Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Hort Update for the week of 6/18/2010
Bold items are new in this issue of Hort Update
|1. No-phosphorus fertilizers||Important to use; can be difficult to find|
|2. Brown patch||Reddish brown patches; tan lesions with red margins on blades|
|3. Dollar spot on golfcourses||Small, tan patches; bleached lesions encircle grass blade|
|4. Grub control||3rd week of June to mid July best time for insecticides|
|5. Mole damage||Raised tunnels caused by moles feeding on earthworms/insects|
|6. Wildlife damage||Peeling back of turf or uprooting of turfgrass for insects|
|7. Ascochyta tip blight||Browning of turf. Similar to drought. Grass blade tips are white.|
|Trees & Shrubs|
|8. Bagworms hatching||Young bagworms ¼ to ½" long. Treat evergreens now.|
|9. Sycamore anthracnose||Severe defoliation. Leaves with brown edges/spots.|
|10. Hackberry & oak tatters||Numerous holes in leaves due to a corn herbicide|
|11. Peach leaf curl||Curling and puckering of leaves; reddish tinge to leaves|
|12. Maple bladder gall||Bladder-like galls on leaves change from green to red to black|
|13. Spindle gall on Lindens||Thin, spindle-shaped galls (green to reddish) on leaf surface|
|14. Rust on many trees||Yellow to orange spots on leaf surfaces and undersides|
|15. Hawthorn leafminer||Squiggly white to tan tunnels or brown areas on leaves|
|16. Iron chlorosis||Pale green to yellow leaves with darker green veins|
|17. Small maple, hackberry & oak leaves||Heavy fruit load = restricted leaf growth; also chill injury|
|18. Hosta X virus||Odd leaf coloration or patterns; crinkled leaves|
|19. Slugs (Hosta, veggies, roses)||Leaf holes or skeletonized leaves; slime trails on leaves|
|20. Rose rust||Raised orange pustules, spots, on leaves|
|21. Asters yellow||Stunted, distorted flowers that fail to open|
|Vegetables & Fruits|
|22. 2, 4-D damage||Curling, twisting, cupping of leaves|
|23. Fruit drop in trees||Sudden drop of small fruit|
|24. Vegetable weed control||Time to mulch, cultural practices, water at base of plant|
|25. Monitor for tomato diseases||Watch of leaf spots and lesions on lower leaves|
|26. Mushrooms||Promoted by moisture. Fungicides will not control.|
|27. Miller migration (North Platte)||Army cutworm adults migrating west|
1. No-phosphorous fertilizer is recommended for turfgrass due to increased impairment of surface water from this nutrient, which can come from fertilizer granules left on paved areas, sediment, or plant material (grass clipping and tree leaves) that are washed into surface water via run-off water during rain storms. Soils in Nebraska typically have adequate to high levels of phosphorous and this nutrient usually does not need to be applied. Look for and use no-phosphorous fertilizers whenever possible.
2. Brown patch causes roughly circular patches of dead and dying grass. Tan colored, irregularly shaped leaf lesions 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 brown patch when applied at monthly intervals in June, July, and August. Curative applications of chlorothalonil beginning a few days after symptoms of brown patch develop may suppress injury. 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.
Brown Patch Disease of Turfgrass, University of Nebraska- Lincoln Extension
3. Dollar spot on golf courses- On greens and fairways symptoms are typically small, round, bleached spots the size of a silver dollar (1-2 inches in diameter). On taller cut lawns, symptoms are 4- to 6-inch, straw-colored patches. Bleached lesions with reddish-brown margins encircle leaf blades. Spots may coalesce into a larger patch. Damage is most severe when there's a nitrogen deficiency. With all the rain, much nitrogen may have been leached out of root zones or lost to de-nitrification. The best control at this time may be to fertilize with nitrogen. Turfgrass can be treated with fungicides listed in the publication below.
Dollar Spot in Turfgrass, University of Nebraska- Lincoln Extension
4. Grub control- On lawns with a history of white grub damage and where preventive type insecticides are used; the best time to apply these insecticides is from the third week of June to mid-July. Insecticides for preventative grub control include Chlorantraniliprole, Imidacloprid, and Halofenozide. Trichlorfon can be applied for curative control if white grubs exceed threshold levels (8-10 per square foot) later in the season.
White Grubs in Turf, University of Nebraska- Lincoln Extension
5. Moles- Raised tunnels across lawns are the feeding tunnels of moles, which feed on earthworms and insects. Moles are most effectively controlled by trapping. Two bait products, Kaput® and Talpirid®/Tomcat®, show promise. Castor oil and castor oil products, such as Mole-Med® or MoleChase®, have shown minor effectiveness in repelling the eastern mole.
It does not work to apply insecticides to control moles by controlling their food source. It does not work to use toxic grain or poison peanuts.
Moles and Their Control, University of Nebraska- Lincoln Extension
6. Wildlife such as skunks, raccoons, and opossums can damage lawns by peeling back turf or uprooting turfgrass to access insects. The best control is to deter wildlife from the area. Trapping is an option.
Why are skunks tearing up my lawn?, eXtension.org
7. Ascochyta Tip Blight- Patches or large areas of lawn suddenly turn straw or tan color, resembling drought stress. Leaf blades have bleached white tips and the blade is constricted where dead tissue merges with green tissue. Considered a minor disease related to environmental and poor management stress. Turfgrass usually recovers in one month or less without treatment. Fungicides are generally not recommended or needed.
Ascochyta Leaf Blight, Colorado State University Extension
8. Bagworms are hatching, so now is the time to monitor for their presence on evergreen conifers. If present, apply insecticides. At this time of year, young bagworms will be approximately ¼ to ½" long.
Bagworms, University of Nebraska- Lincoln Extension
9. Anthracnose is a common fungal disease on sycamore, ash, maple, and oak. It causes irregular brown areas on leaves and minor to severe defoliation of most trees. Sycamore is most severely affected by anthracnose with severe defoliation often occurring year after year. While it is too late to apply fungicides now, a management program for sycamore anthracnose may be needed for next spring. See the link below for more information.
Sycamore Anthracnose, Colorado State University
10. Hackberry or oak leaf tatters is caused by the chloroacetamide herbicides often used in corn. Typically tree leaves are full of holes, giving them a tattered appearance. With 2, 4-D herbicide, typical symptoms are curling, cupping or twisting of leaves along with distorted veins and leaf yellowing.
If herbicide is suspected, inspect other plants in the area as herbicide injury will typically be found on more than one type of plant. Whether long term injury will occur is difficult to assess as it is difficult to know how much herbicide the plant received. In most cases, otherwise healthy woody plants recover. Repeated exposure to herbicides can lead to tree decline and increased susceptibility to pests.
Pictures of tatters and 2,4-D injury, South Dakota State University.
11. Peach leaf curl is a fungal disease, caused by the fungus Taphrina deformans, and causes developing leaves of peach and related species to become severely distorted, thickened and puckered with a reddish or purple cast. As spores form on the leaf surface, leaves become powdery gray in color and leaves may turn yellow or brown and drop. This disease is most severe during cool, wet spring. If there is severe defoliation, the tree will be weakened, especially if a heavy fruit crop is allowed to develop. Control is fairly easy if fungicides are applied very early in spring just prior to leafing.
Peach Leaf Curl, University of Nebraska- Lincoln Extension
12. Maple bladder galls are bright green or red galls that later turn black, usually on upper surfaces of maple leaves. When these galls turn black, they may fall off leaves, resulting in small holes. A few leaves may be so infested they drop off, but this is not common. These galls are caused by the feeding of a very tiny mite and do not affect the health of the tree. Treatment is not recommended and is not effective once galls are present.
Maple Bladder Gall, Spindle Gall and Gouty Vein Gall, Ohio State University
13. Spindle Galls are thin, elongate bladders arising from the upper leaf surface. These galls, caused by the feeding of a tiny mite, rarely distort the leaf but considerable numbers of galls can make leaves unsightly. Control is not needed and it is too late to implement control.
Maple Bladder Gall, Spindle Gall and Gouty Vein Gall, Ohio State University
14. Ash rust causes yellow/orange, raised spots on leaves. This fungus is not a problem for trees. No fungicide control is needed and it is too late to treat.
Ash Rust, University of Nebraska-Lincoln
15. Hawthorne leafminer create sigmoidal or S-shaped tunnels or brown areas on leaves caused by larvae feeding within leaves. By the end of May, larvae leave their mines and pupate within the soil. There is one generation per year. No control is effective once leaf minors are inside leaves. Control is rarely needed.
Hawthorn leafminer, Purdue University
16. Iron Chlorosis- Tree and shrub leaves turn pale green to yellow with darker green veins. Most common cause is high pH soils causing iron in the soil to become less available to susceptible plants. Most often seen in pin oak, red and silver maple, ornamental pear, river birch, Spirea, as well as other woody plants. This issue is best prevented by selecting woody plants adapted to higher pH soils. Established trees can be treated with iron via a soil treatment, trunk injection or foliar spray. Read and follow all label directions.
Iron Chlorosis, Colorado State University
17. Small maple, hackberry, oak leaves- Without a spring freeze to kill flowers, many trees produced a heavy fruit/seed crop. Much of the trees energy went into seed production, resulting in smaller than average leaves and thinner tree canopies in some cases. For most trees, this is not an issue. Be alert for tree seedling weeds in shrub and flower borders. Pull when young. Tree seedlings in lawns will be killed by mowing. There is no need to fertilize trees that had a heavy fruit crop.
18. Hosta Virus X (HVX) is a virus infecting many Hostas. Symptoms range from stunting to leaf puckering, ring spots and other odd leaf colorations. While this disease does not kill plants, it spreads prolifically and infected plants should be destroyed. The virus is transmitted primarily through propagation of the plants or mechanical injuries.
Contact of the infected plant's sap, with sap of a healthy plant will infect the new plant. This can happen whenever cuts are made and tools or hands are not disinfected afterwards. Dividing hostas, removing bloom scapes, removing leaves, stepping on them, even accidentally mowing over them can spread the virus. There is no control. Plants suspected of having HVX should be destroyed.
Hosta X Virus, Ohio State University
19. Slugs are soft, slimy, slender mollusks; not insects. 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.
To reduce slugs, slug traps may be helpful. Beer traps, shallow containers of beer sunk in the ground so the top edge is level with the soil, are only moderately successful if at all. A better method is laying wet newspapers, shingles, burlap, or boards on the ground overnight. Check beneath these the next day and dispose of slugs in a can of soapy water. Gritty materials, such as diatomaceous earth, can be scattered on the soil surface and may 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.
Slugs, Colorado State University
20. Rose rust produces yellow-orange spots on leaves. No alternate host is needed so the fungus can keep re-infecting the rose. Sanitation is important, so remove infected stems and leaves at first appearance. Preventive fungicides include chlorothalonil (Daconil 2787) or systemic fungicides such as triadimefon or triforine (Funginex).
Controlling Rose Diseases, Ohio State University
21. Aster Yellows is a common disease that affects many ornamental flowers. Susceptible plants include Aster, Chrysanthemum, Coreopsis, cosmos, Echinacea (coneflowers), Dianthus, Gladiola, marigold and Petunia. Vein clearing, or loss of green pigment within the veins, is often the first symptom. Stunting, stiff extra bushy yellow growth, deformed or poorly developed flowers which remain green are all common symptoms. There is no cure for infected plants. Remove and discard them to reduce further spread.
Aster Yellows, Kansas State University
22. Herbicide injury appears as curling, cupping or twisting in leaves as well as distorted veins and leaf yellowing. Tomatoes are highly susceptible. If herbicide is suspected, inspect other plants in the area as herbicide injury will typically be found on more than one type of plant. Whether long term injury will occur is difficult to assess as there is usually no way to know how much herbicide the plant received. We cannot recommend affected produce from vegetables and/or fruits are safe to eat if exposed to herbicide drift.
23. Fruit Drop- Natural fruit thinning usually occurs in June when fruit trees drop a number of fruits, often due to poor pollination or to heavier than average fruit set. This is not a concern and most trees will continue to develop a good number of fruit.
If trees do not experience natural fruit thinning, it is important to manually thin fruit, especially this year due to heavy fruit set. The sooner this can be done, the better. Encourage fruit thinning by July 1st. Manual fruit thinning prevents trees having alternate year bearing; reduced fruit size and flavor; and branch breakage.
Thinning is best accomplished by hand picking fruits after June drop and by July 1. Where fruits are clustered, remove all but one fruit per cluster. Space fruits from 5-8 inches apart, removing the small insect and disease injured fruit first. Fruits may be spaced closer together on the outside and top of the tree than in the center, because these branches receive full sunlight.
24. Vegetable weed control is best accomplished through hand weeding, hoeing, and mulching. Place a two to four inch layer of grass clippings or wood chips between rows and hills. Keep mulch away from plant stems. Avoid the use of green grass clippings by allowing them to dry and turn brown first. Wait until after three mowings before using clippings from a lawn to which a herbicide has been applied. Preen herbicide products labeled for use in vegetable gardens are best applied after hand weeding and just prior to mulching if they are used.
25. Tomato diseases such as early blight and Septoria leaf spot are, or will soon, appear on the lower leaves of plants. Monitor plants closely for signs of these leaf spot diseases. Fungicides labeled for use on tomatoes need to be applied at the first signs of disease. Use mulch around the base of plants and avoid overhead irrigation.
26. Mushrooms and slime mold- With the moist weather we've had, fungal slime molds and mushrooms in home lawns are prolific. There is no treatment. Clients should pick and throw away the mushrooms prior to mowing to help reduce the number of spores. Mushrooms will continue to appear until the decaying material (buried wood, decaying tree roots, or thatch) they feed on is gone. They are harmless to lawns.
Slime molds sometimes look like dog vomit (hence the name dog vomit fungi) and can come in many bright colors, while others appear as grayish masses on turf leaf blades. Symptoms of leaf blade smile molds may be seen as irregular patches of discolored turf ranging in size from several inches to several feet in diameter. Some slime molds feed on decaying material and are often found in mulched ornamental beds, while others use turf leaf blades strictly as a structure to grow on.
Slime Molds on Turfgrass, Ohio State University
27. Miller migration in west central Nebraska- Millers can be abundant around homes this time of year. They are most likely one of the spring miller moths, such as armyworm moths, that typically feed at night on the nectar of flowering trees and shrubs. They do not cause damage, unless you smash them on the wall and create a stain. They are usually around in large numbers for a short period of time as they migrate west, but can become a nuisance. Other than turning off night lights, no control is needed or recommended.