Hort Update for the week of 6/26/06
1. Bluegrass Billbug- Billbug larvae are legless, cream colored with reddish brown heads, and about ¼ to ½ inch in size. Their appearance is similar to a puffed grain of rice. Adult is a black weevil. Newly-hatched larvae tunnel in grass stems, hollowing out stems which break away near the crown. Older larvae feed on roots, causing turf to appear drought stressed. Under heavy billbug pressure, the lawn can brown and die. Billbug damage rarely occurs in turf stands less than three years old. Insecticides need to be applied in May to control the adult prior to egg laying.
Online info: http://entomology.unl.edu/turfent/documnts/billbugs.htm
2. Ascochyta Leaf Blight– Patches or large areas of lawn suddenly turn straw color. Leaf blades have bleached white tips and blade is constricted where dead tissue merges with green tissue. Considered a minor disease related to weather and management practices. Turfgrass usually recovers in one month or less. Fungicides generally not recommended. Thiophanate-methyl (Dragon Chemical Systemic; and Fungicide 3336WP) can be used. (NebFact 588).
Online info: http://www.ext.colostate.edu/pubs/garden/02901.html
3. Brown Patch or Rhizoctonia Blight (Rhizoctonia solani)- On home lawns, roughly circular patches of dead and dying grass. The center of diseased patches may be less affected and have a frog-eye-like symptom. Green plants within the affected area will have gray or tan colored, irregularly shaped leaf spots with reddish-brown margins. Preventive applications of Prostar (commercial use), Bayleton, and to some extent chlorothalonil (Daconil), do a fairly good job of suppressing the disease when applied at monthly intervals (June, July, August). Curative applications of chlorothalonil beginning a few days after symptoms of brown patch develop also may do an adequate job of suppressing injury. In many cases, lawns damaged by brown patch will recover in two to three weeks, provided the outbreak is not sustained by continuous hot, humid weather. Therefore, treatments may not be necessary to maintain the turf stand through the growing season.
Online info: http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/brnptch.htm
4. Reflection injury to turfgrass- A Kentucky bluegrass lawn in Lincoln was severely “burned” along a white fence through a combination of reflection off a white fence that had recently been power washed with a surfactant and the soil was extremely clayey and compacted.
5. Two-Spotted Spider Mite on Eastern Red Cedar- Symptoms of injury include flecking, discoloration (off-green to bronzing) and scorching of leaves. Injury can lead to leaf loss and plant death. Tap a branch over a white sheet of paper to monitor for active mites. They will appear as specks moving around on the paper. If mites are present, apply insecticides such as Acephate+fenbutatin-oxide (Ortho Systemic Insect Killer), insecticidal soap or horticultural oils and repeat in 7 to 10 days. NOTE: Carbaryl (Sevin) can increase mites by killing their predators.
Online info: http://www.ext.colostate.edu/PUBS/INSECT/05507.html
6. Verticillium Wilt on Smoke Tree (Cotinus)- Many tree and shrub species are infected by Verticillium wit. Initially, leaves on diseased branches may appear off-color and become limp or flaccid. These symptoms may appear on individual branches in a section of the tree crown or throughout the entire tree. In some cases, the disease progresses slowly over a period of months or years, resulting in gradual defoliation, branch dieback and a general tree decline. There is no control. For a list of Wilt resistant trees see:
Online info: http://ohioline.osu.edu/b614/b614_14.html
Or http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/vertic.htm
7. Fireblight in Crabapple and Cotoneaster-The first sign of fireblight bacterial infection is rapid browning of leaves towards the ends of branches. Brown leaves will hang on the tree/shrub and stem tips will bend over. Infected twigs, stems and branches turn almost black in color and develop cankers. Apples, pears, flowering crabs, mountain ash and cotoneaster are most susceptible. Prune out diseased stems cutting 8-12" beyond signs of the disease. Use a 10% bleach - 90% water mixture to sterilize pruners or saws between cuts. Fireblight is very contagious and easily spread. It can kill shrubs if they are susceptible and branches with canes are not pruned out.
Online info: http://www.extension.umn.edu/yardandgarden/ygbriefs/p223fireblight.html
8. Hawthorn Rust-Yellow-orange spots on leaves. Similar to cedar apple rust. Treat with a fungicide in spring as new growth appears and repeat 3 to 4 times until flower buds open. Too late to spray now. Nebguide 1327 Cedar apple and related Rusts of Apple and Ornamentals (not online).
Online info: http://www.extension.iastate.edu/Pages/plantpath/hawrust.html
Or http://ohioline.osu.edu/hyg-fact/3000/3055.html
9. Dutch Elm Disease- Initial symptoms include discoloration and wilting of foliage, usually detected on one or more small branches relatively high in the tree. Foliage first appears off-color then turns yellow. Wilt symptoms continue to progress on other branches in the tree crown over successive weeks or months. Eventually, foliage throughout the crown wilts and the tree dies. Thiabendazole (Arbotect 205) can be injected into trees prior to or just as they begin to show symptoms. It needs to be applied by trained personnel. Removing and destroying infected elms is critical to reducing the spread of DED. Do not save the wood for firewood at this time of year. http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/dtchelm.htm
10. Poor Planting Problems- We are seeing yellowing and branch dieback in plants planted into beds where weed mats are used and rock is the mulch. In these cases, the soil is either extremely dry or wet beneath the weed mat. This is not a good growing environment for roots.
11. Crumb Rubber Mulch Issue- Some plants in Omaha were dieing back. They were mulched with crumb rubber bark (larger pieces of rubber painted brown to appear like bark). A thermometer was placed next to the plants and temperatures were 120 degrees Fahrenheit. See information on mulches for the home landscape at http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=187
12. Boxelder Bugs- Orange to red nymphs and orangish-red and black adults have been reported in fairly large numbers around some homes. They feed on the seed (samara) of maple trees, but are harmless to trees, people and homes. Rake samaras away from foundations to reduce boxelder bug numbers. Do a good job of caulking and weather stripping to prevent nuisance home entry.
13. Hollyhock Weevil- One-eighth inch long gray weevils with a snout about as long as the body. They feed on hollyhock leaves and buds, chewing small, irregular holes. Females deposit individual eggs in holes in buds and larva attack and feed in maturing hollyhock seed, destroying it from the inside. Dust with carbaryl (Sevin) or spray with acephate (Orthene) to prevent serious damage. This insect is the primary reason hollyhocks do not seem to reseed very well after initial establishment. http://lancaster.unl.edu/hort/pest/Summer.shtml
14. Echinacea problem- In a test plot for Echinacea, some leaves have been chewed on by grasshoppers. The ragged edges now have a white, fungus-like growth on them. We are unsure what this is.
| Current Problems: | Major Symptom: |
Turf |
|
| 1. Bluegrass Billbugs | Browning of turf. May appear drought stressed. |
| 2. Ascochyta Blight | Patches or large areas of lawn suddenly turn straw or tan color. |
| 3. Brown patch | Roughly circular patches of dead and dying grass. |
| 4. Reflection injury to turfgrass | Kentucky bluegrass browning due to reflection & other factors. |
| Trees & Shrubs | |
| 5. Two-spotted spidermite | Evergreen foliage off green to bronze color. |
| 6. Verticillium wilt | Wilting and dieback of branches on trees or shrubs. |
| 7. Fireblight | Browning or blackening of leaves on branch tips. |
| 8. Hawthorn rust | Reddish-orange spots on leaf surfaces. |
| 9. Dutch elm disease | Leaf yellowing, browning and dieback of branches. |
| 10. Poor planting practices | Leaf yellowing, chlorosis, dieback. |
| 11. Crumb rubber mulch | Dieback of plants. |
| 12. Boxelder bugs | Orangish red bugs massing near maple trees. |
| Ornamentals | |
| 13. Hollyhock weevils | 1/8” or larger, round holes chewed in leaves. |
| 14. Echinacea problems | White fungus growing on grasshopper damaged leaf edges. |
1. Bluegrass Billbug- Billbug larvae are legless, cream colored with reddish brown heads, and about ¼ to ½ inch in size. Their appearance is similar to a puffed grain of rice. Adult is a black weevil. Newly-hatched larvae tunnel in grass stems, hollowing out stems which break away near the crown. Older larvae feed on roots, causing turf to appear drought stressed. Under heavy billbug pressure, the lawn can brown and die. Billbug damage rarely occurs in turf stands less than three years old. Insecticides need to be applied in May to control the adult prior to egg laying.
Online info: http://entomology.unl.edu/turfent/documnts/billbugs.htm
2. Ascochyta Leaf Blight– Patches or large areas of lawn suddenly turn straw color. Leaf blades have bleached white tips and blade is constricted where dead tissue merges with green tissue. Considered a minor disease related to weather and management practices. Turfgrass usually recovers in one month or less. Fungicides generally not recommended. Thiophanate-methyl (Dragon Chemical Systemic; and Fungicide 3336WP) can be used. (NebFact 588).
Online info: http://www.ext.colostate.edu/pubs/garden/02901.html
3. Brown Patch or Rhizoctonia Blight (Rhizoctonia solani)- On home lawns, roughly circular patches of dead and dying grass. The center of diseased patches may be less affected and have a frog-eye-like symptom. Green plants within the affected area will have gray or tan colored, irregularly shaped leaf spots with reddish-brown margins. Preventive applications of Prostar (commercial use), Bayleton, and to some extent chlorothalonil (Daconil), do a fairly good job of suppressing the disease when applied at monthly intervals (June, July, August). Curative applications of chlorothalonil beginning a few days after symptoms of brown patch develop also may do an adequate job of suppressing injury. In many cases, lawns damaged by brown patch will recover in two to three weeks, provided the outbreak is not sustained by continuous hot, humid weather. Therefore, treatments may not be necessary to maintain the turf stand through the growing season.
Online info: http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/brnptch.htm
4. Reflection injury to turfgrass- A Kentucky bluegrass lawn in Lincoln was severely “burned” along a white fence through a combination of reflection off a white fence that had recently been power washed with a surfactant and the soil was extremely clayey and compacted.
5. Two-Spotted Spider Mite on Eastern Red Cedar- Symptoms of injury include flecking, discoloration (off-green to bronzing) and scorching of leaves. Injury can lead to leaf loss and plant death. Tap a branch over a white sheet of paper to monitor for active mites. They will appear as specks moving around on the paper. If mites are present, apply insecticides such as Acephate+fenbutatin-oxide (Ortho Systemic Insect Killer), insecticidal soap or horticultural oils and repeat in 7 to 10 days. NOTE: Carbaryl (Sevin) can increase mites by killing their predators.
Online info: http://www.ext.colostate.edu/PUBS/INSECT/05507.html
6. Verticillium Wilt on Smoke Tree (Cotinus)- Many tree and shrub species are infected by Verticillium wit. Initially, leaves on diseased branches may appear off-color and become limp or flaccid. These symptoms may appear on individual branches in a section of the tree crown or throughout the entire tree. In some cases, the disease progresses slowly over a period of months or years, resulting in gradual defoliation, branch dieback and a general tree decline. There is no control. For a list of Wilt resistant trees see:
Online info: http://ohioline.osu.edu/b614/b614_14.html
Or http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/vertic.htm
7. Fireblight in Crabapple and Cotoneaster-The first sign of fireblight bacterial infection is rapid browning of leaves towards the ends of branches. Brown leaves will hang on the tree/shrub and stem tips will bend over. Infected twigs, stems and branches turn almost black in color and develop cankers. Apples, pears, flowering crabs, mountain ash and cotoneaster are most susceptible. Prune out diseased stems cutting 8-12" beyond signs of the disease. Use a 10% bleach - 90% water mixture to sterilize pruners or saws between cuts. Fireblight is very contagious and easily spread. It can kill shrubs if they are susceptible and branches with canes are not pruned out.
Online info: http://www.extension.umn.edu/yardandgarden/ygbriefs/p223fireblight.html
8. Hawthorn Rust-Yellow-orange spots on leaves. Similar to cedar apple rust. Treat with a fungicide in spring as new growth appears and repeat 3 to 4 times until flower buds open. Too late to spray now. Nebguide 1327 Cedar apple and related Rusts of Apple and Ornamentals (not online).
Online info: http://www.extension.iastate.edu/Pages/plantpath/hawrust.html
Or http://ohioline.osu.edu/hyg-fact/3000/3055.html
9. Dutch Elm Disease- Initial symptoms include discoloration and wilting of foliage, usually detected on one or more small branches relatively high in the tree. Foliage first appears off-color then turns yellow. Wilt symptoms continue to progress on other branches in the tree crown over successive weeks or months. Eventually, foliage throughout the crown wilts and the tree dies. Thiabendazole (Arbotect 205) can be injected into trees prior to or just as they begin to show symptoms. It needs to be applied by trained personnel. Removing and destroying infected elms is critical to reducing the spread of DED. Do not save the wood for firewood at this time of year. http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/dtchelm.htm
10. Poor Planting Problems- We are seeing yellowing and branch dieback in plants planted into beds where weed mats are used and rock is the mulch. In these cases, the soil is either extremely dry or wet beneath the weed mat. This is not a good growing environment for roots.
11. Crumb Rubber Mulch Issue- Some plants in Omaha were dieing back. They were mulched with crumb rubber bark (larger pieces of rubber painted brown to appear like bark). A thermometer was placed next to the plants and temperatures were 120 degrees Fahrenheit. See information on mulches for the home landscape at http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=187
12. Boxelder Bugs- Orange to red nymphs and orangish-red and black adults have been reported in fairly large numbers around some homes. They feed on the seed (samara) of maple trees, but are harmless to trees, people and homes. Rake samaras away from foundations to reduce boxelder bug numbers. Do a good job of caulking and weather stripping to prevent nuisance home entry.
13. Hollyhock Weevil- One-eighth inch long gray weevils with a snout about as long as the body. They feed on hollyhock leaves and buds, chewing small, irregular holes. Females deposit individual eggs in holes in buds and larva attack and feed in maturing hollyhock seed, destroying it from the inside. Dust with carbaryl (Sevin) or spray with acephate (Orthene) to prevent serious damage. This insect is the primary reason hollyhocks do not seem to reseed very well after initial establishment. http://lancaster.unl.edu/hort/pest/Summer.shtml
14. Echinacea problem- In a test plot for Echinacea, some leaves have been chewed on by grasshoppers. The ragged edges now have a white, fungus-like growth on them. We are unsure what this is.
