Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Hort Update for the Week of September 16, 2013
|1. Fall fertilization||Crucial for cool season turfgrasses|
|2. Fall seeding||Seeding later than September 15 risky|
|Fall most effective time for herbicide control|
|4. Ignore summer annual weeds||Wait until next year for herbicide control|
|5. Maintain mower height||No need to lower mowing height below 3”|
|6. Zoysia issues||Browning of turfgrass|
|Trees & Shrubs|
|7. Oak lacebug||Discoloration and drying of tree leaves|
|8. Oak twig girdler||Browning of leaves on branch ends|
|9. Shade Tree Borers||Holes in trunks, twig or branch dieback|
|10. Early fall color/leaf drop||Most likely due to heat stress|
|11. Evergreen browning||Drought effects, various diseases, mites|
|12. Natural needle drop||Sudden yellowing of all internal needles|
|13. Delay pruning||Wait until after dormancy to prune|
|14. Fall planting ||Select large, quality trees; plant it right|
|15. Dividing perennials||Fall is ideal time to divide and transplant|
|16. Houseplant transition||Lower light requirements, lower water needs|
|17. Fall fertilization of perennials||Fall application is unnecessary|
|Fruits & Vegetables|
|18. Garden and orchard sanitation||Helps control pests and diseases|
|19. Spider mites, bean leaf beetles, and squash bugs||Three prevalent insects this year|
1. Fall fertilization - With temperatures moderating, fall fertilization needs to begin. This is the most important time to fertilize cool season turfgrasses. Of the total annual N applied, 60 to 75% of it should be applied between Labor Day and the last mowing. September fertilization is crucial on all turf areas regardless if it is a lawn, athletic field, or golf course green, tee or fairway. It encourages the production of new tillers and/or rhizomes and stolons that increase turf density. It also encourages rooting and production of storage products that will help the plant survive the stresses of winter and next year's growing season. This is especially true for areas thinned by the late summer heat and drought.
Almost all turf areas should be fertilized with 1 lb. N/1000 sq. ft. using a fertilizer with 25-50% slow release nitrogen (sulfur or polymer-coated urea, urea formaldehyde, or natural organics). Some recent research suggests higher N rates can be used with fertilizers containing even more slow release nitrogen, which may minimize the need for typical late October or very early November applications (this slow release N in this September application may release over 6-8 weeks or more). This would be very useful on low maintenance areas where labor is limiting. The next most important fertilization is near the last mowing of the season.
2. Fall seeding of cool season turfgrasses like Kentucky bluegrass and turf-type tall fescue is best completed by September 15. While these grasses can be seeded later, the risk of winter injury increases.
3. Broadleaf weed control - Herbicide control of perennial broadleaf weeds like dandelions, clover, and ground ivy is most successful during fall. Late September through October is a good time to apply herbicides. For difficult to control weeds like ground ivy and violets, two applications may be needed. Apply one in September and the second in October. Along with herbicide applications, improving turf stands during fall will increase the turfs ability to better compete with weeds. See the Herbicide Ratings link at turf.unl.edu for information on herbicides to apply for specific weeds. Broadleaf perennial weed control should be started in late September.
Broadleaf Weed Control in Home Lawns, UNL Turf iNfo
4. Ignore summer annual weeds, particularly grasses like crabgrass, goose grass, sandburs and puncturevine for the remainder of this season. Postemergence herbicide control at this time of year may kill the plant, but will have no effect on the seed. As annual plants, these grassy weeds will die with the first freeze.
Next year, apply preemergence herbicides at the correct time of the spring/early summer for effective control. See the Herbicide Ratings link at turf.unl.edu for information on herbicides to apply for specific weeds.
Crabgrass and Other Summer Annuals Grass Weeds Pro Series, UNL Turf iNfo
5. Maintain mowing height of turfgrass at three inches. There is no need to lower the mowing height of turfgrass during the fall. Maintaining the taller height will help shade out winter annuals like henbit and speedwell whose seed is germinating during fall. The taller height also supports the growth of tillers, rhizomes, stolons and roots to increase turf density.
6. Zoysiagrass issues - Reports of zoysiagrass dying over the winter and throughout the summer is most likely due to the 2012 drought, compounded by cool summer temperatures in 2013 and the late summer drought. Recovery will be slow from rhizomes and stolons, but most zoysiagrass will eventually grow and recover.
7. Lace Bugs are small insects with white lacy wings that cluster on leaf undersides of oak, sycamore and other trees. Sapsucking insects, they pierce leaves to feed causing tiny light colored flecks on upper leaf surfaces. If heavily infested, leaf undersides appear dirty with dark spots or stains, and leaves turn yellow or brown. Lace bugs are prevalent in late summer. In most cases, the damage is minor enough, or occurs late enough in the season, that control is not needed. Also, natural enemies can keep lace bug populations down unless insecticides kill predators, allowing lace bug populations to build. A water spray from a high pressure hose can be used to knock lace bugs off of smaller plants to reduce populations
Lace Bugs on Deciduous Trees and Shrubs, University of Minnesota
8. Oak Twig Girdlers and Oak Twig Pruner kill the leaves and twigs on the ends of branches in late summer. The symptom is called “flagging” as leaves on the tips of branches turn brown. Fortunately, these insects are not a serious problem, but their damage creates concern. Heavily infested mature trees can look a little ragged, but the damage is not a serious health problem so chemical control is not recommended or practical. The best way to minimize insect activity is to remove and burn or discard affected twigs in fall and spring that contain the developing larvae.
Twig girdlers can be one of two insects. The metallic wood boring beetle, Agrilus angelicus, has a two-year life cycle. The slender, bronze-to-black beetles are about ¼ inch long at maturity, and emerge from May to September. They deposit eggs on twigs at the junction between the current and previous year's growth. After hatching, larvae bore into twigs and as the insects grow they mine spirally around the twig so that terminal clusters of dead leaves ("flags") appear during August and September. During the next year, the larvae continue to mine into the twigs, but turn and tunnel back into the dead tip before completing development, pupating in the autumn. No girdling on the outside of twigs is evident, as with the longhorn beetle.
The other twig girdler is the longhorn beetle, Oncideres cingulata, which has one generation per year. At maturity, these beetles are grayish-brown, stout-bodied and about 3/4" long. Adults are present from mid-August through early October. The female prepares to lay eggs by chewing through the bark of a small twig, in a grooved channel that goes all the way around the twig, girdling it. She lays an egg in the girdled twig section, which quickly wilts, turns brown and dies. Larvae, which are creamy white, grub-like borers, cannot survive in healthy wood, but do fine in the dead twig even after it falls from the tree. When twigs fall from the tree, a close inspection of the twig’s cut end looks a lot like beaver damage, in miniature.
Twig Pruner, Elaphidionoides villosus, also has one generation per year. Adult beetles are grayish-yellow and about ½” long. Females emerge in spring and lay eggs in leaf axils where a leaf joins the stem. Larvae hatch within a few days and tunnel into the twig. Young insects feed on the twig’s wood and tunnel toward the base of the twig. By late summer the larvae are fully grown, and begin to make concentric cuts in the wood of the twig, spiraling outward until they almost reach the outer bark. The larvae then retreats into the outer portion of the twig. Larvae overwinter inside the twig. On close inspection, twigs severed by the twig pruner will have ragged outer edges but a smooth concave inner surface. Tunneling will also be evident.
9. Shade Tree Borers - There are many different types of shade tree borers. Most borers attack trees stressed by environmental conditions, transplant shock, or disease. While most any tree could be attacked by borers, trees we most often see borers in are ash, birch, lilac, cottonwood, and locust. Trees we are least likely to find borers in include oak, lindens, crabapples and conifers. Signs of borers are twig dieback, emergence holes in the trunk and main branches, and sometimes sawdust found near the base of trees.
Selecting trees less susceptible to borers and then planting and maintaining them correctly is key to avoiding borers. Oncee borers infest a tree, carefully timed insecticide applications may be used for control. Topical treatments of Permethrin or Bifenthrin need to be applied to the trunk and main branches when the adult female is active and laying eggs. The systemic insecticide Imidacloprid is also recommended. It takes a while to become effective in trees and needs to be applied several weeks prior to egg laying. See link below for information on specific borers and timing of insecticide application.
Borers of Shade Trees and Woody Ornamentals, University of Nebraska-Lincoln
10. Early fall color/leaf drop - On otherwise healthy trees, this is a response to the recent heat wave and dry conditions. Avoid applying nitrogen to these trees. Do irrigate in the absence of rain to keep the soil moist until the soil begins to freeze.
11. Browning of Evergreen Conifers can be due to many factors ranging from heat and drought stress to spider mites or spruce mites to various diseases. Identification of the cause is the key to management. With most diseases, fungicide applications would not be applied until next spring. If spider mites or spruce mites are actively feeding, spraying the tree with a strong spray of water can reduce mite populations. For heat and drought stress, avoid nitrogen fertilizer and provide moisture to the tree in the absence of rainfall. Use mulch to moderate extremes in soil temperature and moisture.
Diseases of Evergreen Trees - Nebraska Forest Service
12. Natural needle drop is the sudden yellowing of all the internal needles of evergreens in September. This is natural. Evergreen conifers do not keep their foliage forever. About every three to five years, all of the inner needles are cast. Most conifers only retain needles up to three years of age.
Natural Needle Drop of Evergreens, University of Nebraska- Lincoln Extension
13. Delay pruning shade trees and deciduous shrubs from now until these plants are fully dormant. Delay pruning evergreen trees and shrubs until next spring. Delay pruning spring flowering shrubs until after they bloom in the spring. Pruning now can interfere with the hardening off process of trees.
14. Fall tree planting - September through October is a good time to plant shade trees and shrubs because root growth often occurs long into November, giving plants time to establish a good root system before the tree has to support new growth next spring. Fall planting takes advantage of favorable soil temperatures and moisture conditions that promote root growth. Most container-grown and balled-and-burlapped deciduous trees and shrubs can be fall planted because they already have developed root systems. Conifers, such as pine and spruce, prefer warmer soil temperatures and are best planted before the end of September.
A few trees that are not recommended for fall planting include magnolia, fir, ginkgo, oak, willow, bald cypress and Yews.
For fall planting success, plant at the correct depth, avoid nitrogen fertilizer, apply a two to four inch layer of mulch and keep the soil moist, NOT saturated, up until the soil freezes.
15. Dividing perennials is an important management practice for many species, helping to encourage vigorous growth and optimum blooming. Many perennials benefit from division once every 3-5 years. Dividing is also a good way to propagate perennials.
Dividing Perennials, Backyard Farmer on YouTube
16. Bring houseplants back inside - Most plants are energized and invigorated by a summer outdoors. Even delicate plants like ferns have a growth spurt if placed in a shaded location and watered properly. While outside, houseplants require large amounts of water due to increased light levels, heat and wind evaporation. Now that nighttime temperatures are falling, it’s time to bring them back inside.
When houseplants are brought back indoors in fall, seasonal light levels have started to fall back from their mid-summer high intensity. Light levels drop even more inside the house. Temperatures have also dropped and wind evaporation that plants experienced while outdoors has stopped. All of these environmental changes should be considered when choosing a location indoors, and determining water needs for your plants once they are back inside the house.
Bringing Houseplants Indoors, University of Nebraska- Lincoln Extension
17. Fall fertilizing of perennials is usually unnecessary. The overall annual nitrogen requirement for perennial plants is much lower than turf requirements. Light applications can be made to stressed ornamentals in the spring, as long as irrigations accompanies the fertilizer application.
Growing Perennials, University of Nebraska- Lincoln Extension
18. Garden sanitation during fall involves cleaning up or tilling under plant debris in the vegetable garden and around fruit trees to reduce overwintering pests. The sooner this can be done after a plant dies or after fruit drops to the ground, the better. Plant pathogens are less likely to survive if organic matter is quickly decomposed. Remove plant debris or infected plant parts after each growing season.
- Turn the soil after harvest to help break down small roots that may harbor nematodes, fungi or bacteria.
- Gardeners may compost dead plants if they have a good composting system; otherwise, these piles may serve as a source of pathogens.
- Prune or remove twigs and branches of woody plants affected with fire blight and other bacterial or fungal canker diseases.
- Keep gardens weed free. Weeds often are another source of pathogens. Eradicate weeds to break the life cycle of pathogens and control them. Weed removal also can increase air movement and thus decrease conditions that favor disease development.
- So that pathogens do not spread from one area to another, always disinfest machinery and other tools with steam, hot water under pressure, or a 10 percent solution of household bleach diluted with water.
Orchard sanitation is essential for good maintenance of fruit trees and small fruit plantings. Insects and diseases can overwinter on dead or infected plant material. Dried fruits or "mummies" carry disease organisms through the winter to attack next years' crop. Remove and destroy any fruits that have fallen to the ground, or those appearing to rot on the branches.
Non-chemical Control of Disease, Colorado State University
19. Spider mites, bean leaf beetles and squash bugs - Vegetable gardens have seen their fair share of insect damage this year. Spider mites, bean leaf beetles, and squash bugs are probably the three most encountered insects this year. Continue to scout and control if necessary.