A closeup of the parasite, Rust Fungus, growing on red cedar.

Phomopsis Gall on Forsythia.

Ever notice the balls of orange tentacles on a cedar tree in the spring or red bladder-shaped growths hanging from a maple leaf? Both are common pests in our area that might catch your attention but are nothing to worry about.

There are several hundred insects, mites and fungi that cause abnormal growths commonly referred to as galls. They are typically classified as fungal or insect. Fungal galls are most commonly growths of the fungus itself, like the orange tendrils of Cedar-apple rust fungi. Insect galls are formed by the plant as it reacts to secretions or stimuli from insects and mites within the plant tissue.

This spring’s cool, wet weather seems to have extended the season for fungal galls, and I have seen a lot of cedar-apple rust galls. The gelatinous structures produce spores that infect apple and crabapple leaves and are a problem on those species. Apple and crabapple owners may wish to control the disease on their trees, but control for the galls that appear on cedar trees is not warranted.

Some other fungal galls that have been popping up this spring are phomopsis gall on forsythia and black knot on fruit trees. Phomopsis gall causes pom-pom shaped growths along the stems of forsythia branches. Very little is known about the life cycle of the phomopsis fungi, but researchers recommend pruning out affected branches to prevent dieback of the shrub.

Black knot affects cherry and plum trees primarily. The fungus produces irregular blackened growth along small branches that I think resembles burnt marshmallows. Pruning is the best management for this gall as well.

Insect galls are prevalent this year, too.

Maple bladder gall seems to be the most common insect gall in the Lawrence area right now. Bright red and green growths appear on maple leaves in response to a tiny mite feeding on the leaf surface. Adult mites also deposit eggs within the galls that will hatch into additional mites to continue the cycle. Even though the galls attract attention, they and the mites do not cause any ill effects to the tree, so control is unnecessary.

Galls are also common in oak trees, and most commonly affect twigs and small branches. Two of the most common are the horned and gouty oak galls which cause lumpy, rounded growths around twigs. Insects are protected by plant tissue while feeding and have complicated life cycles that make control difficult.

In small trees, heavy populations of gouty and horned oak galls can weaken trees and should be pruned out. Large trees can typically withstand stress from gall development.

Other interesting galls come in a variety of shapes or even may make leaf veins appear swollen. Overall, they are just another interesting thing for us to look for in our gardens.

• Jennifer Smith is the Horticulture Extension Agent for K-State Research and Extension in Douglas County. Contact her or an Extension Master Gardener with your gardening questions at 843-7058.