09 August 2016 |

Horticulture Newsletter 2016, No. 32

Written by K-State Horticulture Newsletter - Newsletters

Video of the Week:
When is a Watermelon Ripe on the Vine?

Upcoming Events:

August 15       K-State Vegetable Research Field Day, Olathe
                        http://hnr.k-state.edu/events/2016%20GG%20Vegetable%20Research%20Tour.pd

Vegetables:
Harvesting Winter Squash

Picture
Summer squash such as zucchini and scallop are harvested while immature but winter squash such as acorn, hubbard and butternut are harvested later, in the mature stage, after the rind is tough and seeds have developed. We normally think September is the time that winter squash are harvested. Harvesting too early leads to fruit that shrivels and rots.
 
There are two main characteristics that help tell us when winter squash are mature: color and rind toughness.  Winter squash change color as they become mature. Butternut changes from light beige to deep tan. Acorn is a deep green color but has a ground spot that changes from yellow to orange when ripe. Gray or orange is the mature color for hubbard.
     
A hard, tough rind is another characteristic of mature winter squash. This is easily checked by trying to puncture the rind with your thumbnail or fingernail. If it easily penetrates the skin, the squash is not yet mature and will lose water through the skin -- causing the fruit to dry and shrivel. Also, immature fruit will be of low quality. The stem should also be dry enough that excessive water doesn’t drip from the stem.
     
Winter squash should be stored cool with elevated humidity. Ideal conditions would be 55 to 60 degrees F and 50 to 70 percent relative humidity. Under such conditions, acorn squash will usually last about 5 to 8 weeks, butternuts 2 to 3 months and hubbards 5 to 6 months.  (Ward Upham)

Fruit:
Fertilize Strawberries

Picture
An August application of nitrogen on spring-bearing strawberries is important in order to increase the number of strawberries produced next spring. Plenty of daylight and warm temperatures during June, July and August promotes the growth of new runner, or daughter, plants. As daylight hours dwindle and temperatures grow cooler in September and October, fruit buds for the next year's fruit crop develop. To get a good berry crop next spring, it is important for strawberry plants to be vigorous during this period of fruit bud development.
     
Nitrogen, applied mid August, will help promote fruit bud development. A general application rate is ½ to 3/4 pound of actual nitrogen per 100 feet of row. The nitrogen may be in the form of a fertilizer mixture such as ammonium phosphate or 12-12-12, or in a fertilizer containing only nitrogen such as urea or ammonium nitrate. Some specific examples would include:
 
     Iron + (11-0-0) at 6 pounds per 100 feet of row.
     12-12-12 at 5.5 pounds per 100 feet of row.
     Nitrate of Soda (16-0-0) at 4 pounds per 100 feet of row
     Ammonium sulfate (21-0-0) at 3 pounds per 100 feet of row
     Urea (46-0-0) at 1.5 pounds per 100 feet of row
 
On sandy soils, the rate may be increased by about a half. After spreading the fertilizer, sprinkle the area applying at least a half-inch of water to move the nitrogen into the strawberry root areas. (Ward Upham)

Turfgrass:
Recommended Tall Fescue Cultivars

Picture
Though several cool-season grasses are grown in Kansas, tall fescue is considered the best adapted and is recommended for home lawns. The cultivar K-31 is the old standby and has been used for years. However, there is a myriad of newer cultivars that have improved color, density and a finer leaf texture. Most of these newer varieties are very close to one another in quality.
     
Each year the National Turfgrass Evaluation Trial rates tall fescue varieties for color, greenup, quality and texture. Quality ratings are taken once a month from March through October. The cultivars listed below received an average rating of 6.0 or above when 2013 and 2014 ratings were averaged.  Note that  K-31 consistently rates at the bottom. The highest rated cultivars were Thor, Michelangelo, GTO, Traverse 2, Technique, Maestro, Firebird 2, 4th Millennium SRP, Reflection, Black Tail, Avenger II, Falcon V, Terrano, Rowdy, Rockwell, Rhambler 2, Hot Rod, Firewall, Bizem, Titanium 2LS, Hemi, Firecracker, Leonardo and Grande 3.
     
There are a number of other cultivars that did not make this list but should do well in Kansas. Go to http://www.ntep.org/states/ks2/ks2_tf.htm for access to the data.  Keep in mind that mixes of several varieties may allow you to take advantage of differing strengths. It is not necessary for mixes to contain only the varieties mentioned above.
     
Though K-31 may still be a good choice for large, open areas, the new cultivars will give better performance for those who desire a high-quality turf. (Ward Upham)

Kentucky Bluegrass Variety Selection for Cool-Season Lawns

Picture
Though Kentucky bluegrass is not as heat and drought tolerant as tall fescue and the warm-season grasses, it is commonly used in northeastern Kansas, where there is sufficient annual rainfall. It is also grown under irrigation in northwestern Kansas where the higher elevation allows for cooler summer night temperatures. The following cultivars have performed well compared to other bluegrasses in this region. Use this list as a guide. Omission does not necessarily mean that a cultivar will not perform well.
     
Recommended cultivars for high-quality lawns, where visual appearance is the prime concern, include Alexa II, Aura, Award, Bewitched, Barrister, Belissimo, Beyond, Diva, Everest, Everglade, Excursion, Ginney II, Granite, Impact, Midnight, NuChicago, NuGlade, NuDestiny, Rhapsody, Rhythm, Rugby, Skye, Solar Eclipse, STR 2485, Sudden Impact, Washington and Zifandel. Such lawns should receive 4 to 5 pounds nitrogen per 1,000 square feet per year and would typically be irrigated during dry periods to prevent drought stress.   Cultivars that do relatively well under a low-maintenance program with limited watering often differ from those that do well under higher inputs. Good choices for low maintenance include Baron, Baronie, Caliber, Canterbury, Dragon, Eagleton, Envicta, Kenblue, North Star, and South Dakota. Instead of the 4 to 5 pounds of nitrogen per 1,000 square feet per year, low-maintenance program would include 1 to 2 pounds of nitrogen per 1,000 square feet per year. Obviously, a low-input lawn will not be as attractive as a higher-input lawn, but you can expect the cultivars listed above to look fairly good in the spring and fall, while going dormant in the summer. (Ward Upham)

Pests:
Dutch Elm Disease (DED)

Picture
People often assume that all of our American Elms have been killed by Dutch elm disease. Fortunately, such is not the case. Though many have survived thus far, the number diminishes each year. We are still seeing examples of Dutch elm disease on American elms. Though American elms are the species often associated with this disease, red and some hybrid elms are also susceptible. Siberian elm (sometimes referred to as Chinese elm) and the true Chinese elm (lacebark elm) are considered resistant but not immune to the disease.  However, we do have true American Elms that are naturally resistant.  Our January 19 issue of this newsletter has an article on these cultivars. That issue can be found at: http://hnr.k-state.edu/extension/info-center/newsletters/2016/Jan19_2016_3.pdf  .
     
Early diagnosis can help save recently infected trees. Look for branches with leaves that have wilted and suddenly turned yellow to brown. Remove a portion of the branch and peel back an area of the bark. If you notice brown streaking in the sapwood, you may have Dutch elm disease. Healthy bark is more cream-colored and the streaking is absent. Suspect wood should be submitted to the diagnostic lab and control measures started immediately.
     
Dutch elm disease can often be controlled through the use of systemic fungicide injections, judicious pruning of affected trees and removal of nearby diseased elms. However, trees infected through root grafts with nearby infected elms or those in which the disease has reached the main stem cannot be saved. Therefore, preventative measures have a better chance of success and are preferred. Fungicides labeled for Dutch elm disease include Arbotect and Alamo. The Arbotect fungicide is preferred because it is the most persistent with a three-year interval between injections. A trained arborist should administer injections. These treatments are quite expensive. Check with your local arborist for current prices.
 
Megan Kennelly, one of our plant pathlogists, has a more detailed discussion of this disease in our Turf Blog.  See http://blogs.k-state.edu/turf/dutch-elm-disease/  (Ward Upham)

Pine Tip Moth

Picture
Peak flight of the third generation of Nantucket Pine Tip Moth occurred on August 2 in the Wichita area.   The best time for control is a spray 10 days following peak flight of the insect.  Therefore, the OPTIMUM day for control will be on August 12, 2016 for the Wichita area. Note that growers further north will spray later.
 
This is a pest primarily of scotch, ponderosa and mugo pines. Thanks to Willy Goevert of 4C Christmastree Farm that does the local pheromone trapping and monitoring of this pest.  (Ward Upham)
 
 
Contributors: Ward Upham, Extension Associate

Video of the Week:
When is a Watermelon Ripe on the Vine?

Upcoming Events:

August 15       K-State Vegetable Research Field Day, Olathe
                        http://hnr.k-state.edu/events/2016%20GG%20Vegetable%20Research%20Tour.pd

Vegetables:
Harvesting Winter Squash

Picture
Summer squash such as zucchini and scallop are harvested while immature but winter squash such as acorn, hubbard and butternut are harvested later, in the mature stage, after the rind is tough and seeds have developed. We normally think September is the time that winter squash are harvested. Harvesting too early leads to fruit that shrivels and rots.
 
There are two main characteristics that help tell us when winter squash are mature: color and rind toughness.  Winter squash change color as they become mature. Butternut changes from light beige to deep tan. Acorn is a deep green color but has a ground spot that changes from yellow to orange when ripe. Gray or orange is the mature color for hubbard.
     
A hard, tough rind is another characteristic of mature winter squash. This is easily checked by trying to puncture the rind with your thumbnail or fingernail. If it easily penetrates the skin, the squash is not yet mature and will lose water through the skin -- causing the fruit to dry and shrivel. Also, immature fruit will be of low quality. The stem should also be dry enough that excessive water doesn’t drip from the stem.
     
Winter squash should be stored cool with elevated humidity. Ideal conditions would be 55 to 60 degrees F and 50 to 70 percent relative humidity. Under such conditions, acorn squash will usually last about 5 to 8 weeks, butternuts 2 to 3 months and hubbards 5 to 6 months.  (Ward Upham)

Fruit:
Fertilize Strawberries

Picture
An August application of nitrogen on spring-bearing strawberries is important in order to increase the number of strawberries produced next spring. Plenty of daylight and warm temperatures during June, July and August promotes the growth of new runner, or daughter, plants. As daylight hours dwindle and temperatures grow cooler in September and October, fruit buds for the next year's fruit crop develop. To get a good berry crop next spring, it is important for strawberry plants to be vigorous during this period of fruit bud development.
     
Nitrogen, applied mid August, will help promote fruit bud development. A general application rate is ½ to 3/4 pound of actual nitrogen per 100 feet of row. The nitrogen may be in the form of a fertilizer mixture such as ammonium phosphate or 12-12-12, or in a fertilizer containing only nitrogen such as urea or ammonium nitrate. Some specific examples would include:
 
     Iron + (11-0-0) at 6 pounds per 100 feet of row.
     12-12-12 at 5.5 pounds per 100 feet of row.
     Nitrate of Soda (16-0-0) at 4 pounds per 100 feet of row
     Ammonium sulfate (21-0-0) at 3 pounds per 100 feet of row
     Urea (46-0-0) at 1.5 pounds per 100 feet of row
 
On sandy soils, the rate may be increased by about a half. After spreading the fertilizer, sprinkle the area applying at least a half-inch of water to move the nitrogen into the strawberry root areas. (Ward Upham)

Turfgrass:
Recommended Tall Fescue Cultivars

Picture
Though several cool-season grasses are grown in Kansas, tall fescue is considered the best adapted and is recommended for home lawns. The cultivar K-31 is the old standby and has been used for years. However, there is a myriad of newer cultivars that have improved color, density and a finer leaf texture. Most of these newer varieties are very close to one another in quality.
     
Each year the National Turfgrass Evaluation Trial rates tall fescue varieties for color, greenup, quality and texture. Quality ratings are taken once a month from March through October. The cultivars listed below received an average rating of 6.0 or above when 2013 and 2014 ratings were averaged.  Note that  K-31 consistently rates at the bottom. The highest rated cultivars were Thor, Michelangelo, GTO, Traverse 2, Technique, Maestro, Firebird 2, 4th Millennium SRP, Reflection, Black Tail, Avenger II, Falcon V, Terrano, Rowdy, Rockwell, Rhambler 2, Hot Rod, Firewall, Bizem, Titanium 2LS, Hemi, Firecracker, Leonardo and Grande 3.
     
There are a number of other cultivars that did not make this list but should do well in Kansas. Go to http://www.ntep.org/states/ks2/ks2_tf.htm for access to the data.  Keep in mind that mixes of several varieties may allow you to take advantage of differing strengths. It is not necessary for mixes to contain only the varieties mentioned above.
     
Though K-31 may still be a good choice for large, open areas, the new cultivars will give better performance for those who desire a high-quality turf. (Ward Upham)

Kentucky Bluegrass Variety Selection for Cool-Season Lawns

Picture
Though Kentucky bluegrass is not as heat and drought tolerant as tall fescue and the warm-season grasses, it is commonly used in northeastern Kansas, where there is sufficient annual rainfall. It is also grown under irrigation in northwestern Kansas where the higher elevation allows for cooler summer night temperatures. The following cultivars have performed well compared to other bluegrasses in this region. Use this list as a guide. Omission does not necessarily mean that a cultivar will not perform well.
     
Recommended cultivars for high-quality lawns, where visual appearance is the prime concern, include Alexa II, Aura, Award, Bewitched, Barrister, Belissimo, Beyond, Diva, Everest, Everglade, Excursion, Ginney II, Granite, Impact, Midnight, NuChicago, NuGlade, NuDestiny, Rhapsody, Rhythm, Rugby, Skye, Solar Eclipse, STR 2485, Sudden Impact, Washington and Zifandel. Such lawns should receive 4 to 5 pounds nitrogen per 1,000 square feet per year and would typically be irrigated during dry periods to prevent drought stress.   Cultivars that do relatively well under a low-maintenance program with limited watering often differ from those that do well under higher inputs. Good choices for low maintenance include Baron, Baronie, Caliber, Canterbury, Dragon, Eagleton, Envicta, Kenblue, North Star, and South Dakota. Instead of the 4 to 5 pounds of nitrogen per 1,000 square feet per year, low-maintenance program would include 1 to 2 pounds of nitrogen per 1,000 square feet per year. Obviously, a low-input lawn will not be as attractive as a higher-input lawn, but you can expect the cultivars listed above to look fairly good in the spring and fall, while going dormant in the summer. (Ward Upham)

Pests:
Dutch Elm Disease (DED)

Picture
People often assume that all of our American Elms have been killed by Dutch elm disease. Fortunately, such is not the case. Though many have survived thus far, the number diminishes each year. We are still seeing examples of Dutch elm disease on American elms. Though American elms are the species often associated with this disease, red and some hybrid elms are also susceptible. Siberian elm (sometimes referred to as Chinese elm) and the true Chinese elm (lacebark elm) are considered resistant but not immune to the disease.  However, we do have true American Elms that are naturally resistant.  Our January 19 issue of this newsletter has an article on these cultivars. That issue can be found at: http://hnr.k-state.edu/extension/info-center/newsletters/2016/Jan19_2016_3.pdf  .
     
Early diagnosis can help save recently infected trees. Look for branches with leaves that have wilted and suddenly turned yellow to brown. Remove a portion of the branch and peel back an area of the bark. If you notice brown streaking in the sapwood, you may have Dutch elm disease. Healthy bark is more cream-colored and the streaking is absent. Suspect wood should be submitted to the diagnostic lab and control measures started immediately.
     
Dutch elm disease can often be controlled through the use of systemic fungicide injections, judicious pruning of affected trees and removal of nearby diseased elms. However, trees infected through root grafts with nearby infected elms or those in which the disease has reached the main stem cannot be saved. Therefore, preventative measures have a better chance of success and are preferred. Fungicides labeled for Dutch elm disease include Arbotect and Alamo. The Arbotect fungicide is preferred because it is the most persistent with a three-year interval between injections. A trained arborist should administer injections. These treatments are quite expensive. Check with your local arborist for current prices.
 
Megan Kennelly, one of our plant pathlogists, has a more detailed discussion of this disease in our Turf Blog.  See http://blogs.k-state.edu/turf/dutch-elm-disease/  (Ward Upham)

Pine Tip Moth

Picture
Peak flight of the third generation of Nantucket Pine Tip Moth occurred on August 2 in the Wichita area.   The best time for control is a spray 10 days following peak flight of the insect.  Therefore, the OPTIMUM day for control will be on August 12, 2016 for the Wichita area. Note that growers further north will spray later.
 
This is a pest primarily of scotch, ponderosa and mugo pines. Thanks to Willy Goevert of 4C Christmastree Farm that does the local pheromone trapping and monitoring of this pest.  (Ward Upham)
 
 
Contributors: Ward Upham, Extension Associate

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