Hort Update for the week of 7/2/2009
1. Conditions Prime for Disease- Recent rains and high humidity provided prime conditions for a variety of fungal leaf diseases such as Brown Patch, Helminthosporium, powdery mildew and others. With many of these foliar diseases, a fungicide application applied at the first sign of disease will slow the spread of disease.
For assistance in identifying turf diseases refer to Diagnostic Key for Lawn Diseases, http://lawnandgarden.unl.edu/html/toolbar/diagtip/lawnkey.htm
2. Wet Wilt is most common on shallow rooted plants, such as Kentucky bluegrass, when wet weather is followed by hot conditions, often in connection with continued irrigation or turfgrass traffic. Wet wilt results when low oxygen levels in saturated soils lower root function and roots are unable to replace moisture as rapidly as it is transpired from grass leaves. Wilt symptoms are similar to drought symptoms; however leaves often go from wilting to necrosis (browning) rather than from wilting, to a bluish cast, to brown with wet wilt. Allow soil to dry slightly between rainfall and irrigation or between irrigations, and use cultural practices such as core aeration to improve soil drainage and aeration.
3. Summer Patch disease is caused by a fungus attacking turfgrass roots in spring. Fungicide applications should be made in April and May is when fungicide applications are effective in controlling the disease. Summer patch symptoms often do not appear until summer when function of infected roots is lowered. Cultural practices can reduce the degree of injury. These include proper irrigation, avoiding nitrogen fertilization during summer and syringing (lightly irrigating) the turf at midday to cool grass blades. See the publication below for fungicide and cultural management practices.
Summer Patch Disease of Turfgrass, http://www.ianrpubs.unl.edu/sendIt/g1913.pdf
4. Mushrooms and Slime Mold grow on organic matter such as dead tree roots, turfgrass thatch, and wood mulch. They are the spore producing bodies of decay fungi which are decomposing the organic matter. They do not infect and cause diseases in turfgrass. Fungicide applications will not control mushrooms and slime mold. They will disappear in dryer weather and stop appearing once the organic matter they are growing on decomposes. Where a slime mold is shading turfgrass and causing yellowing, remove it by mechanical means such as raking.
Slime mold on Turfgrass, http://ohioline.osu.edu/hyg-fact/3000/pdf/3074.pdf
5. Powdery Mildew appears as a light layer of flour on grass blades. It is found in shaded turf areas with reduced air movement and high moisture or humidity levels. The fungus grows on leaf surfaces, shading the underlying leaf blade and reducing photosynthesis. Some yellowing and thinning of turf may be seen in heavily infected areas. Reduce shade and improve air movement through pruning where possible. Preventative fungicide applications may be needed in areas with a history of mildew.
Powdery Mildew Disease in Turfgrass, http://www.ianrpubs.unl.edu/sendIt/g1911.pdf
6. Spruce and Fir trees are showing wilting and browning of this spring's new growth, primarily on the south side of trees, across much of the state. Environmental conditions are most likely the issue, not a disease or insect problem. It is possible the dormant buds or new growth were damaged by cold temperatures that weakened the tissue which was then infected by a secondary pathogen causing wilting or curling of tips. No control is recommended. Long term damage to trees is unlikely.
7. Storm Damage- When trees are damaged by wind or ice, safety is the first concern. To safely deal with storm damage to trees, follow information in the storm publications series provided on the Nebraska Forest Service web site.
8. River Birch yellowing is often due to chlorosis caused by an iron or, in some cases manganese, deficiency in the leaves when high pH soils make these nutrients less available for root uptake. Compacted soils or conditions that restrict root growth also compound the problem. Avoid applying nitrogen fertilizer to these trees, especially where birch are growing in or near fertilized lawns. Soil apply ferrous sulfate or a chelated iron as label recommends.
9. Oak Lacebug are small insects with white lacy wings that cluster on leaf undersides of oak, sycamore and other trees. Sapsucking insects, they pierce leaves to feed causing tiny light colored flecks on upper leaf surfaces. If heavily infested, leaf undersides appear dirty with dark spots or stains and leaves yellow and brown. Lace bugs are most prevalent in late summer. In many cases, the damage is minor enough or occurs late enough in the season control is not needed. Also, natural enemies can keep lacebug populations down unless insecticides kill predators, allowing lacebug populations to later build. If insecticides are used, spray as soon as eggs hatch in spring with an insecticide labeled for use on trees.
Lacebugs, http://ohioline.osu.edu/hyg-fact/2000/2150.html
10. 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, http://plantclinic.cornell.edu/FactSheets/oakblister/oakblister.htm
11. Leucanium Scale are initially flattened and brown. As they mature, they become hardened and round. They attack a variety of trees and shrubs. With high populations, dieback of twigs, branches and lowered plant vigor result. Control by pruning heavily infested branches and/or applying insecticides just after egg hatch when insects are in the crawler stage in May and June.
Scale Insects of Trees and Shrubs, http://www.extension.umn.edu/distribution/horticulture/DG1019.html#Lecanium
12. Elm Flea Weevil first appeared in the Midwest in 2003 and may now be throughout Nebraska. The adult weevil is very tiny (1.6 mm long), dark brown to black, with a prominent “snout”. They can jump when disturbed. Adult feeding results in tiny shot holes in the leaves. At this time, it appears to feed mainly on Siberian elm (Ulmus pumila) which is commonly called Chinese elm in Nebraska. Morton Arboretum is reporting feeding on hybrids containing U. pumila, particularly “Homestead”. Most trees will recover with good plant health care practices. On high value trees or trees under stress, insecticides may be applied as soon adults appear and feeding is noticed. It is late now to apply insecticides.
Elm Flea Weevil, http://www.ipm.msu.edu/cat08land/l06-27-08.htm#9
13. Ash Rust- Yellow/orange, raised spots (pustules) on leaves. This fungal disease may cause some twisting of foliage and leaf drop. Ash rust is not a serious disease of trees. Fungicide control is not recommended or needed.
Ash Rust, http://www.ianrpubs.unl.edu/sendIt/g1942.pdf
14. Maple bladder galls are bright red galls that later turn black, usually on the upper leaf surface of maple leaves. When galls turn black, they may fall out of leaves, resulting in small holes. A few leaves may be so infested they drop from the tree, but leaf drop is uncommon. Galls are caused by the feeding of a tiny mite and do not affect the health of the tree. If desired, the time to treat is at spring bud swell, with horticultural oil. Treatment is not effective once the galls are visible.
Maple Bladder Galls, http://www.ipm.iastate.edu/ipm/hortnews/1998/6-5-1998/maplegall.html
15. Two-spotted Spider Mites infest a large variety of plants. Mites and their webs can barely be seen with the naked eye. Mites feed by sucking plant juices with piercing-sucking mouth parts, causing white or yellow speckling on leaves; then off-green to bronze discoloration. Controls range from hosing down plants with a strong spray of water (syringing) to using insecticidal soaps, or using miticides (Kelthane) or insecticides (Pyrethrin) when mites are active. Tap a branch over a white sheet of paper to monitor for active mites. They’ll appear as specks moving around on the paper if present. Mites can be in the egg stage so monitoring should continue for one to two weeks. NOTE: Carbaryl (Sevin) can increase mites by killing their predators such as lady beetles and is not recommended.
Spider Mites and Their Control, http://ohioline.osu.edu/hyg-fact/2000/2012.html
Spider Mites, http://www.ext.colostate.edu/PUBS/insect/05507.html
16. Powdery Mildew causes the leaves of many ornamentals to appear dusted with white powder. This fungus commonly infects 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 plants. A number of commercial fungicides are labeled for mildew on ornamentals and can reduce the disease if applied early enough. 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 planting susceptible plants, increase air circulation around plants, avoid excess nitrogen fertilizer and overhead irrigation, and clean up infected plants or plant parts on a regular basis.
Powdery Mildew, http://www.hort.wisc.edu/mastergardener/features/diseases/powderymildew/pm.htm
17. Phlox Plant Bug Feeding occurs on upper leaf surfaces of young phlox leaves and buds. Injury appears as white or pale-green spots that later become yellow-stippled areas. Blossoms may be deformed. In extreme cases, plants become stunted and die. Adult bugs generally have contrasting colors, i.e. orange and black or red and black, sometimes gray and white or yellow; all with black legs. Nymphs are orange or bright red. This insect overwinters in the egg stage with nymphs emerging in early May. Remove infested plant parts. The use of insecticidal soaps, horticultural oils, or systemic insecticides will reduce damage.
18. Slime Mold in Mulch Slime molds sometimes look like dog vomit and can come in many bright colors, while others appear as a grayish mass. Slime molds feed on decaying material and are often found in mulched ornamental beds. They are unsightly, but otherwise harmless to plants. The mulch can be raked to break up the appearance of slime molds. They will disappear during dry weather.
19. Tomato Early Blight and Septoria Leaf Spot are the two most common tomato diseases. Both are fungal and begin as leaf spots on lower leaves, then work their way up the plant causing foliage to die; often leading to fruit sunscald. Both 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. Applications should be 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 tomato 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, http://www.oznet.ksu.edu/hfrr/extensn/problems/earlblht.htm
Tomato Disease I.D. Key, http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/TomKey.html
20. Tomato Leaf Roll is not a disease or insect and no pesticide control is needed. When tomato plants grow vigorously during mild, moist weather; top growth can exceed root growth. When the first hot days of summer arrive, roots cannot keep up and plants slow moisture lost from leaves by rolling leaves upward. Tomato leaf roll can also occur after a heavy cultivation, a hard rain, or any sudden weather change. Too much rain or irrigation can saturate soil and suffocate roots. A root system lacking soil oxygen cannot function well to move water to upper plant parts, resulting in the same symptoms that occur with too little soil moisture. Avoid deep hoeing close to plants, mulch to moderate soil moisture extremes, and water to keep the soil moist but not waterlogged. Leaf roll is temporary.
21. Cucumbers are infected by a number of fungal leaf diseases. As with tomato diseases, apply fungicides at the first sign of foliar leaf spots and repeat application according to label directions. Remove and destroy heavily infected plants. Avoid overhead irrigation. Plant disease resistant varieties and use crop rotation.
Cucumber Disease I.D. Key, http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/CucKey.html
22. Bolting is premature flowering in plants and common in cole crops, beets and rhubarb. It can reduce yields or affect produce quality. When plants send up flower stalks, remove the stalk before seeds are produced. This year bolting was most likely due to the hot, dry conditions encountered earlier this spring. Planting too large of transplants, stress, and weather extremes lead to bolting.
23. Cabbage Loopers are light green with light colored stripes and up to 1½ inches long. They move by a looping motion. Adults are brown, night flying moths that lay eggs in May. Loopers feed from leaf undersides and create ragged holes between leaf veins. They also feed on cabbage, broccoli and cauliflower heads. With two to three generations per season, they are present all season. At this time of year, control with Dipel (Bacillus thuringiensis) or carbaryl (sevin). They can be controlled with floating row covers if these are placed over plants before moths emerge to mate and lay eggs.
24. Tomato Ring Spot Virus of Raspberry is being reported in Omaha. The most common symptom is the production of crumbly fruit, stunted plants and leaf yellowing. Leaves may have pale ring spots in spring which disappear later in the season. For control, purchase only Certified Virus-Tested stock, promptly remove and destroy infected plants, and control aphids which carry the virus from plant to plant.
| Current Problems: | Major Symptom: |
| Lawns | |
| 1. Disease conditions prime | Watch for diseases promoted by recent weather conditions. |
| 2. Wet wilt- environmental | Turfgrass wilts due to saturated soils lowering root function. |
| 3. Summer patch | Too late to apply fungicides for this season. |
| 4. Mushrooms and slime mold | Grow on organic matter. Nonpathogenic. Fungicides do not control. |
| 5. Powdery mildew | Grass blades appear to be dusted with flour in shady areas. |
| Trees/Shrubs | |
| 6. Spruce and fir dead tips | Tips wilt and turn brown. Environmental issue; not disease. |
| 7. Storm damage | Wind and hail damage. See Nebraska Forest Service Resources. |
| 8. River birch yellowing | Leaf yellowing. |
| 9. Oak lacebug | White flecking/speckling on upper leaf surfaces. |
| 10. Oak blister gall | Raised, blister-like spots on oak leaves. |
| 11. Leucanium scale | Brown, rounded bumps (scales) on twigs. Sapsucking insect. |
| 12. Elm flea weevil | Tiny holes chewed into leaves by tiny weevils with long snout. |
| 13. Ash rust | Raised orange spots on leaves; some leaf curling. |
| 14. Maple bladder gall | Red changing to black bladder-like bumps (galls) on leaves. |
| Gardens/Ornamentals | |
| 15. Two spotted spider mite | Leaves become stippled, changing from green to yellow or bronze. |
| 16. Powdery mildew | Leaf surfaces appear dusted by white flour. |
| 17. Phlox plant bug | White or pale green spots on leaves and deformed flower buds. |
| 18. Slime mold on mulch | Flat, vomit-like growth on mulch is not harmful to plants. |
| Fruits/Vegetables | |
| 19. Tomato blight | Leaves turn yellow and brown from the bottom up. |
| 20. Tomato leaf roll | Leaves rolled upward, but otherwise appear normal. |
| 21. Cucumber blight | Leaf spots and browning. |
| 22. Bolting | Early blooming in cool season crops, i.e. beets. |
| 23. Cabbage loopers | Holes in cabbage heads and leaves. Greenish, looping caterpillar. |
| 24. Tomato Ring Spot Virus in Raspberry | Fruit crumbles when harvested. |
1. Conditions Prime for Disease- Recent rains and high humidity provided prime conditions for a variety of fungal leaf diseases such as Brown Patch, Helminthosporium, powdery mildew and others. With many of these foliar diseases, a fungicide application applied at the first sign of disease will slow the spread of disease.
For assistance in identifying turf diseases refer to Diagnostic Key for Lawn Diseases, http://lawnandgarden.unl.edu/html/toolbar/diagtip/lawnkey.htm
2. Wet Wilt is most common on shallow rooted plants, such as Kentucky bluegrass, when wet weather is followed by hot conditions, often in connection with continued irrigation or turfgrass traffic. Wet wilt results when low oxygen levels in saturated soils lower root function and roots are unable to replace moisture as rapidly as it is transpired from grass leaves. Wilt symptoms are similar to drought symptoms; however leaves often go from wilting to necrosis (browning) rather than from wilting, to a bluish cast, to brown with wet wilt. Allow soil to dry slightly between rainfall and irrigation or between irrigations, and use cultural practices such as core aeration to improve soil drainage and aeration.
3. Summer Patch disease is caused by a fungus attacking turfgrass roots in spring. Fungicide applications should be made in April and May is when fungicide applications are effective in controlling the disease. Summer patch symptoms often do not appear until summer when function of infected roots is lowered. Cultural practices can reduce the degree of injury. These include proper irrigation, avoiding nitrogen fertilization during summer and syringing (lightly irrigating) the turf at midday to cool grass blades. See the publication below for fungicide and cultural management practices.
Summer Patch Disease of Turfgrass, http://www.ianrpubs.unl.edu/sendIt/g1913.pdf
4. Mushrooms and Slime Mold grow on organic matter such as dead tree roots, turfgrass thatch, and wood mulch. They are the spore producing bodies of decay fungi which are decomposing the organic matter. They do not infect and cause diseases in turfgrass. Fungicide applications will not control mushrooms and slime mold. They will disappear in dryer weather and stop appearing once the organic matter they are growing on decomposes. Where a slime mold is shading turfgrass and causing yellowing, remove it by mechanical means such as raking.
Slime mold on Turfgrass, http://ohioline.osu.edu/hyg-fact/3000/pdf/3074.pdf
5. Powdery Mildew appears as a light layer of flour on grass blades. It is found in shaded turf areas with reduced air movement and high moisture or humidity levels. The fungus grows on leaf surfaces, shading the underlying leaf blade and reducing photosynthesis. Some yellowing and thinning of turf may be seen in heavily infected areas. Reduce shade and improve air movement through pruning where possible. Preventative fungicide applications may be needed in areas with a history of mildew.
Powdery Mildew Disease in Turfgrass, http://www.ianrpubs.unl.edu/sendIt/g1911.pdf
6. Spruce and Fir trees are showing wilting and browning of this spring's new growth, primarily on the south side of trees, across much of the state. Environmental conditions are most likely the issue, not a disease or insect problem. It is possible the dormant buds or new growth were damaged by cold temperatures that weakened the tissue which was then infected by a secondary pathogen causing wilting or curling of tips. No control is recommended. Long term damage to trees is unlikely.
7. Storm Damage- When trees are damaged by wind or ice, safety is the first concern. To safely deal with storm damage to trees, follow information in the storm publications series provided on the Nebraska Forest Service web site.
8. River Birch yellowing is often due to chlorosis caused by an iron or, in some cases manganese, deficiency in the leaves when high pH soils make these nutrients less available for root uptake. Compacted soils or conditions that restrict root growth also compound the problem. Avoid applying nitrogen fertilizer to these trees, especially where birch are growing in or near fertilized lawns. Soil apply ferrous sulfate or a chelated iron as label recommends.
9. Oak Lacebug are small insects with white lacy wings that cluster on leaf undersides of oak, sycamore and other trees. Sapsucking insects, they pierce leaves to feed causing tiny light colored flecks on upper leaf surfaces. If heavily infested, leaf undersides appear dirty with dark spots or stains and leaves yellow and brown. Lace bugs are most prevalent in late summer. In many cases, the damage is minor enough or occurs late enough in the season control is not needed. Also, natural enemies can keep lacebug populations down unless insecticides kill predators, allowing lacebug populations to later build. If insecticides are used, spray as soon as eggs hatch in spring with an insecticide labeled for use on trees.
Lacebugs, http://ohioline.osu.edu/hyg-fact/2000/2150.html
10. 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, http://plantclinic.cornell.edu/FactSheets/oakblister/oakblister.htm
11. Leucanium Scale are initially flattened and brown. As they mature, they become hardened and round. They attack a variety of trees and shrubs. With high populations, dieback of twigs, branches and lowered plant vigor result. Control by pruning heavily infested branches and/or applying insecticides just after egg hatch when insects are in the crawler stage in May and June.
Scale Insects of Trees and Shrubs, http://www.extension.umn.edu/distribution/horticulture/DG1019.html#Lecanium
12. Elm Flea Weevil first appeared in the Midwest in 2003 and may now be throughout Nebraska. The adult weevil is very tiny (1.6 mm long), dark brown to black, with a prominent “snout”. They can jump when disturbed. Adult feeding results in tiny shot holes in the leaves. At this time, it appears to feed mainly on Siberian elm (Ulmus pumila) which is commonly called Chinese elm in Nebraska. Morton Arboretum is reporting feeding on hybrids containing U. pumila, particularly “Homestead”. Most trees will recover with good plant health care practices. On high value trees or trees under stress, insecticides may be applied as soon adults appear and feeding is noticed. It is late now to apply insecticides.
Elm Flea Weevil, http://www.ipm.msu.edu/cat08land/l06-27-08.htm#9
13. Ash Rust- Yellow/orange, raised spots (pustules) on leaves. This fungal disease may cause some twisting of foliage and leaf drop. Ash rust is not a serious disease of trees. Fungicide control is not recommended or needed.
Ash Rust, http://www.ianrpubs.unl.edu/sendIt/g1942.pdf
14. Maple bladder galls are bright red galls that later turn black, usually on the upper leaf surface of maple leaves. When galls turn black, they may fall out of leaves, resulting in small holes. A few leaves may be so infested they drop from the tree, but leaf drop is uncommon. Galls are caused by the feeding of a tiny mite and do not affect the health of the tree. If desired, the time to treat is at spring bud swell, with horticultural oil. Treatment is not effective once the galls are visible.
Maple Bladder Galls, http://www.ipm.iastate.edu/ipm/hortnews/1998/6-5-1998/maplegall.html
15. Two-spotted Spider Mites infest a large variety of plants. Mites and their webs can barely be seen with the naked eye. Mites feed by sucking plant juices with piercing-sucking mouth parts, causing white or yellow speckling on leaves; then off-green to bronze discoloration. Controls range from hosing down plants with a strong spray of water (syringing) to using insecticidal soaps, or using miticides (Kelthane) or insecticides (Pyrethrin) when mites are active. Tap a branch over a white sheet of paper to monitor for active mites. They’ll appear as specks moving around on the paper if present. Mites can be in the egg stage so monitoring should continue for one to two weeks. NOTE: Carbaryl (Sevin) can increase mites by killing their predators such as lady beetles and is not recommended.
Spider Mites and Their Control, http://ohioline.osu.edu/hyg-fact/2000/2012.html
Spider Mites, http://www.ext.colostate.edu/PUBS/insect/05507.html
16. Powdery Mildew causes the leaves of many ornamentals to appear dusted with white powder. This fungus commonly infects 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 plants. A number of commercial fungicides are labeled for mildew on ornamentals and can reduce the disease if applied early enough. 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 planting susceptible plants, increase air circulation around plants, avoid excess nitrogen fertilizer and overhead irrigation, and clean up infected plants or plant parts on a regular basis.
Powdery Mildew, http://www.hort.wisc.edu/mastergardener/features/diseases/powderymildew/pm.htm
17. Phlox Plant Bug Feeding occurs on upper leaf surfaces of young phlox leaves and buds. Injury appears as white or pale-green spots that later become yellow-stippled areas. Blossoms may be deformed. In extreme cases, plants become stunted and die. Adult bugs generally have contrasting colors, i.e. orange and black or red and black, sometimes gray and white or yellow; all with black legs. Nymphs are orange or bright red. This insect overwinters in the egg stage with nymphs emerging in early May. Remove infested plant parts. The use of insecticidal soaps, horticultural oils, or systemic insecticides will reduce damage.
18. Slime Mold in Mulch Slime molds sometimes look like dog vomit and can come in many bright colors, while others appear as a grayish mass. Slime molds feed on decaying material and are often found in mulched ornamental beds. They are unsightly, but otherwise harmless to plants. The mulch can be raked to break up the appearance of slime molds. They will disappear during dry weather.
19. Tomato Early Blight and Septoria Leaf Spot are the two most common tomato diseases. Both are fungal and begin as leaf spots on lower leaves, then work their way up the plant causing foliage to die; often leading to fruit sunscald. Both 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. Applications should be 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 tomato 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, http://www.oznet.ksu.edu/hfrr/extensn/problems/earlblht.htm
Tomato Disease I.D. Key, http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/TomKey.html
20. Tomato Leaf Roll is not a disease or insect and no pesticide control is needed. When tomato plants grow vigorously during mild, moist weather; top growth can exceed root growth. When the first hot days of summer arrive, roots cannot keep up and plants slow moisture lost from leaves by rolling leaves upward. Tomato leaf roll can also occur after a heavy cultivation, a hard rain, or any sudden weather change. Too much rain or irrigation can saturate soil and suffocate roots. A root system lacking soil oxygen cannot function well to move water to upper plant parts, resulting in the same symptoms that occur with too little soil moisture. Avoid deep hoeing close to plants, mulch to moderate soil moisture extremes, and water to keep the soil moist but not waterlogged. Leaf roll is temporary.
21. Cucumbers are infected by a number of fungal leaf diseases. As with tomato diseases, apply fungicides at the first sign of foliar leaf spots and repeat application according to label directions. Remove and destroy heavily infected plants. Avoid overhead irrigation. Plant disease resistant varieties and use crop rotation.
Cucumber Disease I.D. Key, http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/CucKey.html
22. Bolting is premature flowering in plants and common in cole crops, beets and rhubarb. It can reduce yields or affect produce quality. When plants send up flower stalks, remove the stalk before seeds are produced. This year bolting was most likely due to the hot, dry conditions encountered earlier this spring. Planting too large of transplants, stress, and weather extremes lead to bolting.
23. Cabbage Loopers are light green with light colored stripes and up to 1½ inches long. They move by a looping motion. Adults are brown, night flying moths that lay eggs in May. Loopers feed from leaf undersides and create ragged holes between leaf veins. They also feed on cabbage, broccoli and cauliflower heads. With two to three generations per season, they are present all season. At this time of year, control with Dipel (Bacillus thuringiensis) or carbaryl (sevin). They can be controlled with floating row covers if these are placed over plants before moths emerge to mate and lay eggs.
24. Tomato Ring Spot Virus of Raspberry is being reported in Omaha. The most common symptom is the production of crumbly fruit, stunted plants and leaf yellowing. Leaves may have pale ring spots in spring which disappear later in the season. For control, purchase only Certified Virus-Tested stock, promptly remove and destroy infected plants, and control aphids which carry the virus from plant to plant.
