How to protect your plants from sawflies
Management for sawflies depends on many factors:
Check for sawflies in spring
Monitor plants you suspect may be attacked by sawflies. Early detection allows for more effective treatment and reduced damage to host plants.
Healthy plants can tolerate sawfly damage
Pick sawflies off plants
Using pesticides
Treat sawfly larvae when they are young and half their full-grown size or less when pesticides are more effective. If larvae are fully grown, the damage is done and treatment is not effective.
Most sawflies feed in groups, and it is possible to spot treat them instead of treating the entire plant. This helps reduce the amount of pesticide used.
Low impact pesticides
Insecticidal soap and horticultural oil are effective when managing small numbers of young sawfly larvae.
Azadirachtin and spinosad are effective for one or two weeks so sawflies that feed on treated foliage are still affected.
Bacillus thuringiensis var. kurstaki (Btk) is a common low impact insecticide used against moth and butterfly caterpillars. It is specific to caterpillars and does not kill sawfly larvae.
Contact residual insecticides
Examples of contact residual pesticides that are effective include permethrin, bifenthrin, lambda cyhalothrin, and carbaryl are most effective against young sawfly larvae. One application is usually sufficient.
Systemic insecticides
Systemic insecticides are pesticides that are transported by the plant through tissues that carry food and water to the leaves and needles. When sawflies feed on the needles and leaves, they receive a toxic dose. Common examples are imidacloprid and dinotefuran.
CAUTION: Be careful when applying systemic insecticides to hardwood trees and shrubs that are attractive to bees. This includes linden, crab apple and sugar maple, as well as juneberry (serviceberry), pagoda dogwood, nannyberry viburnum and many other shrubs. This does not include evergreen trees and shrubs.
Apply systemic insecticides to trees and shrubs only after flowering has already occurred to reduce pesticide exposure to bees. If sawflies are active when trees and shrubs are flowering, use an alternative method of treating them.
Do not apply systemic soil drench pesticides when flowering plants are next to trees or shrubs.
Professional services
Commercial tree care companies have experience in managing sawflies and in applying pesticides. When treating trees is not practical, use a licensed pesticide applicator working for a professional company.
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Information source: University of Minnesota Extension
Fall webworm, Hyphantria cunea, is a moth that is better known for its caterpillar stage that creates large webbing at the ends of branches. Webs up to 2 to 3 feet in length can be seen at ends of branches from mid-summer and into fall. When active in the summer, they may contain a colony of hundreds of webworm caterpillars.
This native species feeds on at least 80 species of trees, though most commonly seen on walnut, birch, black cherry, elms, and maples. Young larvae begin to feed in early July in southern Michigan, and at the start of August in northern Michigan. Protected within the webs, newly hatched caterpillars first feed on the upper surface of the leaves, and after several molts, the larger caterpillars consume whole leaves.
Information source: Michigan State University
Forest tent caterpillars in Minnesota attack a number of broadleaf trees and plants like quaking aspens, balsam poplar, basswood, oaks, ashes, birches, alder and fruit trees.
Feeding damage by these caterpillars slows down the growth rate of deciduous trees.
When target trees are defoliated, forest tent caterpillars may also damage other nearby plants.
Damage can be seen on vegetables, fruit trees and other small fruits, and nursery crops.
They are a nuisance when they are found around buildings or on roads.
The forest tent caterpillar (Malacosoma disstria) occurs throughout most of the United States and Canada wherever hardwood trees are found. This caterpillar rarely feeds on red maple and conifers, such as pine and spruce.
Feeding by forest tent caterpillars generally does not kill deciduous trees, as they can produce another set of leaves during the same season.
Healthy trees can tolerate two to three consecutive years of heavy defoliation.
Trees may be killed if the same tree has been heavily defoliated for four or more years, or when trees become stressed, such as during a drought.
Information source: University of Minnesota Extension
Japanese beetles are an invasive species. Japanese beetles feed on the leaves, flowers or fruit of more than 300 species of plants. Japanese beetle grubs are pests of turfgrass. They chew grass roots, causing the turf to brown and die. Grub-damaged turf pulls up easily from the soil, like a loose carpet. Japanese beetle infestations in Minnesota are mostly found in the Twin Cities metropolitan area and southeast region of the state. There are both nonchemical and insecticide options for managing Japanese beetle adults and grubs.
Japanese beetles are a serious pest of flowers, trees and shrubs, fruits and vegetables, field crops and turf. Adults feed on more than 300 plant species, whereas the grubs feed mainly on the roots of grasses.
Adult Japanese beetles feed on the leaves, flowers and fruits of many different plants. Preferred plants include rose, grape, linden, apple, crabapple, cherry, plum and related trees, birch, elm, raspberry, currant, basil, Virginia creeper, hollyhock, marigold, corn silks and soybean. They skeletonize leaves by feeding on tissue between the major veins giving them a lace-like appearance. Damaged leaves turn brown and may fall off.
Information source: University of Minnesota Extension
Read more about Japanese Beetles.
Japanese Beetles In Minnesota, Japanese beetles (Popillia japonica) are primarily found in the Minneapolis-St. Paul Metropolitan area, and in some areas in southeast Minnesota. Japanese beetles have an exceptionally large host range, feeding on the leaves of over 300 species of plants, including apples, grapes, blueberries, raspberries, roses and plums. Identification Japanese beetles are 3/8…
Read more about the white marked tussock moth here.
Information source: University of Minnesota Extension
Information source: University of Minnesota Extension
