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Hort Update for the week of 6/6/08
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1. Yellow Lawns- Due to rainy weather delaying mowing schedules, some homeowners are seeing yellowing symptoms on tall lawns after mowing. Roch Gaussoin, Extension Turfgrass Specialist, recommends raising the mowing height and going ahead with mowing between rainy periods. This is one of the few times where it would be recommended to pick up grass clippings. Some yellowing may be due to scalping (removing more than 1/3 of the grass blade during any one mowing); hence the raised mowing height recommendation. Some yellowing may be due to poor root function in saturated soils.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
2. Saturated soils & systemic pesticides- Saturated soils can interfere with the efficacy of systemic lawn pesticides. Pesticides (insecticides, herbicides and fungicides) that require plant growth and metabolism for movement of the product throughout the plant will be affected. In the case of herbicide applications on weeds, some foliar burning may be seen after the herbicide application, but a lot of recovery will occur on weeds due to poor uptake of the herbicide. We may also see strange symptoms on turfgrass this year due to poor root development in saturated soils early in the season.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
3. Pythium blight- Conditions have been favorable for Pythium development, which usually occurs later in the season. The rule of thumb is if night temperature and humidity level numbers combine to reach 150, then pythium is favored. Night temps are still cool, but humidity levels have been very high, combined to push into the 150 range. Although conditions have been favorable, Roch Gaussoin does not recommend treating at this time. It is recommended turf managers monitor areas with a history of Pythium blight. As conditions dry out, Pythium will become less of a threat. Pythium blight, brown patch, and dollar spot can look similar. Pythium blight can kill turfgrass and controls are recommended on susceptible turfgrass. Brown patch and dollar spot usually do not kill turf, therefore it is not always necessary to apply fungicides to control these two diseases. For positive diagnosis, send samples to Plant Diagnostic Clinic.
Pythium Blight of Turfgrass, http://www.oznet.ksu.edu/path-ext/factSheets/Turf/PythiumBlightofTurfgrasses2.asp
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4. Wind damage to trees can lead to structural problems and potential hazardous conditions and future problems for a tree if corrective pruning is not done. As the saying goes "an ounce of prevention is worth a pound of cure" and preventative/corrective pruning is well worth the time and effort to prevent further and more serious problems. Some key points when wind damage occurs are:
For information on identifying hazards in trees, see, http://www.na.fs.fed.us/spfo/pubs/howtos/ht_haz/ht_haz.htm
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5. Flood Damage- A tree's tolerance to flooding is dependant upon many factors including the species, soil conditions and type, and the condition and health of the tree prior to flooding. In general, very little can be done for trees in a flooding event. Proper species selection and preventative management are the best long-term strategies to help trees recover from flooding and prolonged saturated soils. Recommendations include:
Understanding the Effects of Flooding on Trees, http://www.extension.iastate.edu/Publications/SUL1.pdf
Flooding and It’s Effects on Trees, http://www.na.fs.fed.us/spfo/pubs/n_resource/flood/table.htm
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6. Diplodia (Sphaeropsis) blight infects pine, mainly older Austrian pine. New shoot tips die in the spring. Entire branches and trees may die if disease pressure is very high, or if the tree is otherwise stressed. Small black fruiting bodies appear on the base of cones and the base of infected needles. A fungicide application made during the third week in April and repeated the first week in May provides optimum disease control in most years. Fungicides applied after mid-May are usually ineffective.
Diseases of Evergreen Trees, http://www.nfs.unl.edu/documents/foresthealth/diseasesevergreen.pdf
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7. Dothistroma Needle Blight- Browning of needles on the lower half of Austrian, ponderosa and Scotch pine trees. On close inspection, needles will have turned brown from the tip down to a reddish-purple lesion or band on the needle. Lesions or bands may be found on other green needles as well.
Dothistroma Needle Blight, http://extensionhorticulture.unl.edu/Current/Dothistroma.shtml
PLEASE NOTE: Fungal diseases, like Diplodia and Dothistroma, are wet weather diseases. They can be common problems in eastern Nebraska; however, they are not commonly seen in western Nebraska during most years.
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8. Winter dessication continues to show up in evergreen conifers and on broadleaf evergreens as a fairly uniform browning, often on the south or west facing side of trees and the outer parts of plants. Evergreens lose moisture on sunny winter days. If the soil does not contain enough moisture to replace the loss, needles - starting from the tip - dry out and turn brown. Sometimes the soil is moist but the roots can't absorb it due to frozen soil or damaged roots.
To avoid winter desiccation, provide adequate moisture to the plants throughout the year. The damaged growth can be pruned or you can wait to see if new growth will cover up damaged needles. If the browning extends into the plant far enough so that pruning would remove all green growth, the plant will not recover. Evergreens should not be pruned back beyond green growth.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
9. Hackberry decline/leaf drop- Hackberry trees often experience leaf drop in June. This may simply be due to an excessive amount of leaves set on. Hackberries are sensitive to herbicides and it may be a response to herbicide drift. If the trees continue to have a full leaf canopy, they should be fine. Over the last few years, a decline has also been noted in hackberries where trees experience excessive leaf drop, crown thinning, and some branch dieback. The cause is unknown but suspected to be related to a combination of stresses such as drought, herbicide drift, poor growing conditions, and other factors. Provide good growing conditions. When planting new trees, select for diversity.
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10. Abundant blooming/fruit set has been noted across the state. Many trees did not bloom and set fruit in 2007 due to the April freeze. Lack of or reduced blooming/fruit set one year often leads to prolific blooming/fruit set the next year. Questions range from “Why do my tree flowers smell this year? (ornamental pear and Hawthorne) to “Why are there so many maple seeds this year?” to “What is all the yellow stuff on the streets?” (tree pollen). Heavy fruit set one year can lead to reduced fruit set next year. See below for issues related to fruit bearing plants.
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11. Fruit thinning- The April 2007 freeze reduced or prevented fruit set in many plants. That, along with good growing conditions this spring, has lead to prolific fruit set in some fruit bearing trees. To prevent fruit trees going into alternate year bearing; having reduced fruit size and flavor; and to avoid branch breakage, it would be wise to thin fruit on fruit trees. Thinning is best accomplished by hand picking fruits after June drop, about July 1.
Where fruits are clustered, remove all but one fruit per cluster. Space fruits from 5-8 inches apart, removing the small insect and disease injured fruit first. Fruits may be spaced closer together on the outside and top of the tree than in the center, because these branches receive full sunlight. June drop is referred to as “natural thinning” when trees drop a number of fruit in June. It can occur due to poor pollination and/or heavy fruit set.
Thinning Fruit Trees, http://hort4.unl.edu/fruit/thin.html
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12. Peach Leaf Curl- A fungal disease, Taphrina deformans, causes developing leaves of peach and related species to become severely distorted, thickened and puckered, and have a reddish or purplish cast. As spores form on the leaf surface, leaves become powdery gray in color and leaves may turn yellow or brown and drop. This disease is most severe during cool, wet spring. If there is severe defoliation, the tree will be weakened, especially if a heavy fruit crop is allowed to develop. Control is fairly easy if fungicides are applied in very early in spring just prior to leafing.
Peach Leaf Curl, http://ohioline.osu.edu/hyg-fact/3000/3006.html
Hort Update for the week of 6/6/08
| Current Problems: | Major Symptom: |
| Lawns | |
| 1. Yellow lawns | Yellowing symptoms on tall lawns after mowing |
| 2. Saturated soils & systemic pesticides | Pesticide effectiveness may be reduced this year |
| 3. Pythium blight | Conditions favorable for the disease; monitor susceptible turfgrass |
| Trees/Shrubs | |
| 4. Wind damage | Hire a Certified Arborist; correct pruning cuts are important |
| 5. Flooding effects | Effects variable depending on tree species |
| 6. Diplodia tip blight (eastern Nebraska) | Tip growth brown & stunted. Entire branches may die. |
| 7. Dothistroma needle blight (eastern Nebraska) | Reddish bands and browning on needles in lower half of tree |
| 8. Winter dessication | Browning in Arborvitae, Japanese Yew & other evergreens |
| 9. Hackberry decline | Crown thinning and leaf drop |
| 10. Abundant blooming/fruit set | Excessive amount of pollination and heavy seed crops |
| Fruits | |
| 11. Fruit thinning | Expect natural fruit drop in June. Manual thinning recommended. |
| 12. Peach leaf curl | Distict puckering and reddening of leaves in various fruit trees. |
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1. Yellow Lawns- Due to rainy weather delaying mowing schedules, some homeowners are seeing yellowing symptoms on tall lawns after mowing. Roch Gaussoin, Extension Turfgrass Specialist, recommends raising the mowing height and going ahead with mowing between rainy periods. This is one of the few times where it would be recommended to pick up grass clippings. Some yellowing may be due to scalping (removing more than 1/3 of the grass blade during any one mowing); hence the raised mowing height recommendation. Some yellowing may be due to poor root function in saturated soils.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
2. Saturated soils & systemic pesticides- Saturated soils can interfere with the efficacy of systemic lawn pesticides. Pesticides (insecticides, herbicides and fungicides) that require plant growth and metabolism for movement of the product throughout the plant will be affected. In the case of herbicide applications on weeds, some foliar burning may be seen after the herbicide application, but a lot of recovery will occur on weeds due to poor uptake of the herbicide. We may also see strange symptoms on turfgrass this year due to poor root development in saturated soils early in the season.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
3. Pythium blight- Conditions have been favorable for Pythium development, which usually occurs later in the season. The rule of thumb is if night temperature and humidity level numbers combine to reach 150, then pythium is favored. Night temps are still cool, but humidity levels have been very high, combined to push into the 150 range. Although conditions have been favorable, Roch Gaussoin does not recommend treating at this time. It is recommended turf managers monitor areas with a history of Pythium blight. As conditions dry out, Pythium will become less of a threat. Pythium blight, brown patch, and dollar spot can look similar. Pythium blight can kill turfgrass and controls are recommended on susceptible turfgrass. Brown patch and dollar spot usually do not kill turf, therefore it is not always necessary to apply fungicides to control these two diseases. For positive diagnosis, send samples to Plant Diagnostic Clinic.
Pythium Blight of Turfgrass, http://www.oznet.ksu.edu/path-ext/factSheets/Turf/PythiumBlightofTurfgrasses2.asp
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4. Wind damage to trees can lead to structural problems and potential hazardous conditions and future problems for a tree if corrective pruning is not done. As the saying goes "an ounce of prevention is worth a pound of cure" and preventative/corrective pruning is well worth the time and effort to prevent further and more serious problems. Some key points when wind damage occurs are:
- Safety first. Assess the situation and hire a certified arborist to prune/remove damaged branches that are clear hazards using correct pruning practices.
- In many instances time only allows for broken branches and ‘hangers’ to be removed quickly for safety purposes. Be sure to have an arborist return to make a correct pruning cut so stubs and/or broken branches are not left in the tree.
- Do not treat the wind damage or wounds with a pruning paint or dressing of any kind as a tree’s best line of defense is a proper pruning cut.
- Do not apply fertilizers or over-irrigate in hopes of helping the tree recover more quickly. These types of activities typically further stress the tree, are unnecessary, and can provide a more favorable growing environment for harmful decay causing organisms. (Source: Eric Berg, Nebraska Forest Service)
For information on identifying hazards in trees, see, http://www.na.fs.fed.us/spfo/pubs/howtos/ht_haz/ht_haz.htm
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5. Flood Damage- A tree's tolerance to flooding is dependant upon many factors including the species, soil conditions and type, and the condition and health of the tree prior to flooding. In general, very little can be done for trees in a flooding event. Proper species selection and preventative management are the best long-term strategies to help trees recover from flooding and prolonged saturated soils. Recommendations include:
- Select flood tolerant species for lowland areas (willow, bald cypress, cottonwood and red maple).
- Maximize tree health and vigor with proper planting and maintenance activities including a structural pruning program
- Monitor and control insect and disease outbreaks by following Plant Heath Care guidelines and recommendations. (Source: Eric Berg, Nebraska Forest Service).
Understanding the Effects of Flooding on Trees, http://www.extension.iastate.edu/Publications/SUL1.pdf
Flooding and It’s Effects on Trees, http://www.na.fs.fed.us/spfo/pubs/n_resource/flood/table.htm
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6. Diplodia (Sphaeropsis) blight infects pine, mainly older Austrian pine. New shoot tips die in the spring. Entire branches and trees may die if disease pressure is very high, or if the tree is otherwise stressed. Small black fruiting bodies appear on the base of cones and the base of infected needles. A fungicide application made during the third week in April and repeated the first week in May provides optimum disease control in most years. Fungicides applied after mid-May are usually ineffective.
Diseases of Evergreen Trees, http://www.nfs.unl.edu/documents/foresthealth/diseasesevergreen.pdf
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
7. Dothistroma Needle Blight- Browning of needles on the lower half of Austrian, ponderosa and Scotch pine trees. On close inspection, needles will have turned brown from the tip down to a reddish-purple lesion or band on the needle. Lesions or bands may be found on other green needles as well.
Dothistroma Needle Blight, http://extensionhorticulture.unl.edu/Current/Dothistroma.shtml
PLEASE NOTE: Fungal diseases, like Diplodia and Dothistroma, are wet weather diseases. They can be common problems in eastern Nebraska; however, they are not commonly seen in western Nebraska during most years.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
8. Winter dessication continues to show up in evergreen conifers and on broadleaf evergreens as a fairly uniform browning, often on the south or west facing side of trees and the outer parts of plants. Evergreens lose moisture on sunny winter days. If the soil does not contain enough moisture to replace the loss, needles - starting from the tip - dry out and turn brown. Sometimes the soil is moist but the roots can't absorb it due to frozen soil or damaged roots.
To avoid winter desiccation, provide adequate moisture to the plants throughout the year. The damaged growth can be pruned or you can wait to see if new growth will cover up damaged needles. If the browning extends into the plant far enough so that pruning would remove all green growth, the plant will not recover. Evergreens should not be pruned back beyond green growth.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
9. Hackberry decline/leaf drop- Hackberry trees often experience leaf drop in June. This may simply be due to an excessive amount of leaves set on. Hackberries are sensitive to herbicides and it may be a response to herbicide drift. If the trees continue to have a full leaf canopy, they should be fine. Over the last few years, a decline has also been noted in hackberries where trees experience excessive leaf drop, crown thinning, and some branch dieback. The cause is unknown but suspected to be related to a combination of stresses such as drought, herbicide drift, poor growing conditions, and other factors. Provide good growing conditions. When planting new trees, select for diversity.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
10. Abundant blooming/fruit set has been noted across the state. Many trees did not bloom and set fruit in 2007 due to the April freeze. Lack of or reduced blooming/fruit set one year often leads to prolific blooming/fruit set the next year. Questions range from “Why do my tree flowers smell this year? (ornamental pear and Hawthorne) to “Why are there so many maple seeds this year?” to “What is all the yellow stuff on the streets?” (tree pollen). Heavy fruit set one year can lead to reduced fruit set next year. See below for issues related to fruit bearing plants.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
11. Fruit thinning- The April 2007 freeze reduced or prevented fruit set in many plants. That, along with good growing conditions this spring, has lead to prolific fruit set in some fruit bearing trees. To prevent fruit trees going into alternate year bearing; having reduced fruit size and flavor; and to avoid branch breakage, it would be wise to thin fruit on fruit trees. Thinning is best accomplished by hand picking fruits after June drop, about July 1.
Where fruits are clustered, remove all but one fruit per cluster. Space fruits from 5-8 inches apart, removing the small insect and disease injured fruit first. Fruits may be spaced closer together on the outside and top of the tree than in the center, because these branches receive full sunlight. June drop is referred to as “natural thinning” when trees drop a number of fruit in June. It can occur due to poor pollination and/or heavy fruit set.
Thinning Fruit Trees, http://hort4.unl.edu/fruit/thin.html
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
12. Peach Leaf Curl- A fungal disease, Taphrina deformans, causes developing leaves of peach and related species to become severely distorted, thickened and puckered, and have a reddish or purplish cast. As spores form on the leaf surface, leaves become powdery gray in color and leaves may turn yellow or brown and drop. This disease is most severe during cool, wet spring. If there is severe defoliation, the tree will be weakened, especially if a heavy fruit crop is allowed to develop. Control is fairly easy if fungicides are applied in very early in spring just prior to leafing.
Peach Leaf Curl, http://ohioline.osu.edu/hyg-fact/3000/3006.html
