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I had a client call me because her Texas Red Oak tree (Quercus buckleyi) in the backyard was dripping large droplets of sap on her patio. When I think of trees or plants dripping sap, I typically think of aphids but not in the middle of the Texas summer and not large droplets the size of a quarter. Brenerria quercina or Drippy Acorn is favored by heat, moisture, and insect wounding. The bacterium enters the acorn shell through puncture wounds, which a variety of insects cause during egg laying and feeding. As the acorns grow and weather warms, the bacteria ooze, drip, and spread to surrounding acorns. Infection has shown to strongly correlate to warm weather, insect population, and whether or not the tree has previously been infected. Acorn production and/or size is typically reduced when infected, and may continue in subsequent years. Dripping usually subsides within a few weeks of onset, though, and exudate can be washed off of surfaces below the tree with soap and water.