Use this guide to figure out what’s wrong with your trees.
Don’t panic if you see spots on your tree’s leaves or something strange on the bark.
The powdery material can be scraped off.
Credit: Peter Krumhardt
Control:Usually, rust fungi are harmless to the plant and rarely require control measures.
Where practical, remove and destroy leaves in fall.
Severalfungicidesare available that can control rust fungi.
Credit: Scott Little
Check with your local tree service for current recommendations.
Blossoms and leaves of some twigs suddenly wilt and turn brown or black.
Fire blight is a tree disease due to bacteria that are particularly active in warm, moist weather.
Credit: Dean Schoeppner
Bees, rain, and infected pruning tools spread the disease.
Damage:Tips of infected branches may hang down.
Control:Prune off12 inches beyond discoloration and destroy the pruned branches.
Credit: Denny Schrock
Disinfectpruning toolsafter each cut by dipping in one part chlorine bleach and nine parts water.
Avoid excess nitrogen fertilizer in spring and early summer.
It encourages succulent growth, which is more susceptible to fire blight infection.
Credit: Dean Schoeppner
Several fungi varieties cause this tree disease, affecting plants that grow in the shade the most.
The leaves may become distorted.
Infected leaves may turn yellow or red and drop.
Credit: William M. Ciesia
In late fall, tiny black dots are scattered over the white patches like pepper grains.
Control:When planting new trees and shrubs, choose resistant varieties.
Several fungicides are available that will control this mildew.
Credit: Denny Schrock
It can vary from 1/8-inch growth on leaves to massive swells on a tree’s trunk.
Damage:Swollen growth on leaves, shoots, or the trunks of trees.
Because of these factors, it’s best to consult atree care professionalif you observe an outbreak of gall.
Credit: Denny Schrock
Control:Prune and destroy brooms and injured branches.
Then, spray the affected tree with locally recommended fungicides in fall or early spring.
Canker
Canker is a tree disease characterized by a localized dead area on a trunk or branch.
Credit: Denny Schrock
Cankers on young trees can kill them.
They rarely kill established trees, but they may cause severe growth deformities.
Control:Most canker-causing fungi infect stressed or injured trees.
USDA Forest Service Northern Research Station, Bugwood.org.Credit: Leah Bauer
The best defense against canker is prevention.
Keep trees healthy and prevent infection.
In periods of drought, water trees thoroughly.
Credit: Denny Schrock
In the case of infectious cankers, remove branches six to 12 inches below the canker.
Dead or dying branches should also be removed.
Prune during dry weather or winter to minimize the spread of the disease.
Leaf Spot
Leaf spot is fungi that cause reddish brown spots that rot holes in foliage.
Damage:Infected leaves develop spots, turn yellow or brown and drop off the tree.
When the beetles find a food source, they release a scent that attracts more beetles.
Females lay eggs in the soil, which hatch into grubs, a major lawn pest.
Damage:Japanese beetles eat leaf tissue between the veins, creating a skeletonized effect.
They may also eat large holes in flower petals.
EAB kills trees in 2 to 4 years after initial infection.
Damage:An EAB-infected tree has a thin or dying crown and erratic growth along the tree’s trunk.
This is where the beetle exited the tree.
Control:Many preventive treatments are available for trees within 15 to 20 miles of other infected trees.
Treatment outside this risk zone is not prudent.
Bagworm
Bagworms eat the leaves of many trees and shrubs.
Larvae hatch in May or June and immediately begin feeding.
Each larva constructs a “bag” that covers its entire body.
Larvae pupate in the bags.
When adult males emerge from pupal cases, they fly to find females and mate.
After mating, the female lays eggs in the bag and overwinters on a tree or shrub.
Larvae emerge in spring to continue the cycle.
Damage:Leaves are chewed, and branches or entire plants may be defoliated.
Brown, 1- to 3-inch-long “bags” hang from the branches.
Control:Spray with Bacillus thuringiensis (Bt) between late May and mid-June to kill young worms.
Handpick and destroy bags in winter to reduce the number of eggs and young the following year.
1.Think before you treat.Pest damage is often cosmetic.
The plant will cast off the damaged leaves and continue to thrive.
A healthy ecosystem makes this possible.
2.Plant diverse species.Pests tend to prey on particular plant groups.
3.Choose plants that are well-suited to your site.Healthy, thriving plants will naturally overcome many pest attacks.
4.More is not always better in gardening.More water, fertilizer, andmulchcan all lead to disease andpest problems.
