Maine Home Garden News
July 2009

July is the month to . . .

• Strawberries are ripe now. Pick them in the cool of the morning and leave the hulls on until you are ready to rinse them with water. Harvest season usually lasts about three weeks. After you finish harvesting your berries for the season, it is time to renovate the bed. Mow the leaves off to within one inch of the crown of the plants. Apply fertilizer and narrow your rows by using a rototiller or by hand. Keep weeds under control.
• Raspberries will be ready to pick in a few weeks. If you notice the tops of the new canes bending over in the shape of a shepherds hook, you have raspberry cane borers. The female makes two rings in the top of the cane and lays her egg between the two rings. Cut the affected part of the tops off your raspberries and take to the landfill. Do not compost.
• Last month's wet weather has led to an explosion in the slug population. You can set slug traps using either  beer or a mixture of yeast and water. Put in a shallow dish and place in the garden so the edge of the dish is even with the soil. Slugs will slime in and drown their sorrows in the beer or yeast mixture. As an alternative to trapping, consider using the organic slug bait containing iron phosphate. See an article on its effectiveness at OSU's Extension Service Garden Hints Web page.
• Check your garden at least once per week for signs of pest activity and decide if you need to apply any controls.  If you do not know what the pest is, bring a sample of insect, diseased leaves or damaged leaves into the Extension Office for identification. Many gardeners have started emailing digital pictures of pest problems. For a list of Extension offices in Maine, visit the UMaine Extension Web site or call 1-800-287-0274.
• "Dead heading" of annual flowers will maintain their flowering habit longer. 
• Remember to plant seeds for succession crops in your vegetable garden: lettuce, radish, broccoli, cabbage, cauliflower, summer squash, carrots, beets, spinach and bush beans.
• The red lily leaf beetles are attacking the Asiatic lilies in flower gardens. You can hand pick the adults and larvae (they are yellow and carry their excrement on their backs), spray an insecticide (carbaryl, malathion, pyrethroid or neem) or plan to replant to another perennial. Day lilies are not affected by the lily leaf beetle. Researchers continue to test a number of parasitic wasps that they hope result in the release of one or more of these predator species.  For more information see UMaine Extension's bulletin #2450 Lily Leaf Beetle .
• This is the height of weed season. It’s easier to control a small weed than a large weed. Do not allow weeds to go to seed. Organic or plastic mulches can help you keep weeds under control. Clipping is another option if hand-pulling is too difficult.
• Leave your grass a half inch higher during dry weather to help conserve moisture.
• Fill in bare spots in your perennial bed with annual flowers.
• Prune spring flowering shrubs. 
• Be on watch and ready to manage tomato hornworms. For a recent article on the pest, see the UMass Amherst Insect Management Web site or call UMaine Extension at 207-780-4205.
• Order fall bulb crops for fall planting
• Hand thin fruit trees. Peaches, nectarines, plums, apples and pears will benefit from a controlled reduction in crop load. Remove plum fruits so that fruit are spaced roughly four inches apart on the branch.  Other fruit types should be roughly six to eight inches apart. 

By the UMaine Extension Home Horticulture Program Leadership Team

Common Tomato Diseases
By Dr. Bruce Watt, Extension Plant Disease Diagnostician, Pest Management Office, Orono, Maine, bwatt@umext.maine.edu

The two most common diseases of tomato that we receive at the Plant Diagnostic Lab are: 1) Early blight and 2) Septoria leaf spot. Both of these diseases are caused by fungi and are very similar in the way they affect the plant. Early blight can attack all parts of the plant other than the roots but occurs most typically on the leaves. Symptoms on the leaves appear as brownish spots that typically have concentric circles within (Fig 1.). Spores from the infected leaves can land on the fruit causing infections that will produce rotten areas.

Septoria leaf spot generally appears as small circular spots and upon close inspection, tiny spore producing structures (pycnidia) can be seen within (Fig 2.). This disease is almost always limited to the leaves.

Both of these diseases begin around mid-season on the lower leaves as the foliage becomes dense and the plants begin to grow in on each other. The reason this happens is that the fungus spores require liquid water to germinate. As the foliage becomes dense, the leaves dry more slowly allowing enough time for the spores to germinate and infect the tissues. If left unchecked, these fungi will work their way up the plant as spores are splashed or windblown to new foliage initiating new infections. Eventually all the foliage may wither and die. In the case of early blight the fruit may also rot whereas Septoria will leave behind green unripe fruit. 

Control measures for these two diseases are essentially the same. Good sanitation will limit the amount of the fungus that is present each season. Remove the plants from the garden at the end of the season because this is where the fungi will spend the winter. Tilling the garden at the end of the year will bury any remaining plant tissues which will break down in the soil environment. Watch the crop carefully each year for signs of infection and remove the affected leaves as they appear. This is best done during dry weather. Planting the tomatoes in a different area each year will further separate the plants from any fungus that is left over from previous years. A three-year rotation is desirable.  Good water management will help to keep the plants dry so that even if the fungus spores are present they will be unable to infect. Set the plants at a sufficient distance from each other to maintain good air circulation as they mature. Air movement will help to dry wet plants more rapidly so try to plant the garden itself in an open area. When watering the plants, keep the foliage as dry as possible. Using soaker hoses, or similar methods, is ideal for this. Water early in the day rather than allowing foliage to stay wet all night.

Fungicides may also be used to achieve acceptable control of these diseases and during the wetter seasons may be necessary. When using fungicides it is important to remember that they protect the plants against infection. Once an infection has occurred and the fungus is growing within the plant a fungicide will not stop it. Keep a close watch on your plants throughout the season and when the first symptoms of infection occur it is time to spray. Depending on the weather and the fungicide used (Read the label!), sprays should be used thereafter on a 5-14 day schedule. Some fungicides labeled for these diseases are Bacillus subtilis, chlorothalonil, copper  products, mancozeb, and potassium bicarbonate.  Your local garden center could be a good source for these fungicidal products. 

Japanese Beetles and Your Landscape
By Clay Kirby, Extension Insect Diagnostician, Pest Management Office, Orono, Maine, ckirby@umext.maine.edu

Description:
The recent gloomy wet weather may have delayed the appearance of the Japanese beetle this year. The Japanese beetle, Popillia japonica, is a scarab beetle about 3/8" long. The head and thorax are metallic green and the elytra (outer wing covers) are copper-colored. Adult feeding damage appears as lacey leaves. The Japanese beetle feeds on hundreds of plants including rose, raspberry, bean, grape and blueberry. The adults are good fliers and can move from one area to another in large swarms. When threatened, adults will feign death, dropping from the plant.

The larval stage is a C-shaped white grub similar in appearance to the June beetle, rose chafer and European chafer. Japanese beetle grubs can be a major turf pest. A good indicator of a white grub infestation is skunks and crows digging up the lawn. White grub treatment threshold is typically 8-10 grubs per square foot.

Life Cycle:
Japanese beetles usually begin to emerge during the last week in June in central Maine and can be found right through September. After mating, the females lay eggs in turf. The eggs hatch and the young white grubs feed from late July and early August until the first hard frosts of fall drive them deeper into the soil. After hibernating through the winter, the grubs migrate into the turf root zone to feed again in May and June. Around mid-June, the grubs pupate, eventually emerging as adults in one to three weeks.

Management:
Managing adult Japanese beetles is challenging because of the large numbers that can occur throughout the summer. A combination of approaches is suggested. Consistent handpicking of the adults can help protect your plants from the ravages of this pest. A coffee can, about a third full of soapy water, can be used to collect the beetles. Although controversial, you may want to consider pheromone/bait traps as part of your management strategy. Be sure to place traps at least 50 feet away from the plants you want to protect. Also, do not wait for the trap bags to completely fill before emptying. Poorly maintained traps can be a liability instead of a help.  In spite of some evidence that they may draw in more beetles than would normally be present, some gardeners have reported positive results with the traps. Protective barriers (e.g. spun-bonded material) can be used to protect susceptible plants during massive influxes of beetles.  Foliage can be protected with sprays of neem (Azadirachtin), cyfluthrin/imidacloprid, malathion, or carbaryl (Sevin). Repeat applications (if permitted by the label) are often necessary for protecting plants from this pest.

Japanese beetle white grub management is best timed when the white grubs are small and feeding in the turf root zone. In New England, beneficial nematodes (best application time: last three weeks of August) have been shown to be somewhat effective in managing white grubs, whereas milky spore has had spotty results at best, and is not recommended. Insecticides such as imidacloprid or halofenozide are also an option to consider (best results obtained from June or July application). Targeting the grub stage in anticipation of relief from the adult beetle often leads to disappointment.

Be sure to read and follow label instructions on all management tools (traps, nematodes, and insecticides). If considering pesticides, please keep in mind the environment and beneficial organisms. 

For a fact sheet and more information about Japanese Beetles and other pests, visit the UMaine Pest Management Office Web site.

Home Gardeners Late Blight Alert!
By Dr. James Dill, Pest Management Specialist, Pest Management Office, Orono, Maine, jdill@umext.maine.edu

Late blight, a highly destructive fungal disease, if left unmanaged, has recently been discovered on tomato plants throughout the state of Maine. University of Maine Cooperative Extension strongly encourages home gardeners to check tomato and potato plants for symptoms of late blight, especially those who may have recently planted tomato seedlings obtained from a big box store. Late blight was the plant disease that greatly contributed to the "Irish Potato Famine"in the mid-1800’s.

The long stretch of cool, cloudy and rainy weather this June has provided classic conditions for the spores of this fungus to disperse. The symptoms include irregular-shaped, water-soaked, yellow to gray spots surrounded by white mold on the top leaf surface and whitish mold on the underside, which eventually turn into blackened areas on the stems and leaves. These blackened areas dry up, wilt and die. The disease will also attack and destroy the tomato fruits. The threat exists of the late blight spreading to potatoes, therefore, if home gardeners find late blight on their plants they should pull, bag and throw out these plants. Do NOT compost them.

For pictures go to:
Potato Late Blight
Tomato Late Blight

© 2009

Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Call 800-287-0274 or TDD 800-287-8957 (in Maine), or 207-581-3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit www.extension.umaine.edu.

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