• Austin Campbell

Tree Galls What Causes Them and How Do We Help


The galls on oaks are caused by pesky little wasp and an array of other parasites such as mites aphids but today we will be talking about the wasps as the are the main cause of gall.The Gall Wasp lays parasitic larva in the leaves and soft tissue of the tree creating a pinhole sized brown spot to form on that leaf where the lavra begin to feed and grow.This cause the tree to produce growth around that spot and feed the larva because of chemicals enzymes and toxins produced by the wasp. When the lavra reach maturity they drill out of the gall to reproduce and lay more eggs starting the vicious cycle all over. When this browning and leaf drop happens lots of people assume the tree is dying and will remove it.The problem looks a lot worse than it actually is.The gall are just extra tissue growth around the larva.These wasp don't do this to all trees only oaks,beech,chestnut,coral,hickory,elm, and maple trees. There are many natural and manmade solutions to gall.For instance, some have introduced predator wasp, these wasps lay their own eggs and when the predatory wasp hatch they begin to feed on the larva or pupa of the gall wasp.This will eliminate any possible gall wasp offspring and stop the cycle of gall wasp reproduction in the area.In a surprising discovery in 2018, botanists discovered a vine that actually fed off galls formed by gall wasp on oak trees. When the vine was present, gall wasp pupae and larvae would only hatch in half the cases. Normally, gall wasps on oak nearly always mature to term.This spectacular vine, called the “Love vine” or Cassytha filiformis, was capable of creeping up towards galls and attacking the gall wasp that was forming inside, depriving it of nutrients.In most cases,the gall wasp do not spiral into a problematic situation there is usually no need to act but in some cases you must implement more effective methods.An example, if you wish to stop the gall wasp you can prune to the branch just below the gall.To prune properly you want to check in the season when gall are visible but not yet hatched,and with a clean pair of shears or a saw cut the branch below just above the bud to promote and direct healthy new tree growth.



Austin@campbellsprotreellc.com if you have any further questions

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