Spring brings out all of the bugs, and while most of the ones we think about are damaging or annoying, there are thousands that go about their life nearly out of sight and out of mind. Every once in a while, one of these thousands can be pretty enough, large enough, or odd enough to catch our attention as we rush through our own lives. The jumping oak gall wasp is just such an insect. You can see it on many of Virginia’s oaks this time of year, and it might just warrant a pause in your day to see something unique and new.
The jumping oak gall wasp will almost exclusively damage mature white oaks (and other oaks in that family) around home landscapes. In most cases, tree owners never notice the insects or the galls they create on the white oak leaves, as they are tiny and non-damaging until the population hits a level that the tree cannot sustain. When this occurs, the young leaves will brown and prematurely fall causing stress to the tree. The real reason that jumping oak gall wasp is of interest is because of the jumping action that gives it the title.
The galls are actually tiny vegetative growths made by the tree’s leaves. They act as shelter and a food source for the larvae of a small stingless wasp where the insect spends most of its life. The gall wasps fall from the trees in late spring and will do a little dance on the ground to lodge themselves into cracks and crevices to wait out the rest of the year before they emerge as adults the following spring, when they start the lifecycle again. (Click here to see the jumping gall wasp in action.) If you have a white oak in your landscape, you can likely see this occurring on your sidewalks and driveways right now. This movement is caused by the larvae moving inside the dry gall much the same way “Mexican Jumping Beans” work.
As white oaks begin to leaf out in the spring, the adults hatch from the overwintered galls and begin the cycle again by laying eggs on newly emerging leaves when they are extremely small and still expanding. The eggs produce hormones that hijack the normal leaf growth and make the leaves grow fleshy tissue around the developing eggs. As the eggs hatch, the larvae begin to feed on the gall and grow. In heavy infestations, extensive foliage damage occurs and the oaks will drop the damaged leaves in an attempt to protect themselves from further injury, while light to moderate infestations go unnoticed. In some cases, it can warrant supplemental watering, mulching, and soil amendments to help reduce the stress caused by the leaf drop but preventative treatment is not recommended as it is very hard to time properly and requires very large applications of broad-spectrum insecticides that can damage non-target insects and invertebrates.
If you have white oaks on your property, it is likely that you have seen what looks like very tiny orange to tan dots all over your car, driveway, sidewalk, and landscape plants. These dots are about the size of the head of a pin and are extremely easy to overlook, but will hopefully now your eye will know what to look for. Take a minute or two to walk your landscape and see if you can detect the telltale jumping of this little wasp as it goes through its life underfoot and nearly out of sight.
It’s that time of year when you might find yourself admiring the trees along the highway covered in cascades of purple flowers. If you’re left wondering what type of tree that may be and why you never noticed it before, it might surprise you that it could be anything from an oak to a pine covered in those beautiful flowers. What you are seeing is not the tree but, actually, the plant that is slowly killing it. Let me introduce you to my favorite plant to hate — Wisteria.
My distaste for Wisteria does not spread across the genus but only falls on the two Asiatic species, Wisteria sinensis and Wisteria floribunda, which are both non-native, introduced species that have become exceptionally invasive in the urban forests of the Mid-Atlantic. This flowering vine will establish itself quickly in nearly any garden and begins climbing anything it can reach. Once fully established it will begin its spread through both seeds and above-ground stolons. A small trellis of Wisteria beside a deck or patio can quickly turn into a backyard filled with vines and nearby trees being overwhelmed. As the vines grow they climb as high as possible to seek out sun and will climb to the top of 50- to 70-foot tall trees, the whole time growing in diameter and slowly choking the tree. Heavy infestations can choke out entire trees and even woodlots. But what to do if it has already started its invasion of your property?
Control can be a tedious and sometimes hard-fought battle that may need a lot of elbow grease, herbicides, and even professional help. Smaller plants and clumps can be culled by simple hand pulling with a watchful eye for additional sprouts popping up. Larger infestations may require chainsaws, herbicides, and even the ever-popular goat to get things under control. It may take several years of repeated treatments to full eliminate the vines.
One final tidbit to note is that while goats can eat modest amounts of the plant, Wisteria should definitely be kept away from children or curious pets as the smooth and sizable seeds are very poisonous. And the rest of the plant poses a smaller threat, but still a threat if eaten. This does not mean that Wisteria doesn’t have a place in our landscapes and urban forests. It is indeed a beautiful plant that adds a splash of color in the spring. The native version of the plant, Wisteria frutescens, will still give you the showy flowers and some climbing without the nearly uncontrollable spread. It is also very well suited to remaining a small clumping shrub without support for climbing. If you can’t find this species in your local nursery, ask for it by name, which may help them to decide to stop carrying the Asiatic species.