The Penn State Extension of Berks County Master Gardeners will be featuring questions and answers to inquiries received through their Garden Hotline.
Q. I’m seeing small insects on the stems of my plants. What are they? What is the best method to eliminate them?
A. The insects are aphids. Depending on the species, they may be black, gray, white, red, yellow, green, blue-green, blue, purple, brown, and tan. Some aphids are generalists feeding on many kinds of plants and some are specialists feeding on one species of plants. All are sap-feeders which excrete “honeydew,” which evaporates, and later black sooty mold grows on the honeydew, interfering with the plant’s photosynthesis.
You may see ants tending the aphids to harvest their honeydew. Distorted leaves or stems are signs of the presence of the tiny insects. Before treating the aphids, look for their natural predators, such as ladybugs and especially their orange and black larvae. Also flower fly larvae, lacewing larvae and itty-bitty parasitoid wasps, birds, especially warblers and hummingbirds are consumers of aphids.
The easiest management of these insects is to squish them gently with your fingers. A blast with a stream of water from the garden hose will knock them off, spraying up, then down to include the undersides of the leaves.
If you need more control for the aphids, a simple treatment with insecticidal soap, horticultural oil, or neem oil is also effective after flowering. Remember that a solution made with dish detergent will damage plant tissue, so do not use homemade recipes.
Avoid systemic insecticides which travel throughout the plant, including the flowers. These products impact good insects like aphid predators and pollinators.
Q. What’s happening with Colorado Blue Spruce trees? They all look like they are dying in my neighborhood.
A.: There are a number of factors causing the decline in blue spruce trees including environmental changes, poor site conditions and new pathogens. The trees are native to the arid regions of the Rocky Mountains. The Pennsylvania climate is more humid, wet and warmer, which is ideal for fungal pathogens to thrive. As a result, the trees are stressed and more susceptible.
There are three major types of diseases that affect blue spruce trees: needlecasts, tip blights, and canker diseases. The two most common insects are gall adelgids and spruce spider mites, both of which are so small you will need a hand lens to see them.
It is advised to consult a certified arborist to access your trees and suggest a course of treatment. Once the die-back starts, it’s hard to control and most trees will eventually need to be removed. Homeowners can slow the spread of the problem by trimming off and removing the lower dead branches, spacing newly planted trees to promote good air circulation, improving tree vigor through mulching and watering when needed.
Penn State Master Gardeners with advanced diagnostic training staff the hotline, answering questions on lawn care, landscape plants, houseplants, fruit, vegetables and herbs, insect and disease issues, and identification of unknown plants or insects. Advice is based on Integrated Pest Management strategies and environmentally-friendly approaches. For more information on these and other gardening-related topics, email the Garden Hotline at berksmg@psu.edu or call 610-378-1327 to speak to a Master Gardener.