by: ISA Master Arborist: Gilbert A Smith
You may not have liked the weather we’ve had this spring/early summer, the wettest June in Chicago area history. I did not enjoy it either, but your trees love moist cool weather. Have you noticed how verdant they look this year? Trees, even in stressed locations, like in your parkway or parking lots show a good healthy green. Stress related problems like Euonymus Scale or Apple Tree Borer are significantly reduced. This is because trees are getting plenty of moisture with none of the heat stresses. So they take advantage by over producing leaves to harvest as much sunshine as possible. When it heats up the trees will dump some leaves. Don't be alarmed. The tree is just balancing itself out dumping lower food producers and bracing for the heat.
During wet cool springs some fungal diseases such as Anthracnose or Apple Scab also proliferate. Are you noticing a pattern here? Trees over produce leaves and there are fungi there to "eat" the leaves. It’s scary to look at. We get calls about falling or browning leaves every summer; and that’s good because it shows that you’re looking at and concerned about your trees. In general you can relax and enjoy this well balanced system.
Not to be left out of the bounty there are a host of bugs that take a bite out of the tree leaves. Moth and butterfly caterpillars are chewing holes in those healthy green leaves. Leaf hoppers, scale, aphids, thrips, spittle bugs and many others join in the banquet. Is this horrible for the trees? Actually a healthy tree can withstand as much as 40% defoliation without any ill effect. Should Arborsmith protect them from the bugs? When the damage is severe, we sometimes need to, but in many cases, the birds are already doing that. They depend on the explosion of tree eating insects to feed their voracious young chicks. That's right, birds survive almost entirely on bugs and the huge protein demands of growing young can't be supplied with seeds or fruit.
So what is happening when trees get sprayed using non-organic pesticides to keep tree leaves looking perfectly green? Unless it is for an invasive insect like Emerald Ash Borer there is an upset in the delicate balance. We are killing bees, butterflies, birds and polluting our home landscapes. We’re also worrying needlessly. If you have a certified arborist who makes “regular house calls” you can relax and enjoy the wonderful give and take in your own back yard.