Hort Update for the week of 7/29/2009
1. Chinch Bugs damage Buffalograss and Zoysiagrass usually in sunny locations during hot, dry periods. Damage appears as patchy areas which turn yellow, then dry out and turn brown. Chinch bugs feed by sucking juices from leaves and stems. While feeding, they inject a toxin which disrupts movement of water and nutrients. Chinch bug nymphs are red with a white band, then orangish, and finally brown to black. Short-winged adults are black and 1/10th of an inch long. Control thatch to reduce chinch bugs. If bugs exceed 20 per square foot, apply the insecticide containing bifenthrin for control.
Chinch Bugs in Buffalograss and Zoysiagrass Turf
2. Summer fertilization with nitrogen is not recommended during July and August on the cool season turfgrasses Kentucky bluegrass and Tall Fescue. Nitrogen promotes growth during a period when Kentucky bluegrass would naturally be dormant. This can increase heat and drought stress leading to increased susceptibility to some insects and diseases and a need for more frequent irrigation. If turfgrass loses color during summer, an application of iron will improve color.
3. Maple Bladder Galls are small, bright red galls that turn black, usually found on upper leaf surfaces of maple leaves. When galls turn black, they may fall out of leaves, resulting in small holes. A few leaves can be so infested they drop from the tree, however leaf drop is uncommon. Galls are caused by the feeding of a tiny mite. Neither the mite or the galls adversely affect tree health. Insecticide treatment is not needed or recommended. If desired, the time to treat is at spring bud swell with a horticultural oil. Treatment is not effective once the galls are visible.
Most Leaf Galls Don’t Hurt Trees: Maple Bladder Gall
4. Erineum galls appear as a velvety patch on leaves, typically on leaf undersides, and may be reddish in color. They are caused by microscopic eriophyid mites. Mite feeding causes the plant to produce the abnormal growth that provides a sheltered location from which mites feed. Like many galls, there is no need to treat for eriophyid mites as the damage only affects leaf appearance and does not harm plant health.
Erineum Galls on Ornamental Plants
5. Leaf Scorch A uniform yellowing or browning on leaf edges of broadleaf plants or the tips of evergreen needles is a symptom of a condition called scorch. This environmental problem commonly occurs on linden, maple, ash and cottonwood. Scorch is usually is more severe on the south or southwest side of a tree or on the side nearest a source of radiated heat, such as a brick wall or street. Severe scorch can result in premature leaf or needle loss. Prolonged dry periods accompanied by warm, dry winds can cause leaves to transpire moisture faster than roots can supply it to the leaves, resulting in drying out of plant tissue. Young trees with un-established roots, or any tree growing in soils that are not conducive to healthy root function (i.e. compacted clay soil or overwatered soil) can lead to leaf scorch. Properly siting trees, avoiding overwatering, and encouraging healthy root growth can decrease leaf scorch in some situations.
Leaf Scorch of Ornamental Trees and Shrubs
Leaf Scorch of Trees and Shrubs
6. Oak leaf blister causes yellowish, blister-like, raised areas to form on leaves. It is a fungal disease. It does not cause serious damage to trees as they can still photosynthesize even though infected by the disease. Control is not needed and it is too late for control. Fungicides need to be applied just before bud break to be effective.
Oak Leaf Blister
7. Zimmerman pine moth larvae tunnel beneath the bark of pine trees, particularly in branch crotches, causing branches to die or break off readily in wind and snow storms. A pinkish mass may be found at the base of infested branches. Insecticides, such as bifenthrin or permethrin, applied during the second week of April and the second week of August are required for control. Use the label rate for borers and apply to the trunk and major branches.
Zimmerman Pine Moth, Colorado State University
Zimmerman Pine Moth, Iowa State University
8. Hail damaged plants found on sale at a retailer are often not a good deal in the long run; particularly trees. Wounds from hail can be infected by canker causing diseases. Cankers grow to eventually kill the branch or tree and there is no control other than to prune out the canker. When buying trees, which are long term investments that add much value to property and lead to energy savings, always purchase trees that are in good health.
9. Powdery mildew causes the leaves of many ornamentals to appear dusted with white powder. The fungus commonly infects Lilac, Zinnia, Phlox, Monarda (Bee Balm), Asters and other perennials. Susceptible plants along with shade, poor air circulation, high humidity, rainfall or overhead irrigation promote mildew. Mildew lowers the appearance of plants more often than killing perennial plants. A number of commercial fungicides are labeled for mildew on ornamentals and can reduce the disease if applied early. An alternative is to spray approximately once a week with a solution of baking soda (1.5 tablespoon/gallon) and horticultural oil (3 tablespoons/gallon). Culturally, avoid susceptible plants, increase air circulation around plants, avoid excess nitrogen fertilizer and overhead irrigation. Clean up infected plants or plant parts on a regular basis.
Powdery Mildew
10. Black spot disease causes the leaves of roses to turn yellow and develop black spots. Subsequent defoliation affects a plants appearance, reduces plant vigor, and increases the chance of winter kill. Fungicide applications are recommended for black spot of roses. For the best results, applications of a fungicide labeled for use on roses needs to begin in the spring as roses begin to grow, and applications repeated according to label directions. Sanitation, removing and destroying affected leaves and diseased canes should be done throughout the season.
Black Spot of Roses
11. Tobacco (Geranium) Budworms feed on the buds/petals of many flowers, especially Geranium (Pelargoniums), Petunias and Nicotiana. Flower buds may have holes, fail to open, or petals appear chewed as flower buds open. Monitor flowers closely for small holes chewed into flower buds. For control, handpick the small striped caterpillars at dusk (they hide during the day), choose a different type of flower to grow, or apply a labeled insecticide. Insecticides are not fully effective. If used, apply a pyrethrins or spinosad. Bacillus thuringiensis (B.t.) as limited effectiveness since the caterpillar does not ingest large amounts when boring holes into flower buds.
Tobacco (Geranium) Budworm
12. Wave Petunia is experiencing browning and dropping of lower leaves. This most likely is a fungal disease, possibly mildew, caused by our cooler and moister than average weather. Avoid overhead irrigation and improve air circulation around plants where feasible.
13. Bacterial canker/speck/spot on tomatoes is most common during wet summers. Bacterial canker causes lesions or cankers on any portion of the plant and may cause wilting, curling of leaflets, and yellowing or browning of leaves, often on one side or a portion of the plant. Fruit spots are dark and bordered by a distinct white halo which may disappear as fruit ripens.
Bacterial speck and spot cause small (1/8-1/4 inch) black lesions, usually with a yellow halo, on leaves. Bacterial spot causes small, slightly raised, water-soaked spots on the fruit which may enlarge to 1/4 inch in diameter and become very rough and cracked. Bacterial speck fruit lesions are also slightly raised but typically smaller (1/16 inch). Bacterial speck lesions do not crack or become scaly.
To control, use a 3 year crop rotation, practice good sanitation, and select bacterial free seed/transplants. Copper-based fungicides may be effective in suppressing bacterial speck and spot if applied at the first sign of leaf spotting or at the time of first blossom and applications continued at 7 to 10 day intervals. These fungicides will not control bacterial canker.
Bacterial Spot, Speck and Canker
14. Powdery & Downy Mildew in Cucurbits- Powdery mildew appears as a white flour-like dusting growing on leaf surfaces. Downy mildew first appears as pale green areas on upper leaf surfaces which change to yellow irregular shaped spots. A fine white-to-grayish downy growth soon appears on lower leaf surfaces. Infected leaves generally die but may remain erect while the edges of the leaf blades curl inward. Usually, the leaves near the center of a hill or row are infected first. The infected area spreads outward, causing defoliation, stunted growth, and poor fruit development. The entire plant may eventually be killed. Spores are carried by wind so crop rotation is not as effective. Plant resistant cultivars. Avoid overhead irrigation. Space correctly. Improve air circulation. Copper based fungicides are recommended for mildew in cucurbits, but can damage plants. Read and follow label directions.
Managing Downy Mildew in Cucurbits
Powdery Mildew of Vine Crops
15. Early Blight and Septoria Leaf Spot are the two most common fungal diseases of tomatoes. Symptoms begin as leaf spots on lower leaves, with infections moving up the plant causing foliage to die; often leading to fruit sunscald. These diseases can be reduced with fungicides labeled for use on tomatoes. For best results, applications need to begin as soon as symptoms first appear on lower leaves, and applications made every 7 to 10 days. Avoid overhead irrigation and increase air circulation around plants with proper spacing and caging. Mulch the soil around tomatoes to reduce soil splash of fungus onto lower leaves. Plant resistant varieties and avoid planting tomatoes in the same area year after year. Severely infected plants are best pulled and destroyed. Use fall sanitation to reduce the amount of fungus overwintering.
Early Blight and Septoria Leaf Spot of Tomatoes
Tomato Disease I.D. Key
16. Herbicide injury is most common on tomatoes, but all plants can show leaf curling, leaf cupping, distorted veins and sometimes discoloration caused by herbicide drift. If more than one type of plant in the garden or yard is affected, herbicide injury is a likely cause.
17. Blossom end rot is a common problem of tomatoes, but also occurs on peppers, eggplant, squash and watermelon. It appears as a flat, dry, sunken, brown rot on the blossom end of the fruit, opposite the stem end. The size of the rotted area varies, but can cover up to 50% of the fruit. This problem is a physiological disorder associated with a calcium deficiency in the developing fruit. Rarely is the problem a lack of calcium in the soil. Drought stress, low daytime humidity, high temperatures and rapid, vegetative plant growth caused by excess nitrogen applications favor blossom end rot development. To reduce it, prevent drought stress, mulch with organic mulch and avoid excess nitrogen fertilization.
Blossom End Rot
18. Early fruit drop may be due to natural fruit thinning that usually occurs in June when fruit trees drop a number of fruits, usually due to poor pollination, or excessive fruit set.
19. Small apples are being reported on apple trees, most likely due to a heavy fruit crop and a lack of fruit thinning, either naturally or by hand. Conducive growing conditions this spring has lead to another prolific fruit crop on the heels of a bumper crop last year. To prevent fruit trees going into alternate year bearing; having reduced fruit size and flavor; and to avoid branch breakage, fruit thinning is recommended in early July. For information on fruit thinning, see the link below.
Fruit Thinning
20. Omaha Grounds Maintenance Association Trade Show, August 11
There will be companies representing grounds maintenance equipment, snow removal equipment, and grounds maintenance supplies, including fertilizer, seed, insecticides, and more. Free food and beverages for all. Everyone is welcome, including non-members and the public.
Date: Tuesday, August 11
Location: Seymour Smith Park, 68 & Harrison Street, Omaha, NE
Time: 3-8 p.m., rain or shine
Web Site: http://www.ogma.org/
| Current Problems: | Major Symptom: |
| Lawns | |
| 1. Chinch bugs in zoysia & buffalograss | Patchy areas which turn yellow, then dry out and turn brown |
| 2. Avoid summer fertilization | Increases drought and heat stress in cool season turfgrass |
| Trees & Shrubs | |
| 3. Maple bladder gall | Red changing to black bladder-like bumps (galls) on leaves |
| 4. Erineum galls | Flat, sometimes reddish, velvety patches (growths) on leaves. |
| 5. Leaf scorch (maple) | Brown leaf edges on broadleaves and brown tips on evergreen needles |
| 6. Oak leaf blister | Slightly raised, yellowish, blister-like spots on leaves |
| 7. Zimmerman pine moth | Dead branches and large pinkish pitch masses on Scotch & Austrian |
| 8. Hail damage (nursery stock) | Be wary of buying hail damaged trees, even at low prices |
| Landscape Ornamentals | |
| 9. Powdery mildew | White, flour-like growth on leaf surfaces |
| 10. Black spot of roses | Yellowing leaves with black spots |
| 11. Tobacco budworm (geranium) | Holes in flower buds, buds failing to open, chewed petals, frass pellets |
| 12. Wave petunia disease | Lower leaves turning brown and dying |
| Vegetables & Fruits | |
| 13. Bacterial canker/ speck/ spot (tomato) | Tomato leaf spots and fruit spots with white or yellow halos |
| 14. Early blight/ Septoria (tomato) | Brown leaf spots with concentric rings, leaf yellowing from bottom up |
| 15. Powdery/ Downy mildews (cucurbits) | White powdery mildew, or leaf spotting and a downy mildew |
| 16. Herbicide drift | Leaf curling or cupping, vein distortion; especially on tomatoes |
| 17. Blossom end rot | Brown leathery rot on blossom end of vegetable fruits |
| 18. Early fruit drop | Due to poor pollination or heavy fruit set |
| 19. Small apples | Due to a lack of thinning on trees with a heavy fruit set |
| Upcoming Programs | |
| 20. Omaha Grounds Maintenance Association Trade Show, August 11 | |
| 21. Late Blight and Other Important Diseases of Tomato in the Home Garden- recorded webinar | |
| 22. Diagnosing and Controlling Important Diseases of Cucurbit Crops in the Home Garden- recorded webinar | |
1. Chinch Bugs damage Buffalograss and Zoysiagrass usually in sunny locations during hot, dry periods. Damage appears as patchy areas which turn yellow, then dry out and turn brown. Chinch bugs feed by sucking juices from leaves and stems. While feeding, they inject a toxin which disrupts movement of water and nutrients. Chinch bug nymphs are red with a white band, then orangish, and finally brown to black. Short-winged adults are black and 1/10th of an inch long. Control thatch to reduce chinch bugs. If bugs exceed 20 per square foot, apply the insecticide containing bifenthrin for control.
Chinch Bugs in Buffalograss and Zoysiagrass Turf
2. Summer fertilization with nitrogen is not recommended during July and August on the cool season turfgrasses Kentucky bluegrass and Tall Fescue. Nitrogen promotes growth during a period when Kentucky bluegrass would naturally be dormant. This can increase heat and drought stress leading to increased susceptibility to some insects and diseases and a need for more frequent irrigation. If turfgrass loses color during summer, an application of iron will improve color.
3. Maple Bladder Galls are small, bright red galls that turn black, usually found on upper leaf surfaces of maple leaves. When galls turn black, they may fall out of leaves, resulting in small holes. A few leaves can be so infested they drop from the tree, however leaf drop is uncommon. Galls are caused by the feeding of a tiny mite. Neither the mite or the galls adversely affect tree health. Insecticide treatment is not needed or recommended. If desired, the time to treat is at spring bud swell with a horticultural oil. Treatment is not effective once the galls are visible.
Most Leaf Galls Don’t Hurt Trees: Maple Bladder Gall
4. Erineum galls appear as a velvety patch on leaves, typically on leaf undersides, and may be reddish in color. They are caused by microscopic eriophyid mites. Mite feeding causes the plant to produce the abnormal growth that provides a sheltered location from which mites feed. Like many galls, there is no need to treat for eriophyid mites as the damage only affects leaf appearance and does not harm plant health.
Erineum Galls on Ornamental Plants
5. Leaf Scorch A uniform yellowing or browning on leaf edges of broadleaf plants or the tips of evergreen needles is a symptom of a condition called scorch. This environmental problem commonly occurs on linden, maple, ash and cottonwood. Scorch is usually is more severe on the south or southwest side of a tree or on the side nearest a source of radiated heat, such as a brick wall or street. Severe scorch can result in premature leaf or needle loss. Prolonged dry periods accompanied by warm, dry winds can cause leaves to transpire moisture faster than roots can supply it to the leaves, resulting in drying out of plant tissue. Young trees with un-established roots, or any tree growing in soils that are not conducive to healthy root function (i.e. compacted clay soil or overwatered soil) can lead to leaf scorch. Properly siting trees, avoiding overwatering, and encouraging healthy root growth can decrease leaf scorch in some situations.
Leaf Scorch of Ornamental Trees and Shrubs
Leaf Scorch of Trees and Shrubs
6. Oak leaf blister causes yellowish, blister-like, raised areas to form on leaves. It is a fungal disease. It does not cause serious damage to trees as they can still photosynthesize even though infected by the disease. Control is not needed and it is too late for control. Fungicides need to be applied just before bud break to be effective.
Oak Leaf Blister
7. Zimmerman pine moth larvae tunnel beneath the bark of pine trees, particularly in branch crotches, causing branches to die or break off readily in wind and snow storms. A pinkish mass may be found at the base of infested branches. Insecticides, such as bifenthrin or permethrin, applied during the second week of April and the second week of August are required for control. Use the label rate for borers and apply to the trunk and major branches.
Zimmerman Pine Moth, Colorado State University
Zimmerman Pine Moth, Iowa State University
8. Hail damaged plants found on sale at a retailer are often not a good deal in the long run; particularly trees. Wounds from hail can be infected by canker causing diseases. Cankers grow to eventually kill the branch or tree and there is no control other than to prune out the canker. When buying trees, which are long term investments that add much value to property and lead to energy savings, always purchase trees that are in good health.
9. Powdery mildew causes the leaves of many ornamentals to appear dusted with white powder. The fungus commonly infects Lilac, Zinnia, Phlox, Monarda (Bee Balm), Asters and other perennials. Susceptible plants along with shade, poor air circulation, high humidity, rainfall or overhead irrigation promote mildew. Mildew lowers the appearance of plants more often than killing perennial plants. A number of commercial fungicides are labeled for mildew on ornamentals and can reduce the disease if applied early. An alternative is to spray approximately once a week with a solution of baking soda (1.5 tablespoon/gallon) and horticultural oil (3 tablespoons/gallon). Culturally, avoid susceptible plants, increase air circulation around plants, avoid excess nitrogen fertilizer and overhead irrigation. Clean up infected plants or plant parts on a regular basis.
Powdery Mildew
10. Black spot disease causes the leaves of roses to turn yellow and develop black spots. Subsequent defoliation affects a plants appearance, reduces plant vigor, and increases the chance of winter kill. Fungicide applications are recommended for black spot of roses. For the best results, applications of a fungicide labeled for use on roses needs to begin in the spring as roses begin to grow, and applications repeated according to label directions. Sanitation, removing and destroying affected leaves and diseased canes should be done throughout the season.
Black Spot of Roses
11. Tobacco (Geranium) Budworms feed on the buds/petals of many flowers, especially Geranium (Pelargoniums), Petunias and Nicotiana. Flower buds may have holes, fail to open, or petals appear chewed as flower buds open. Monitor flowers closely for small holes chewed into flower buds. For control, handpick the small striped caterpillars at dusk (they hide during the day), choose a different type of flower to grow, or apply a labeled insecticide. Insecticides are not fully effective. If used, apply a pyrethrins or spinosad. Bacillus thuringiensis (B.t.) as limited effectiveness since the caterpillar does not ingest large amounts when boring holes into flower buds.
Tobacco (Geranium) Budworm
12. Wave Petunia is experiencing browning and dropping of lower leaves. This most likely is a fungal disease, possibly mildew, caused by our cooler and moister than average weather. Avoid overhead irrigation and improve air circulation around plants where feasible.
13. Bacterial canker/speck/spot on tomatoes is most common during wet summers. Bacterial canker causes lesions or cankers on any portion of the plant and may cause wilting, curling of leaflets, and yellowing or browning of leaves, often on one side or a portion of the plant. Fruit spots are dark and bordered by a distinct white halo which may disappear as fruit ripens.
Bacterial speck and spot cause small (1/8-1/4 inch) black lesions, usually with a yellow halo, on leaves. Bacterial spot causes small, slightly raised, water-soaked spots on the fruit which may enlarge to 1/4 inch in diameter and become very rough and cracked. Bacterial speck fruit lesions are also slightly raised but typically smaller (1/16 inch). Bacterial speck lesions do not crack or become scaly.
To control, use a 3 year crop rotation, practice good sanitation, and select bacterial free seed/transplants. Copper-based fungicides may be effective in suppressing bacterial speck and spot if applied at the first sign of leaf spotting or at the time of first blossom and applications continued at 7 to 10 day intervals. These fungicides will not control bacterial canker.
Bacterial Spot, Speck and Canker
14. Powdery & Downy Mildew in Cucurbits- Powdery mildew appears as a white flour-like dusting growing on leaf surfaces. Downy mildew first appears as pale green areas on upper leaf surfaces which change to yellow irregular shaped spots. A fine white-to-grayish downy growth soon appears on lower leaf surfaces. Infected leaves generally die but may remain erect while the edges of the leaf blades curl inward. Usually, the leaves near the center of a hill or row are infected first. The infected area spreads outward, causing defoliation, stunted growth, and poor fruit development. The entire plant may eventually be killed. Spores are carried by wind so crop rotation is not as effective. Plant resistant cultivars. Avoid overhead irrigation. Space correctly. Improve air circulation. Copper based fungicides are recommended for mildew in cucurbits, but can damage plants. Read and follow label directions.
Managing Downy Mildew in Cucurbits
Powdery Mildew of Vine Crops
15. Early Blight and Septoria Leaf Spot are the two most common fungal diseases of tomatoes. Symptoms begin as leaf spots on lower leaves, with infections moving up the plant causing foliage to die; often leading to fruit sunscald. These diseases can be reduced with fungicides labeled for use on tomatoes. For best results, applications need to begin as soon as symptoms first appear on lower leaves, and applications made every 7 to 10 days. Avoid overhead irrigation and increase air circulation around plants with proper spacing and caging. Mulch the soil around tomatoes to reduce soil splash of fungus onto lower leaves. Plant resistant varieties and avoid planting tomatoes in the same area year after year. Severely infected plants are best pulled and destroyed. Use fall sanitation to reduce the amount of fungus overwintering.
Early Blight and Septoria Leaf Spot of Tomatoes
Tomato Disease I.D. Key
16. Herbicide injury is most common on tomatoes, but all plants can show leaf curling, leaf cupping, distorted veins and sometimes discoloration caused by herbicide drift. If more than one type of plant in the garden or yard is affected, herbicide injury is a likely cause.
17. Blossom end rot is a common problem of tomatoes, but also occurs on peppers, eggplant, squash and watermelon. It appears as a flat, dry, sunken, brown rot on the blossom end of the fruit, opposite the stem end. The size of the rotted area varies, but can cover up to 50% of the fruit. This problem is a physiological disorder associated with a calcium deficiency in the developing fruit. Rarely is the problem a lack of calcium in the soil. Drought stress, low daytime humidity, high temperatures and rapid, vegetative plant growth caused by excess nitrogen applications favor blossom end rot development. To reduce it, prevent drought stress, mulch with organic mulch and avoid excess nitrogen fertilization.
Blossom End Rot
18. Early fruit drop may be due to natural fruit thinning that usually occurs in June when fruit trees drop a number of fruits, usually due to poor pollination, or excessive fruit set.
19. Small apples are being reported on apple trees, most likely due to a heavy fruit crop and a lack of fruit thinning, either naturally or by hand. Conducive growing conditions this spring has lead to another prolific fruit crop on the heels of a bumper crop last year. To prevent fruit trees going into alternate year bearing; having reduced fruit size and flavor; and to avoid branch breakage, fruit thinning is recommended in early July. For information on fruit thinning, see the link below.
Fruit Thinning
20. Omaha Grounds Maintenance Association Trade Show, August 11
There will be companies representing grounds maintenance equipment, snow removal equipment, and grounds maintenance supplies, including fertilizer, seed, insecticides, and more. Free food and beverages for all. Everyone is welcome, including non-members and the public.
Date: Tuesday, August 11
Location: Seymour Smith Park, 68 & Harrison Street, Omaha, NE
Time: 3-8 p.m., rain or shine
Web Site: http://www.ogma.org/
