Hort Update for the week of 3/15/07
1. Prairie and Meadow Voles scar lawns by constructing surface runways (one to two inches wide) and clipping grass very close to the roots. Runways are most visible after snow melts. Small holes lead to underground runways or nesting areas. Vole damage to lawns usually repairs itself during spring growth and is not permanent. Voles are small, mouse-like rodents that exist throughout Nebraska. Their short tails (about 1 inch long), stocky build and small eyes distinguish them from true mice. Vole damage is costliest when they eat the inner green bark layer of trees and shrubs during winter. This gnawing can severely damage or kill young trees and shrubs. In gardens, voles can clip off young plants and dig up seeds. They also eat leaves, shoots, roots, tubers and seeds of most grasses, forbs and broadleaf flowering plants.
Internet Resource: http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=100
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2. Snow Mold appears as pinkish or gray roughly circular patches appear on affected grasses, especially after a winter where much snowfall persisted for a period of time. The fungal mycelium may dry to a papery crust. Repair snow mold damage by raking in early spring to disrupt the matted areas and lightly fertilize to encourage new growth. Fungicides are not recommended at this time, as most of the damage is already done. Fungicides can be used preventively in November and repeated during mid-winter thaws, especially for high-value turf or areas prone to problems with snow mold.
Internet Resource: http://www.extension.umn.edu/yardandgarden/ygbriefs/p320snowmolds.html
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3. Pine Wilt infects primarily Scotch pine trees. Pines that have recently died or are exhibiting rapid crown dieback may have pine wilt. If this is suspected, these trees need to be removed by April 30 to slow the spread of this disease.
Pine wilt is a fatal disease of exotic pine species, such as Scotch pine, and consequently Scotch pine should no longer be planted in Nebraska without homeowners being aware of this potentially lethal threat. The disease has already killed thousands of Scotch pines in southeastern Nebraska. Across the state, most infections have been found east of Grand Island, however, a few pine wilt cases have also been reported in western Nebraska.
Pine wilt is caused by a microscopic organism called a pinewood nematode, which is spread by pine sawyer beetles. Adult beetles can carry thousands of nematodes within their bodies as they fly from tree to tree in spring, feeding on young twigs in the upper tree canopy.
Trees infected with pine wilt cannot be saved. They must be cut down and burned, buried or chipped before beetles emerge from the wood in May. Do not save the wood from these trees for firewood.
Internet Resource: http://www.nfs.unl.edu/publications.asp#foresthealth
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4. Aspen & Other Landscape Scales- http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
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5. Dormant Oil Sprays for Insects/Mites: March is the month to apply dormant oil sprays to fruit, nut and ornamental trees to kill insects and mites overwintering in cracks and crevices on trunks and branches. Temperatures need to be above 40 degrees Fahrenheit when applying dormant oils, which are commonly used to control pests such as aphids, scales, spider mites, insect eggs and some hibernating caterpillars. A few dormant oils are labeled for use on white flies, mealybugs and lacebugs. Dormant oils kill by suffocating insects and mites. Dormant oils are most effective if applied as late in winter as possible, but before spring growth begins. At this time, insects are weakened and easier to kill. Also, dormant oils can damage tender plant tissue and should not be used once flowers or leaves begin to grow. Follow label directions when using any pesticide.
Dormant Sprays for Taphrina Leaf Curl: Peach leaf curl and plum pocket can be controlled with a single application of an appropriate fungicide. The timing of the fungicide spray is extremely important and should be applied as a dormant spray, either in the fall after leaf drop or in late winter before buds begin to swell. These diseases cannot be controlled once the leaves have started to expand. Some of the fungicides registered for control of peach leaf curl and plum pocket include liquid lime-sulfur, ferbam, chlorothalonil , Bordeaux mixture and other copper chemicals. Do not add oil to lime-sulfur or spray oil treatments for three weeks after application of lime-sulfur. Lime-sulfur should not be applied to trees when temperatures are below 45 or above 80 F. Follow recommended label rates for all commercial fungicides.
Internet Resource: http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/pchlfcrl.htm
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6. Delay Mulch Removal on plants such as strawberries, roses, or Chrysanthemums that have been protected with a winter mulch. Early removal may cause new growth to begin too early and be susceptible to cold temperature damage. Ideally, delay mulch removal as long as possible but do remove it before new growth begins beneath the mulch. If warm temperatures cause new growth to begin early, rake the mulch to the side of the plant so it can be raked over the plants if freezing temperatures are forecast.
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7. When to Water? Water lawns and landscapes when the soil begins to dry out. Most portions of Nebraska have had good moisture this winter so check the soil with a soil probe prior to beginning irrigation. Water conservation is important and correct watering of plants is necessary for a healthy root system. Overwatering or overly saturated soils can cause major issues for plant roots.
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8. Pruning Tips:
| Current Problems: | Major Symptom: |
Lawns |
|
| 1. Voles | Runways of clipped grass on lawn surfaces |
| 2. Snow mold | Matted, grayish or pinkish patches in the lawn |
| Trees & Shrubs | |
| 3. Pine wilt | Dead Scotch Pine trees or rapid crown dieback - remove by April 30 |
| 4. Aspen scale | Grayish, corky “scale” on surface of trunk and branches |
| To Do's for March | |
| 5. Apply dormant sprays | For overwintering insects & Taphrina leaf curl |
| 6. Delay mulch removal | For roses, strawberries, Chrysanthemums |
| 7. When to water | When the soil begins to dry, not before |
| 8. Pruning | Shade trees, summer blooming shrubs, fruit trees, grapes |
1. Prairie and Meadow Voles scar lawns by constructing surface runways (one to two inches wide) and clipping grass very close to the roots. Runways are most visible after snow melts. Small holes lead to underground runways or nesting areas. Vole damage to lawns usually repairs itself during spring growth and is not permanent. Voles are small, mouse-like rodents that exist throughout Nebraska. Their short tails (about 1 inch long), stocky build and small eyes distinguish them from true mice. Vole damage is costliest when they eat the inner green bark layer of trees and shrubs during winter. This gnawing can severely damage or kill young trees and shrubs. In gardens, voles can clip off young plants and dig up seeds. They also eat leaves, shoots, roots, tubers and seeds of most grasses, forbs and broadleaf flowering plants.
Internet Resource: http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=100
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2. Snow Mold appears as pinkish or gray roughly circular patches appear on affected grasses, especially after a winter where much snowfall persisted for a period of time. The fungal mycelium may dry to a papery crust. Repair snow mold damage by raking in early spring to disrupt the matted areas and lightly fertilize to encourage new growth. Fungicides are not recommended at this time, as most of the damage is already done. Fungicides can be used preventively in November and repeated during mid-winter thaws, especially for high-value turf or areas prone to problems with snow mold.
Internet Resource: http://www.extension.umn.edu/yardandgarden/ygbriefs/p320snowmolds.html
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3. Pine Wilt infects primarily Scotch pine trees. Pines that have recently died or are exhibiting rapid crown dieback may have pine wilt. If this is suspected, these trees need to be removed by April 30 to slow the spread of this disease.
Pine wilt is a fatal disease of exotic pine species, such as Scotch pine, and consequently Scotch pine should no longer be planted in Nebraska without homeowners being aware of this potentially lethal threat. The disease has already killed thousands of Scotch pines in southeastern Nebraska. Across the state, most infections have been found east of Grand Island, however, a few pine wilt cases have also been reported in western Nebraska.
Pine wilt is caused by a microscopic organism called a pinewood nematode, which is spread by pine sawyer beetles. Adult beetles can carry thousands of nematodes within their bodies as they fly from tree to tree in spring, feeding on young twigs in the upper tree canopy.
Trees infected with pine wilt cannot be saved. They must be cut down and burned, buried or chipped before beetles emerge from the wood in May. Do not save the wood from these trees for firewood.
Internet Resource: http://www.nfs.unl.edu/publications.asp#foresthealth
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
4. Aspen & Other Landscape Scales- http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
5. Dormant Oil Sprays for Insects/Mites: March is the month to apply dormant oil sprays to fruit, nut and ornamental trees to kill insects and mites overwintering in cracks and crevices on trunks and branches. Temperatures need to be above 40 degrees Fahrenheit when applying dormant oils, which are commonly used to control pests such as aphids, scales, spider mites, insect eggs and some hibernating caterpillars. A few dormant oils are labeled for use on white flies, mealybugs and lacebugs. Dormant oils kill by suffocating insects and mites. Dormant oils are most effective if applied as late in winter as possible, but before spring growth begins. At this time, insects are weakened and easier to kill. Also, dormant oils can damage tender plant tissue and should not be used once flowers or leaves begin to grow. Follow label directions when using any pesticide.
Dormant Sprays for Taphrina Leaf Curl: Peach leaf curl and plum pocket can be controlled with a single application of an appropriate fungicide. The timing of the fungicide spray is extremely important and should be applied as a dormant spray, either in the fall after leaf drop or in late winter before buds begin to swell. These diseases cannot be controlled once the leaves have started to expand. Some of the fungicides registered for control of peach leaf curl and plum pocket include liquid lime-sulfur, ferbam, chlorothalonil , Bordeaux mixture and other copper chemicals. Do not add oil to lime-sulfur or spray oil treatments for three weeks after application of lime-sulfur. Lime-sulfur should not be applied to trees when temperatures are below 45 or above 80 F. Follow recommended label rates for all commercial fungicides.
Internet Resource: http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/pchlfcrl.htm
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6. Delay Mulch Removal on plants such as strawberries, roses, or Chrysanthemums that have been protected with a winter mulch. Early removal may cause new growth to begin too early and be susceptible to cold temperature damage. Ideally, delay mulch removal as long as possible but do remove it before new growth begins beneath the mulch. If warm temperatures cause new growth to begin early, rake the mulch to the side of the plant so it can be raked over the plants if freezing temperatures are forecast.
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7. When to Water? Water lawns and landscapes when the soil begins to dry out. Most portions of Nebraska have had good moisture this winter so check the soil with a soil probe prior to beginning irrigation. Water conservation is important and correct watering of plants is necessary for a healthy root system. Overwatering or overly saturated soils can cause major issues for plant roots.
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8. Pruning Tips:
- February and March are key pruning times for many plants.
- Only prune if pruning is needed. Do not prune just for the sake of pruning.
- Make proper pruning cuts and use sharp pruning tools.
- Do not use pruning paints or wound dressings on pruning wounds.
- When pruning fruit trees, understand what age wood the different species bear fruit on.
- For the best time to prune different plants, see the “When to Prune Common Landscape Plants” chart at the following web site: http://www.platte.unl.edu/yardandgarden
