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Why are my sycamore trees struggling? What is chewing on my cabbage?
My plum trees are sticky, and the leaves are curling. Why are the leaves on my maple trees yellow? What are the notches around my shrub leaves?
If only gardening — and life — were more simple and problem-free.
These and many other problems are showing up in Utah gardens, so I will attempt to relieve some stress that gardeners might be experiencing.
Hopefully, the solutions will work for you and make your gardening more successful.
Many sycamore trees, including the London Plane trees, are not looking good because they are infected with sycamore anthracnose.
It is a fungal infection that comes from wet weather as the leaves are emerging in the spring.
In addition to sycamore trees, the disease affects oaks, ashes and maples. The pest overwinters in the infected twigs, and in the spring, the spores spread to the new growth.
Anthracnose damage shows as large, dead lesions along the leaf mid-rib, and young, infected leaves curl.
The new buds appear to be frost-damaged, and the small twigs die back. Severe infestations leave the trees almost leafless.
Once the trees are infected, controls are not effective. Preventive fungicide applications must start as soon as the buds open in the spring and continue until the weather remains warm and dry.
My broccoli and cabbage have been relatively unscathed by the worms this year, but that changed this past week.
The cabbage moth has started laying eggs, and the green worms are now feeding on my produce.
Covering the plants with a floating row cover would have excluded the moths, but now I will have to rely on a spray of Bacillus thuringiensis commonly sold as Dipel or Thuricide.
This microbial preparation is not toxic to people or pets and is specific for butterfly and moth larvae.
The curled leaves on plums, cherries, snowballs, roses and many other plants are caused by aphids, which are small sucking insects.
They seem to be worse this year because the cool weather prevented predators from developing.
Without the lady bird beetles and other creatures that feed on aphids, they reproduce rapidly and feed on the undersides of the leaves. This causes them to curl, and the dripping sap is from the excess sugar the aphids excrete from the plant sap.
If the predatory insects are feeding, leave the plants alone, and they will clean up the problem. Otherwise, wash the plants off with a strong stream of water or spray with insecticidal soap. If this is a persistent problem, use a dormant oil spray before the leaves unfold in the spring. Stronger measures are seldom needed.
The cold, wet spring has left many plants with yellow, chlorotic leaves. The prevalent alkaline soils in Utah tie up the iron and make it unavailable to the plants.
Adding iron chelate will help, but the most permanent solution is to select plants that are not as susceptible to the problem.
Silver, vine and red maples, peach, raspberry, strawberry and blueberry plants, as well as any azalea, rhododendron and birch plants are almost guaranteed to have problems in high pH soils. Avoid these and other susceptible plants.
The notches around the leaves of your plants are likely caused by root weevils. These pestiferous insects feed on many garden plants and can be life-threatening if they are numerous enough.
Among their favorite victims are strawberry, raspberry, clover, spruce, Douglas fir, roses, peonies, euonymous, lilacs, aspens, privet, laurel and dogwood plants. Their diet can include almost any plant in your garden under many conditions.
The adult weevils are dark-colored snout beetles that may reach a half-inch in length. They do not fly but overwinter as nearly full-grown, pale, legless larvae under the soil, or as adults in debris under the plants.
Adults are emerging and feeding now and making the familiar notched leaves. While these are a noticeable symptom, the larvae feeding on the roots cause much more serious damage.
The best prevention is healthy plants. Select well-adapted plants that will thrive in their selected location. Add organic matter, water and fertilizer as needed to promote good plant growth and if the damage is severe, start a control program.
There are several registered insecticides for root weevil control. For adults, use azadirachtin (Neemix, Aza-Direct, Azatin, Bioneem), carbaryl (Sevin), esfenvalerate (Bug-B-Gone) some pyrethroid insecticides and malathion (Malathion).
For larvae control, certain parasitic nematodes give some control, and the systemic insecticide imidacloprid provides some control when used as a soil drench.
The beetles can also be trapped if they are only bothering a few plants. Bury straight-sided glass or slick plastic tumblers around the plants so the top edge is even with the soil surface. Pour a half-inch of cooking oil in the bottom of the glass. As the beetles fall into the containers, they will be trapped and killed. Clean the traps and replace the oil regularly.
Problems are aggravating but not insurmountable. Learn to tolerate cosmetic damage because you can never control every garden malady. Concentrate on those that cause serious economic problems and ignore the rest.
