Hort Update for the week of 10/1/07
| Current Problems: | Major Symptom: |
Lawns |
|
| 1. Violets | Broadleaf perennial weed with heart shaped leaves. |
| 2. Stem rust | Yellowing in lawns. Orange powder on shoes, mowers. |
| 3. Overseeding and turfgrass cultivars | Fescue should be seeded no later than September 20. Kentucky bluegrass can be seeded into late September/early October. |
| 4. Moles | Raised tunnels in lawn. Round, volcano shaped dirt mounds may be present. |
| Trees & Shrubs | |
| 5. Natural needle shed | Inner needles turn yellow, then brown and drop off the tree. |
| 6. Wind damage/ hazard tree I.D. | Dealing with wind damage & identifying hazardous trees. |
| 7. Pruning decidous plants | Best avoided in the fall. Wait until woody plants go dormant to prune. |
| Ornamentals | |
| 8. "Endless Summer" hydrangea | Plants have not been blooming in the Midwest this season. |
| 9. Cutting back herbaceous perennials | Wait to cut back the tops until after a frost kills the tops. |
| 10. Fall chrysanthemums | Those on market now not likely to survive winter. Use as fall annuals. |
| Vegetables | |
| 11. Carrot weevils | Tunneling on surface of carrot roots. |
| Miscellaneous | |
| 12. Fall sanitation and composting | Clean up plant debris to reduce overwintering pathogens and insects. |
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 1. Violets are difficult weeds to kill. For violets, homeowners can use post-emergence combination type herbicides, such as Trimec. Commercial applicators can apply the post-emergence herbicide Certainty to violets in Kentucky bluegrass lawns. Certainty cannot be used on tall fescue lawns. Mid September through early October is the best time to control perennial, broadleaf weeds like violets. Plants are moving photosynthetic products into the roots for winter storage and more herbicide is moved into roots, increasing root kill. Landscape Weed Management: http://www.ianrpubs.unl.edu/sendIt/ec1256.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 2. Stem Rust of Kentucky Bluegrass is appearing, mainly in western Nebraska. Stem rust appears as an orangish-yellow powder (spores) on grass blades in late summer and the lawn may develop a yellow or brown appearance. Rust typically develops on lawns with slow growth. Fall lawn care, including fertilization and correct irrigation, along with cooler fall weather promotes turfgrass growth and rust usually disappears. Stem rust is often a problem on compacted soils; hence core aerification is effective in reducing rust in lawns. Fungicide controls are rarely suggested for home lawns. Note for Sports Turf: If stem rust occurs on sports fields, the fungal spores can cause problems for allergy/asthma sufferers. Control of stem rust is recommended on sports turfs using a combination of turf management and timely fungicide applications. Rust Turns Lawns Orange, http://www.urbanext.uiuc.edu/turf/rustlawn.html Rust on Sports Turf, http://hcs.osu.edu/sportsturf/notes/detail.lasso?id=1094 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 3. Overseeding and Cultivars- Overseeding to increase lawn density, fill in bare areas, or introduce improved cultivars is best done by September 20 for tall fescue lawns. When overseeding, use improved cultivars and those considered to have disease resistance. A list of turfgrass cultivars recommended for Nebraska can be found on the UNL Extension Horticulture website at http://extensionhorticulture.unl.edu/ToDo/ToDo.shtml. Click on "Recommended Turfgrass Cultivars." When overseeding, it’s critical to achieve good seed to soil contact. Methods to use include a slit seeder that plants seed through existing grass into the soil; power raking and removing all dead grass and debris before overseeding; and/or, core aerating (plugging) the lawn to relieve soil compaction and provide openings for seed to soil contact. Core aerate the lawn twice, running the machine at a 90 degree angle to the first aeration. Leave the plugs on the lawn to decompose. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 4. Moles cause damage to lawns when burrowing for insects. They create raised surface tunnels and one foot diameter conical shaped mounds. Trapping and the use of repellants containing caster oil are recommended controls. Applying insecticides to reduce their food source is not recommended. Moles and Their Control, http://www.ianrpubs.unl.edu/sendIt/g1538.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 5. Natural needle drop may be causing the interior needles of spruce and pine trees to turn yellow then brown and drop readily from branches. 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. It is most noticeable in pines. One evergreen tree that is very noticeable as it loses its leaves in fall is Eastern White Pine. This tree only holds its needles for two years which leaves less growth at the tip of branches to hide the needles as they are shed. Combined with the soft texture and open structure of the Eastern White Pine this makes fall needle shed easily seen. Fall needle drop is a natural condition and is not a sign of disease or insect infestation, however, any factor that increases stress on evergreen trees will intensify the autumn needle drop. Stress factors include drought, herbicide injury, root damage and insect or disease damage. Natural needle drop occurs only on the inner needles; if entire branches or needles at the tips of branches are dying, then something else is happening. A sample of the affected branches should be submitted to your local UNL Extension office for diagnosis. A close inspection of any brown foliage should also be done to eliminate the presence of fungal leaf spots, spider mites, aphids or other potential pest problems. Natural Needle Drop, http://extensionhorticulture.unl.edu/Current/EverNeedleDrop.shtml """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 6. Wind damage care/hazard tree identification- Wind damage to trees can lead to hazardous conditions or future problems for a tree if corrective pruning is not done. Some key points when wind damage occurs include the following.
How To Recognize Hazardous Defects In Trees, http://www.na.fs.fed.us/spfo/pubs/howtos/ht_haz/ht_haz.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 7. Pruning deciduous plants is best avoided from late August through October. Pruning at this time could delay a plant's natural hardening off process for dormancy or stimulate new growth that may not harden off before winter. Decay organisms tend to be more prevalent during fall which may increase the risk of decay developing in pruning wounds. Prune most deciduous trees and shrubs while dormant from mid November through March. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 8. ‘Endless Summer’ hydrangeas have not been blooming well in the Midwest this summer. No disease or insect problem has been associated with this issue. The likely cause is freeze injury sustained by the plants during our April freeze which delayed their growth. The plants may have been further stressed by hot, dry conditions in late June and July and may not have been properly watered. Most likely, the plants did not have enough energy (stored food) to set flower buds. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 9. Cutting back herbaceous perennials is best done after the foliage naturally dies or is killed by frost. As long as the foliage is green and healthy, photosynthesis is taking place and the carbohydrates and sugars being produced are moved into roots for winter storage. If a plant has diseased foliage, remove and destroy the diseased portions as soon as possible as a means of good sanitation. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 10. Fall Chrysanthemums- there are many Chrysanthemums on the market at this time of the year and people often ask if they are hardy. In most cases, these fall mums are best treated as annuals as they are not likely to survive the winter due to a lack of time for root growth after planting. If a homeowner wishes to try and over-winter a fall planted mum, the plant should be mulched after the soil begins to freeze, sometime in November. Use a six to 12 inch layer of a coarse mulch that will not mat down over winter. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 11. Carrot weevil larvae tunnel along the outer root surfaces, causing unsightly damage and decay. Tunneling into stems or stalks can cause the foliage to wilt. There are two generations per year and so damage occurs from May to late August. To minimize damage to carrots, plant them in a different location each year. Control weedy hosts such as dock, plantain, wild parsnips and wild carrots. If insecticides are used, these need to be applied when the adults (brown to black, one-fourth inch long weevils) are present and before egg laying takes place. Adults are present from about mid-April to mid-May and in July. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 12. Fall Sanitation and compost piles. Fall sanitation is the removal and disposal of dead or dying plant material from gardens and from beneath fruit trees to help reduce overwintering pathogens and insects. Many diseases and insects can overwinter on weeds so don’t overlook cleaning these up as well. Plant debris can be tilled under or removed and destroyed. It can be added to compost piles. However, if the material comes from a plant which had a disease or insect problem this year or is a weed that has gone to seed; it may be best not to add this material to compost piles. While a properly managed compost pile may reach temperatures hot enough to kill most pathogens and weed seeds, many piles are not managed to reach this temperature. Garden Compost, http://www.ianrpubs.unl.edu/sendIt/g810.pdf |
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