By Whitney Cranshaw, Colorado State University Cooperative Extension, Entomology
Late in the season yellowjackets and honeybees are often seen buzzing around trees and shrubs, sometimes in tremendous numbers. Only very rarely does this indicate that there is a hive associated with the plant; far more commonly they are foraging for honeydew produced by other insects infesting the plant.
Aphids are the most common of the honeydew-producing insects and late-September/October outbreaks are common. These pose little threat to the health of the plant as they occur very late. However, the build-up of sticky honeydew can be a significant nuisance, particularly when they also attract stinging insects. One fortunate result of rainy weather is that this honeydew is regularly washed off, reducing these problems.
Other insects that produce honeydew may indicate more significant problems. In particular the soft scales infesting pines, such as pine tortoise scale and striped pine scale, have proved to be very serious problems in most areas where they have become established. At this time of the year active scale colonies will attract foraging yellowjackets to their honeydew. By examining plants closely you may be tipped off to an incipient problem.
Photos: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010