Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Hort Update for the Week of July 27, 2012
|1. Dormant Kentucky bluegrass lawns||Need ¼” inch irrigation every 4 weeks. Do not let fescue go dormant.|
|2. Windmill grass||Warm season, perennial causing weed issues|
|3. New Turf iNfo articles||Check them out at turf.unl.edu|
|4. Grub control rescue treatments||If needed, use the correct insecticide and irrigate|
|5. Improving turf in fall||Prepare now with grass selection and reserving equipment|
|Trees & Shrubs|
|6. Watering trees||Keep soils moist, not saturated. Use mulch wisely.|
|7. Early dormancy signs||Coloration & leaf drop seen in maples, boxelder, hackberry|
|8. Pruning times||Avoid pruning during heat and drought stress|
|9. Oak twig girdler||Small clusters of brown leaves on twig tips|
|10. Bagworms||Monitor evergreens for signs of small, brown bagworms|
|Emerald Ash Borer Found in Kansas City, Missouri||Missouri Department of Agriculture confirmed presence of EAB|
|11. Spider mites||Leaf stippling, yellowing and browning on the rise|
|12. Deadheading/ deadleafing perennials||Remove spent blossoms, flower stalks & dead leaves|
|13. Watering established flowers||Keep soil moist, but not saturated|
|Fruits & Vegetables|
|14. Fall gardening||Delay planting due to hot soil temperatures|
|15. Heat effects on vegetables||Bitterness, fruit sunscald, potatoes dying back, etc.|
|16. Heat effects on fruit||Watch for rapid ripening, quickly followed by rotting|
|17. Blister beetles||Gray, striped or black linear beetles; cause blistering|
1. Lawns and summer drought: With water use restrictions in place, and ongoing drought, Kentucky Bluegrass is going dormant or can be allowed to go dormant. Once the grass is dormant (brown), keep it alive by applying about ¼” inch of water every 4 weeks to hydrate plant crowns. Limit mowing and foot traffic on dormant lawns to avoid damage.
If possible, do not allow tall fescue lawns to go dormant. Tall fescue does not have as good of drought survival as Kentucky bluegrass and will likely thin if allowed to go extremely dormant. Watering with about ¼ inch every two to three weeks on tall fescue may be a good compromise. As tall fescue acreage expands, we’ll learn more. Use deep and infrequent irrigation when watering.
In communities with water use restrictions, there could be some dieback in tall fescue lawns. Overseed these areas in early September as needed. More info at Turf iNfo “How long will Kentucky bluegrass or tall fescue survive when dormant?
2. Windmill grass is a perennial warm season grass showing up in many lawns around the state. Other than digging out individual plants, the best means of control for homeowners are multiple applications of glyphosate (Roundup). Spot treat individual weeds and overseed bare areas in September. Commercial applicators can spot treat with Tenacity. Windmill grass must be green and actively growing for herbicides to be successful.
- Long summer: Crabgrass preemergence herbicide breakthrough.
- Goosegrass Marching Along
- Growth regulators losing impact as temperatures increase?
4. Grub control rescue treatments- In situations where preventive insecticides fail to provide adequate control or preventative products were not used and populations have reached 8 grubs per square foot, turf managers may need to use a rescue treatment. Curative treatments are with fast acting, short residual products such as carbaryl (Sevin) or trichlorfon (Dylox).
Post‐treatment irrigation is critical in these situations. To optimize the effectiveness of any these products, irrigate with ½ inch of water immediately following application. If conditions have been very hot and dry and grubs are deeper in the soil, a pretreatment irrigation of up to 1/2 inch applied 48 hours before the insecticide application should encourage grubs to move closer to the soil surface and enhance the level of white grub control.
5. Preparation for fall seeding/overseeding- Our hot, dry summer will lead to an increased need for seeding or over-seeding in September. Now is the time to select the turfgrasses and/or cultivars to plant; and to reserve equipment, like power rakes and core aerators, if needed.
Refer to the UNL Turf Info article on 1. Improving Turf in the Fall, 2. Choosing grasses for lawns in the Northern Great Plains (NEW).
Coming this week on the turf web page: “Establishing lawns with seed” and “Establishing lawns with sod”
6. Watering trees- Maintain a moist but not saturated soil to a depth of 12 inches around trees and just beyond the dripline. Moisture and oxygen are both critical to root establishment, root function, and to reducing drought stress. Frequency and amount of irrigation is dependent on soil type, site conditions, age, species of tree, and environmental conditions. As a general rule, for trees planted in the last 1 to 3 years moisten the soil to 12 inches about once a week.
Trees in place for more than five years benefit from a 12 inch deep watering every few weeks; in the absence of rain. Monitor the soil to determine the need to water and use a four inch layer of mulch in a four foot diameter ring around the tree to help conserve soil moisture.
7. Early dormancy signs in the form of leaf coloration and leaf drop have been showing up in trees, notably maple, hackberry and boxelder maple. This is due to the extreme heat and drought. These trees should be watered correctly and mulched.
8. Pruning trees is best avoided when trees are stressed or there energy is focused elsewhere. Typically, it is recommended not to prune trees during spring when they are leafing out and during late summer and early fall when they are going dormant and dropping leaves. With current heat and drought stress, pruning is best avoided this summer as well. Ideally, wait until trees go dormant to prune if possible.
9. Oak twig girdler may soon cause twig dieback in oaks. Squirrels chewing leaves off trees may be confused with girdler damage. Twig girdler is a small, slender, bronze-to-black beetle that emerges from May to September and deposits eggs on twigs at the junction between current and previous year's growth. Larvae hatch and bore into twigs. As they grow, they mine spirally so terminal clusters of dead leaves ("flags") appear in August and September. During the next year, larvae continue to mine deeper into twigs and complete development, pupating in the fall. While damage is obvious, it is rarely severe, and there is rarely a need for control.
Flat Headed Borers, University of Nebraska-Lincoln
10. Bagworms continue to be found on a variety of landscape plants. Damage is most severe on evergreens and these plants bear watching. If bagworm numbers are small, insecticide control is not justified or needed on broadleaf plants. On evergreens, bagworm control is justified. When bagworms are small (one-fourth to one-half inch long), the organic Bacillus thuringiensis is effective. Other insecticides for bagworms include Spinosad, carbaryl (Sevin), permethrin and bifenthrin.
At this time of year, bagworms are typically one-half to one inch long and feeding from inside brown, somewhat triangular shaped bags. In some cases, smaller bagworms are being found leading some to wonder if a 2nd generation is occurring this year.
Bagworms, University of Nebraska-Lincoln
Insect Threat to Missouri’s Ash Trees Expanding, Survey Underway
New Emerald Ash Borer Populations found in Platte and Reynolds Counties
(JEFFERSON CITY, Mo.) – One of the top threats to Missouri’s hundreds of thousands of ash trees has extended its reach beyond the existing quarantine area. The Emerald Ash Borer has killed more than 50 million U.S. ash trees in the last 10 years and researchers have now found signs of the invasive insect near Kansas City as well as signs of an expanding population in southern Missouri.
A single Emerald Ash Borer was identified in the Kansas City area last week by an alert aborist, near Parkville. Staff from the Missouri departments of Agriculture and Conservation and the USDA immediately joined that individual at the site. Emerald Ash Borers were also identified in Reynolds County last week through routine surveillance, adjacent to the known population in Wayne County. The Wayne County population was first identified in 2008.
The Missouri departments of Agriculture and Conservation work with federal staff from USDA Plant Protection and Quarantine and the U.S. Army Corps of Engineers, as well as researchers at the University of Missouri to monitor Missouri’s forests and urban areas for signs of the insect, as well as to inspect incoming shipments of nursery stock which may harbor the borers.
Representatives from those organizations, as well as other members of Missouri’s Invasive Forest Pest Council, will be collaborating on possible changes to Missouri’s Emerald Ash Borer Quarantine as a result of finding the insect in two new locations within the state this month. The group has already begun work on a survey to determine the extent of infestation in Platte and Reynolds counties. Those surveys will be ongoing throughout the summer and fall in a cooperative effort by local, state and federal agencies.
Wayne County is currently under federal and state quarantines, which prohibit moving hardwood firewood and living or cut ash trees and ash wood to prevent the accidental spread of the borer.
Although the Emerald Ash Borer can fly short distances on its own, much of its spread is due to humans transporting it burrowed under the bark of firewood, logs and tree debris. Consumers are encouraged to use other native tree species, rather than Ash trees, in their landscape plantings and to purchase firewood harvested near their destination when traveling and camping. Individuals can also check their trees for signs of the Emerald Ash Borer using the online guide available at eab.missouri.edu and report concerns about their trees by calling (866) 716-9974.
Researchers have not been able to determine exactly how or when the Emerald Ash Borer came into Missouri, but it’s believed the insect hitch-hiked into the state in a load of firewood carried by a vacationer from another area, as signs of the insects were first found at a campground in Wayne County near Wappapello Lake. The Emerald Ash Borer was first discovered in the U.S. in 2002, in Michigan. It has since spread to more than 15 states, including Missouri and Illinois, and Canada.
11. Spider mite populations are promoted by hot, dry weather. Mites affect a variety of plants from trees and shrubs to vegetables and flowers. They can be are difficult to detect. The first signs are yellowing and a whitish flecking on leaves. Check leaf undersides for spider mites or their webbing. A hand lens is needed to see them; or branches can be tapped over a white sheet of paper to check for active mites. Spider mites can be reduced with a strong spray of water directed at leaf undersides and repeated on a regular basis to remove mites, webs and dust. If insecticides are used, the right insecticides must be applied or mite population can increase.
Insecticides increasing Spider Mites: Spider mites frequently become a greater problem after application of insecticides. Such outbreaks can be a result of the insecticide killing natural enemies or certain insecticides stimulating mite reproduction. For example, spider mites exposed to carbaryl (Sevin) in the laboratory have been shown to reproduce faster than untreated populations. Carbaryl, some organophosphates, and some pyrethroids apparently favor mites by increasing the level of nitrogen in leaves. Insecticides applied during hot weather appear to have the greatest effect on mites, causing dramatic outbreaks within a few days.
If insecticide treatment for mites is needed, use selective materials, preferably insecticidal soap or insecticidal oil. Petroleum-based horticultural oils or neem oils are both acceptable. Do not use soaps or oils on water-stressed plants or when temperatures exceed 90°F. These materials may be phytotoxic to some plants, so check labels and/or test them out on a portion of foliage several days before applying a full treatment. Oils and soaps must contact mites to kill them so excellent coverage, especially on leaf undersides, is essential and repeat applications are often needed.
12. Deadheading and dead-leafing of perennials improves their appearance for the remainder of the season and can extend blooming in some cases. Deadheading is the removal of spent blossoms and flowering stalks on a regular basis. Dead-leafing is the removal of damaged or brown leaves. Do this practice on a regular basis.
13. Watering established flowers- Like trees and shrubs, most perennial flowers benefit from a consistently moist but not saturated soil. This year, even native drought tolerant plants are showing signs of water stress and will benefit from correct irrigation.
14. Hold off on fall gardening- Late June into mid-August is typically when some vegetables are planted for fall harvest. Vegetable seeds have a minimum and maximum soil temperature at which they will germinate. With above average soil temperatures this year, optimum and even maximum temperatures at which seed will germinate are exceeded. It would be wise to hold off on planting until soil temperatures moderate. If seed does germinate, heat and drought stress will be a challenge unless average conditions return. When conditions do moderate, be sure to check number of days to harvest and determine if there will still be time for plants to reach harvest age prior to our average fall frost date.
Fall Vegetable Gardening, University of Nebraska-Lincoln
15. Heat effects on veggies are wide ranging but include bitter cucumbers; blossom-end rot in tomatoes, peppers, zucchini and watermelon; poor fruit set; rapid or slow ripening; early plant dieback (i.e. potatoes); sunscald on fruit; poorly filled sweet corn ears; and the list could go on. About all we can do is to provide adequate moisture and mulch to conserve moisture and moderate soil temperatures. Monitor vegetable gardens closely and promptly harvest ripe produce. If potato plants dieback, harvest as soon as possible or the tubers may rot in warm soil.
16. Heat effects in fruits include slow ripening peaches, a yellow color to apples and pears, smaller fruit, lowered quality from reduced sugar content and shortened storage times. Again, provide adequate moisture and harvest promptly.
17. Blister beetles are about ¾ inch long, slender-bodied beetles that are typically gray, 3-striped, or black. Blister beetles release a caustic substance when crushed that can cause skin blisters. Blister beetles tend to move in swarms and can cause a great deal of plant defoliation, but tend not to stay in one area for long. They often move on in a day or two and plant damage stops. Blister beetles often feed on beans, peas, potatoes and other vegetables. Young beetles feed on grasshopper eggs and are considered somewhat beneficial.
If blister beetles are handpicked to control them, be sure to wear gloves to avoid skin blisters. Sevin insecticide is registered for their control, but does not do a good job of killing blister beetles. The greatest concern with blister beetles is if they get into grass hay and are eaten by horses. Blistering caused by beetles when horses eat the hay can kill a horse.
Blister Beetles in Alfalfa, Kansas State University
Trees & Shrubs
- Aster Yellows
- Hold off on dividing perennials until cooler temperatures
Fruits & Vegetables
- Tomato Early Blight
- Poor Fruit Set
- Blossom End Rot
- Squash Bug Scouting
- Squash Vine Borer
- Spray schedules