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| Landscape Alert newsletter | ||||
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| Vol. 22, No. 8, June 1, 2007 |
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In this issue |
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| Diagnostic testing for aster yellows Symptoms of aster yellows may be subtle and resemble those caused by other factors. (See separate article about scouting and identification in this issue.) In many situations with ornamentals, a definitive diagnosis is helpful and allows managers to make better disease management decisions. One of the services that the MSU Diagnostic Services lab offers is molecular based (PCR) testing for aster yellows. This test method is accurate and extremely sensitive. |
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| Samples submitted for aster yellows testing should include live plant tissue (foliage, stems, flowers). Leaves from multiple areas of the plant should be submitted. Entire plants may be submitted, but this is not required. Samples should be accompanied by a diagnostic submittal form, note on the form that you would like the sample tested for aster yellows. There is a $25 diagnostic charge for aster yellows testing of plant samples. Test results will be completed in approximately one week. Samples can be dropped off in person or shipped via USPS or another postal carrier; this is true for all diagnostic samples. Samples should be shipped in boxes with overnight or priority mail delivery, do not ship samples on Fridays. |
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| Scouting for disease: Aster yellows Pathogen: Aster yellows phytoplasm. (view images) Hosts include: Anemone, Bellis, Campanula, Chrysanthemum, Coreopsis, Delphinium, Gaillardia, Rudbeckia, Salvia and Scabiosa. Symptoms: Symptoms vary, depending on the host. Possibilities include stunting, yellowing, twisting, distortion of flowers or flower petals, and bushy, broomlike growth. Infected plants have stunted and, possibly, malformed roots. Infected Echinacea and Rudbeckia may have deformed, yellowish flower heads. Spread: The pathogen is vectored by aster leafhoppers (Macrosteles fascifron), as well as a few other leafhopper species. Aster leafhoppers can migrate into production areas on air currents, bringing the pathogen with them. Management: Infected plants cannot be treated and should be removed and destroyed. Susceptible field-grown perennials should be scouted regularly for leafhoppers. Good control of leaf-hoppers in the growing area is important to limit spread of the disease. Weeds can be infected; many are symptomless hosts. Maintain good weed control, especially of overwintering weeds, to reduce sources of inoculum. |
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| Scouting for pests: Leafhoppers (sucking pest) Leafhopper feeding causes stippling of plant leaves that is similar to damage caused by twospotted spider mite. (view image) Leafhopper feeding can result in leaf distortion, chlorosis, plant stunting, leaf curling, leaf yellowing and necrosis. Extensive feeding damage gives plants a scorched appearance. Both the adults and nymphs are active, typically moving sideways when disturbed. Leafhoppers feed on a wide variety of herbaceous perennials. The aster leafhopper transmits aster yellows disease. Management: Remove weeds from adjacent areas – many weeds serve as a reservoir for leafhoppers. Contact insecticides may be used against leafhoppers, but control can be difficult because leafhoppers are very mobile. |
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| Scouting for weeds: Common cottonwood Common cottonwood: Populus deltoids Marshall (view images) Life cycle: Fast-growing, weedy tree. Leaves: Alternate, simple, broadly triangular, 3 to 5 inches long with coarse, incurved-toothed margins and a smooth base. Leaves are shiny green above and have two to five prominent, fingerlike glands where the long, flattened petiole attaches to the leaf. Margins are outlined by a colorless border. Stems: Up to 100 feet at maturity with a straight trunk and minimal branching. Bark is ash gray on mature trees and greenish yellow on young stems. Plants have the ability to form many vigorous, weedy sprouts. Flowers and fruit: Male and female flowers are found on separate plants and are clustered in drooping, up to 4-inch-long spikes. Male flowers are reddish; female flowers are greenish. Fruit are three- to four-valved capsules that release cottony, wind-disseminated seeds. Reproduction: Seeds. |
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| Scouting for weeds: Virginia creeper Virginia creeper: Parthenocissus quinquefolia (L.) Planch. (view images) Life cycle: Perennial woody vine. Leaves: Alternate, palmately compound, usually with five leaflets, although leaves may consist of three to seven leaflets. Leaflets have toothed margins and turn deep red in the fall. Tendrils: Branched three to eight times with adhesive disks at their tips that enable plants to grip and climb vertical surfaces. Stems: Climbing woody vines with white pith. Young stems are red to green and turn brown with age. Flowers and fruit: Flowers are small, inconspicuous and green to white. Fruit are small, blue to black, grapelike berries (drupes). Reproduction: Seeds. Often dispersed by birds. Stems in contact with the ground may root. |
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| Honeylocust trees suffering from plant bug injury Many honeylocust trees in the Lansing area have small brown and distorted leaves from plant bug feeding injury (view images). The best way to check for honeylocust plant bug is to rap a branch over white paper or cloth. If the tree is heavily infested, small green bugs will rain down on the paper and scurry off. When adults are present, they will fly when disturbed. These bugs can be easily overlooked because they are only 1/8 inch-long. In the most extreme cases, trees can be completely defoliated. The plant bugs will continue feeding through the second and third week of June. By July 1, the damage will be over for this year. Sorry-looking honeylocust trees will quickly return to a green state in a week or two after spraying with Sevin, Merit, Meridian or Safari. |
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| Emerald ash borer news Emerald ash borer treatment survey Tree care professionals in Indiana, Ohio and Illinois would like to learn from the experiences of our professionals here in Michigan. Dr. Deborah McCullough at MSU has joined efforts with Shawn Bernick at Rainbow Tree to put together an on-line survey to find out what has worked and what has not worked for protecting trees from emerald ash borer. Information on how to participate in this survey can be found at: 6-1Survey.pdf Best management practices for treating ash trees with imidacloprid Because of the extensive use of Merit or Bayer Tree and Shrub Insect Control as a basal soil drench or basal soil injection to protect ash trees from emerald ash borer, Bayer asked for the input of university extension specialists in developing a set of best management practices to use the product safely and minimize impact on the environment. The best management practices for Merit can be viewed at: 6-1Best.pdfand 6-1Merit.pdf |
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| Is your maple tree dropping lots of leaves? Early June is when maple petiole borer larvae finish feeding in the petioles of maple leaves, causing the blackened, restricted petiole (leaf stems) to break and the leaf to fall. The stems usually break at a darkened area near the leaf blade. Usually, infestations are limited to sugar maples and only about 25 to 30 percent or less of the leaves fall to the ground. While spectacular, the leaf drop has little effect on tree health. Sometimes spring storms also cause some maple leaves to drop. The best way to tell is to look at where the leaves came from. If you can still see a small petiole stub attached to the tree, it was most likely due to maple petiole borer. However, if the petiole broke cleanly at the base where it is attached to the tree, it was probably due to wind damage. (view images) |
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| Japanese beetle grubs still active on some golf courses I received two phone calls this week about skunks and raccoons tearing-up fairways to find Japanese beetle grubs. One was from Traverse City and the other from Oxford, Michigan. Japanese beetle grubs will continue feeding for another week or two before most of them will begin to pupate. Adults will start to emerge about July 1. If a few hotspots on fairways need to be protected, spray with Dylox or Sevin now to stop the grubs. Also, Dr. Niemczyk from Ohio told me this week that applying milorganite to the infested areas will slow-down or stop skunks and raccoons from feeding for a few days, giving the insecticide time to work. Only spot-treat with Sevin and Dylox at this time, and plan to apply Merit, Arena or Meridian to the most troublesome fairways between June and early August to prevent grub damage this coming fall and next spring. |
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| Waitea patch appearing on golf courses A relatively new turfgrass disease called Waitea patch (Waitea circinata) has been making appearances in Poa annua putting greens in Michigan. Waitea patch has also been referred to as brown ring patch in Japan, but until the causal organism is confirmed to be the same in the United States, the Waitea moniker seems to be the name of choice. Waitea patch is a Rhizoctonia disease. The symptoms of Waitea patch involve Poa annua turning yellow in a ring and looking very similar to yellow patch. (view image)The warm weather in the last several days is favorable to development of Waitea patch, but would not be conducive to yellow patch, which is usually seen during cooler weather. Dr. Frank Wong at the University of California – Riverside in cooperation with the Pace Turfgrass Research Institute, has research results in controlling Waitea patch posted at 6-1OSUcontrol.pdf Waitea patch appears to be a moving target when it comes to fungicide efficacy. Dr. Vargas at MSU has advised me that he has seen control with Heritage, Prostar, Insignia, Compass and Disarm. Some superintendents are also reporting success with Banner, Medallion and Endorse. Please refer to the label for recommended rates and application procedures. |
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| Insect update Aphids on white pine I have received several reports of white pine trees turning black. Black sooty mold grows on honeydew secreted by aphids, turning affected shoots and foliage black. When you look closer at the trees we find large colonies on aphids on the stems and branches. Aphids suck juices from the branches, shoots and needles and heavily, affected trees may loose needles. Trees affected by aphids tend to be in pockets. So, if you find you have a large aphid population treat only the infested trees. This helps minimize the effects on helpful predators such as lady bugs. Cooley on Douglas-fir On Douglas fir the cottony egg masses of Cooley spruce gall adelgid are now visible on this year’s growth in some areas. Once you find these cottony masses, it is too late to apply an insecticide. If you are having problems with this pest, you now need to wait for the second adults to be active in July/August (1500-1600 GDD50). Pine spittlebugs These are feeding on Scotch pine and other pines. This species of spittlebug really causes little damage to the tree. Don't worry about trying to control them unless you have huge numbers. |
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| Scout for pine tortoise scale in southern Michigan If you have Scotch pine trees with moderate or high populations of pine tortoise scale, you need to start scouting your trees in the southern portion of the Lower Peninsula. 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. Trees can look pretty awful if the scale population builds up to even moderate levels. The black sooty mold seldom comes off the needles, even if you spray them with a power washer. Usually, growers have to wait for two years or so until the affected needles are shed before they can sell these trees. Pine tortoise scale has a single generation per year. Eggs usually begin to hatch around 400-500 GDD50, so that is not too far off for southern Michigan growers. What has been difficult for growers trying to control this scale, is that the eggs hatch over a relatively long period of time continuing thru 1000-1200 GDD50 (end of egg hatch and the last of the crawlers). Horticultural oil might be something to consider, especially if you can apply the oil after the crawlers settle and begin to feed. The oil will suffocate and kill the crawlers, but will have much less effect on the ladybird beetles. If you choose to use a conventional insecticide, choose a product with some systemic activity or a longer residual. Pine tortoise scales suck sap from the phloem and systemic products will get into the phloem. In contrast, pine needle scale sucks sap from parenchyma cells (the cells in between the outer epidermis layers) and systemic products will not be anymore effective than contact insecticides. Whether you use horticultural oil or a conventional insecticide, be sure to get good coverage. Apply at least 50 gallons of water per acre. While you are scouting, keep an eye out for white, fuzzy insects that look like little mealy bugs. These little white insects are actually larvae of a ladybird beetle in the genus Hyperaspis. This species of ladybird beetles specializes on pine tortoise scale. The adults and larval ladybugs will eat the scale eggs and crawlers. At this time of the year, the ladybird beetle larvae will be very small. They may even crawl up and hide under the female scales on the needles. Once the eggs are laid, the Hyperaspis larvae will feed aggressively on the eggs and then on the crawlers. They will get larger over the next few weeks, and you will probably see them on the infested shoots and branches. These ladybird beetles can be pretty amazing. Dr. Deb McCullough of MSU reports seeing a number of fields where this ladybird beetle controlled even heavy tortoise scale infestations in a single summer. |
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| Gypsy moth spray window dates Gypsy moth larvae are in their late instars in the more southerly portions of the state. Due to recent warming trends across the state, the spray window for both Zone 1 and Zone 2 for Dimilin will be closed as of June 5. Growers should pay close attention to degree day accumulations and larval development in their area. Warm weather has sped up gypsy moth development. Based on current accumulations, it is anticipated that spray windows for all other compounds in Zone 1 and Zone 2 may be closed earlier than projected. The chart below shows actual and projected open/close dates for application of the two groups of pesticides used for regulatory treatment of gypsy moth in nursery stock and Christmas trees. Always monitor development around your farm as local conditions can affect gypsy moth development. Watch the Landscape CAT Alert next week for any new announcements of possible early closing for other zones.
** Projections are based on 30 year historical degree day data. |
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| Homeowner safety tips for pesticide use on lawns When pest problems occur in lawns, always consider whether a non-pesticide solution to the problem is practical and feasible. There are many integrated pest management solutions to lawn problems that may involve no, or reduced, use of pesticides. If pesticides are chosen to control the problem, be sure that the pest has been accurately identified. Always consult the product label to see if the pest is listed in the “pests controlled” section. Read the label carefully and follow all mixing and application instructions and safety precautions. Do not apply more pesticide than listed on the label. Adding a “little more” than the label rate may seem like a good idea, but it will increase the risk of pesticide exposure to people and pets and harm to the environment. It is illegal to apply pesticides at rates greater than specified by the product label. Before applying a pesticide to your lawn area, always remove toys and pets’ food and water dishes. When applying the pesticide, be sure to follow directions for skin protection, which most commonly includes waterproof or chemically resistant gloves. Avoid glove materials of cotton, canvas or leather when handling materials because they absorb and hold pesticide residues. Consult the pesticide’s label for statements regarding specific treatment in the event of an exposure. Take the label with you to the medical facility should an exposure occur. Symptoms such as dizziness, headache or nausea may indicate pesticide exposure. After applying pesticide to a lawn, keep people, especially children, and pets off the lawn for an appropriate amount of time. This may or may not be specified by the label. Generally, it is a good idea to wait at least a day or two before allowing children to play on treated lawns. If you hire a professional lawn care company to treat your lawn, they are required by law to post a “caution” sign after treating the lawn that warns people and pets to stay off for 24 hours. Be sure children are familiar with the sign and understand what it means. |
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| Weather news An upper air trough across the northern Great Plains the morning of Friday, June 1, will very slowly move eastward across the Great Lakes region by the end of the weekend, setting the stage for one more day of very summer-like weather with increasing chances for showers and thunderstorms. As the upper air trough approaches, thunderstorms will be possible both Saturday and Sunday, especially Saturday night and early Sunday, when widespread 0.25-0.50 inch rainfall totals are expected over most of the state. Temperatures Saturday will range from highs in the upper 70's in lakeshore areas to the upper 80's inland, with lows generally in the upper 50's to mid 60=s. Temperatures are forecast to fall back to the highs in the mid 60's to mid 70's by Monday and Tuesday, with lows in the 40's and 50's. Cooler, unsettled weather is expected early next week, with the possibility of showers each day through Tuesday. Drier and warmer weather is expected for the latter half of next workweek, with rainfall a possibility again by next weekend. In the medium range time frame, forecast guidance suggests that upper air troughing will dominate regional weather conditions during the latter part of next week before being replaced by a ridging pattern by the following week. With the troughing pattern in place, the NOAA 6‑10 day outlook for June 6-10 calls for cooler than normal temperatures and for above normal precipitation totals statewide. During the 8-14 day period covering June 8-14, the outlook calls for mean temperatures to moderate to near normal levels over all of the state except for the southwestern Lower Peninsula, where above normal temperatures are expected. Precipitation during this time frame is forecasted to return to near normal levels statewide. New long lead outlooks NOAA long lead outlooks for the next few months call for the gradual development of cooler than normal sea surface temperatures (La Nina conditions) in the equatorial Pacific. However, any related impacts in the United States, at least for the remainder of the summer and fall seasons are expected to be only minor. For Michigan and the Great Lakes region, the official outlooks for June and the June-August periods both call for the climatology scenario of near equal odds of below-, near-, and above-normal temperatures and precipitation. By late summer and fall, the outlooks are a bit less vague, calling for increased chances for above normal temperatures across most of the region, with no direction on precipitation. The outlooks also call for milder than normal temperatures during the upcoming winter season. |
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