Our coast live oaks were so happy to get almost 50 inches of rain in Topanga this winter, pushing out new shoots and leaves like crazy! While that lovely new growth is providing lots of new energy for the tree (leaves photosynthesize and produce tree food!) the bounty is also coming with some problems. What is that white powder covering many new shoots? Powdery mildew is common after a cool wet winter and spring. Caused by several fungi, the growth can cause leaf distortion and limit growth as they take nutrients from the newly formed leaves. The good news is that once the warm days turn hot, this fungi will disappear and does not cause lasting damage. No treatment is needed! Why are all these drops of sticky gooey sap dropping down from my coast live oak tree? The calls keep coming and folks are understandably concerned, especially when their cars windshields are covered, but there is no simple answer and a site visit from a certified arborist is probably needed to identify the source of the problem. There are over 5,000 native insects that rely on oaks to survive, and with the cool wet conditions we experienced this spring, the boom cycle is in full swing. Everything from honeydew excreted from leaf sucking insects like aphids, scale to other insects like filbert worms, filbert weevils, fruit tree leaf rollers can be the culprits. To confirm which insect is causing the problem, you can set a white sheet under the canopy and then hit the lower branches with soft end of a broom to see what falls out. Take a photo of those insects and contact an arborist to see if they are a problem or not. Most of the time, these insect pest cycles are short lived, and the trees have years of experience in coping, so treatments are not often needed. The exceptions to that are for trees that are severely stressed by other issues such that loss of any functional leaf area makes it hard for the tree to survive. What about those twigs throughout the tree that have turned brown? The twig girdlers are having a great summer enjoying the new growth on the trees! These insects are sometimes referred to as “natures pruning team”, and while the “flagging” of brown twigs is unsightly, these insects rarely cause any significant damage to the oaks. So watch how they work to keep the canopy in balance and check out the interesting tunnels they make which disrupt transfer of water and nutrients to the shoots. Be on the lookout for the Bad Beetles! While most of our native insects are annoying they rarely kill trees. That is not the case for Invasive Shot hole borers and Gold spotted oak borers. Please keep an eye out for these guys as early detection and rapid response are the key to preventing massive tree loss. The RCDSMM will be hosting trainings in Fall 2023 to help community volunteers learn how to identify these pests. Infestations are often spread by moving firewood cut from infested trees. Be super careful about NOT moving firewood especially into our national and state parks! In the meantime, you can learn more at: ucanr.edu/sites/pshb; ucanr.edu/sites/gsobinfo Our native coast live oaks are incredible survivors! Benign neglect is often the best way to ensure that they continue to grow and thrive. Avoid removing green leaves which produce the food for the tree, protect roots, and enjoy the wonder of our leafy neighbors! By Rosi Dagit, Certified Arborist