There are a few odds and sods kicking around this time of year. Usually late season feeding injury is not a big deal. However when the pest is going to make your ornamental plants its “forever” home…..you might want to do something about it.
Bagworm (Thyridopteryx ephemeraeformis) has been reported widely in the neighbouring United States. This is a moth whose caterpillar stage feeds on foliage (spring-summer) from inside a tiny protective “case” that looks like it was made out of tiny bits of wood (i.e. casebearer larvae). Look for damage on cedar, spruce, and several different deciduous hosts including honeylocust and crabapple. Foliage will turn brown and become quite sparse. At this time, the overwintering female can be found inside “bags” hanging from branch tips, they resemble small conifer cones (see photo above). The bags can be picked off and destroyed in the autumn/winter to prevent the next generation from hatching next spring. This pest has been reported in Ontario in the Windsor and Cobourg areas.
Black vine weevil (Otiorhynchus sulcatus) larvae have hatched and are feeding on roots of ornamental plants in CONTAINER production nurseries. Where black vine weevil larvae are a problem in container production (e.g. perennials, evergreens), nematode applications for larvae should begin in September. A good species choice for nematodes is Heterohabditis bacteriophora (“H.b.”). This species has shown excellent efficacy in container production trials. Drench containers with a backback sprayer (with no filters, low pressure) and keep containers moist for the first couple of weeks.
Assess nematode viability before spraying. 1) Make a stock solution of nematodes (i.e. submerge nematode product in 500-1000 mL of warm water 2) scoop a teaspoon of nematode stock solution into a clear glass of warm water. 3) use hand lens (or microscope) to check nematode viability: look for wiggly-shaped nematodes, many will be moving. Live nematodes should outnumber “dead straight” nematodes 8:2.
Beech Scale (Cryptococcus fagisuga) crawlers will be hatching soon (from early August to mid-September). Adult females are covered in a white, wooly mass when mature and so they are easy to monitor this time of year. Beech scale can be found on the bark of large beech trees (≥ 40cm DBH), mostly on the trunk and on the major limbs. Although the scale insect does not kill the tree, beech scale seems to predispose the tree to other problems and create wound sites that facilitate the entry of beech bark disease (Nectria coccinea var. faginata). Beech bark disease is a devastating fungal disease that has caused the death of several native and introduced beech trees in Ontario. So far, the scale and the disease have been found in beech forests throughout much of southern Ontario (including cottage country). Monitor scale populations for crawlers and treat crawlers about 3 times, every 7-10 days to target staggered emergence. Use insecticidal soap and Landscape Oil (as a targeted bark application) or other registered chemical insecticides when peak hatch occurs, in the next couple of weeks or so. Fall and spring (dormant) bark applications of horticultural oil may also reduce beech scale populations.
Taxus or Fletcher Scale (Parthenolecanium fletcheri) crawlers may be migrating around foliage of Thuja and Taxus. Look for honeydew, black sooty mould and small, brown bumps (dead adult females) on foliage. The nymphs are pale tan, flattened, and about 1-2 mm long with tiny red eyes. Applications of insecticides are not nearly as effective against these older nymphs as they were for the crawlers. In the nursery, systemic insecticides may be warranted where populations are still significant. Overwintering taxus scale will cause most of their feeding damage next spring.
Spruce spider mites (Oligonychus ununguis) will feed on conifer foliage this fall and believe it not, a lot of injury can happen in the months leading up to Christmas. Adult spruce spider mites are tan brown and black with 8 legs, nymphs are smaller and paler while the tiny spherical eggs are red and cling tightly to foliage. We can find all life stages at this time. Monitor lower branches, this is where most of the feeding damage is done, on the east side of the tree. Shake branches vigorously over a sheet of white paper (on a clip board) and count mites to assess populations. More than 5-10 mites per branch test may indicated significantly damaging populations.
Spruce Spider mite injury looks like bronzing (tiny, yellow flecks on the needle seen through hand lens). Miticide applications (e.g. Floramite, Kanemite, Vendex) are recommended where populations are at damaging levels.