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Hort Update for Oct. 18, 2016

Major Symptom:
1. Kentucky bluegrass stem rust Orange-red powder in lawn, fungal, due to low N
2. Fall fertilization

Use quick release N only up until end of October

3. Too late to seed

Seeding after September 30 is not recommended

4. Broadleaf weed control

Okay to continue; process slowed by cold temperatures

5. Wildlife digging up earthworms/insects Sod turned over (raccoons); small holes with loose soil (skunks)
Trees & Shrubs


6. Pruning

Fall is not a good time to prune deciduous trees/shrubs

7. Pruning and oak wilt Avoid pruning oak in April, May or June
8. Rose pruning and winterization Avoid fall/winter pruning. Wait to put on winter protection.   
9. Random leaf spots Minor fungal diseases cause typically harmless leaf spots
10. Bagworms Highly visible on trees now. Handpick or plan to treat in June
Landscape Ornamentals  
11. Tender bulbs and bulb-like plants Dig tender bulbs and bulb-like plants ASAP
12. Planting bulbs October still a great time to plant hardy bulbs
13. Chrysanthemum winterization Improving fall-planted mum survival for spring
Fruits & Vegetables  
14. Strawberry fall care Good care ensures next year's harvest
15. When to prune fruit trees Best done in February/March
16. Cutting back asparagus Allowing stems to stand over winter provides some benefits
17. Minute pirate bugs Tiny dark-colored biting insects
18. Oak itch mites May be encountered when working under oak trees
19. New NebGuide available Fruit Tree Cultivars for Nebraska

1. Kentucky Bluegrass Stem Rust is a fungal disease that develops late in the season on lawns with slow growth due to low nitrogen. The obvious symptom is rust colored "powder" (fungal spores) on grass blades, shoes and lawn mower. Heavily infected turf may show yellowing of grass blades. Fungicide controls are rarely recommended or needed for home lawns. Fall lawn care, especially correct nitrogen fertilization, along with cooler fall weather promotes turfgrass growth and rust disappears.

Note for Sports Turf- If stem rust occurs on low maintenance athletic fields, the fungal spores can cause problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of wise turf management and timely fungicide applications. It is too late this season for fungicide controls.


2. Fall fertilization with nitrogen can continue up until the end of October.  Fertilizer products with fast release (water soluble) sources of nitrogen need to be used. Unless a soil test shows the need for phosphorous, avoid applying this nutrient to turfgrass. Examples of fast release nitrogen sources include Urea, Ammonium sulfate, any source listed as “ammoniacal or water soluble. Fertilization should not be done in November, or later, to reduce the risk of nutrient leaching or runoff.  

Transition From Slow to Quick Release Nitrogen, Nebraska Extension Turf iNfo


3. Window for seeding has closed in eastern and western Nebraska - Fall is the most successful time for seeding cool season turfgrasses. However, the window has closed for seeding this fall. The ideal window for seeding tall fescue is August 15 to September 15 and about August 20 to September 20 for Kentucky bluegrass. While both can be seeded up until late September into early October in eastern Nebraska, this later seeding is risky. Lawns can continue to be established from sod, although early fall is better for sodding too.

Establishing Lawns from Sod, Nebraska Extension
Establishing Lawns from Seed, Nebraska Extension


4. Perennial broadleaf weed control – how late? As temperatures become colder, the process of herbicide movement and weed kill slows, but can still be effective as long as the weed has green leaves. Broadleaf weed control is most effective with spot treatments of herbicides applied during fall. When night temperatures begin to fall into the 30s, plants initiate carbohydrate movement into the root system. This increases the movement of herbicide into roots to increase weed kill. Combination herbicides are generally more successful than individual active ingredients in controlling perennial broadleaf weeds.

Broadleaf Weed Control, Nebraska Extension Turf iNfo


5. Wildlife digging up white grubs and other insects - Shallow holes and loose soil (skunks), chunks of sod turned over (raccoons) or raised tunnels (moles) in lawns during fall are often due to wildlife. Skunks, raccoons and moles feed aggressively on earthworms and insects during fall to fatten up for winter.  Applying insecticides to prevent wildlife feeding is not recommended. Keep in mind that having wildlife dig in the lawn does not confirm there are white grubs. Wildlife feed on a variety of critters from earthworms to white grubs and numerous other types of insects. For suggestions on reducing damage, see the link below from Michigan State Extension.

Reduce Lawn Damge Caused by Moles, Skunks, and Raccoons, Michigan State University Extension


6. Pruning trees and shrubs is not recommended during fall coloration period. Disadvantages of fall pruning include: 1). new growth is stimulated and does not harden off before winter; 2). stored “food” in branches is removed before trees transport it into roots; 3). fall pruning wounds do not begin to callus over until new growth begins in spring and wounds are open to disease and/or insect pests; and 4). The risk of decay in wounds is increased during fall.  Dead, broken or diseased branches can be pruned when they are noticed. Otherwise, the ideal time to prune is late winter or early spring, except for oaks. 

Tree Pruning References, Nebraska Forest Service


7. Pruning to reduce oak wilt - If you live in an area where oak wilt is a concern, pruning of oaks should not be done during April, May or June to avoid spreading this disease. Oak wilt is caused by a fungus that is often carried by sap beetles attracted to fresh pruning wounds. It is lethal to oaks. Oaks in the red oak group (black oak, red oak and others with pointed leaf edges) are most easily infected and typically die within one to four months after being infected. Oaks in the white oak group (bur, white, swamp white and others with rounded leaf edges) are less susceptible. It may take one to seven years after infection for a white oak to die.

Oak Wilt – Identification and Management, University of Missouri Extension


8. When to prune roses and preparing roses for winter - Research has shown roses sustain less winter injury if they are pruned later in April. To prepare roses for winter, now is the time to clean up old leaves to reduce overwintering organisms. If a rose is a species or cultivar that requires winter protection, the key is not to put protection like mulch or rose cones in place too early. Wait until after two or three hard freezes before applying winter protection to insure the rose is fully dormant; which is a plants best protection against cold temperature. The goal of winter mulch is to help keep dormant plants dormant and help avoid freezing and thawing of soil that may injure roots. Putting mulch in place too early can delay dormancy and increase the risk of winter injury.

Preparing Roses for Winter, Nebraska Extension


9. Random leaf spots - After a fairly rainy summer, minor fungal leaf spot diseases infected some deciduous trees and shrubs; resulting in yellow, reddish or purple-brown spots on leaves or brown blighted areas. These leaf diseases are not a concern; especially late in the season. The infected leaves will soon drop off and the plant will produce new leaves next season. Even if infected, most leaves still had enough green leaf surface area for photosynthesis to occur; hence minor leaf spot diseases do little damage to trees. Unless a leaf disease causes severe defoliation earlier in the season, and for a number of years in a row, control is not necessary.   


10. Bagworms are about two inches long at this time of year and much easier to see on evergreen trees than they are during early to mid-summer; when they are smaller and moving about the tree to feed. Being easier to find, now into May is the time to hand-pick and destroy bagworms. While bagworms have stopped feeding, female bags can contain from 500 to 1000 eggs. Being in the egg stage now, insecticides will provide no control until after eggs hatch next year, typically from late May into June. If hand-picking bagworms is not feasible, mark calendars for insecticide control at the appropriate time next season. On evergreen trees, pesticide applications are justified from late May through July if bagworms are present.

Bagworms, Nebraska Extension


11. Tender bulbs and bulb-like plants are not winterhardy in Nebraska gardens if left in the ground. Dig them up as soon as possible and provide good storage conditions, so they can be grown again next year. This includes Canna, Gladiola, tuberous Begonia, Dahlia, Caladium, Alocasia (elephant ears) and Colocasia (elephant ears or taro plants).

Check bulbs and bulb-like plant, being overwintered indoors, monthly for signs of rot or excess drying. Any residual moisture and/or disease on the bulbs when they went into storage could cause problems down the road. Discard any bulb with mold or signs of rot.  If bulbs start to shrivel, this could indicate they are becoming too dry.  Dunk them in water to rehydrate them.  Repacking them for storage with dry sand, sawdust, vermiculite or peat moss may help reduce excessive drying.

Tender Perennials Need Indoor Protection, Purdue University Extension
Storing Tender Bulbs and Bulblike Structures, University of Minnesota Extension


12. Planting bulbs - October is still a great time to plant hardy bulbs.

Spring Flowering Bulbs, University of Nebraska-Lincoln
Planting Fall Bulbs, Backyard Farmer on YouTube


13. Chrysanthemum winterization - Maintain a moist, not wet, soil well into fall; especially for fall planted mums. Winter hardiness of chrysanthemums can vary from extremely hardy to non-hardy. Even "hardy" chrysanthemums may not consistently over-winter in Nebraska. Loose mulches, such as leaves, can increase winter survival. Plants should be mulched in late fall as soils begin to freeze. Winter mulch needs to be removed in early spring. Studies have also indicated that leaving the tops of chrysanthemum plants standing over winter can increase winter survival.

Garden Chrysanthemums, Nebraska Extension


14. Strawberry fall care - Strawberry flower buds begin to form in late summer, making this an important time of year to maintain soil moisture. Renovation of the planting should have been done in late June, but additional thinning is required in late summer. Strive for a spacing of 5 to 7 plants per square foot by mid-October for optimum fruit production next year. Thin by removing small, weak plants and any new runners or daughter plants that have not rooted down. Removing these will redirect plant energy into flower buds. Cultivate, or hoe carefully to remove weeds without damaging roots. Strawberry plantings must be mulched for winter to reduce damage to strawberry crowns and flower buds. Most unprotected cultivars are injured at 15°F. Do not apply mulch too early as it can delay hardening off, making plants more susceptible to winter injury, and increase crown rot. Wait until late November or early December when the soil has frozen to a depth of 1/2 inch or air temperatures have dropped to the 20s; then apply mulch to a depth of four to six inches. Suitable mulches include wood chips, pine straw, straw, clean hay or any loose mulch that will not compact heavily.

Fall and winter care of strawberries, Nebraska Extension
Growing Strawberries, University of Illinois Extension


15. Wait to prune fruit trees until late February-March. The best time for pruning fruit trees for fruit production is in late winter, into early spring, depending on the weather. See the following publication for more information on fruit tree pruning.

Pruning Fruit Trees, Nebraska Extension


16. Cutting back asparagus in fall is a common practice for many gardeners. But allowing asparagus stems to stand does provides some benefits to plants.

  • Standing asparagus fronds trap snow during winter, providing moisture for the crown as the snow melts.
  • Nutrients in the stems are transported into the plants' crown if stems are allowed to stand until later winter, February or March. By then the stems will be brown and all nutrients will have moved into the plant crown.
  • Allowing asparagus fronds to stand in late winter delays new stem emergence, which can be a useful technique where late freezes are common.

However, if you have an older female cultivar of asparagus, such as Mary or Martha Washington, asparagus seedlings can become a problem in the garden. In this case, cutting back stems in the fall and removing as much seed as possible from the garden minimizes asparagus weed problems next year.


17. Minute pirate bugs - During the late summer, small insects known as minute pirate bugs cause painful bites that seem out of proportion with their size. The minute pirate bug is about 1/8-inch long, oval to triangular in shape, flattened and black with whitish markings on the back. Normally, they are predators and feed on insect eggs and small insects. They feed by impaling their prey with their short blunt beak and sucking the juices.

Minute pirate bugs are found throughout the summer in fields, woodlands, gardens and landscapes. In the late summer, they begin the unpleasant behavior of biting humans. They do not feed on blood or inject a venom or saliva.

People differ in their response to pirate bug bites. Some people have no reaction to the bite, but others have bites that swell like a mosquito bite or turn red. Because the bite is noticeable and the pirate bug doesn't fly quickly, the victim is usually able to successfully smash the offending insect.

Control of minute pirate bugs is not practical. Repellents are generally not effective, although some people have found applying baby oil or suntan oil liberally to the skin may prevent some bites by coating the pirate bugs with oil.

Tiny Biting Bugs - Minute Pirate Bugs & Hackberry Lacebugs, Nebraska Extension


18. Oak itch mites – Reports of itch mite bites are being received from workers performing landscape clean up tasks beneath oak trees. Female itch mites are present in oak leaf margin galls in fall and could fall on people working beneath trees. Signs of itch mite attack on humans are red welts on the neck, face, arms and upper torso. Normally bites are not found on the legs, which distinguishes these bites from those of chiggers.

Oak trees with margined leaf fold galls indicate the likelihood of itch mite activity. When working under trees, especially if raking leaves, wear long sleeves, long pants and a hat. Use an insect repellent containing DEET or picaridin. Avoid direct handling of leaves and lawn clippings. Remove clothing each day and launder them, since mites can remain in the fabric for several days. Take a warm shower soon after coming indoors, since the mites need about four hours on your body to produce a bite. Let homeowners know about this problem and advise that they should not sit under these trees.

Pymotes Itch Mites, Nebraska Extension


19. New NebGuide available - Fruit Tree Cultivars for Nebraska is now available through Nebraska Extension at Proper fruit cultivar (variety) selection is important for successful and satisfying results from the home gardener’s efforts. Selection should be based on family preferences, available space, and intended use of the fruits. If properly chosen, harvest can be spread over several weeks if cultivars with different periods of maturity are planted.

Horticulture industry professionals should homeowners select fruit cultivars best-adapted for cultivation in the part of the state in which they live. The cultivars must have adequate hardiness to survive the winter; heat and drought tolerance to thrive in the summer; and the ability to escape or survive spring frosts.