Hort Update for the week of 6/13/07
| Current Problems: | Major Symptom: |
Lawns |
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| 1. Necrotic ring spot | Tan patches or rings (‘frog-eye’) |
| 2. De-icing salt damage | Declining turfgrass near a paved area |
| 3. Dollar spot | Small, tan patches in lawns. Tan lesions with red margins on blades. |
| 4. Yellow nutsedge | Yellowish-green, grass-like weed in landscapes |
| Trees & Shrubs | |
| 5. Honeysuckle aphids | Folding/curling of leaves and distortion of terminal growth |
| 6. Cedar-apple rust | Yellowish leaf spots on apple and crabapple leaves |
| 7. Fireblight | Apple and pears leaves appear as if brushed by fire |
| 8. Herbicide injury | Curling, cupping, distortion, discoloring of foliage |
| 9. Needle yellowing in spruce | One year old growth turns bright yellow |
| 10. Squirrel damage | Stripping of bark and girdling of twigs |
| Ornamentals | |
| 11. Phlox plant bug | White or pale-green leaf spots, deformed blossoms, stunted plants |
| Vegetables/Fruits | |
| 12. Tomato white fly | Tiny white flies with powdery white wings on leaf undersides |
| Miscellaneous | |
| 13. Frost damage | In Sioux, Scottsbluff and Banner Counties on Friday, June |
| 14. Spring millers | Numerous moths flying around lights and yards |
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""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 1. Necrotic ring spot- Two common "patch" diseases in home lawns are necrotic ring spot and summer patch. Both cause identical symptoms and cannot be distinguished in a lawn. They usually occur when wet weather is followed by hot, dry periods. Necrotic ring spot occurs under a wider range of temperature and moisture conditions, so outbreaks can occur from mid-spring through late fall. Patch or ‘frog-eye’ symptoms at this time of year are more likely to be Necrotic ring spot. Summer patch occurs from mid-June through September. Both diseases cause crown and root rots, causing these to appear dark brown rather than the normal white color. Patches are circular-, crescent-, or serpentine- shaped. Older patches are often one- to two-foot rings of dead grass around a tuft of green grass; called the "frog-eye" pattern. Correct cultural practices and overseeding with disease resistant cultivars are important to the management of both diseases. Chemical control of patch diseases are best applied preventively, rather than curatively. In Nebraska, make the first application to control Necrotic ring spot no later than mid-April and repeat in mid- to late May. Applications for control of summer patch should be made in early to mid- May and repeated 30 days later. Treatment after mid-August is usually not needed. Products commonly used to control patch diseases include propiconazole (Banner), fenarimol (Rubigan), Thiophanate-methyl (Cleary 3336), and triadimefon (Bayleton). Necrotic Ring Spot, http://www.ces.purdue.edu/extmedia/BP/BP-116-W.pdf Necrotic Ring Spot in Turfgrass, http://www.ext.colostate.edu/Pubs/Garden/02900.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 2. De-icing salt damage- Near a paved sidewalk where a sodium chloride de-icing product is used in winter, turfgrass now is not growing well and may continue to decline. Salt damage to the turfgrass is possible. If a potassium chloride de-icing product was used, salt damage may not be the problem. Avoid shoveling or plowing snow containing high levels of deicing salts onto turf areas. Try to clear snow before putting down salt and only use enough salt to get the job done. Avoid using sodium chloride (rock salt). Use DeIcing Salts With Care, http://lancaster.unl.edu/hort/articles/2005/DeicingSalt.shtml Winter Deicing Agents for Homeowners, http://www.ianrpubs.unl.edu/sendIt/g1121.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 3. Dollar spot-Small (three to six inches in diameter), roughly circular patches in lawns. Spots may coalesce into a large patch. Grass blades have tan, band-like lesions with red margins. Damage usually most severe where there’s a nitrogen deficiency. With all of the rain this year, nitrogen may have been leached out of the root zone. The best control may be to fertilize with nitrogen. The turf can be treated with products containing benomyl, mancozeb, propiconazole, thiophanate-methyl. Dollar Spot on Turfgrass, http://ohioline.osu.edu/hyg-fact/3000/3075.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 4. Yellow nutsedge-A 3-ranked, yellow-green, waxy grass-like weed. At this time of year it can be controlled by pulling. Nutlets will not start to form until after the longest day of the year, June 21 st. Pulling before this stage is worthwhile. Chemical treatment is most effective when applied before June 21. Recommended chemicals- Sedgehammer (replaces Manage), or Certainty (Sulfosulfuron) is a new product that can only be applied by commercial applicators. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 5. Honeysuckle aphid- Sapsucking insects which inject a toxic saliva as they feed, causing leaves to fold over and become stunted; producing a shelter in which female aphids feed and give birth to young. Feeding stunts terminal growth and results in proliferation of side shoots referred to as "witches-brooms". Unroll affected terminal leaves and you may find aphids. Populations may be greatly reduced in mid-summer by natural enemies. Prompt clipping and destroying of witches brooms can reduce reinfestation. Aphids are readily controlled with insecticides, but these need to be applied at least twice - in May and August to prevent damage. Insecticidal soaps are also beneficial, especially in early spring when overwintered eggs are beginning to hatch. Honeysuckle Aphid, http://entomology.unl.edu/ornamentals/pestprofiles/hsaphid.htm """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 6. Cedar-apple rust-Small, yellow spots on upper leaf surfaces. Spots gradually enlarge and become a bright yellow-orange color. Heavily infected leaves may drop prematurely. Cedar-apple rust requires two hosts: cedar trees, and apple or crabapple trees. Fungal spores can travel up to 2 miles so removal of cedar trees will not provide control. Select disease resistant apple or crabapple cultivars to plant. Fungicide sprays may be used to protect apples and crabapples from infection. For effective control, read and follow label directions. Spray applications need to begin at the petal drop flowering stage. Applications made now will only protect new growth. Cedar-apple rust, http://lancaster.unl.edu/hort/articles/2002/CedarAppleRust.shtml """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 7. Fireblight- This bacterial disease affects apples and pears, including ornamental pears. Infected plants appear as if they’ve brushed by fire. Leaves turn black to brown, shrivel, and droop. Cankers appear on branches and trunks and in the spring will have a yellowish ooze coming from canker margins. Fruit also appears water-soaked, then turns dark. Infected flowers will appear water-soaked at first, then turn brown. See website for disease management. Fireblight of Apples, Crabapple & Pear, http://ohioline.osu.edu/hyg-fact/3000/3002.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 8. Herbicide injury-Injury to nontarget plants from herbicide drift may be seen at this time of year. Symptoms include abnormally twisted, cupped or distorted growth. Some herbicides interfere with photosynthesis resulting in yellowing of the foliage. However, similar symptoms may also be due to a variety of other factors. Mite, insect, or disease damage; adverse weather; soil compaction; drought; root stress; improper soil pH; misapplied fertilizers; genetic mutations; and damage from road salt are conditions that can mimic herbicide injury. Once mites, insects, and disease are ruled out, it may be difficult to determine the cause of the injury. If herbicide injury is suspected, determine what herbicide was used, when it was applied, and what the weather conditions were at the time of application. Also, inspect nearby plants as more than one plant species is usually affected if herbicide drift is the cause. Herbicide Injury in the Nursery or Landscape, http://osuextra.okstate.edu/pdfs/F-6704web.pdf Diagnosing Herbicide Injury on Garden and Landscape Plants, http://www.ces.purdue.edu/extmedia/ID/ID-184.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 9. Needle yellow in spruce-One year old growth turns bright yellow with no clear signs of disease or insect. New growth is green and healthy. According to Mark Harrell with the Nebraska Forest Service, this is most likely due to drought stress or some other stress factor. Chlorophyll in leaves has to be replaced continuously as it breaks down fairly quickly. When trees are stressed, they are not able to make more chlorophyll as readily and so foliage begins to yellow. This often happens with evergreens that go through a dry summer and fall. In spring, trees put a lot of energy into new growth, so the new foliage is greener. Improve tree health with adequate watering and mulching. In most cases, avoid fertilizing with nitrogen; especially where trees are growing in or near a fertilized lawn. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 10. Squirrel damage-The bark on twigs and branches are stripped and girdled by squirrel feeding. There appears to be an unusual amount this year in the Douglas County area; possibly due to flower buds and fruit being damaged by the early April freeze. Squirrel Damage to Trees, http://www.ext.colostate.edu/ptlk/2303.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 11. Phlox plant bug-Feeding occurs on upper leaf surfaces of young phlox leaves and buds. Injury appears as white or pale-green spots that later become yellow-stippled areas. Blossoms may be deformed. In extreme cases, plants become stunted and die. Adult bugs generally have contrasting colors, i.e. orange and black or red and black, sometimes gray and white or yellow; all with black legs. Nymphs are orange or bright red. This insect overwinters in the egg stage with nymphs emerging in early May. Remove infested plant parts. The use of insecticidal soaps, horticultural oils, or systemic insecticides will reduce damage. Plant Bugs on Perennials and Landscape Shrubs, http://bugs.osu.edu/~bugdoc/Shetlar/factsheet/ornamental/plantbugs-perennials.PDF """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 12. Tomato white fly- Tiny flies with powdery white wings on leaf undersides. Feed on plant sap with piercing-sucking mouthparts. Damage can appear as deformed new growth, wilting, chlorotic leaves, and deformed or discolored fruit. Whiteflies can also transmit some plant viruses; and, like aphids, secrete honeydew on which a black sooty mold can grow. Select clean plants at the greenhouse. Insecticidal soaps and oils are effective for killing whiteflies. Be sure to read the label first. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 13. Frost damage- A late spring frost damaged some plants in some western Nebraska counties on June 8 th. Damaged leaves on perennials can be clipped off and new growth will occur. Warm season vegetables may have been damaged enough to affect yields. Any damage to trees and shrubs should be minimal. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 14. Spring millers- Millers can be abundant in and around homes each year, especially in May and early June. At this time of year, the moths are most likely the adult stage of the army cutworm, a common pest of wheat and alfalfa. When abundant, these moths may be very annoying because of their activity and their habit of invading homes, garages and vehicles. They may cause agitation when great clouds of moths suddenly disperse from landscape bushes, shrubs, doors and windows when disturbed. Although the moths can be dispersed statewide, the potential for large moth aggregations increases the further west you go in Nebraska. They cause little harm and are present in large numbers for only a few weeks. Spring Millers- http://www.ianrpubs.unl.edu/sendIt/nf526.pdf |
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