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Hort Update for October 8, 2021

Hort Update for October 8, 2021, Nebraska Extension,

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Serious ConcernsMajor Symptom
1. Armyworm turf recovery Pupa may be found now in areas with turf damage but survival is unlikely; focus on turf recovery
2. October growing degree days (GGD) Lincoln Airport 10/4/21 GGD -  3825,  Understanding Growing Degree Days
3. Fall drought concerns  Current conditions range from normal to extreme drought
4. Prepare for dormant lawn seeding Good seed-soil contact important for dormant seeding success
5. Magnolia scale control  Dormant season horticultural oil applications aids in control
Minor Issues
6. Fall sod installation  Moisture - through irrigation or rain - key to success
7. Complete fall fertilizer applications by October 30th  Later applications not well utilized by turf; contribute to water pollution
8. Late fall perennial weed control Guidelines for late fall applications
9. Fall lawn care to avoid snow mold  Fall cultural control prevention strategies
Timely Topics
10. Mowing leaves into the lawn Up to three inches of leaves can be mowed into turf at a time
11. Evergreen natural needle drop Yellowing & browning of interior needles
12. Avoid pruning spring blooming shrubs now Next year's flower buds are present and will be removed
13. Minute pirate bugs Tiny dark-colored biting insects active now; cause itchy welts

1. Armyworm turf recoveryPupa may be found now in areas with turf damage, but survival is unlikely; focus on turf recover

Fall armyworm pupal cases. Image by Gerald Bruning. Damage from an unusually high number of fall armyworm caterpillars has been widespread since early September. These insects, which are the immature stage of a moth, have moved on to the pupation stage. Many pupal cases, pictured right, may be found now in turf areas which had significant damage. UNL entomologists think it is unlikely the insects will survive the coming normal Nebraska fall frosts long enough to lay eggs and hatch a new generation of caterpillars. There just isn't enough time left for them to go through the pupal, adult and egg stages before another round of caterpillars could cause damage. If actively feeding insects are no longer present in damaged lawns, then insecticide applications will not be effective and are no longer recommended.

So what now? Many homeowners have significant turf damage. Fortunately, armyworm damage is primarily through leaf feeding with little damage to turf crowns. Lawns can recover if only partial leaf removal has occured or if the grass crowns - now exposed to much higher levels of sunlight - are protected from excess water loss and total desiccation before new leaves can be generated. Keep damaged areas watered and watch for the emergence of new leaf blades. A light 1/4 fertilizer application can be made to further stimulate new leaf development, if an early September application has not already been applied. 

If the turf is too badly damaged to recover, then overseeding is recommended. However, we are now out of the ideal window for Kentucky bluegrass and tall fescue seeding. If temperatures stay warm long enough for new seedlings to emerge, they are very susceptible to winter damage which could make the entire seeding a failure. A better option is dormant seeding, as outlined in Item #4 below. 

Another option is to lay new sod in damaged areas, as outlined in Item #6 below. 

Preventive fall armyworm control in 2022 is not recommended, because this insect seldom reaches high enough numbers to cause damage. It was about 15 years ago an outbreak like this last occurred. 

More information.
Fall Armyworms March Across Ohio, The Ohio State University
Controlling Fall Armyworms on Lawns and Turf, Alabama A& M and Auburn University Extension


3. Fall droughtCurrent conditions range from normal to extreme drought

2021 Sept Drought MapNebraska's current drought conditions range from normal to extreme drought. For more detail, refer to the Nebraska Drought Monitor map. In areas experiencing dry conditions, fall/winter watering are extremely important. Along with an increased risk of winter dessication and cold temperature injury, drought stressed trees and shrubs are more susceptible to attack by harmful pests like borers, canker disease and Verticillium wilt. Plant owners often believe their landscape plants survived a drought year, but then dieback shows up three to five years after a drought.

While most plants benefit from fall watering, the priority should be evergreens, newly planted trees and shrubs and younger woody plants. Soil needs to be kept moist to an 8” to 12” depth from the trunk/stems out to at least the dripline of trees and preferably well beyond. If plants are not mulched, a 3” to 4” deep layer of organic mulch, like wood chips, should be applied in at least a 4’ diameter ring around plants to conserve soil moisture. Be sure mulch is not piled against tree trunks and avoid continuously saturated soils. Winter watering may be needed in the absence of rain/snowfall. Water can be applied early in the day when soils are not frozen and air temperatures are above 40 to 45 degrees Fahrenheit.

Turf - September has been dry for much of the state and the non-irrigated turf is starting to look pretty stressed. While some fall drought stress can help induce deeper winter dormancy, too much drought stress can actually make turf more susceptible to winterkill. Apply enough irrigation to prevent visible drought stress but don’t overdo it. Let your eyes be your guide. Also, remember that aboveground irrigation components (such as a backflow preventer) should be turned off and drained before a hard frost or freeze. In-ground systems should be drained or blown out before winter. 

Professionals should monitor ongoing drought concerns as fall and winter progress, so you can advise clients on best practices to maintain plant health. 


4. Prepare for dormant lawn seedingGood seed-soil contact important for dormant seeding success

Dormant seeding is defined as such because seed lies dormant until soil temperatures warm in April or May. It can be done as early as Thanksgiving or as late as March in most Nebraska locations. The key is to seed after the soil is cold enough that germination will not occur until after soils warm in spring. The benefit of dormant seeding is as soil heaves and cracks during winter, crevices are created for seed to fall into, providing ideal germination conditions in spring. Dormant seeding may be easier to schedule than spring seeding, because spring rains can make it difficult to do final soil preparation and seed after March.

However, there are risks with dormant seeding. It is most effective if weather remains cold enough to delay germination until spring. Occasionally, extended warm periods in winter could allow seed to germinate, and seedlings may then be killed by ensuing cold weather.

As with any seeding, soil preparation needs to be done prior to seeding. For dormant seeding, this would be in fall before the soil freezes or during dry winter periods when the soil is not frozen. If using dormant seeding, monitor the area in mid spring for the need to do additional over-seeding.

On new sites, use a rototiller or other tillage equipment to work the soil six inches deep. To improve a clay or sandy soil, spread about one inch of compost over the area just before tilling. Do not incorporate sand to improve clay soil. It will likely become even more compacted. Do not till wet soil or soil clods will form. Avoid over-tilling any soil as this destroys soil structure.

To overseeding a thin lawn, core aerate the lawn a number of times to create holes for seed to fall into. If needed, compost can be spread over the turf and the area raked to work compost into aeration holes.

Next, buy quality seed from a reputable dealer. Blue tag certified seed is recommended to ensure a high germination percentage and fewer weed issues. Avoid buying seed from bulk bins.

Seeding is best done using a drop spreader. The easiest way to apply seed uniformly to a small area is to calculate and weigh out the amount of seed needed for an area. Set the spreader adjustment very low, sow seed in one direction and then sow at a right angle to the first. Repeat until the seed is gone.

The amount of seed recommended is two to three pounds per 1000 square feet for Kentucky bluegrass and six to eight pounds per 1000 square feet for tall fescue. It is not recommended to dormant seed perennial ryegrass.

Establishing Lawns from Seed, Nebraska Extension Turf Fact Sheet


5. Magnolia scale controlDormant season horticultural oil application aides in control

If customer trees had magnolia scale this summer, now is a good time to scout and determine the status of the infestation. It's likely infested plants will require more than one year of treatment, but fall applications to crawlers and early spring horticultural oil application can help reduce populations. 

Magnolia Scale, Morton Arboretum
Green and Growing Tip: Dormant Oil Spray, Backyard Farmer
Scale Insect Control, Backyard Farmer


6. Fall sod installationMoisture - through irrigation or rain - key to success

It is too late to seed or overseed turfgrass, but sod can still be laid until the soil freezes. The cool conditions of late fall and early winter can translate into a successful installation as long as irrigation is available to minimize desiccation on exposed sites. Soil preparation for late season sod installation is just as important as summer installation. Continue to ensure the turf has sufficient moisture during any dry period (November through March) occuring after installation, until spring rain begins. Delay fertilizer applications until spring if sod is installed in late fall. 

Establishing Lawns from Sod, Nebraska Extension Turf Fact Sheet


7. Complete fall lawn fertilization by October 30thLater applications not well utilized by turf; contribute to water pollution

Mid-September is the best time to apply fertilizer to cool season lawns. If fall fertilizer has not yet been applied, or a second application is to be made, only use fertilizers with fast release nitrogen sources and make the application no later than mid-late October.

Cool Season Lawn Calendar - Eastern Nebraska, Nebraska Extension


8. Late fall perennial weed controlGuidelines for late fall applications

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.

Herbicide applications for perennial weed control can still be made effectively while the following conditions apply. 

  • Daytime temperatures are above 50°F.
  • Weeds have green leaves and can uptake herbicides.
  • Soils are not frozen. 

Broadleaf Weed Control, Nebraska Extension Turf iNfo


9. Fall lawn care to avoid snow moldFall cultural control prevention strategies

Snow mold is a minor fungal disease that can develop on turf under specific conditions. Snow mold is more likely to develop if turfgrass remains taller than 3.5” going into winter, under tree leaf layers, or if snow falls, and remains, on turfgrass that is not dormant. Prevention strategies include the following. Fungicide treatment for home lawns is not usually warranted in Nebraska.

  • Complete fertilization by October 30th
  • Continue to mow at 2.5-4 inches tall and follow 1/3 rule until leaf growth stops
  • Remove heavy piles of leaves
  • Aerify turf regularly in areas with a history of disease. 
  • Improve surface water drainage.


10. Mowing leaves into the lawnUp to three inches of leaves can be mowed into turf at a time

While many homeowners bag tree leaves each fall, most professional turf managers mulch mow leaves. Mulch mowing can be easier and returns complex organic matter and nutrients to the soil. Some research suggests mulch mowing can even help control weeds. While this weed control benefit can be sporadic, it can help improve the health of your lawn and soil. Mulching leaves is also easier and less time consuming than bagging. Sometimes a double mowing at a slightly higher cutting height will help shred those leaves and bury them in the lawn. The ground tree leaves won’t add to thatch.  Sometimes tree leaves come fast and quickly pile over the lawn. If you need to rake and bag, compost those leaves and don’t put them on the street or other concrete surfaces. Leaves can leach nutrients that pollute waterways; or be carried to surface water through storm drains where they release nutrients leading to algal problems.


11. Evergreen natural needle dropYellowing & browning of interior needles

Older needles on the inside of evergreen trees are shed each fall after they turn yellow, brown or reddish tan in color. Sometimes this natural process is very subtle and goes unnoticed, but this year is quite evident in many trees, particulary spruces. However, the bottomline is natural needle drop is a normal process, not a disease or insect problem. 

Pine trees can hold their needles for 2-5 or more years, depending on the species. Spruce trees generally hold onto their needles longer than pine trees do, approximately 5-7 years, which serves to hide the browning needles.

However, if there is question about a potential pathogen causing browning needles and needle drop, contact your local Extension office or submit pictures through UNL's Digital Diagnostic Network

Evergreen Needles Are Falling, Iowa State Research and Extension


12. Avoid pruning spring blooming shrubs nowNext year's flower buds are present and will be removed

Shrubs like lilac, forsythia, mockorange and some Spireas develop flower buds the previous growing season. If they are pruned from late fall through winter, flower buds will be removed and there will be little to no blooming next spring, which customers may not appreciate. Other than rejuvenation pruning (cutting a shrub back to 4 to 6” tall), wait until after early spring blooming shrubs have finished blooming in spring to prune.

Rejuvenation pruning is best done while the shrub is dormant, ideally just before new spring growth in March or early April. 


13. Minute pirate bugsTiny dark-colored biting insects active now; cause itchy welts

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.

Minute Pirate Bugs: Little Bugs, Big Bite, Nebraska Extension


Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Nebraska Extension is implied. Use of commercial and trade names does not imply approval or constitute endorsement by Nebraska Extension. Nor does it imply discrimination against other similar products.

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