Growing Concerns: If it’s all gone haywire, it must be August

August 12, 2018

August always brings an onslaught of questions. For many homeowners, shrubs are growing out of control, insect pests are actively feeding, weeds have gone wild in lawns, tree limbs are sagging with the weight of new growth, and plant diseases have gotten to a level that symptoms are alarmingly apparent.

In fact, I simply don’t have enough hours in the day to keep pace with the questions in addition to the daily workload. If you have tried to contact me and I have not replied, please try again.

During the past couple of weeks, Japanese beetles and lawn weeds have topped the list of questions. Both of these pests have been active for some time but are most visible this time of year.

Japanese beetles that are on plants small enough to be sprayed can be treated for as needed. There are several products available from local garden centers that are effective for controlling them.

Remember, these products also kill pollinators, so read labels and avoid spraying blooming plants when pollinators are active. In larger trees, it is not practical to spray the canopy and it is too late in the beetles’ feeding cycle to get systemic insecticides to translocate into the foliage to control the beetles.

Fortunately, if trees are healthy, the defoliation from the Japanese beetles will not kill the tree. At this point, these insects will just need to run their course in larger trees.

I have frequently heard comments that Japanese beetles will just keep getting worse. They have been in Rochester for several years and are well-established. However, they are a more recent invader in some neighborhoods. Over time, beetle populations will cycle from high to low populations. We should typically see a cycle of several years with low to moderate populations that gradually peak.

In years of high population, diseases of the beetle will cause the population to fall back to lower levels. We will have some level of Japanese beetles every summer, but very high populations should be intermittent so trees won’t suffer from heavy defoliation season after season. Trees are well-adapted to tolerate these intermittent pest outbreaks.

By late summer, weeds have reached their mature size and are very visible in lawns. While it is tempting to get out and start spraying, it is probably best to delay this practice until the end of August or early September. If done too early, the spaces that are left when the weeds die are likely to be filled with warm season weeds such as crabgrass.

Delaying just a few weeks will get us to a point where lawn grasses recover from the stress of summer. These grasses will begin a growth stage where they produce new plants which will quickly fill the spaces left by dead weeds. There is not a specific date that is best for fall weed control, but it should be timed when the forecast shows cooler daytime temperatures and increased rainfall. September through November generally offer optimum growing conditions for our cool season turf. This is also the optimum time to get control of lawn weeds, fertilize, aerate and over-seed when needed.