Before you plant any type of tree, shrub or flower into your garden, make sure it's disease resistant. Spending hundreds of dollars on a tree only to have it die six months later because it was diseased isn't going to help your wallet, your landscaping plan or neighboring trees or plants. Before choosing trees for your yard, do your homework about the most common types of flowering trees that resist disease.
Flowing Crabapple Varieties
A beautiful, hardy tree, a flowering crabapple in Adams, Bob White, Camelot, Dolgo, Donald Wyman and Jackis are just a handful of the types most disease resistant, according to the University of Missouri Extension Agricultural department.
Varieties of hawthorn trees are considered disease resistant, especially the Washington hawthorn, though its leaves and fruits may be susceptible to rust fungus in some locations.
The paperbark maple is an excellent example of a tree with bark that rolls and exfoliates, much like a native birch, though the paperbark maple is native of China.
The Persian parrotia offers a stunning spring display of reddish-crimson stamens in early spring. Especially hardy and mostly disease-free and disease resistant, the tree is low maintenance, and after the leaves change and fall, the bark itself offers a fall and winter display of various shades of colors.
Alder trees are most susceptible to the alder phytophthora disease (Phytophthora alni). They are also vulnerable to a fungal disease called artist’s bracket (Ganoderma lipsiense).
Alder phytophthora causes stunted leaf growth, premature leaf drop and tarry spots to form on the tree's dying bark. Artist’s bracket can cause root rot, butt rot and white rot, all of which impair the alder tree’s stability.
Alder trees are vulnerable to several pests, including the alder leaf beetle (Agelastica alni), the common sawfly (Heterarthrus vagans) and the birch leaf-roller (Deporaus betulae).
Alder leaf beetle larvae eat large holes in the leaves, while sawfly larvae cause premature leaf drop. The birch leaf-roller causes the affected alder tree's leaves to brown and curl.
Since many alder tree diseases are caused by excess moisture, alders should never be planted in locations vulnerable to flooding. Prune out and destroy the infected leaves and limbs, to avoid spreading any infection.
Lethal yellowing, also called phytoplasma, is the most common and widespread disease that affects coconut trees. The near-microscopic bacterium causes yellowing fruit to drop and, in more severe cases, the death of the tree.
Bud rot is a fungal disease that affects coconut trees. Early symptoms include brown, sunken spots on young, developing leaves. The infection then moves inward toward the bud, then to surrounding leaves. Once a tree is affected with bud rot, young nuts will not develop. Bud rot can affect both juvenile and adult trees.
Trunk rot is a devastating disease that causes one side of a coconut trunk to rot and eventually collapse. A wound in the soft trunk tissue must be present in order for trunk rot to establish itself. No treatment is available for trunk rot.
Clip away diseased leaves and fruits from plants with garden shears. Remove any vegetable plants that appear to be overcome with disease; any plants that are wilting, covered with fuzzy mold or discolored spots are suspect. Place all bad leaves and plants in a garbage bag for disposal.
Rake debris away from plants affected by blight, including organic mulch.
Apply a garden fungicide that is approved for use on vegetables. Follow directions carefully regarding harvesting after applying these chemicals as many fungicides require a waiting period before harvesting the vegetable. Wash the vegetables especially well.
Stake vegetables to keep them from drooping and touching the ground. Prolonged contact of leaves, stems or fruit with the soil facilitates disease.
Avoid watering vegetables in the late evening as watering any outdoor plant during this time means water evaporates too slowly, leaving the soil damp longer and the area humid and, therefore, more prone to fungus.
Watch your trees for fungal infections during the rainy season of spring. Fungal diseases such as peach leaf curl, brown rot, perennial cankers and bacterial spots rely on the changing seasons to come out of dormancy and spread to trees.
Examine your tree's branches, leaves, fruit and bark. Look for spotted leaves, discolored bark, fungal spores, disfigured fruit, tree cankers (wounds), scabby fruit, stunted growth or dead tree limbs. For an analysis, take a picture of the diseased tree and take to your local nursery.
Remove the damaged areas from the tree with bypass shears, lopping shears and a pruning saw. Dip the pruning tool in a mixture of 70 percent denatured alcohol and 30 percent water in between cuts to prevent spreading the disease. Cut in a 45 degree downward angle to right above a healthy outward growing bud. If you are cutting off an entire branch, cut next to the tree collar (swelling of the tree from the branch to the trunk).
Burn or throw away all diseased leaves, branches, fruit or bark. Rake any diseased debris from underneath the tree and remove from the area.
Spray your tree with a fungicide according to the tree's disease.
Select a location for the plants that will protect them from severe winter weather. They can be planted in containers and brought indoors during winter.
Protect the flowers from clubroot disease. Add lime to the soil before planting to reduce the effect of the disease or plant the wallflowers in clean containers with sterile potting soil. Destroy any flowers affected by clubroot.
Watch for bacterial wilt, a fungus that causes the leaves to lose their color, wilt and die. Remove any affected flowers and destroy; do not add to the compost.
Watch for white rust on the wallflowers. This disease forms white, pus-filled spots on the leaves, which may shrivel. The spores can be transported to other gardens. Remove affected flowers and destroy them.
Thyronectria is an opportunistic fungal disease that feeds on drought- and heat-stressed honeylocusts. The disease causes branch dieback and cankers that distort the tree’s shape and stunt its growth. If left untreated, Thyronectria can cause death.
Crown canker is a pathogen disease that attacks the bark around the base of the tree. The deadened base of the tree results in the dieback and eventual death of the entire tree.
Ganoderma Root Rot
Ganoderma root rot is a fungal disease that produces shelf fungus on the trunk, near the soil line. This disease causes fungal tissue growth under the bark and can kill untreated trees.
Phymatotrichum Root Rot
Phymatotrichum root rot is a soil-born fungal disease. It attacks alders that rest in alkaline soils with low amounts of organic matter. This slow spreading disease will quickly kill the tree once infected.
Spiculosa cankers are fungal cankers that grow under the bark of the tree. The cankers leave rough, circular swellings on the tree and rot the tree’s internal tissue, leaving it dead and unusable. Infected trees must be removed.