How to Rid Flies From Flowering Plum Trees

Flowering plum trees can be threatened by insect pests.

If you have a flowering plum--scientifically known as Prunus cerasifera--you are already familiar with the pleasures of owning this stunning ornamental tree. With its display of pastel pink or pure white blossoms, the flowering plum provides a welcome infusion of texture and color to early spring landscapes, while its purplish, oval leaves add visual interest in summer and fall. Unfortunately, there are several flying insect pests that can infest your flowering plum tree; their effects range from being a mild nuisance to presenting a serious threat to your tree's health.

Things You'll Need

• Yellow sticky cards
• Garden hose
• Insecticidal soap
• Bacillus thuringiensis, a biological insecticide
• Commercial pesticide containing malathion, carbaryl or permethrin (optional)

Instructions

1. Use yellow sticky cards, available at garden supply stores, to trap and kill whiteflies. These sap-sucking insects--which resemble small, powdery moths--are often found on the undersides of leaves, where they cause damage by sucking out the juices. These pests can reproduce many generations per year, developing from egg to adult in little more than three weeks.

2. Spray the flowering plum tree with vigorous blasts from a garden hose to dislodge the whiteflies from the leaves. Make sure to thoroughly douse the undersides of leaves.

3. Spray affected leaves of your flowering plum tree with insecticidal soap if whiteflies still persist. In order for the solution to work, you must provide thorough coverage, contacting the insects directly with the spray.

4. Use bacillus thuringiensis, a natural biological insecticide, to control fungus gnats around your flowering plum tree. These small flies, which rarely exceed 1/8 inch long, look like tiny black mosquitoes. The adult fungus flies are little more than an unsightly annoyance, but their larvae feed on decaying organic matter, and are capable of damaging the roots of plants.

5. Examine your flowering plum tree in late spring and summertime for the presence of sawfly larvae--shiny, olive green worms about 1/2-inch long--and pick them off and destroy them. Sawflies--small wasp-like insects--are stingless, but their larvae can be very destructive to your flowering plum. According to the University of Minnesota Extension website, sawfly larvae feed on the upper leaf surface, leaving only the veins uneaten; an infested plum tree may have a scorched appearance, with prematurely dropping leaves. Larvae appear in early June, feed for a month, then drop to the soil to pupate and start a new generation in August.

6. Use mechanical means--such as spraying with a hose--and non-toxic products--such as insecticidal soap--to control sawflies on your flowering plum tree.

7. Use a pesticide containing malathion, carbaryl or permethrin if sawflies still persist in spite of your efforts. According to the University of Minnesota Extension website, these chemicals offer good control of sawflies, but should be directed toward the young larvae, and toward affected parts of the tree. Spraying the entire tree is unnecessary unless the sawfly population is widespread throughout it.

Tips & Warnings

• Correct any overly wet conditions--such as nearby areas of damp moss or algae-filled puddles--to help control fungus gnats; these insects thrive on excess moisture.

• To avoid injury, carefully read all labels on pesticides, and follow the directions exactly.

References

• Planet Natural: Whitefly Control
• University of Minnesota Extension: Sawflies of Trees and Shrubs
• Yardener: Yardeners Plant Helper