Beginning in late spring through summer, we are often asked to investigate and treat high value trees with aphid problems.
Symptoms and signs of aphid infestation include:
Leaves which are unnaturally curled inward
Black sooty mold on leaf surfaces
Sticky substances on sidewalks, driveways, or vehicles
Ant trails on tree trunks and limbs
Numerous yellow jackets hovering around tree canopies in late summer
By mid summer, when honeydew production is at its highest, copious amounts of the sticky substance may accumulate on vehicle and sidewalk surfaces causing great annoyance.
Aphids
Aphids have natural enemies. The most well known predator is the lady beetle. Adult and larvae alike are voracious consumers of aphids and can eat up to 50 aphids per day. Dense groups of aphids provide a generous food supply for these predators.
Maintaining a healthy growing environment and growing plants that attract beneficial insects helps your plants defend against pests. Should an uncontrolled outbreak occur, see Pesticide Application recommendations below.
Aphid Management
If treatment is necessary, we strongly recommend against using canopy sprays using persistent full spectrum insecticides. Many of the chemicals used persist in the environment a long time and have a very detrimental effect to the beneficial insect population, birds, fish and humans. The availability of sub-surface soil applications, trunk drench options make tree canopy sprays unnecessary. For more in-depth information about aphids, use the following link which will guide you to the UC IPM web site.
Pesticide Application
High levels of nitrogen fertilizer favor aphid reproduction. The University of California Extension recommends that we do not apply high rates of Nitrogen fertilizer throughout the growing season. Excessive applications of high Nitrogen (N) fertilizer may cause a burst of new leaf growth, which encourages reproduction of aphids and other plant juice feeding insects. The industry standard calls for spring and fall applications. Tree Solutions Soil Restore fertilizer program uses the guidelines suggested by the University of California Integrated Pest Management program by applying small amounts, if any Nitrogen fertilizer.
Leaf growth response to high rates of fertilizer can actually cause more harm than good. Your tree or shrub may initially show a vigorous response, but ensuing pest outbreaks may lead to expensive pest management treatments to control them. Applicators generally will blame the pest not the practice of over fertilization. You do not always have to treat for aphids. If infestations are extremely high, treatment may be warranted. We recommend treatment if copious amounts of sticky honeydew, which is produced by the insect, leads to the production of sooty mold, on leaf surfaces. This condition may interfere with photosynthesis. We recommend treatment of stressed trees.