Horticulture 2022 Newsletter No. 29

Horticulture News



Blog Post: http://www.ksuhortnewsletter.org

Video of the Week: Dividing Iris

The Kansas Turf & Ornamental Field Day will be held Thursday, August 4 at the John C. Pair Horticulture Research Center (1901 E. 95th St. S., Haysville, KS)
The field day program is designed for all segments of the turf & ornamentals industry – lawn care, athletic fields, golf courses, landscape, nursery, and grounds maintenance. Included on the program are research presentations, problem diagnosis, commercial exhibitors, and equipment displays. There will be time to see current research, talk to the experts and get answers to your questions.
One hour of pesticide recertification credit in both 3A and 3B are available, as well as GCSAA education points.
For more information, go to www.kansasturfgrassfoundation.com, or you can register online at https://2022turfday.eventbrite.com

• Deadhead annual flowers that need it.
• Spray sweet corn for corn earworm if silks haven’t turned brown yet.
• Take soil test if establishing or overseeding a lawn this fall.

Anthracnose on Cucumbers
This is a disease that appears whenever we have a hot and humid summer. Vegetables most affected include cucumbers, muskmelons and watermelons. This year, cucumbers seem to be most impacted this year. Squash and pumpkin are not attacked.
Look for brown to black lesions on the leaves that my disintegrate resulting in a tattered appearance to the leaves. There may also be elliptical lesions on the stems and leaf petioles. During wet weather, these lesions may be covered with a pink to buff-colored spor mass.
Crop rotation can help prevent the disease as can the use of clean seed. Crop rotations should be a minimum of 3 to 4 years long to prevent carryover of disease spored from crop debris. Periodic
fungicide applications may be necessary during wet weather in mid-summer. Apply chlorothalonil (Bonide Fungonil Concentrate, Daconil, Ortho Garden Disease Control, Fertilome Broad-Spectrum Landscape and Garden Fungicide, others) or mancozeb (Bonide Mancozeb Flowable). (Ward Upham)

Pine Needle Scale Control Window Approaching
Pine needle scale is an armored scale that is found across the United States but especially in the eastern half of the country. Pine needle scale appears as conspicuous white specks on the needles. Scales feed by sucking sap from needles causing them to yellow and eventually brown. Heavy infestations can kill twigs, branches and even entire trees.
Though both female and males are white, the female is larger (1/8-inch long) and wider at one end with the narrow end sporting a yellow or orange cap. Males are 1/32-inch long and narrow. Crawlers are bright red to purple to brown.
Pine needle scale overwinters as eggs underneath female covers. Each female produces about 100 eggs. There are two generations per year in Kansas with crawlers appearing in May to early June and again in mid- to late-July. So now is the time to start looking for the second-generation crawlers. Use a hand lens to look for the crawlers. Crawlers may be easier to see by wrapping a group of needles with one of the following:
– double sticky tape
– white tape smeared with petroleum jelly
– colored electrical tape smeared with petroleum jelly.
Choose a color that allows the crawlers to show up. Spray when the crawlers start showing up on the tape.
Effective insecticides include but are not limited to acephate (Acephate, Orthene), cyfluthrin (Tempo, BioAdvanced Vegetable & Garden Insect Spray), and permethrin (38 Plus Turf, Termite & Ornamental Insect Spray; Eight Vegetable, Fruit & Flower Concentrate or Garden and Farm Insect Spray). Remember, insecticides must be applied to crawlers soon after they emerge. Once the scale has settled down and formed its waxy cover, insecticides are ineffective. (Ward Upham)

When to Harvest Grapes
It takes more than color to determine when to harvest grapes. Grapes often are fully colored before they are fully ripe. Look for a whitish coating on the fruit and look for the seeds to change from green to brown. The final test is to taste the berries for sweetness. Grapes don’t continue to ripen once they are removed from the vine so be sure the quality is there before harvesting.
Once harvested, grapes can be stored for up to eight weeks if kept at 32 degrees with 85 percent relative humidity. Other attractive options are available as well including making juice, jellies, jams and wine. (Ward Upham)

Prop Up Fruit Tree Limbs if Needed
Heavy fruit loads this season may cause limbs to break if they are not given extra support. As fruits increase in size, the additional weight on individual branches may be substantial. One-inch thick boards that are 4 inches wide can be used to prop up limbs. You may wish to use two boards that overlap so the amount they overlap can be adjusted to change the total length of the board. Two to three screws can hold the two boards together. Cut a “V” on the top edge of the board on which the limb will rest so that it doesn’t slip off. Long limbs that are heavily loaded with fruit may need a prop in the center and another to support the outer part of the limb.
A plastic belt-like material that is about 2 inches wide may also be used. This can be tied to a heavily loaded limb, then to a large diameter limb above for support. Where a large limb is used for support, it is good to have it supporting limbs on opposite sides so the weight is balanced.
Another solution is to wrap a tape or belt material around the tree in a spiral to prevent limbs from bending until they break. Heavy twine may be used, but it should be removed when the fruit is picked or soon after so it does not cut into the bark on the limb.
Check trees regularly, up to two times a week during the last month the fruit are maturing. You will find additional limbs that need support. Tending to the heavily loaded tree limbs will reduce the number of broken limbs and help keep a balance of the fruiting wood in your tree. Next year, prune long, weak branches back to a side branch to help prevent this problem. (Ward Upham)
Dividing Iris
Bearded irises are well adapted to Kansas and multiply quickly. After several years, the centers of the clumps tend to lose vigor, and flowering occurs toward the outside. Dividing iris every three to five years will help rejuvenate the planting and increase flowering.
Iris may be divided from late July through August, but late July through early August is ideal.
Because iris clumps are fairly shallow, it is easy to dig up the entire clump. The root system of the plant consists of thick rhizomes and smaller feeder roots. Use a sharp knife to cut the rhizomes apart so each division consists of a fan of leaves and a section of rhizome. The best divisions are made from a double fan that consists of two small rhizomes attached to a larger one, which forms a Y-shaped division. Each of these small rhizomes has a fan of leaves. The rhizomes that do not split produce single fans. The double fans are preferred because they produce more flowers the first year after planting. Single fans take a year to build up strength.
Rhizomes that show signs of damage due to iris borers or soft rot may be discarded, but you may want to physically remove borers from rhizomes and replant if the damage is not severe. It is possible to treat mild cases of soft rot by scraping out the affected tissue, allowing it to dry in the sun and dipping it in a 10 percent solution of household bleach. Make the bleach solution by mixing one-part bleach with nine parts water. Rinse the treated rhizomes with water and allow them to dry before replanting.
Cut the leaves back by two-thirds before replanting. Cut the leaves at an angle rather than straight across to allow water to be shed. Prepare the soil by removing weeds and fertilizing. Fertilize according to soil test recommendations or by applying a complete fertilizer, such as a 10-10-10, at the rate of 1 pound per 100 square feet. Mix the fertilizer into the soil to a depth of 6 inches. Be wary of using a complete fertilizer in areas that have been fertilized heavily in the past. A growing number of soil tests show high levels of phosphorus. In such cases, use a fertilizer that has a much higher first number (nitrogen) than second (phosphorus). (Ward Upham)

Peonies with the “Measles” and Powdery Mildew
This is the time of year that peonies show symptoms of “measles” and/or powdery mildew.
Measles: Measles is a disease, also known as red spot, that causes distinct, reddish-purple spots on the upper leaf surfaces. These spots often coalesce and become large, reddish purple blotches on the upper leaf surfaces but are a light brown color when viewed from the underside of the leaves. The spots on stems will merge and form streaks that are reddish brown.
Powdery Mildew: Plants infected with powdery mildew look like they have been dusted with flour and can lead to death of the leaves. This disease isn’t as common in Kansas than Measles but does show up at times.
Sanitation is the best control for both these diseases. Remove all diseased tissue, including stems, at the end of the growing season. Actually, all foliage can be removed in mid-August with no harm to the plants as the plants will be essentially dormant. Foliage that has already died should be removed now.
Mulch that contains plant debris should also be discarded and then replaced with fresh mulch. Reducing the source of the inoculum will reduce the chances of another severe outbreak next year. (Ward Upham)

Contributors: Ward Upham, Extension Associate
Division of Horticulture
1712 Claflin, 2021 Throckmorton
Manhattan, KS 66506
(785) 532-6173

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