Question
QUESTION: Will these aphids affect the health of my maple tree or are they more of a nuisance? Also, my maple is very large, will it take a long time for treatment to work? Thank you, Tammy.

ANSWER: More tthan likely you are talking about cottony scale.
The cottony maple scale, Pulvinaria innumerabilis (Rathvon), is a highly modified insect pest that commonly attacks silver and red maples. The scales are usually first noticed when the females produce an egg sac which appears as a 1/4 to 1/2-inch long ball of cotton. Heavy infestations can result in branches being turned completely white with the egg sacs. Like most scale insects, the nearly mature insects, the adults and the eggs are resistant to pesticides and the anxious tree owner must wait until the correct time for management.

Normally, this scale is a mere curiosity and nuisance. The white egg sacs easily attract attention and the developing scales produce honeydew. Honeydew is the excess water and sugar excreted by many plant sap-feeding insects. Honeydew is commonly mistaken for "plant sap" being dropped on cars, sidewalks and lawn furniture lying under trees. When honeydew collects on leaves and branches, bees, wasps and ants are attracted to the area. If the honeydew is allowed to remain, molds called "sooty fungus" grow on the material, turning the surface a gray-black color.

Occasionally, heavy outbreaks of this scale occur, usually on weakened or stressed trees. These outbreaks can cause the death of numerous small branches and occasionally the death of a tree.

This pest has numerous parasites and predators that normally keep its populations in check. However, every few years, these natural controls seem to fail and the cottony maple scale can reach epidemic proportions. Unfortunately, weak trees can be severely damaged during these outbreak years. Healthy trees often loose a few small branches and have no apparent long term problems. What makes management of this scale more difficult is the fact that insecticide applications may actually cause the scale problem to continue longer than normal. This is caused by poor timing of a pesticide application that kills most of the parasites and predators but allows survival of the resistant scale stages.

Maples in restricted street lawns or suffering other stresses from drought, compacted soils, poor fertilization, etc. are the ones most likely to exhibit major branch or crown dieback. Improving the tree growing conditions will significantly help the trees survive the cottony maple scale attacks until the natural predators and parasites build up to effective levels. The most important predators are several black lady beetles that have two red spots on the upper surface.

Imidacloprid (Bayer Advanced Garden Tree & Shrub Insect Control Concentrate) is applied as a drench around the root zone of infested plants. This water soluble insecticide is taken up by the roots and transported throughout the plant where it is ingested by sap feeding insects. This provides a means of scale control without reliance on sprays. However, it may need to be applied several weeks before crawlers are active for best results.

 





---------- FOLLOW-UP ----------

QUESTION: Can the black lady beetles become a problem over a period of time? Tammy

Answer
No the lady beetles may build up in population but will go away as soon as their food supply (the aphids) is gone. There have been cases of population build ups where the beetles have become a nuisance with large numbers *getting into houses and buildings seeking a winter hiding place) but they cause no harm.