spotting round headed apple borers
Round headed apple borers have become an increasing problem for me over the last 5 years or so.
We keep the orchard organic, which limits pretty heavily the solutions available to us for this particular pest....and it is a serious pest that can kill and or set back a young tree with just a few grubs.
I have not seen too many others on the forum complaining about them, so perhaps our pressure is high for some reason. But I thought I would throw out some observations for others to consider, and if any have suggestions I would love to hear them.
I have been painting the trunks white with various slurries. I don't believe it has much effect in deterring egg laying, but it does make it easier to spot the presence of the grub and dig them out.
Everything I have read suggests inspecting the trees mid-late summer, but I have never found them at this time, I think they are there but not readily visible. When I find them is this time of year, as the tree begins to shut down and usually a few days after the first good autumn rains. That's when the cambium seems to give one last push of fluid that floods the damaged areas under the bar. This in turn shows as a brown/purple stain on the white paint weeping through an egg slit. So now I do my inspections at the same time I install mouse guards for the winter.
The other thing I have noticed is that it is much harder to chase them down and dig them out when they are in the root flare...more nooks and crannies. When they are up a few inches on the trunk they are both easier to spot (less dirt and mulch stain on the paint) and easier to remove.
This makes me tempted to leave small screen "booties" on the lower 6" of the the trees all summer to force egg laying adults up off the root flare.