Spring is here! The sun is shining, skies are blue and plants are… sticky? One cause of sticky plants, especially sticky roses and fruit and ash trees, is a sweet substance known as honeydew. Honeydew is excreted by small, soft-bodied insects called aphids. Aphids may be winged or wingless, and they come in many colors, including pink, yellow, green, dark blue, gray and black. Many aphids overwinter as eggs. They hatch in spring and begin to give birth to live young in one to two weeks.
Do you have aphids? Look for them on leaves and shoots, especially at the tips of new shoots. Inspect the undersides of leaves and fresh, new growth for their presence. Young leaf and flower buds are favorite targets of aphids.
To control aphids, protect the environment and save money, turn to integrated pest management (IPM). With IPM, actions to control pests begin with the least toxic. An IPM approach to aphid management includes: selecting plants that are unattractive to aphids, knocking aphids off affected plants with strong streams of water and pruning and destroying heavily-infested plant parts. Remember to clean and sanitize pruners after each cut. As you work to control aphids, watch for helpers like birds, lady beetle adults and larvae, lacewings and parasitic wasps. These critters feed on aphids. Help them do their job by controlling the ants that protect aphids.
Under most conditions, strong streams of water and help from aphids’ natural enemies render pesticides unnecessary for aphid control. If you choose to use a pesticide, keep in mind that most kill beneficial insects too. This may disrupt the beneficial versus pest insect battle for balance in your garden and increase your pest problem. Select products least toxic to beneficial insects, spray only where the infestation is occurring and always read and follow label directions.
Another cause of sticky bark, fruit or leaves on trees, shrubs and other perennial plants is honeydew produced by soft scales. Soft scales are small, are brown or black in color and have antennae. Their covers may be smooth or cottony. Armored scales do not excrete honeydew. Armored scales are smaller than soft scales, they are flattened and circular to irregular in shape, and their covers are waxy. They appear on plants as crusty sections that are gray, brown or yellow in color.
IPM tools for dealing with both soft and armored scales include: proper plant selection and care to increase resistance to scale damage; pruning and destroying heavily-infested plant parts, cleaning and sanitizing pruners between each cut; and performing yearly pruning to maintain open tree canopies.
Just as with aphids, helpful beneficial insects like lady beetles and parasitic wasps will work alongside you in the garden to fight scale; help them by controlling ants that protect scale. Using insecticides may kill these scale enemies, but if you decide to apply a pesticide for scale control, stop by Cooperative Extension first. It is important to have an expert identify scale before treatment, as application of the wrong scale control product can be ineffective or worsen the problem by killing only scale enemies and not scale itself.
Andrews, A., 2016, Plants Getting Sticky?, Reno Gazette-Journal
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