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The Garden Plot for May 23, 2008
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Fruit Tree Pests”
When apples finish blooming, gardeners want to spray for insects, but it’s too early to spray fruit trees now. Leaf rollers are starting to hatch and you may see a few around your fruit trees on silken threads. But the population is very low now. There’s no need to spray yet.
Codling Moth, the wormy apple culprit, is just starting to emerge. Later they will mate and lay eggs near or on developing apples. The eggs hatch after a specific time period at 50 F. This is the unknown and is based on weather. If it is warm, eggs could hatch in two weeks. If the weather is cold it could be three to four weeks. Once Codling moth eggs hatch, tiny white Codling Moth caterpillars tunnel into apples in 4 to 48 hours. Then, these worms we hate to find as we crunch into our first home-grown apple are home-free. Bird and insect predators, as well as our sprays can’t touch them.
Timing is everything! If you spray too early, you’ll still have wormy apples. Timing Codling Moth control requires monitoring. We use pheromone traps to catch the first emerging male moths. Pheromones are a little like insect perfume; they help male Codling Moths find female Codling Moths. Fortunately for gardeners, male Codling Moths will follow synthesized pheromone right into the sticky traps we use to monitor them. Remember that pheromone traps ONLY CATCH MALE MOTHS! PHEROMONE TRAPS DO NOT CONTROL FEMALE, EGG-LAYING CODLING MOTHS. When we catch the first Codling Moth, we start our 50 degree temperature clock and measure until a specific number of hours above 50 F have passed. This gives us the window for Codling Moth hatch and first spray timing. The warmer it is, the more quickly the Codling moth development hours accumulate. So, the first Codling Moth spray-timing window may be earlier this year. Last year the first spray window began in the last week of May. It will be later this year.
In Missoula, we use an expensive field computer to monitor the temperature-based development of insect pests. If you don’t have one in your garden, you can call our 24 hour Garden and Landscape Phone Line at 258-3820 or call your local Extension Agent. There are usually two Codling Moth spray windows (late spring and early summer).
There is just one treatment window for Western Cherry Fruit Fly, the wormy cherry culprit. Western Cherry Fruit Flies spend the winter underground. They emerge, mate, and begin to lay eggs on cherries just as the first blush of color appears on green fruit. Gardeners can hang yellow sticky traps in cherry trees to catch these house fly-sized insects. Look for their distinctive clear wings that sport black stripes in a W pattern. The egg-laying treatment window is usually 2-3 weeks and may require 1-3 sprays depending on how long we continue to catch flies in traps. If the warm weather continues, Western Cherry Fruit flies could be earlier this year too. Last year we began to catch fruit flies towards the middle of June.
Helen Atthowe's new short program of gardening tips
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