Hort Update for the week of 8/20/07
| Current Problems: | Major Symptom: |
Lawns |
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| 1. Fall weed control | Control broadleaf perennial weeds & winter annuals in fall. |
| 2. Overseeding & turfgrass cultivars | September is the best time to overseed cool season grasses. |
| 3. White grubs | Dead, brown areas in lawns. Sod rolls back readily & grubs are found. |
| 4. Yellow nutsedge control timing | Yellow-green, grass-like weed with waxy leaves. |
| 5. Stem rust | Orange-yellow powder (fungal spores) on grass blades, mowers, shoes. |
| 6. Brown patch | Roughly circular, brown patches in lawns. Tan lesions with red margins. |
| 7. Dollar spot | Small, brown patches in lawns. Tan lesions with red margins. |
| Trees & Shrubs | |
| 8. Oystershell scale | Branch dieback in shrubs (lilac, privet, etc.). Scales found on twigs. |
| 9. Lilac borer | Branch dieback. Borer holes & frass at base of stems. |
| 10. Fall webworm | Fairly large, unsightly webs filled with worms in deciduous trees. |
| 11. Lacebugs | Discoloration of leaves on hackberry, sycamore, oak, etc. |
| 12. Oak twig girdler | Small clusters of brown leaves on twig tips. |
| 13. Bagworms | Defoliation of evergreens and small brown bags attached to stems. |
| Miscellaneous | |
| 14. Wolf spiders | Nebraska ’s largest spider. May be found indoors in the fall. |
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 1. Fall Weed Control- Mid September to early October is the best time to control perennial, broadleaf weeds (dandelions, bindweed, white clover, ground ivy) in lawns. Plants are moving photosynthetic products into the roots for winter storage and more herbicide is moved into roots, increasing root kill. Herbicides labeled for lawns and broadleaf weed control such as 2,4-D and combination herbicides, such as Trimec, are recommended. Winter annuals (Henbit, Speedwell, Shepardspurse) germinate in the fall then grow, flower and produce seed the following spring and summer. For their control, apply preemergent herbicides (Dimension, Barricade or pendimethalin based products for lawns and Preen for ornamental beds) in early September or post emergent herbicides, 2,4-D, in late October. Landscape Weed Management, http://www.ianrpubs.unl.edu/sendIt/ec1256.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 2. Overseeding and Turfgrass Cultivars- Overseeding to increase lawn density, fill in bare areas, or introduce improved cultivars is best done in September. When overseeding, use improved cultivars and those considered to have disease resistance. When overseeding, it’s critical to achieve good seed to soil contact. Methods to use include using a slit seeder that plants seed through existing grass and into the soil; power raking and then removing all dead grass and debris before overseeding; and/or, core aerating (plugging) the lawn to relieve soil 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. A list of turfgrass cultivars recommended for Nebraska can be found on the UNL Extension Horticulture website at http://extensionhorticulture.unl.edu/ToDo/TurfCultivar07.shtml. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 3. White Grubs cause lawn areas to brown and die. On inspection, the sod can be easily rolled back as the grubs have eaten the roots, and the c-shaped, cream colored and red headed beetle larvae will be found. If 8 white grubs are found per square foot, an insecticide application may be justified. At this time of year, Dylox is the insecticide of choice. Imidacloprid (Merit) provides better control for white grubs but needs to be applied before eggs hatch; ideally in June or early July. White Grubs In Turf, http://www.ianrpubs.unl.edu/sendIt/g1619.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 4. Yellow Nutsedge control timing- Hand-pulling and herbicide applications are most effective in controlling yellow nutsedge when applied prior to June 21st. Prior to June 21st, the tubers (nutlets) attached to the visible plant (mother plant) are in the maturation process but will normally not break dormancy and grow if the mother plant is damaged from pulling, spraying or other injury. After June 21st, any activity which removes the mother plant results in the now mature tubers breaking dormancy and sprouting. If a plant has multiple tubers attached to it, it is not uncommon for 3-5 sprouts to emerge resulting in an increase in nutsedge plants. Some of these will overwinter resulting in an increase in nutsedge the following year. Ideally, spray before June 21st to control the mother plant before it can make daughter tubers. This is not always possible so go ahead and spray after June 21st realizing that it is not the optimal time for maximum efficacy. Multiple sprays after June 21st or the use of a contact nutsedge herbicide like Dismiss or Q4 helps circumvent some of the physiological problems associate with spraying after June 21st. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 5. 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 also 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, http://hcs.osu.edu/sportsturf/notes/detail.lasso?id=1094 """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 6. Brown Patch causes r oughly circular patches of brownish grass. Patch centers may be less affected and have a frog-eye-like symptom. Tan colored, irregularly shaped leaf spots with red margins are found on leaf blades. In many cases, lawns damaged by brown patch recover in two to three weeks, provided the outbreak is not sustained by continuous hot, humid weather; and treatment may not be necessary. Treatments after August 15 th are not very effective. Use good fall lawn care practices to encourage turf recovery. Core aerate and overseed with disease resistant cultivars in September. Rhizoctonia Brown Patch of Tall Fescue, http://www.oznet.ksu.edu/path-ext/factSheets/Turf/RhizoctoniaBrownPatchOfTallFescue2.asp """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 7. 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. Dollar Spot on Turfgrass, http://ohioline.osu.edu/hyg-fact/3000/3075.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 8. Oystershell Scale is a common insect pest of many woody plants. It feeds on plants by sucking plant sap. Heavy infestations can kill branches and even cause the decline and death of a plant. Oystershell scales overwinter in the egg stage. The eggs hatch in the spring and newly emerged insects attach themselves to the plant and develop the protective scale. Oystershell scales are best controlled when eggs hatch and light yellow crawlers appear, about late May. There may be a second hatch in August. Monitor plants at this time for the presence of yellow crawlers. Horticultural oils, insecticidal soaps, Acephate or Malathion are recommended controls. Oystershell Scale, http://www.ext.colostate.edu/pubs/insect/05513.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 9. Lilac Borer is actually the ash/lilac borer. On lilac, infested branches suddenly wil t and dieback. The base of infested stems are swollen and bark separates from the wood. A fine sawdust-like material may be present around holes in the stems. On ash, the trunk and major branches will show exit holes of adults. Ash/lilac borers overwinter as larvae in infested trees and shrubs. Pupation occurs in spring and moths emerge to lay eggs with egg laying beginning in May. Around May 10 th, thoroughly treat the trunk and larger limbs of ash or the lower portion of the stems of lilac or privet with insecticides containing permethrin (High Yield, Super Eight, Astro). Repeat application in 3 weeks. Clearwinged Borers, http://entomology.unl.edu/ornamentals/pestprofiles/clearwinged_borers.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 10. 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 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 11. 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 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 12. 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 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 13. Bagworms cause browning or defoliation mainly of spruce and juniper. Small bags covered with brown needles are 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 the population 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 and during winter. Insects of Evergreen Trees, http://www.nfs.unl.edu/documents/foresthealth/insectevergreen.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 14. Wolf Spiders are among the largest spiders in Nebraska. Wolf spiders are not considered poisonous, although a bite may cause a reaction in certain individuals. The presence of wolf spiders in the house is fairly common in late summer and fall when they accidentally wander indoors. Wolf spiders do not trap their prey in webs. They are appropriately named because they pounce on their prey; hence they can move quite rapidly. Because there usually are only a few spiders at most, it isn't necessary to use an insecticide. Instead, put sticky traps (i.e., mouse glue boards) in the corners of rooms to passively trap unwanted spiders and other insects. Outdoors, wolf spiders are beneficial because they feed on so many insects. Wolf Spiders, http://www.uky.edu/Ag/CritterFiles/casefile/spiders/wolf/wolf.htm Spiders (images), http://entomology.unl.edu/images/spiders/spiders.htm |
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