Hort Update for the week of 8/20/07
| Current Problems: | Major Symptom: |
Lawns |
|
| 1. Stem rust | Orange-yellow powder (fungal spores) on grass blades, mowers, shoes. |
| 2. Brown patch | Roughly circular, brown patches in lawns . Tan lesions with red margins. |
| 3. Dollar spot | Small, brown patches in lawns. Tan lesions with red margins. |
| 4. Denver billbug | Dry, brown areas in the lawn. Turfgrass has chewed crowns. |
| 5. Yellow nutsedge | Yellow-green, 3-ranked, grass-like weed with waxy leaves. |
| Trees & Shrubs | |
| 6. Fall webworm | Fairly large, unsightly webs filled with worms in deciduous trees. |
| 7. Lacebug | Discoloration of leaves on hackberry, sycamore, oak, and other deciduous trees. |
| 8. Oak twig girdler | Small clusters of brown leaves on twig tips. |
| 9. Oak galls | Various abnormal growths, some fuzzy, on leaves, petioles & twigs. |
| 10. Yellow necked & walnut caterpillars | Caterpillars feeding in masses on deciduous trees. |
| 11. Bagworm | Defoliation of evergreens and small brown bags attached to stems. |
| 12. Sphaeropsis tip blight | Current year’s growth is brown and stunted. Entire branches may die. |
| Vegetables/Fruits | |
| 13. Bacterial wilt | Vine crops suddenly wilt and do not recover. |
| 14. Tobacco mosaic virus | Stunted plants. Distorted leaves. Mottled or streaked fruit. |
| Ornamentals | |
| 15. Tobacco budworm | Poor flowering in annuals or ragged appearance to petals. |
| Miscellaneous | |
| 16. Spidermites | Foliage has whitish specks, then turns off green to bronze color. |
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 1. 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. 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, http://hcs.osu.edu/sportsturf/notes/detail.lasso?id=1094 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 2. Brown patch- Roughly circular patches of dead and dying grass. Patch centers may be less affected and have a frog-eye-like symptom. Tan colored, irregularly shaped leaf spots with reddish margins are found on leaf blades. Preventive applications of Prostar (commercial use), Bayleton, and chlorothalonil (Daconil) do a fairly good job of suppressing the disease when applied at monthly intervals (June, July, August). Curative applications of chlorothalonil beginning a few days after symptoms of brown patch develop may do an adequate job of suppressing injury. In many cases, lawns damaged by brown patch wll recover in two to three weeks, provided the outbreak is not sustained by continuous hot, humid weather; and treatment may not be necessary. Brown Patch of Tall Fescue, http://www.oznet.ksu.edu/path-ext/factSheets/Turf/RhizoctoniaBrownPatchOfTallFescue2.asp """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 3. Dollar spot- Small (three to six inch 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, much nitrogen may have been leached out of the root zone. The best control may be to fertilize with nitrogen. Turf can be treated with products containing benomyl, mancozeb, propiconazole, thiophanate-methyl. (NebFact 462 Management Program for Dollar Spot). Dollar Spot of Turfgrass, http://ohioline.osu.edu/hyg-fact/3000/3075.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 4. Denver Billbug causes damage to KBG lawns in western Nebraska. Billbug injury is easily mistaken for white grub or sod webworm damage, disease, or plant stress. Newly-hatched billbug larvae tunnel in grass stems, hollowing out the stem and leaving fine sawdust-like debris and excrement. Infested stems discolor and when pulled, readily break away at or near the crown. Subsurface feeding by older larvae can destroy the plant's root system, causing lawns to appear drought stressed. Under heavy billbug pressure, turfgrass turns brown and dies. Adult Denver billbugs are larger than bluegrass billbug, reaching 1/3 to 1/2 inch in length. Adult billbugs also feed on grass stems and blades, but cause only minor injury to lawns. Billbug damage rarely occurs in turf stands less than three years old. Billbug Grubs, http://entomology.unl.edu/turfent/documnts/billbugs.htm Billbugs in Turfgrass, http://ohioline.osu.edu/hyg-fact/2000/2502.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 5. Yellow nutsedge is a 3-ranked, yellow-green, waxy, grass-like weed. At this time of year it cannot be effectively controlled by pulling. Tubers (nutlets) have formed and pulling prompts regrowth. Herbicide treatment is most effective if applied by June 21 or as soon as Nutsedge first appears. Applications now will provide limited control. The products Sedgehammer and Certainty (Sulfosulfuron) are recommended prior to June 21st. Certainty cannot be used on Tall Fescue lawns. The herbicide Dismiss (Sulfentrazone) can be applied now to provide some control. """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 6. Fall Webworm appear as large, unsightly webbed nests in fruit, ornamental and shade trees from Iate summer through fall. The webs are filled with caterpillars, dead leaves, frass and worm excrement. While unsightly, they are fairly harmless to established trees at this time of year. Mechanical removal of the nests on small or newly planted trees is the best avenue of control. Insecticides applied when the webbed nests are small will reduce fall webworm numbers. Fall Webworm Management, http://ohioline.osu.edu/hyg-Fact/2000/2026.html Fall Webworm, http://www.oznet.ksu.edu/hfrr/extensn/problems/fallwebw.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 7. Lacebugs cause shade tree leaves to discolor and turn yellowish, whitish or brown. On close inspection, leaves appear stippled and tiny lacebugs, or specks of their shiny black excrement, may be found on leaf undersides. Lacebugs are sap feeders. Damage this late in the season is more unsightly than harmful to trees. Homeowners may complain about bites. This could be lacebugs, but more likely their predator, the minute pirate bug. Leaves Looking Strange?, http://www.dakota.unl.edu/newsitems/news040805153332 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 8. Oak Twig Girdler (Agrilus angelicus) is a small, slender, bronze-to-black beetle that emerges from May to September and deposit eggs on twigs at the junction between current and previous year's growth. Larvae hatch and bore into twigs. As they grow, they mine spirally so terminal clusters of dead leaves ("flags") appear in August and September. During the next year, larvae continue to mine deeper into twigs and complete development, pupating in the fall. While damage is obvious, it is rarely severe, and there is no need for control efforts. Flatheaded Borers, http://entomology.unl.edu/ornamentals/pestprofiles/flatheaded_borers.htm Twig Girdlers, http://extensionhorticulture.unl.edu/Current/Twig.shtml Twig Girdler & Twig Pruner, http://extension.missouri.edu/explore/agguides/pests/g07276.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 9. Oak Gall- Oaks are susceptible to a number of galls which range in appearance from pink fuzzy balls or tan fuzz growing on leaves to green or brown galls growing around leaf petioles and twigs. Most galls form in response to insect feeding, often a very small wasp. Oak galls are interesting, but usually harmless, and control is not needed nor effective at this time of the season. Gall Wasps, http://entomology.unl.edu/ornamentals/pestprofiles/gallwasps.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 10. Yellownecked and Walnut Caterpillars are closely related late season caterpillars that feed on tree leaves. Yellow-necked caterpillars feed on a wide range of trees while walnut caterpillars feed primarily on walnut, pecans and some hickories. Walnut caterpillars gather in clumps on tree trunks to molt. Young caterpillars skeletonize leaves, then strip off foliage as caterpillars mature. Large caterpillars pupate in soil where they over winter. Control of these caterpillars is usually not needed on established trees unless defoliation is occurring during the middle of season. Defoliation in late August and early September has minimal impact on tree health because leaves being eaten are close to the time of normal leaf drop. Yellownecked Caterpillar, http://www.oznet.k-state.edu/hfrr/extensn/problems/YellowneckedCaterpillar.htm Walnut Caterpillar, http://www.na.fs.fed.us/spfo/pubs/fidls/Walnutcat/walnutfidl.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 11. Bagworms cause browning or defoliation of mainly spruce and juniper. Small bags covered with brown needles found on stems. Bacillus thuriengiensis or insecticides containing carbaryl, permethrin, etc. work best if applied at hatching (late May into June). Effectiveness is minimal at this time of year, but may reduce damage if larvae have not pupated. Larvae usually pupate in August. Cut open bags to see if larvae are still active. If larvae are in pupal stage, it is too late to apply an insecticide. Pick off and destroy bags at this time of year. Insect Pests of Evergreen Trees, http://www.nfs.unl.edu/documents/foresthealth/insectevergreen.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 12. Sphaeropsis Tip Blight infects pine trees. New shoots die in spring. Entire branches may die if the tree is otherwise stressed. Small black fruiting bodies appear on the base of cones and the base of infected needles. A fungicide application made during the third week in April and repeated the first week in May provides optimum disease control in most years. Fungicides applied after mid-May ineffective. Diseases of Evergreen Trees, http://www.nfs.unl.edu/documents/foresthealth/diseasesevergreen.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 13. Bacterial Wilt is spread on the mouthparts of striped and spotted cucumber beetles. It causes plants in the cucurbit family to quickly wilt and die. Diagnose bacterial wilt by cutting the stem near the soil line and squeezing the cut ends between your fingers. Place the tip of a knife blade on the bead of sap squeezed from the stem and slowly pull the knife blade away. If a slimy string develops between the blade and vine, the plant is likely infected with the bacteria. There is no cure for this wilt disease and most cucumbers and muskmelon are susceptible. Use crop rotation and control cucumber beetles to reduce the disease. Options for Managing Bacterial Wilt, http://vegetablemdonline.ppath.cornell.edu/NewsArticles/CucBW.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 14. Tobacco Mosaic Virus commonly infects tomatoes to cause stunting of young plants and leaf distortion which may be confused for herbicide damage. Older leaves curl downward and may be slightly distorted. Fruit may be mottled, streaked or necrotic. Virus diseases cannot be controlled once a plant is infected. Sanitation is the primary means of controlling virus diseases. Infected plants should be removed immediately to prevent spread of the virus. Perennial weeds, which may serve as alternate hosts, should be controlled in and adjacent to gardens. The use of tobacco products while working with tomato plants should be avoided to prevent inoculation of plants with the virus. People who use tobacco products or work with infected plants should wash their hands thoroughly in soapy water before handling tomato plants. Tobacco Mosaic Virus of Tomato, http://www.oznet.k-state.edu/dp_hfrr/extensn/problems/tomtotmv.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 15. Tobacco Budworm attacks many garden flowers including geranium, petunia and nicotiana. Roses are occasionally damaged. Caterpillars of the tobacco budworm usually attack the flower buds and ovaries of developing flowers. The damaged buds fail to open and a failure of flowering ("loss of color") is noticed. Petals of emerged flowers are chewed, giving the flowers a ragged appearance. The amount of damage the insects cause progresses through the growing season, becoming most noticeable in late summer. Handpick the caterpillars in small plantings. Insecticides containing permethrin or spinosad are effective. Tobacco Budworm, http://www.ext.colostate.edu/pubs/insect/05581.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 16. Spider Mites affect a wide variety of plants from trees and shrubs to ornamentals and vegetables. Reports of damage to burning bush (winged euonymous), honeylocust, evergreens, impatiens, and green beans have been common. Mites and their webs can barely be seen with the naked eye. They feed by sucking plant juices with piercing-sucking mouth parts, causing white or yellowish specks on leaves; then off-green to bronze discoloration. Controls range from hosing down plants with a strong spray of water (syringing) to using insecticidal oils or soaps; or using insecticides such as Kelthane, malathion, Cygon or Orthene when mites are active. Tap a branch over a white sheet of paper to monitor for active mites. They’ll appear as specks moving around on the paper. NOTE: Carbaryl (Sevin) can increase mites by killing their predators. Spider Mites and Their Control, http://ohioline.osu.edu/hyg-fact/2000/2012.html Spider Mites, http://www.ext.colostate.edu/PUBS/INSECT/05507.html |
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