Over the past week I've been scouting my pecan orchard for signs of summer foliage feeders. At this time of year, we can have outbreaks of Fall webworm and/or walnut caterpillar and I don't want to be caught unaware.
I did not find any colonies of either species of caterpillar in my orchard but spotted several Fall webworm nests on roadside trees (photo above).
Fall webworm colonies are the easiest to spot because they spin a white web over the entire colony designed to protect the caterpillars inside from birds and predacious insects. In the close-up photo at left, you can see numerous Fall webworm larvae clustered in the center of the web. These larvae will move to the margins of the web at night to feed on green foliage and spin silken threads to expand their web. Once the larvae reach full size, they will drop out of the web, fall to the ground, and pupate in the leaf litter. The colony of webworms I spotted this week represent the first summer generation. A second and often larger generation will appear in late August.
While I collecting leaf samples this past week, I also spotted a few Japanese beetles feeding in my trees (photo at right). The Japanese beetle is an introduced pest that has moved steadily across the US since first landing in New Jersey in 1916. I've seen it sporadically on my farm for the past 3 years. Last year, a large colony of Japanese beetles practically defoliated a young sweet cherry tree in my fruit orchard before I sprayed the tree with an insecticide.
I have yet to see large numbers of beetles feeding on my pecan leaves. For the most part the damage has been minor and not damaging enough to warrant pest control measures. The photo at left illustrates the light feeding damage I found on one tree in my grove. This insect seems to scrape off the surface of a leaf until it finds soft leaf tissue between the veins. At that point, the beetle eats through the leaf blade leaving an irreagular shaped hole.
I don't think Japanese beetle will become a major problem in commercial pecan groves where insecticides are applied regularly to control major nut-feeding pests.
