Gypsy moth is often in the news and with it comes the promise of aerial spraying of Btk by the department of agriculture. While the idea of the government spraying pesticides over an entire neighborhood may be frightening, a gypsy moth out-break would be devastating to the trees of the Emerald City or any city. Gypsy moths defoliate over 500 species of trees, both deciduous and evergreens.
Bacillus thuringiensis var. kurstakiis a bacterium that affects only caterpillars. It is considered an acceptable pesticide by organic gardeners, provided it used only when really needed. The major caterpillar pests in our area include:
- the larvae stage of the gypsy moth;
- cutworms that feed in winter and spring on primroses, chives and other perennials;
- tent caterpillar often seen later in the spring on apple trees;
- keep in mind that sawfly larvae which can strip a flowering red currant bare in a few weeks are not caterpillars, and Btk will not control them.
Btk will kill caterpillars of butterflies, which is why it must be used with caution only when pest populations are high or the potential damage is intolerable. Btk is typically sold as \”caterpillar killer\” where other pesticides are sold.
A list of the best books, articles and websites on pests, diseases and their control.
By Brooklyn Botanic Garden. The article covers microbial pesticides, horticultural oils, insecticidal soaps, alcohol, and botanical insecticides.
Virginia Tech insect id, including organic/biological controls
Integrated pest management fact sheets from WSU for the home and garden.
To find pictures of insects go online to www.insectimages.org, Developed by Bugwood Network and the USDA Forest Service, this free database can be browsed by category of insect or keyword searched.
Once a mystery insect has been identified go to Plant Disease and Insect Identification Pests Leaflet Series from WSU for information on insects commonly found in western Washington or Insect and Pest Series Index from Ohio State University for general garden pest fact-sheets.
Act in October to defeat the Winter moth (Operophtera brumata). These moths mate in autumn and then the wingless females climb up tree trunks to lay their eggs. In early spring the little green inch-worm like larvae eat flower and leaf buds from the inside out. The many host plants include maples, oaks, crabapples, apple, blueberry, and some spruces such as Sitka spruce. To detect female moths place a band of heavy paper covered with Tanglefoot (a sticky goo available at nurseries) around susceptible tree trunks. If females are found it may be a good idea to spray the tree (trunk and branches) with dormant oil to smoother the eggs for reliable control. If the little caterpillars start \”ballooning\” out of trees in high numbers spraying with Bt (caterpillar killer) will provide control. For more information go to this University of Massachusetts Extension publication
A trip through the garden at night with a flashlight will reveal a surprising amount of animal and insect activity. Earthworms crawl across the ground looking for decomposing plants to consume while weevils, slugs and cutworms feed on our prized shrubs and perennials. Remember that the new non-toxic iron phosphate slug baits, such as Sluggo, must be reapplied about every two weeks. More slug-coping advice can be found online at www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7427.html
By November Seattle has usually had a good hard frost and most of our herbaceous (non-woody) perennials have either turned to mush or look a bit tattered. Before you give in to the temptation to cut back everything in sight, consider the advice of natural gardening advocates James Van Sweden, author of Gardening with Nature (Random House, 1997) and Jackie Bennett, author of The Wildlife Garden (David & Charles, 1993):
- Leaving seed heads and dead stems over the winter gives the garden winter interest, especially if we get some snow
- Seed heads from Black Eyed Susans, Echinacea, Larkspur and Evening primrose provide bird food
- Beneficial insects hibernate or over-winter as eggs on plant waste
- Marginally hardy plants like some salvias and lavenders benefit from the little bit of frost protection from the desiccated stems
On the other hand, sanitation is critical if your apples suffered from codling moth or scab or your roses suffered from black spot. Rake up and dispose of every single diseased leaf or infected fruit. Insect and disease organisms also over-winter on plant debris, so if you had a problem this year, start the treatment now with a thorough clean-up.