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| Landscape Alert newsletter | |||||||
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| Vol. 23, No. 11, June 20, 2008 |
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In this issue |
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| Emerald ash borer adults are flying now Watch for the bright metallic-green beetles that are three-eighths to a half-inch long on warm, sunny afternoons. The beetles have started emerging from infested trunks, leaving “D”-shaped holes. They will feed on ash leaves for several weeks, depositing their eggs on the trunks and branches of ash trees in late June and July. See previous Landscape alert articles and emeraldashborer.info for more information on protecting ash trees from emerald ash borer. |
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| European chafer beetles expected soon If you had grub damage in a low maintenance, no irrigation lawn last fall or this spring, watch for European chafer beetles to emerge in the next two weeks. They become active late in the evening just before sunset. You will see the dark silhouettes of beetles flying around the treetops, and you may hear the buzzing of their wings. They will be active for the next three weeks; mating and laying eggs. Females seek relatively dry lawns to deposit their eggs in, so keeping your lawn moist for the next four weeks may help. Also, we know from several research tests that daily irrigation in July and August with an inch of irrigation per week will prevent European chafer grub problems. If that is not an option, you can always treat your lawn between now and August 1 with GrubEx, Season-Long Grub Control, or another product containing imidacloprid. Professionals can also use Merit, Arena, Aloft, Meridian, Allectus or Mach2. |
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| Black vine weevils emerging now in nursery fields This is a good time to look for black vine weevil in nursery fields. Look under boards or debris around the base of shrubs where the weevils hide during the day and for fresh notches in the leaves where they have been feeding. Now is the best time to apply Talstar to infested portions of nursery fields. It is important to spray the weevils in the first two weeks after they emerge, before they have time to mate and lay eggs. |
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| Flood damage relatively minor in Ottawa County Heavy rains from the recent round of storms left many nursery fields underwater in Ottawa County. In touring the area yesterday with MSUE educator Tom Dudek, it appears that flood damage to field grown nursery crops was relatively minor. We observed some flooding-related mortality in lilac stock plants at a nursery and some limber pine transplants that were washed out. Overall, however, most fields seem to be in good shape. Based on conversations with growers, flooded fields were inundated for two days or less. Areas flooded for longer, may have resulted in more serious problems. Growers should be aware that plants were likely stressed by flooding even though they weren’t obviously damaged. Keep an eye on plants for signs of stress, particularly if we encounter an extended dry spell moving into July.
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| Why trees fail Storm clean-up continues to dominate the landscape business. Examining damaged trees can provide a lot of insights into why trees fail during windstorms (as Yogi Bera noted, you can observe a lot just by watching). Two of the most common forms of tree damage during windstorms are limb breakage and wind-throw. Major limbs often fail during windload to the formation of included bark. Included bark is bark that forms between the main trunk and a branch that is attached by a narrow branch angle. As the branch and the trunk grow, the attachment is weakened as a greater proportion of the limb connection is compromised by bark. MSU graduate student Sara Tanis shared some photos of a maple that broke up during one of recent storms. Note the amount of branch connection that contains included bark. Also note the limb on the right side of the tree that shows a narrow attachment angle and could be the next candidate for trouble. When trees are blow down, roots and all, it is often referred to as wind-throw. Wind-throw is typically associated with trees with shallow root systems. For example, in the recent storms I noticed a lot of spruces that were wind-thrown. Wind-throw is also common when high winds are accompanied or preceded by heavy rains. When the ground is soaked and soft, trees are easily up-rooted. Some landscape practices can also contribute to wind-throw. For example, the root zone of a spruce was confined by landscape edging material and landscape fabric became a prime target for high winds after a day-long rain.
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| Water and nutrient management website Southern and mid-Atlantic universities have put together a very useful website for nursery growers. Waternut.org is being developed as an on-line Knowledge Center for Water and Nutrient management and Conservation, for the Nursery and Greenhouse industries. This website is an excellent resource and teaching aid for growers. There are several “how-to” learning modules, full color photos, and links to original research. I encourage growers to pay a visit to www.waternut.org. Assessing the learning modules requires a registration, but it’s free. |
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| Gypsy moth numbers up We are receiving lots of reports, particularly from southern lower Michigan about large numbers of gypsy moth caterpillars. Growers should be checking their fields (especially spruce), surrounding fence rows and woodlots for gypsy moth caterpillars and possible feeding damage. Gypsy moth larvae will feed on some species of Christmas trees such as Colorado blue spruce and white pine. However, the most serious problem is not feeding damage, but rather the fact that they may lay egg masses on trees that can hitchhike to new areas. Make sure to take the time now to look for gypsy moths to avoid having your fields restricted this fall just before harvest.
Gypsy Moth Spray Window Update Growers should note that for Zone 3 the spray window closing date for all other compounds has been set as Saturday, June 28. Cool weather has resulted in delaying the close date for Dimilin in Zone 4 until after June 28. The following chart shows actual and projected open and close dates for application of the two groups of pesticides used for regulatory treatment of gypsy moth in nursery stock and Christmas trees. We are listing the projected dates as guidelines to help you plan your pest management program. Since gypsy moth development will vary by location, you will need to monitor development around your farm. Weather conditions will affect caterpillar development and may effect end date of the spray windows. Growers should watch the Landscape Alerts for additional announcements.
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| Check for spider mites This is a good time to check your trees for spruce spider mite, especially if you grow spruce or fir Christmas trees. We are seeing lots of spider mite activity especially on Fraser fir. In fields that we are scouting, we are finding the very small nymphs. Look on the oldest needles near the stem of the tree for webbing and the bronzing or grayish, dirty-looking foliage that is indicative of spider mite feeding. To see mites, shake an injured branch over a piece of white paper, and focus a hand lens on the tiny moving specks. If you see just a few mites, but the damage does not appear to be heavy, give it another seven to ten days and check the trees again. Several predators feed on spider mites and you want to give them a chance to do their thing. Predatory mites are the most important predators of spider mites, but are very difficult to see without a microscope. If you check the trees and mites seem to be abundant, then you may want to apply a miticide, especially if you plan to sell the trees this year. If you are spraying Christmas trees for spider mites, do everything you can to get good coverage. |
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| Insect damage begins to show up The small oval galls from balsam gall midge are visible on the needles of the new growth of balsam fir. Growers in Wisconsin have also reported having problems with this in Fraser fir. Adult female midges lay eggs on newly emerged shoots in May. The larvae feed on the new needles causing the small galls to form. Mature larvae will drop from the needles in the fall and over-winter in the soil beneath the tree. If growers have had heavy damage this year, they will need to time their insecticide next May when the adult females are laying eggs. Adult emergence traps can be placed beneath previously affected trees to estimate timing of the adult. Wilted leaders of white pine and spruce trees that have been attacked by white pine weevil will begin showing up. These leaders can also be effectively pruned out when the first symptoms appear. Cut the terminal leader off an inch or two below the area damaged by the weevils. Use your fingernail and pull the bark away from the leader. Just below the bark, you will see the frass, small white larvae and maybe some chip cocoons where weevils are pupating. Cut out the infested terminal and burn it or otherwise destroy it, do not leave the cut terminals lying in the field. Then select a new lateral shoot on the upper whorl to become the new leader. Trim the rest of the shoots back to one-half of their original length. This will enable the tree to recover its apical dominance and good form faster. The early signs of damage from Douglas-fir needle midge are showing up on new growth. (Photo 1). If you were able open up the gall and look inside, you would find one or more white maggots (Photo 2). The damaged area is initially pale in color, but as the season progresses, will darken and eventually turn brown. In late summer, larvae emerge from the undersides of the needle and drop to the soil. Damage to Douglas-fir needles from Cooley spruce gall adelgid feeding may also superficially resemble Douglas-fir needle midge damage. In summer, adelgid damaged needles frequently have chlorotic areas (Photo 3) where the insects have fed. Later in the year, the chlorosis may not be as evident, but the needles may be distorted and bent. To distinguish between midge damage and adelgids damage, look for the cast skins of the adelgids at the needle bend. Again, the galled needle will appear swollen if viewed from the side. Scout for pine tortoise scale If you have Scotch pine trees with moderate or high populations of pine tortoise scale, you need to start scouting your trees. Growers have reported seeing the first signs of crawler activity. Pine tortoise scale is the reddish-brown, roundish scale that feeds on the woody part of pine shoots and small branches. It excretes amazing amounts of sugary honeydew. Black sooty mold then grows on the honeydew that coats the needles and branches. Remember to slow down and use lots of water to get full coverage of the trees.
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| Weather news A new record? A large area of training thunderstorms (storms which form and move repeatedly across the same areas) brought torrential rains and widespread flooding to sections of northwest lower Michigan last Thursday and Friday (June 12-13). More than six inches of rain fell from Mason and Manistee counties northeastward into Wexford, Lake, Osceola, and Missaukee counties. There was an observation of 11 inches in the Ludington area from roughly 9:00 PM on the Thursday through 7:00 AM on Friday. If this observation stands, it would be a new state record for precipitation in both 12 hour and 24 hour periods (the old one day record of 9.78 inches was set in Bloomingdale in 1914). Considering that the statistical 100-year, 24 hour extreme precipitation event (an event expected to occur on average only once every 100 years) for Michigan ranges from about four inches in far northern and eastern sections of the state to about seven inches in the extreme southwest, this event will serve as a new upper end benchmark for extreme precipitation. In contrast to the stormy and quickly changing weather experienced earlier this month in Michigan and across much of the Midwest, conditions this week have been relatively quiet and fall-like, in association with the formation of an upper air trough across the Great Lakes region late last weekend. This feature is expected to persist for the next several days, resulting in a cloudy and unsettled weather pattern through much of the weekend into early next week. A series of disturbances moving counterclockwise around the trough will bring a chance for showers and a few thunderstorms Saturday, Sunday, and Monday. With somewhat limited low level moisture expected to be in place this weekend, rainfall totals through next Monday are expected to remain on the light to moderate side, with 0.25-0.50-inch totals where rain falls. Some areas may remain dry. Temperatures during the next few days will moderate from recent levels, with highs Saturday through Monday generally ranging from the upper 60s north to the upper 70s south and lows from the upper 40s north to the upper 50s south. Next week, warmer temperatures (highs in the mid-70s to mid-80s and lows in the 50s and 60s) are likely once again, with another chance for rainfall by Wednesday continuing into Thursday. In the medium range forecast, the upper air pattern mentioned above is expected to continue for much of the remainder of June. The National Weather Service 6‑10 day outlook covering June 25 through June 29 calls for near normal temperatures and for precipitation totals to remain at below normal levels. The outlook for the 8-14 day period (June 27- July 3) calls for mean temperatures to range from near normal levels across northern sections of the state to above normal levels in the south and for near normal precipitation totals. Further ahead, it is interesting to note that forecast guidance is also hinting that the very turbulent, active upper air pattern of late May and early June may return to the upper Midwest, possibly during early July. |
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