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Evergreen Needle Drop (Bagworms)
(Dave Shetlar - OSU Entomologist) |
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| Evergreen needle drop – a lot of you are concerned that many of the evergreens in your landscape have been dropping needles from the inside branches. This should not be confused with Red Spider or drought damage that can kill entire sections to a whole evergreen tree, for example, Spruce or Pine. Every spring evergreens shed their oldest needles and replace them with new ones. This is a common function on evergreens like the leaves are of a leafy, deciduous plant. We talked about Bagworms last week; here is some more information about Bagworms. |
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| Bagworms begin to hatch when catalpa trees are in bloom. I actually recommend waiting until the blooms are finished as this gives all the eggs time to hatch. There are always some bags that were attached to fence posts, branches and other sites that are in shaded or protected habitats. The eggs in these bags usually take a bit longer to hatch. As the larvae hatch, they drop out the bottoms of the bags on a strand of silk. If there is a breeze, the tiny larvae are picked up and blown to nearby plants (we call this ballooning). While most of the larvae don’t blow any further than the plant on which their parents resided, some can be blown quite a distance (several hundred feet). This is why you can get a bagworm infestation on plants that are not near other infested plants! Bagworms do their worst damage by defoliating conifers, especially junipers, arborvitae, spruces and even white pine. Remember that conifers can’t replace eaten foliage once they have put out their current year’s growth. I’ve seen entire tops of trees, one side or even whole trees killed in one season by bagworm defoliation. |
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| Remember that bagworms feed on a pretty wide range of deciduous plants, but their defoliation doesn’t kill these plants. My personal belief is that these are usually missed, but they serve as sources of reinfestation in subsequent years. When bagworm bags are less than 3/8 inch in length, even the biobased insecticide, Bt will kill them. Of course, the pyrethroid will kill them too as will the one neonic, acetimiprid (TriStar). Unfortunately, we are still looking for something that can be applied as a basal drench to protect all conifers without having to resort to tall tree sprays. |
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Lace Bugs
(Dave Shetlar - OSU Entomologist) |
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| Lace Bugs. Overwintered HAWTHORN LACE BUG (Corythucha cydoniae) and OAK LACE BUG (C. arcuata) adults were observed laying eggs on the leaves of their namesake hosts in southwest Ohio. Like most lace bugs, hawthorn lace bugs live on the underside of leaves. They have a cosmopolitan palate and may be found on several species in the Rosaceae family including cotoneaster and Amelanchier as well as hawthorn. Oak lace bugs focus their attention on their namesake host, but they are particularly fond of oaks in the white oak group. These lace bugs are unusual in that they live on the upper leaf surface. |  |
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| Lace bugs use their piercing/sucking mouth parts to suck juices from their host plants. Their feeding produces tiny yellow or whitish leaf spots (stippling) that may coalesce to produce large, yellow-to-copper colored areas on leaves, and early leaf drop. Lace bugs also deposit unsightly hard, black, varnish-like tar-spots of excrement onto the leaf surface as they feed. The bugs have multiple generations per season, and their damage builds with each succeeding crop of bugs. It is important to closely monitor and control lace bugs early in the season to avoid the collective damage produced by successive generations. | |||||||||||||||