge Spurgia esula was introduced into Montana and North

Dakota from Italy in 1985. Sweep nets are not used to redistribute this small delicate fly because it will damage the very fragile adults. Instead, clipped leafy spurge stems should be bunched and the bottoms wrapped in damp towels or damp cotton. They should be taken to the field as quickly as possible and placed upright in a wire frame or other device so that the larvae will not be found by ants and other predatory insects. The tip (leaf bud) gall midge adults and larvae attack the growing parts of the plant destroying the shoots’ ability to flower and produce seeds. The tips eventually die, and the plants then produce new shoots from below the attacked areas. These shoots are then attacked by the next generation of midges.

The hawk moth Hyles euphorbiae behaves much like a hummingbird and feeds on nectars in the flowers.