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Hort Update for the week of 9/15/08
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1. Kentucky Bluegrass Stem Rust symptoms are an orange-yellow powder (fungal spores) on grass blades in late summer. The turfgrass may develop a yellow or brown appearance. Rust typically occurs on lawns with slow growth. Sound fall care practices, including proper fertilization and correct irrigation, along with cooler fall weather promotes turfgrass growth and rust usually disappears. Control with fungicides is rarely suggested for home lawns.
Kentucky Bluegrass Stem Rust, http://www.urbanext.uiuc.edu/turf/rustlawn.html
Note for Sports Turf: If stem rust occurs on sports fields, the fungal spores can present problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of sound turf management and correctly timed fungicide applications, usually in July and August.
Sports Turf Internet Rust Resource, http://hcs.osu.edu/sportsturf/notes/detail.lasso?id=1094
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2. Winter Annual Weeds such as henbit, speedwell, and shepardspurse germinate during fall. The plants complete growth, blooming, and seed production the following spring and summer. In areas with a history of winter annual infestation, preemergence herbicides (Dimension, Barricade or pendimethalin based products for lawns and Preen for ornamental beds) can be applied in early September; or postemergence herbicides such as 2,4-D applied in late October.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
3. Perennial Weed Control- Mid September to early October is the best time to control perennial, broadleaf weeds (dandelions, bindweed, white clover, ground ivy) with herbicides. Plants are moving photosynthetic products into the roots for winter storage and more herbicide is translocated into roots, increasing root kill. Herbicides labeled for lawns and broadleaf weed control such as 2,4-D and combination herbicides such as Trimec are recommended for homeowner use.
Landscape Weed Management, http://www.ianrpubs.unl.edu/sendIt/ec1256.pdf
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4. Overseeding Tips- Overseed Kentucky bluegrass by September 30 and tall fescue by September 20. Mow the turf as short as possible. Check the true thatch layer; if it exceeds one-half inch, power rake and remove debris. Core aerate prior to overseeding in 2-3 directions to achieve good seed to soil contact. Select disease resistant cultivars and buy certified, blue tag seed from reputable retailers. Check cultivars on the National Turfgrass Evaluation Program (NTEP) website for disease resistance and other desired characteristics. Irrigate if needed to promote germination and establishment. Fertilize with a starter fertilizer. Tall fescue should be evident in the coring holes 7-10 days after seeding and bluegrass 14-21 days after seeding.
NTEP website, http://www.ntep.org/contents2.shtml
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5. Skunk Damage to Lawns- Skunks may damage turfgrass by digging in lawns and golf courses while looking for white grubs. This damage appears as patches of upturned earth or small 3- to 4-inch cone-shaped holes. Repair the damage and overseed if needed. If 8 white grubs can be found per square foot, an application of the insecticide Dylox may be justified at this time of year.
Dealing With Skunks, http://www.ianrpubs.unl.edu/sendIt/g1769.pdf
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6. Premature Leaf Drop in trees can be due to a fungal leaf spot or leaf blight. If there are no leaf spots or blighted areas on leaves, it is usually related to environmental stress. Leaf drop this past month was most likely due to the hot, dry conditions of August.
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7. Mycosphaerella Leaf Spot of Ash, previously called "Phyllostica leaf spot," can occur in large ash trees. Initial leaf spots caused by M. fraxinicola are small, pale-green, irregular blotches. Spots sometimes coalesce and entire leaflets may die. Trees may appear scorched due to necrotic blotches on foliage. Severe infections can result in premature defoliation. There is no practical control for these leaf diseases.
Mycosphaerella Leaf Spots, http://www.forestpests.org/ash/mycosphaerella.html
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8. Aphids- When items beneath a shade tree become sticky, aphids are the likely cause. Aphids are small, soft-bodied insects that feed in dense groups on leaf undersides. Aphids feed on plant fluids and exude a honeydew; hence the sticky residue. Able to give birth to live young without mating, and to mature in as little as seven days, aphid populations can build up rapidly. Large populations may cause curling, yellowing, and distorted leaves; along with the sticky honeydew, which often turns black from a harmless sooty mold. Aphid feeding can continue until frost.
For the most part, sap feeding by aphids is harmless to otherwise healthy, well established trees at this time of year and control with insecticides is not recommended, however, applying insecticides or insecticidal soaps to small, recently planted trees to reduce aphids may be beneficial. Trees with a history of chronic aphid infestation, excluding fruit or nut trees, may be treated using a soil drench application with the systemic insecticide imidacloprid commonly sold as Merit or Bayer Advanced Tree and Shrubs Insect Control.
To deal with the honeydew, park cars elsewhere and wash or hose items until aphids stop feeding.
Aphids on Shade Trees and Ornamentals, http://www.ext.colostate.edu/pubs/insect/05511.html
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9. Cytospora Canker of Cottonwood- The fungus attacks trees or parts of trees that are injured or in a weak or stressed condition. The infected are is called the canker. It girdles the area infected and can cause dieback of branches or central leaders. Trees affected by drought, insects, diseases, sunscald, herbicides, or mechanical injury, especially root damage, are susceptible to cytospora infection. Cankers, sunken dead areas of bark with black pinhead-sized speckling or pimples, may be evident. There are no fungicide controls for canker diseases. Prune branches with cankers. Disinfect all pruning tools such as knives and saws by wiping them with rubbing alcohol. Avoid stress by spacing trees correctly, then mulching and watering correctly. Avoid wounds.
Cytospora Canker, http://www.ext.colostate.edu/Pubs/Garden/02937.html
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10. Sphareopsis Tip Blight of pine can cause entire branches, usually near the tops of trees, to die after a few years of infection by the disease. Most common symptoms are browning and stunting of shoot tips and fungal spores (black specks) on the bottoms of second year cones. Sphareopsis tip blight can be controlled with fungicides applied during the third week of April and repeated in 10 - 14 days.
Sphareopsis Tip Blight of Pines, http://www.ianr.unl.edu/PUBS/plantdisease/g646.htm
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11. 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.
NOTE: Fungal diseases like Sphareopsis 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.
Dothistroma Needle Blight, http://extensionhorticulture.unl.edu/Current/Dothistroma.shtml
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12. Natural needle drop may be causing the interior needles of spruce and pine trees to turn yellow then brown and drop readily from branches. Pine trees can hold their needles for 2-5 or more years, depending on the species. Spruce trees generally hold onto their needles longer than pine trees do, approximately 5-7 years. It is most noticeable in pines.
One evergreen tree that is very noticeable as it loses its leaves in fall is Eastern White Pine. This tree only holds its needles for two years which leaves less growth at the tip of branches to hide the needles as they are shed. Combined with the soft texture and open structure of the Eastern White Pine this makes fall needle shed easily seen.
Fall needle drop is a natural condition and is not a sign of disease or insect infestation, however, any factor that increases stress on evergreen trees will intensify the autumn needle drop. Stress factors include drought, herbicide injury, root damage and insect or disease damage.
Natural needle drop occurs only on the inner needles; if entire branches or needles at the tips of branches are dying, then something else is happening. A sample of the affected branches should be submitted to your local UNL Extension office for diagnosis. A close inspection of any brown foliage should also be done to eliminate the presence of fungal leaf spots, spider mites, aphids or other potential pest problems.
Natural Needle Drop, http://extensionhorticulture.unl.edu/Current/EverNeedleDrop.shtml
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13. Bagworms did cause severe damage to some conifer trees. At this time of year, bagworms are up to 2 inches long and there is only one larva per “brown bag”. Larvae have pupated and insecticide applications at this time will not be effective. Remove and destroy bags to reduce the number of overwintering eggs. Insecticides, such as Bifenthrin or Bacilllus thuringiensis should be applied after eggs hatch in early to mid June next year.
Bagworms, http://extensionhorticulture.unl.edu/Current/Bagworm.shtml
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14. Tomato Fruit Cracking- Growth cracks affect the stem end of tomatoes and typically appear as the fruit matures. Concentric cracking produces circular cracks around the stem end of the fruit. Radial cracks spread outward from the stem scar. Growth cracks often appear when conditions drastically change the rate of growth, such as wide fluctuations in temperature and moisture. Cultivars vary in their ability to withstand cracking. High nitrogen and low potassium may lead to fruit cracking. Proper fertilization and consistent irrigation will reduce the likelihood of growth cracks.
Common Tomato Fruit Disorders, http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Tom_ComDis.htm
Hort Update for the week of 9/15/08
| Current Problems: | Major Symptom: |
| Lawns | |
| 1. Kentucky Bluegrass stem rust | Orange-yellow powder on grass blades, mowers, and shoes. |
| 2. Winter annual weed control | Apply preemergence herbicides in early to mid September. |
| 3. Broadleaf perennial weed control | Apply postemergence herbicides from mid Sept. to mid Oct. |
| 4. Overseeding tips | Prepare site well. Select certified, blue-tag seed. |
| 5. Skunk damage to lawns | Patches of upturned earth or small, cone-shaped holes. |
| Trees & Shrubs | |
| 6. Premature leaf drop | Fungal leaf diseases or environmental stress. |
| 7. Mycosphaerella leaf spot on ash | Browning of leaflets. Scorched appearance to tree. |
| 8. Aphids | Sticky substance on leaves/items beneath trees. Leaf curling. |
| 9. Cottonwood canker | Branch dieback. Sunken, discolored areas on branches. |
| 10. Sphaeropsis tip blight of pine | Brown or stunted shoot tips. Branch dieback. |
| 11. Dothistroma needle blight | Reddish bands and browning on needles in lower half of tree. |
| 12. Natural needle drop | Interior needles suddenly yellow and are easily knocked off. |
| 13. Bagworm | Larvae have pupated. Insecticides will no longer work. Hand-pick. |
| Vegetables/ Fruits | |
| 14. Tomato fruit cracking | Fruit cracks near stem. |
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1. Kentucky Bluegrass Stem Rust symptoms are an orange-yellow powder (fungal spores) on grass blades in late summer. The turfgrass may develop a yellow or brown appearance. Rust typically occurs on lawns with slow growth. Sound fall care practices, including proper fertilization and correct irrigation, along with cooler fall weather promotes turfgrass growth and rust usually disappears. Control with fungicides is rarely suggested for home lawns.
Kentucky Bluegrass Stem Rust, http://www.urbanext.uiuc.edu/turf/rustlawn.html
Note for Sports Turf: If stem rust occurs on sports fields, the fungal spores can present problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of sound turf management and correctly timed fungicide applications, usually in July and August.
Sports Turf Internet Rust Resource, http://hcs.osu.edu/sportsturf/notes/detail.lasso?id=1094
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2. Winter Annual Weeds such as henbit, speedwell, and shepardspurse germinate during fall. The plants complete growth, blooming, and seed production the following spring and summer. In areas with a history of winter annual infestation, preemergence herbicides (Dimension, Barricade or pendimethalin based products for lawns and Preen for ornamental beds) can be applied in early September; or postemergence herbicides such as 2,4-D applied in late October.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
3. Perennial Weed Control- Mid September to early October is the best time to control perennial, broadleaf weeds (dandelions, bindweed, white clover, ground ivy) with herbicides. Plants are moving photosynthetic products into the roots for winter storage and more herbicide is translocated into roots, increasing root kill. Herbicides labeled for lawns and broadleaf weed control such as 2,4-D and combination herbicides such as Trimec are recommended for homeowner use.
Landscape Weed Management, http://www.ianrpubs.unl.edu/sendIt/ec1256.pdf
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
4. Overseeding Tips- Overseed Kentucky bluegrass by September 30 and tall fescue by September 20. Mow the turf as short as possible. Check the true thatch layer; if it exceeds one-half inch, power rake and remove debris. Core aerate prior to overseeding in 2-3 directions to achieve good seed to soil contact. Select disease resistant cultivars and buy certified, blue tag seed from reputable retailers. Check cultivars on the National Turfgrass Evaluation Program (NTEP) website for disease resistance and other desired characteristics. Irrigate if needed to promote germination and establishment. Fertilize with a starter fertilizer. Tall fescue should be evident in the coring holes 7-10 days after seeding and bluegrass 14-21 days after seeding.
NTEP website, http://www.ntep.org/contents2.shtml
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5. Skunk Damage to Lawns- Skunks may damage turfgrass by digging in lawns and golf courses while looking for white grubs. This damage appears as patches of upturned earth or small 3- to 4-inch cone-shaped holes. Repair the damage and overseed if needed. If 8 white grubs can be found per square foot, an application of the insecticide Dylox may be justified at this time of year.
Dealing With Skunks, http://www.ianrpubs.unl.edu/sendIt/g1769.pdf
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
6. Premature Leaf Drop in trees can be due to a fungal leaf spot or leaf blight. If there are no leaf spots or blighted areas on leaves, it is usually related to environmental stress. Leaf drop this past month was most likely due to the hot, dry conditions of August.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
7. Mycosphaerella Leaf Spot of Ash, previously called "Phyllostica leaf spot," can occur in large ash trees. Initial leaf spots caused by M. fraxinicola are small, pale-green, irregular blotches. Spots sometimes coalesce and entire leaflets may die. Trees may appear scorched due to necrotic blotches on foliage. Severe infections can result in premature defoliation. There is no practical control for these leaf diseases.
Mycosphaerella Leaf Spots, http://www.forestpests.org/ash/mycosphaerella.html
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
8. Aphids- When items beneath a shade tree become sticky, aphids are the likely cause. Aphids are small, soft-bodied insects that feed in dense groups on leaf undersides. Aphids feed on plant fluids and exude a honeydew; hence the sticky residue. Able to give birth to live young without mating, and to mature in as little as seven days, aphid populations can build up rapidly. Large populations may cause curling, yellowing, and distorted leaves; along with the sticky honeydew, which often turns black from a harmless sooty mold. Aphid feeding can continue until frost.
For the most part, sap feeding by aphids is harmless to otherwise healthy, well established trees at this time of year and control with insecticides is not recommended, however, applying insecticides or insecticidal soaps to small, recently planted trees to reduce aphids may be beneficial. Trees with a history of chronic aphid infestation, excluding fruit or nut trees, may be treated using a soil drench application with the systemic insecticide imidacloprid commonly sold as Merit or Bayer Advanced Tree and Shrubs Insect Control.
To deal with the honeydew, park cars elsewhere and wash or hose items until aphids stop feeding.
Aphids on Shade Trees and Ornamentals, http://www.ext.colostate.edu/pubs/insect/05511.html
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
9. Cytospora Canker of Cottonwood- The fungus attacks trees or parts of trees that are injured or in a weak or stressed condition. The infected are is called the canker. It girdles the area infected and can cause dieback of branches or central leaders. Trees affected by drought, insects, diseases, sunscald, herbicides, or mechanical injury, especially root damage, are susceptible to cytospora infection. Cankers, sunken dead areas of bark with black pinhead-sized speckling or pimples, may be evident. There are no fungicide controls for canker diseases. Prune branches with cankers. Disinfect all pruning tools such as knives and saws by wiping them with rubbing alcohol. Avoid stress by spacing trees correctly, then mulching and watering correctly. Avoid wounds.
Cytospora Canker, http://www.ext.colostate.edu/Pubs/Garden/02937.html
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
10. Sphareopsis Tip Blight of pine can cause entire branches, usually near the tops of trees, to die after a few years of infection by the disease. Most common symptoms are browning and stunting of shoot tips and fungal spores (black specks) on the bottoms of second year cones. Sphareopsis tip blight can be controlled with fungicides applied during the third week of April and repeated in 10 - 14 days.
Sphareopsis Tip Blight of Pines, http://www.ianr.unl.edu/PUBS/plantdisease/g646.htm
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
11. 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.
NOTE: Fungal diseases like Sphareopsis 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.
Dothistroma Needle Blight, http://extensionhorticulture.unl.edu/Current/Dothistroma.shtml
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
12. Natural needle drop may be causing the interior needles of spruce and pine trees to turn yellow then brown and drop readily from branches. Pine trees can hold their needles for 2-5 or more years, depending on the species. Spruce trees generally hold onto their needles longer than pine trees do, approximately 5-7 years. It is most noticeable in pines.
One evergreen tree that is very noticeable as it loses its leaves in fall is Eastern White Pine. This tree only holds its needles for two years which leaves less growth at the tip of branches to hide the needles as they are shed. Combined with the soft texture and open structure of the Eastern White Pine this makes fall needle shed easily seen.
Fall needle drop is a natural condition and is not a sign of disease or insect infestation, however, any factor that increases stress on evergreen trees will intensify the autumn needle drop. Stress factors include drought, herbicide injury, root damage and insect or disease damage.
Natural needle drop occurs only on the inner needles; if entire branches or needles at the tips of branches are dying, then something else is happening. A sample of the affected branches should be submitted to your local UNL Extension office for diagnosis. A close inspection of any brown foliage should also be done to eliminate the presence of fungal leaf spots, spider mites, aphids or other potential pest problems.
Natural Needle Drop, http://extensionhorticulture.unl.edu/Current/EverNeedleDrop.shtml
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
13. Bagworms did cause severe damage to some conifer trees. At this time of year, bagworms are up to 2 inches long and there is only one larva per “brown bag”. Larvae have pupated and insecticide applications at this time will not be effective. Remove and destroy bags to reduce the number of overwintering eggs. Insecticides, such as Bifenthrin or Bacilllus thuringiensis should be applied after eggs hatch in early to mid June next year.
Bagworms, http://extensionhorticulture.unl.edu/Current/Bagworm.shtml
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
14. Tomato Fruit Cracking- Growth cracks affect the stem end of tomatoes and typically appear as the fruit matures. Concentric cracking produces circular cracks around the stem end of the fruit. Radial cracks spread outward from the stem scar. Growth cracks often appear when conditions drastically change the rate of growth, such as wide fluctuations in temperature and moisture. Cultivars vary in their ability to withstand cracking. High nitrogen and low potassium may lead to fruit cracking. Proper fertilization and consistent irrigation will reduce the likelihood of growth cracks.
Common Tomato Fruit Disorders, http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Tom_ComDis.htm
