CORRECTION: The gopher bait referred to in this column last month is called Wilco Gopher Getter. Sorry about that!

QUESTION: I have some juniper trees whose tips are turning brown. The trees were planted over 20 years ago and they receive enough water. When the branches are moving a yellow powder falls out of the "infected" area. What is causing the browning of the tips. Is it an insect or a fungus of some kind?

ANSWER: After examining a sample of the plant it was determined to have normal growth. The small brown tips are the developing male portion of the trees and when mature will produce pollen. The yellow power that falls off the plant when disturbed is indeed pollen.

QUESTION: We live up in the mountains and have many oaks on our property. We have noticed brown growths near the end of branches that looks as if someone had thrown cow manure into the trees and it stuck! Also, we have some round "balls" hanging from the oak trees as well as some growths that are near the end of young twigs that look to be impaled on the twigs. What are these and where do they come from?

ANSWER: Wherever oaks occur, they are attacked by a small group of insects called galls makers. These insects cause deformities of plant tissue. The majority of gall making insects that attack oaks are wasps. Galls are produced by powerful plant growth-regulating chemicals or other stimuli produced by the insect that react with plant hormones. Some stimuli are feeding or egg laying. The inner walls of the galls are rich in protein and thus provide the larvae living in the gall a concentrated food source. The larvae are somewhat protected from predators while they are in the galls. Galls come in several shapes and sizes. They can be globular, dish-shaped or look like thorny, spiny balls. Galls are specific as to the kind of oak they occur on. For example, those found on the black oak group do not occur on the white oak group. Many galls exhibit a characteristic gall alternation of generations. That is that the offspring of a gall wasp may produce galls that are completely different from those produced by their parents, but identical with those by their grandparents. Also, the site of the galls usually will be produced on a different part of the tree than those of their parents. It is reported that 717 species of gall wasps are found in North America. That number is decreasing as biologists unravel the mystery of alternating generation pairs and identify single species.

Source: Insects That Feed on Trees and Shrubs, 2nd Edition. Warren T. Johnson and Howard H. Lyon. 1991. Page 440.