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S1996
A bi-weekly newsletter on Landscape IPM for the Green Industry
| Volume 1, Issue 6---------- | Bonnie J. Gonzalez | ---------- July 7 - July 21, 1996 |
PHENO: Roadside Indicators
Look for Canada Thistles, Cirsium arvense to be just past bloom and beginning to form seed heads in the Northern Virginia area. Both Flat-headed and Round-headed Apple Tree Borers will be entering their vulnerable periods when timing of controls is optimum. Another easily recognized indicator is Queen Anne's Lace, Daucus carota. This plant is just beginning to bloom along roadsides and will go through a long bloom time. It is, therefore, useful to recognize the beginning of the bloom period and finally when the seeds form and the umbels curve upward. During the latter stage, you can scout for Juniper Webworm caterpillars and complete trunk applications for Peachtree Borers on affected plants.
Boxwood Leafminers
The newly hatched larvae are currently feeding on varieties of American Boxwood. To determine the extent of infestation, take a cutting with the current season's growth and hold it up to the sky. You will notice small, yellow dots on the new leaves. If there are several per leaf, consider spraying now with a residual material before the larvae get any bigger, thereby damaging the appearance of this season's growth. Boxwood psyllid adults may also be present and can be controlled at the same time. Psyllids are responsible for the cupped leaves.
Dutch Elm Disease (DED)
Elms infected with Dutch Elm Disease may be showing signs of flagging branches. Have these branches pruned out immediately and destroyed. Valuable specimens should be regularly treated with a preventative fungicide at this time. Alamo is currently recommended and is injected into the trunk flare of the tree. This process should be done by an experienced arborist. These injections are good for two years. This lethal disease of elms is usually exacerbated by Elm Bark Beetles which feed on elms and spread the fungus to other trees.
Fall Webworms (FW)
The first generation of Fall Webworm has made its quick appearance on a number of hosts. The loose webs form almost overnight on the terminals of branches. Look for these caterpillars and their webs in cherries, plums, pears, and apple hosts. Prune out affected branches now or you can spray with Bt, Orthene, Oil, Soap, or Tempo 2. Other hosts may also be affected. FW is not serious and will return again later in the summer but in lower numbers.
Dogwood Anthracnose
Summer management of Discula destructiva includes judiciously removing any sucker growth occurring along the trunk and branches. Once the fungus affects this fast growth, it becomes a fast route to the trunk where the fungus will form a canker. Once the canker girdles the tree, it is curtains for that tree! Remove the suckers. A fall fungicide will be discussed later in the season.
Hemlock Wooley Adelgids (HWA)
Mature hemlocks are most often affected by HWA. Look for white, fluffy wax near the base of needles, especially on the lower branches. The recently hatched crawlers have settled here and are beginning to feed causing the needles to eventually appear yellow and drop. A residual material may be warranted if the infestation is severe. Oil or soap will work on light infestations if spray coverage is good. I have seen phenomenal results on trees that have been soil injected or drenched with Merit. Bear in mind that it may take up to two months for complete uptake of the material into the tree. You can drench in the fall so that the materiel will be translocated into the canopy by March when they begin spring feeding.
Lacebug Update
A second generation of lacebugs is currently feeding on azaleas, rhododendrons, cotoneaster, and pieris. Keep on top of lacebugs with frequent monitoring on the underside of foliage. Signs of newly hatched nymphs look like concentrated bleached areas on the top of leaves. Use Orthene now. There will be at least four or more generations by the end of this season. Other lacebug species will soon be affecting Amelanchier, Cherries, and also Sycamore. The monitoring and controls are similar to the azalea lacebugs. Plants that are growing in full sun will likely be more infested and are less likely to have many predators than plants growing in more shaded conditions. I think I'll grow lavender instead of all those azaleas!
IPM Component: Evaluation
Evaluate the effectiveness of your spray activities by observing and comparing old and new growth of plants. You can actually count back several seasons of growth on some plants and see the reduction of plant damage as you have managed various pests. Being observant of these indicators is a barometer of your successes (or failures). By evaluating your controls you can fine tune your future activities. Practice makes perfect (or at least better)!
Food for Thought: Opportunities for Change
Often times it is our job as plant managers to tell a client that a plant or tree is not working in a certain location. It does not have to be a gloom or doom situation, but rather an 'opportunity for change'. This may be an optimum time to introduce an insect or disease resistant selection, or even get them to try an underused but exciting new plant. A picture is worth a thousand words...
Until next time, keep on scouting!!
Bug Bytes is written, distributed and owned by HORTSERVICES, and produced by Gregg Leonard Graphic Artistry, both of Loudoun County, Virginia. All rights reserved---no part may be reproduced without permission.
Bonnie J. Gonzalez
16 Berkeley Court
Sterling, VA 20165
(703) 430-4545
when your plants need help. She knows her plants as well as her bugs.
Remember, IT’S NOT OVER… UNTIL THE BUG LADY STINGS!