AUTUMN PEST REVIEW: Although the season is beginning to wind-down, there are still a number of insect & mite pests that require scouting during the fall weeks. The pests discussed in this blog include soft scale nymphs, boxwood leafminers, white pine aphids, spruce spider mites, southern red spider mites, hemlock rust mites, eastern spruce gall adelgids & hemlock woolly adelgids. The use of low %-rates of horticultural oils this fall can be especially valuable against controlling many of these pests.

SOFT SCALE NYMPH MIGRATIONS: Most soft scale species (exceptions include magnolia, tuliptree, and globose) have 1st instar nymphs that spend July and August feeding along veins on the undersides of leaves of their deciduous host (the use of a hand lens may be needed). During the weeks of late summer and early fall, these nymphs migrate off the leaves onto woody stem tissue and molt into the overwintering 2nd instar stage. The size of the nymphs increases 3-times after molting and their presence is usually observable even without magnification (they can be as large as lenticels). Typically, overwintering soft-scale nymphs have a dark coloration, to help absorb sunlight and maintain body warmth.

European elm 1st-instar nymphs settled along the main vein underneath elm leaf. During the early weeks of fall they migrate from leaves onto the bark to overwinter. (Photo Credit: Cornell University)

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Many landscapers are familiar with the larger beneficial insects such as lady beetles, praying mantids, lacewings, and flower flies. Although common, parasitic wasps/flies (parasitoids) are examples of landscape beneficials that are typically less recognized because of their small size, and that magnification is needed for best viewing. Also many parasitoids feed unseen on the interior organs within their hosts. Although the majority of parasitoids are found in the two orders mentioned above (Hymenoptera & Diptera), there are more than 50 families that have been identified. Many of these insects do not have distinctive differences in general appearance & therefore attempting to ID the specific species or even family is not practicable for the landscaper or nursery grower. Learning about & being aware of the activity of these less observed but exceptionally important biological control organisms are photographed & reviewed in this blog.

An apparent parasitoid wasp inadvertently captured on the edge of a yellow sticky trap. Most of these adult wasps are exceptionally small & will often have a constricted waist & beaded antennae. The vast majority of observed landscape parasitoids will be wasp or fly species. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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Too often, landscape plant managers ignore or confuse beneficial organisms with insect pests and inappropriately apply control materials. This is especially the case with the larvae or immature stages of beneficial insects. An observant and knowledgeable IPM scout needs to learn how to recognize and conserve these “good guys,” so they are not needlessly destroyed. Remember, “we must look before we shoot,” when spraying pesticides and take advantage of natural pest control that works for free!

Home entrance walkway with diverse plantings of numerous species. An ideal setting to attract many beneficial insects. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

The classical definition of biological control is the use of natural enemies to control insect pests. These natural enemies include predators, parasitoids, and pathogens. Pathogens are microorganisms (bacteria, viruses, fungi, protozoan, and nematodes) that kill pests. Parasitoids are parasites that kill their hosts by their feeding activities. Most parasitoids of landscape pests are wasps and flies. This blog will discuss some of the more valuable ornamental landscape predators.

Over one hundred praying mantids can emerge from a typical sized egg case (ootheca). Although excellent predators, praying mantids are NOT considered to be valuable in the home landscape. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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