Hort Update for the week of 7/2/07
| Current Problems: | Major Symptom: |
Lawns |
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| 1. Crabgrass | Light green annual weedy grass |
| 2. Annual bluegrass, Poa trivialis | Patches of a finer bladed, light green grass going turning brown |
| 3. Broadleaf weeds | Ground ivy, white clover, etc. |
| Trees & Shrubs | |
| 4. Spruce needle miner | Inner needles of Spruce turn brown; may be webbed together |
| 5. Sycamore lacebug | Sycamore leaves become off-color; stippled with black specks |
| 6. Hackberry leaf drop | Green leaves dropping from tree; some yellowing |
| 7. Spider mites | Leaves turning off-color with stippling; some webbing |
| 8. Euonymus scale | Browning of leaves; twigs covered with scales |
| 9. Squirrel damage | Stripping of bark on trees; some twig girdling |
| Ornamentals | |
| 10. Slugs | Holes chewed in leaves, particularly on hosta |
| Vegetables/Fruits | |
| 11. Tomato leaf roll | Leaves roll up along the vein in an upward fashion and remain green. |
| 12. Tomato leaf spot diseases | Yellow to brown spots appear on the lower leaves and move upward. |
| 13. Aphids | Yellowing and browning of leaves. Aphids found on leaf undersides. |
| 14. Broccoli not heading | Large, healthy plants, but no head (flower bud) development |
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""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 1. Crabgrass- The best control of crabgrass is proper cultural practices; in particular a mowing height of 2.5 to 3” tall and the use of pre-emergence herbicides applied in late April to mid May. At this time of year, control by hand-pulling or with post emergence herbicides. Post emergence herbicides are most effective when crabgrass plants are small and coverage of plants is uniform. Adjuvants are often needed. Follow label directions carefully as some of these products may injure turfgrass. Post emergence herbicides for crabgrass control include the methanearsonates MSMA and DSMA, Fenoxaprop (Acclaim Extra), Dithiopyr (Dimension), and Quinclorac (Drive). Postemergence herbicides can be combined with preemergence herbicides to insure late germinating summer annual grasses are controlled along with weeds that have already emerged. Be sure to follow label directions when considering combinations of herbicides. Control of Crabgrass in Home Lawns, http://www.agry.purdue.edu/turf/pubs/AY-10.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 2. Annual bluegrass, Poa trivialis- A light green, shallow rooted grass that goes dormant in July and August creating brown patches in the lawn; especially in shady, moist, or overwatered sites. Usually comes from seed contamination during the original seeding or during overseeding, or may occur naturally. Control Poa trivialis selectively in Kentucky bluegrass with Sulfosulfuron (Certainty) or nonselectively with glyphosate. ID and Control of Annual Bluegrass and Rough Bluegrass in Lawns, http://www.agry.purdue.edu/turf/pubs/AY-41-W.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 3. Broadleaf Perennial Weeds- If perennial broadleaf weeds like ground ivy and white clover are a problem in lawns, homeowners should check their lawn management practices. See link for Kentucky bluegrass Lawn Calendar. If needed, make changes in management practices that will help promote a dense turf better able to compete with weeds. The preferred time to control broadleaf weeds with herbicides is late summer through early fall, before a hard freeze. Kentucky Bluegrass Lawn Calendar, http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=486 Fall Is Prime Time For Controlling Broadleaf Weeds, http://lancaster.unl.edu/hort/Articles/2006/Broadleaf.shtml """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 4. Spruce Needle Miner – Clumps of dead needles in the inner part of Spruce trees. The clumps are held together by webbing and the miner leaves a hole near the base of the needles. Adult moths are active in June, laying eggs on spruce needles. Larvae feed from late June until frost, then over winter as partly grown larvae in needles and resume feeding in early spring until mid-May when they pupate. During egg-laying is the best time to apply insecticides. Once eggs hatch and the miner bores into needles, control is difficult. Control spruce needle miner by removing infested needles. These can be hosed out of the tree, cleaned up, and destroyed. Apply insecticides, such as malathion, in late June with a repeat application in a week or ten days. Spruce Needle Miner, http://cru.cahe.wsu.edu/CEPublications/eb1089/eb1089.pdf """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 5. Sycamore Lacebug- cause shade tree leaves to discolor and turn yellowish or whitish. On close inspection, the leaves appear stippled and tiny lacebugs or specks of their shiny black excrement may be found on leaf undersides. Lacebugs are sap feeders. Damage is usually more cosmetic than harmful to trees. Tree Leaves Looking Strange?, http://www.dakota.unl.edu/newsitems/news040805153332 Lacebugs on Deciduous Trees & Shrubs, http://www.extension.umn.edu/yardandgarden/ygbriefs/e452lacebug.html """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 6. Hackberry Leaf Drop- Over the years, we hear reports of hackberry trees dropping a large amount of leaves in June. In most cases, no disease or insect is found and no controls are needed. Suggested causes are cold temperature injury when the leaves were in the bud stage, chemical sensitivity to herbicides, and drought stress. In many cases, the tree drops a number of leaves, then develops healthy new leaves. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 7. Spider Mites- Spider mites have been reported on burning bush, but these mites can affect a wide variety of plants from evergreens to shrubs and ornamentals. Mites, which can barely be seen with the naked eye, feed by sucking plant sap with piercing-sucking mouth parts, causing white or yellowish specks on the leaves. Leaves eventually turn yellow to bronze colored. Dust may build up in the very tiny webs, making them noticeable. Controls range from hosing down the plants with a strong spray of water (syringing) to using insecticidal oils or soaps, or insecticides such as Kelthane, malathion, Cygon or Orthene when the mites are active. Spider Mites and Their Control, http://ohioline.osu.edu/hyg-fact/2000/2012.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 8. Euonymous Scale- Leaves turn yellow and drop off. Stems are covered with a gray or whitish scale. Scales feed from beneath the protective scale, removing plant sap from stems and leaves. Controls are most effective when the insect is in the crawler stage. Monitor for the presence of crawlers by wrapping a few stems with black electrical tape with the sticky surface facing out near where scales are present. Crawlers are yellowish to orange. When in the crawler stage, control with insecticidal soaps. Systemic insecticides are also effective. Read and follow label directions for effective application. Euonymus Scale, http://entomology.unl.edu/ornamentals/pestprofiles/euonymous.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 9. 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 the failure of common shade trees, such as maple and oaks, to set seeds due to April's freezes. Both maple and oak seeds are an important summer food source for squirrels. Squirrel Damage to Trees, http://www.ext.colostate.edu/ptlk/2303.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 10. Slugs - Slugs are soft, slimy, slender mollusks, not insects, and are particularly a problem on hosta. During the evening, slugs feed on leaves and flowers causing various sized holes. During the day, slugs hide beneath plants, pots, weed mats, boards, or in the soil. Traps are helpful to reduce slug populations. Beer traps, shallow containers of beer sunk in the ground so the top edge is level with the soil, are only moderately successful. A better method is laying wet newspapers, shingles, or boards on the ground overnight. Check beneath these the next day and kill the slugs. Gritty materials, such as diatomaceous earth, can be scattered on the soil surface to reduce slugs. For chemical control, baits containing metaldehyde (Deadline, Defender) or iron phosphate (Escar-Go, Sluggo) are available. As with all pesticides, label directions must be followed carefully. For best control, apply these products on a warm, clear night during dry weather. Place them under boards or traps to help protect birds and pets. Two or more treatments at 5 to 7 day intervals may be needed for adequate control. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 11. Tomato Leaf Curling- There are a variety of causes of leaf curling in tomatoes ranging from environmental conditions to herbicide injury. If leaves are rolling, but are not distorted or turning brown, this is most likely leaf roll. When tomato plants grow vigorously in mild, spring weather the top growth often exceeds root development. When the first few days of warm, dry summer weather hit, the plant increases root development and reduces leaf area by rolling leaves. The leaves curl along the length of the leaf in an upward fashion. Leaf roll is worse on some varieties than others. Though rolling usually occurs during the spring to summer shift period, it may also occur after heavy cultivation or hoeing, hard rain, or any sudden change in weather. Too much rain can saturate the soil and suffocate the roots. A root system lacking oxygen cannot move water to the upper parts of the plant resulting in the same symptoms that occur with too little soil moisture or a limited root system. Avoid deep hoeing close to plants, mulch to keep the soil cooler and to moderate moisture extremes and do a good job of watering by keeping the soil moist but not waterlogged. Leaf roll is a temporary condition that goes away after a week or so when the plant has a chance to acclimate, recover from injury, or the soil has a chance to dry out. Leaf Roll on Tomatoes, http://www.oznet.k-state.edu/dp_hfrr/extensn/problems/Tomatoleafroll.htm """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 12. Tomato Diseases- Wet, rainy weather promotes fungal diseases, and tomatoes are susceptible to a number of fungal leaf diseases. The pathogen is often carried to the lower leaves through water splashing soil and fungal spores onto leaves during rain or overhead irrigation. Symptoms vary from brown spots with concentric rings to yellow spots. Infected leaves turn yellow or brown and drop from the plant. The disease moves up the plant as the season progresses. Control includes selecting disease resistant varieties, using mulch to reduce soil splash, caging tomatoes to keep the leaves off the ground and avoiding overhead irrigation. Fungicides applied when leaf spots are first noticed on the lower leaves can slow the disease progress. For identification of tomatoes diseases, see the below link. Tomato Disease Identification Key, http://vegetablemdonline.ppath.cornell.edu/DiagnosticKeys/TomLeaf/TomLeafKey.html """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 13. Aphids on Potatoes and Peppers- Aphids are small, soft-bodied insects with long, slender mouth parts used to pierce stems, leaves, and other tender plant parts to suck out plant fluids. They feed on a wide variety of plants and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. Large populations cause curling, yellowing, and leaf distortion. Check plants regularly for aphids, especially when plants are growing rapidly, by inspecting leaf undersides. Small populations may be controlled by natural enemies, dislodging with a strong spray of water, or removing and destroying infested leaves. Chemical controls include insecticidal soaps, neem oil and malathion or permethrin. Purchase products labeled for use on vegetables and follow all label directions for application and the waiting period between application and harvest. Carbaryl is not recommended because it is not very effective against aphids. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 14. Broccoli not producing heads- Healthy broccoli plants not producing heads might be the result of cold temperatures in April, if the transplants were set out at that time. Overfertilization with nitrogen may also result in large plants and few heads. |
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