The world is beginning to come alive. Each spring we have a front row seat to a rebirth of our landscape as it comes back into life.
All winter long the tree has packed up itself into a dormant shell to protect itself from insects, diseases, and the environment. As we start the spring growth process, the plant is now making itself more vulnerable to the world. Right now, buds of trees and shrubs are beginning to swell as hormones within the plant start the process.
The bud scale is a hard structure that has been protecting the leaf buds through the winter. They will be the first to fall and, in some cases, they can be large and easily seen. While other smaller one’s float to the ground and are less visible. With these protective coverings gone, the potential leaves become more susceptible to cold damage, insects, and diseases.
One of the issues I see in our area is a disease called Peach Leaf Curl. Later on, in the late spring, you can find leaves that have puckered with an assortment of colors including reds, yellows, and a light gray. This is a bacterial disease that infects the plant just as bud swelling starts. Fungicide applications must take place before plants break dormancy.
There are many insects that take advantage of trees that have just lost their bud scales. There are over 1500 species of galls on a variety of plants. That newly expanding leaf tissue is an invitation for gall makers. These are certain species of aphids, midges, mites, psyllids, or wasps. Galls result from an intricate interaction between the highly specialized gall maker and a specific part of the host plant. It results in a distortion that is distinctive to that insect. That benefits the life cycle of the bug. Galls form at the time of plant cell multiplication in growing tissue. Normal plant growth is abruptly changed and the unique, identifiable gall replaces the ordinary growth.
If you ever marvel at how a caterpillar turns into a moth then this is another awe-inspiring insect process. They inject a chemical that causes deformities at the right time and the plant tissues actually form a structure that protects a developing insect.
The oak apple gall is a large ball about 2 inches in diameter that looks like a green apple on an oak tree. If you cut one open there is a small single wasp larva at the center surrounded by stringy foam.
Why all this protection for a single larva? This insect has a predator wasp that will feed upon the larva with a long egg-laying ovipositor. The apple-like structure has to be big enough that the ovipositor will not reach the larva inside.It is amazing how the structure is formed, to begin with then add to this, its defense mechanism.
With spring here, the tree armor comes off and another issue will be potential cold damage. As the leaves start to emerge cold damage is a possibility. Should that occur, many trees will just send out new leaves, but flower buds that have reached advanced stages can be thinned. This is especially true on all fruit trees and berries. Reports from Purdue this spring have pointed already to a reduction of grape buds stemming from the December 2022 cold spell. Even with their scales intact, grapes are more susceptible to cold injury than other fruits.
It is similar to humans curling up under the blankets in bed. You may feel protected from life’s issues but someday you will have to get out and go meet the cold cruel world. There are a lot of challenges and I would like to say there is nothing wanting to sting and deform you to carry their egg. Unfortunately, we humans also have several parasites. That is a topic for another day.