Issue 17, September 28, 2009
Scouting Watch
Magnolia scale crawlers should be present throughout the state. These first-stage nymphs, or crawlers, are oval and gray, with a reddish brown ridge running down the back. Each crawler has two white, waxy spots, one on each side. Crawlers mass on the undersides of 1- and 2-year-old twigs for the winter. From the time that they emerge from the female until they molt to the second nymphal instar in late April or early May, they are vulnerable to insecticide sprays.
White grub reports continue to be few and far between. There was a reduced emergence of Japanese beetle adults in central and northern Illinois. We also experienced timely, periodic rainfall. These caused eggs to be laid in smaller numbers and to be scattered over wide areas, making widespread, damaging infestations less likely.
Keep alert for small areas of damage, scout to determine the extent of the infestation, and treat only areas with damaging grub numbers. Keep an eye on soil temperatures. Japanese beetle grubs descend deeper into the soil when the turf root zone temperature drops to 60 degrees F. Masked chafer or annual white grubs and May beetles or true white grubs descend deeper into the soil when the turf root zone drops to 50 degrees F. At root zone temperatures above that level, insecticide treatments will still be effective.
Japanese Beetle adults continue to be present in small numbers. Generally, these numbers are not large enough to cause serious damage. Ohio has reported late season damaging beetle numbers for several years, indicating an apparent late emergence of some beetles. So far, I have not heard of this happening in Illinois. Let me know if you have seen high, damaging numbers of beetles after August.--Phil Nixon
Author:
Phil Nixon