Sudden Branch Drop
At this time of the year, it is not uncommon for large branches to suddenly drop from oak trees without warning. Although this phenomenon is not limited to oaks, the sheer size of their branches makes summer branch drop (also known as “sudden limb failure”) in oaks much more hazardous for life and property than branch drop by other tree species.
Summer branch drop is not related to wind and often occurs in the afternoon on hot, calm days. Unlike most breaks due to wind, which occur where a branch attaches to the trunk, a break due to summer branch drop usually occurs 3 to 12 feet away from the trunk, along the length of the branch. The branches that break are usually long and horizontal, as opposed to upright, frequently extending to or beyond the average tree canopy. While some limbs that drop show evidence of wounds or decay, many of these failed limbs appear to be quite sound. Older, less vigorous trees seem to be more prone to this problem. Once a tree has lost a limb due to summer branch drop, it is more likely to lose another.
Another consideration is that these long, horizontal branches may have been damaged by earlier storms. While there is usually no visible cracking on the outside of the limb or bark, the branch may have over-flexed in heavy winds, sort of like how we get a sprained ankle. A number of the interior wood fibers snapped in the wind, but not enough for the branch to immediately fail. The weight of the branch continues to snap these wood fibers one by one, until “the final straw that breaks the camel’s back” occurs, and the limb fails.
Although there is no guaranteed way to prevent summer branch drop, several things can be done to mitigate this hazard in oaks and other commonly affected tree species. On mature trees, shorten and lighten long horizontal branches and open up the tree by thinning to healthy lateral branches to reduce branch weight. (This does NOT mean topping the tree!) Inspect the tree for externally visible defects and prune out damaged or sickly low-vigor limbs that have decay or cavities. Finally, do not park cars or place play structures, benches, or picnic tables beneath older, susceptible trees. Falling limbs can’t harm people (or property) if they aren’t under the tree.
No Fruit This Year?
I’ve had numerous complaints this year about a lack of fruit in home orchards. I meant to discuss this in an earlier newsletter, but it get slipping my mind. It came back to me as I was examining the complete crop failure on my bush cherry this weekend.
We had a a lot of strange weather this spring. It was very cool and wet most of the spring…especially during bloom time for many of our home fruit trees. We did not have any killing freezes during bloom time, so we can rule that out. However, the weather did play a minor role in our problems: it reduced bee flying.
I noticed that my bush cherry was absolutely loaded with flowers this spring. But, unlike previous years, I did not notice any bees working the blossoms. Neither my neighbors nor I use any insecticides, so there should have been plenty of bees in the neighborhood. But the problem is, bees don’t like to fly during cold, wet weather. Bees CAN fly in the rain, but they don’t like to; the rain (even mist) adds heavy droplets to the bees’ furry bodies, which inhibits their ability to fly, and reduces the amount of pollen they can collect.
There’s nothing to be done for this year. Keep up with irrigation this summer; be sure to prune properly this winter (or have me come out and prune your fruit trees for you!); and if you are spraying fungicides for foliar disease, continue to do so. Also, try to reduce insecticide usage, especially on blooming plants
Japanese Beetles Flying
Japanese beetles are flying throughout the tri-state. They were a little slow getting started this year, most likely due to the prolonged cool spring we had. But, they are out in abundance right now…at least, in some neighborhoods.
Adult Japanese beetles are about 1/2 inch long, metallic green and bronze in color, with a row of white hairy tufts along each side of the body.
Japanese beetles have an annual life cycle. The adult beetles emerge from the soil, usually in early June in southern Indiana. They will feed on the foliage, flowers, and fruits of over 350 species of plants. After feeding for a few weeks, the beetles will mate. The females will drop to the ground and, if the soil is soft and moist enough, will burrow down several inches to lay their eggs. The eggs will hatch after 2 or 3 weeks into white, C-shaped grubs. The grubs feed on the roots of turfgrass throughout the summer. As the weather cools, the grubs move downwards into the soil profile, where they will spend the winter. In the spring, the grubs will move back towards the surface, where they will pupate. After several weeks in the pupal stage, they will emerge as adult beetles and start the life cycle again.
An interesting observation I’ve made over the years: Japanese beetles will appear in a new neighborhood in huge numbers. They will be very troublesome for three years or so. After the third or fourth year, the population crashes, and from that point on, they are more of a nuisance than a serious pest problem.
Controlling Japanese beetles is difficult, partly because the adults do not emerge from the ground all at once. While there is a wide range of insecticides that will kill the adults, the beetles have to eat some of the plant in order to be poisoned, so your plants will still be damaged. Also, the beetles you kill today will be replaced by a new emergence of beetles tomorrow. Avoid over-applying insecticides, because this can be harmful to bees and other pollinators.
For non-flowering ornamentals, the best product to use is a soil application of imidacloprid, sold as Bio Advanced Tree and Shrub Insect Control. This systemic product is applied to the ground next to the plant and watered in; it will move upwards through the entire plant, providing about 90 days worth of control. This product should not be used on summer-blooming plants, as the product has been reported to be harmful to bees.
Control the beetles on food plants with foliar applications of insecticides. Bifenthrin, carbaryl, cyfluthrin, neem, and permethrin are safe to use on fruit and vegetables if harvest restrictions on the label are followed. Sevin is also available as a 5% dust to be used at the rate of 1/2 pound per 1,000 square feet (be aware: the dust form of Sevin is extremely toxic to honeybees!). For other products to use on ornamentals, check out this publication:
Beetle traps are not very useful for controlling Japanese beetle, because the traps tend to bring more beetles to the property than would have been there anyway. If you use a trap, try to place it as far from the garden beds you are trying to protect as you can. The idea is lure the beetles away from your garden, not toward it.
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