Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
Hort Update for the Week of July 10, 2012
|1. Stem rust- Kentucky bluegrass||Early infections producing powdery orange spores|
|2. Summer patch- Kentucky bluegrass||Circular tan to brown patches. Too late for fungicides.|
|3. Brown patch- Tall fescue||Reddish brown patches. Avoid over fertilization & overwatering|
|4. Japanese beetles/ masked chafer beetles||White grubs adults laying eggs; treat lawns with a history of grub damage.|
|5. Dormant Kentucky bluegrass||Water ¼” every 4 to 5 weeks. Do not let tall fescue go dormant.|
|6. Yellow nutsedge||Tubers maturing, but herbicides can still be applied|
|Trees & Shrubs|
|7. Heat stress symptoms||Leaf margins browning; leaves with odd coloration|
|8. Ash rust||Raised orange postules on leaves; some leaf distortion|
|9. Watering trees||Keep soils moist, not saturated. Use mulch wisely.|
|Zimmerman Pine Moth||Dead branches and large pinkish pitch masses on Scotch & Austrian. Spray 3rd week of July.|
|10. Aster yellows||Flowers with stiff, bushy growth that remains green|
|11. Daylily leaf streak & rust||Leaves yellow and die from the tip downward|
|12. Powdery mildew||Grayish white powder on leaf surfaces|
|Fruits & Vegetables|
|13. Squash vine borer||Vines wilt. Base of stem soft and covered with frass.|
|14. Bagworms found on unusual plants||Tiny brown bagworms chewing on leaves of fruiting plants|
|15. Peaches not ripening||High temperatures slowing ripening|
|16. Poor fruit set- tomato and other vegetables||Caused by high nighttime temperatures and humidity|
|17. Sap/picnic beetles||Small black beetles feeding in ripe and over-ripe fruits|
|18. Ticks and chiggers||UNL has good resources on identifying & dealing with|
|19. Cicada killer wasps||2” long black & yellow wasps; gentle & rarely sting|
|20. Bats in houses||Young bats leaving roosts; deal with safely to avoid rabies|
1. Stem rust is showing up in Kentucky bluegrass much earlier this year. Symptoms are an orangish-yellow powder (spores) on grass blades, shoes, pant legs and mowers. Infected turf may develop a yellow or brown appearance. Rust develops on lawns with slow growth. Fungicides are not recommended for home lawns. When the disease shows up later in the season, fall fertilization usually takes care of it. However, fertilizing cool season turfgrass in July and August is stressful due to heat and drought. On turf with heavy rust infection, a light fertilization and adequate watering can be helpful. Fungicides might be justified but need to be applied in conjunction with adequate watering and a light fertilization.
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 in Lawns, Purdue University
2. Summer patch is showing up in Kentucky Bluegrass turf but it is too late for fungicide applications. Symptoms are one to two foot, tan colored, circular, crescent, or serpentine shaped patches in full sun areas and south facing slopes. Tufts of healthy green grass may remain in patch centers. No leaf spots will be found on grass blades. The fungus attacks roots in spring. Infected plants may have dark brown to black roots. Control includes proper lawn care practices that reduce stress, overseeding with resistant cultivars, and fungicide applications made in May.
3. Brown patch is infecting susceptible tall fescue lawns that are overwatered and overfertilized. Brown patch appears as roughly circular reddish-brown to tan patches in turfgrass. Irregular shaped tan lesions with reddish margins are found on grass blades and confirm brown patch. To manage this disease, avoid overwatering and over-fertilizing tall fescue lawns.
Brown Patch Disease NebGuide, University of Nebraska-Lincoln
4. Japanese beetles and masked chafer adults present- Japanese beetles are present in far eastern Nebraska. Masked chafer adult beetles are present statewide. Both are adults of white grubs. On turfgrass with a history of white grub damage, the preventive insecticides imidacloprid (Merit) or halofenozide (Mach 2) are recommended to be applied by mid-July. With above average early temperatures this year, the recommended application timing was earlier. This year, these products were best applied from June 14 to the 4th of July. They can still be applied, but the sooner the better. There is no need to apply insecticides to lawn that do not have a history of white grub damage. Correct irrigation is important to effectiveness.
White Grubs in Turf, University of Nebraska-Lincoln
5. Kentucky bluegrass and summer dormancy- To conserve water and reduce maintenance, KBG can be allowed to go dormant for summer by reducing watering. Once the grass is dormant, keep it alive by applying ¼” inch of water every 4 to 5 weeks to hydrate plant crowns. Do not allow tall fescue to go dormant. Tall fescue does not have natural summer dormancy. If it turns brown, it is dead. However, avoid overwatering tall fescue. It does not require as much water as KBG. Use deep and infrequent irrigation.
6. Yellow Nutsedge control- Ideally, herbicides are applied by June 21. After the summer solstice, tubers mature and while herbicides will kill the mother plant, they may stimulate tuber germination. If herbicides applied for nutsedge have not been applied, they still can be; possibly with reduced control overall.
Yellow Nutsedge: Identification, Management and Control, University of Nebraska-Lincoln
7. Heat stress symptoms in trees is typically leaf scorch. We are also seeing odd coloration such as a reddish-purpling of leaves. Leaf scorch causes a uniform yellowing or browning of leaf edges. Browning may extend between the veins. Scorch indicates leaves are transpiring moisture from leaves faster than it is replaced by roots. Leaf scorch occurs for a variety of reasons. Young trees with unestablished root systems, especially those growing on exposed, windy sites, often show leaf scorch. Young tender growth, especially lush growth promoted by nitrogen fertilizer, can scorch during hot, windy days even with established root systems. Leaf scorch may be a symptom of a root and/or trunk related problem. Both over-and underwatering may lead to leaf scorch. When this symptom appears, avoid fertilization; check soil moisture for dryness or saturation; then use correct irrigation practices to encourage recovery.
Leaf Scorch, University of Nebraska-Lincoln
8. Ash rust- Yellow/orange, raised areas on leaves are signs of a fungal rust disease. On ash, rust may cause some twisting of foliage and leaf drop. It is not a serious disease and fungicides are not needed. Applications need to begin just as trees are leafing in spring to be effective. Applications made now will do very little to control disease. The best management practice is selection and planting of resistant cultivars.
Ash Rust, University of Nebraska-Lincoln
9. Watering trees is beneficial when done correctly. Ideally, the soil is moist but not saturated to a depth of about 8 to 12 inches when trees are watered correctly. Moisture is critical to root establishment, root function, as well as reducing drought stress; however, adequate levels of soil oxygen are also critical to root growth and function. How much and how often to water trees is dependant on soil type, site conditions, age, species of tree and environmental conditions.
For wise watering tips, see:
Watering Tips for Trees and Shrubs, University of Nebraska-Lincoln
Tree & Shrub Late Addition:
Zimmerman pine moth larvae tunnel beneath the bark of pine trees, particularly in branch crotches, causing branches to die or break off readily in wind and snow storms. A pinkish mass may be found at the base of infested branches.
Insecticides, such as bifenthrin or permethrin, are normally recommended to be applied during the second week of April and the second week of August for best control. However, Zimmerman moths are emerging early this year due to the unusually warm spring and subsequent early development of many insects. So Mark Harrell, Nebraska Forest Service Forest Health Program Leader recommends that this year the second application be made next week- the third week of July- in eastern Nebraska. If you’ve been scouting trees and have seen pupae or empty pupal skins, then the best time to spray would be about a week after the adults have emerged. Use the label rate for borers and apply to the trunk and major branches.
10. Asters yellow is a common disease that affects many ornamental flowers. Susceptible plants include asters, Chrysanthemum, Coreopsis, cosmos, Echinacea (coneflowers), Dianthus, Gladiola, marigold and petunias. Vein clearing, or loss of green pigment within the veins, is often the first symptom. Stunting; stiff, bushy yellow growth and deformed or poorly developed flowers that remain green are symptoms. There is no cure for infected plants. Remove and discard them to reduce further spread.
Aster Yellows, Kansas State University
11. Daylily leaf streak and daylily rust are two diseases causing daylily leaves to yellow and die from the tip back. With leaf streak, symptoms begin as small, reddish-brown flecks and brown lesions on leaves and a yellow streak along the mid-vein that begins at the leaf tip. Rust begins as leaf yellowing from the tip back and reddish brown leaf lesion. With both diseases, entire leaf yellow and die. Run fingers along an infected leaf. If an orangish powdery residue remains on fingers, this confirms rust disease. Overcrowding and warm, wet conditions result in a fungal leaf infections. Control by dividing and increasing the spacing of plantings so leaves dry quickly after rain or heavy dew. Prune out affected plant tissue and maintain good sanitation practices in the garden. Avoid overhead irrigation. Plant healthy, disease-free stock.
12. Powdery mildew appears as a white to gray powdery growth on leaf surfaces, stems, or flowers of a variety of landscape ornamentals. Severe infections can cause yellowing, drying, and browning of leaves; disfigurement of shoots and leaves; and premature defoliation of plants. Powdery mildew is rarely fatal to plants. It is best managed by selecting and planting resistant cultivars and encouraging air circulation by avoiding overcrowding and shading.
Powdery Mildew on Landscape Plants, University of Nebraska-Lincoln
13. Squash vine borers bore into plant stems (mainly squash, pumpkins, and gourds) and their feeding restricts water and nutrient movement. The point where a borer enters a stem, usually at the plant base, may have a sawdust-like frass around it and be decayed. Infested plants are weakened or die; depending on the number of borers. Control borers by practicing good sanitation, physically removing borers by slitting stems when borer activity is noticed, or applying insecticides labeled for vegetables during egg laying, usually about the time vines begin to run, and re-apply every 7 to 10 days for 3 to 5 weeks.
14. Bagworms have been found feeding on the leaves of raspberry, grapes and other fruits and landscape ornamentals. While they typically damage evergreens, monitor fruiting crops and ornamentals for bagworms. If bagworm numbers are small, insecticide control is not justified on broadleaf plants. If bagworm numbers are high and defoliation is severe, insecticides may be justified. When bagworms are small, the organic Bacillus thuringiensis is effective. Other insecticides for bagworms include Spinosad, carbaryl (Sevin), permethrin and bifenthrin. At this time of year, bagworms are one-fourth to one-half inch long, brown and triangular shaped.
Bagworms, University of Nebraska-Lincoln
15. Peaches are not ripening due to extreme heat. Peaches have the best quality when allowed to ripen on the tree. Once picked, they will no longer continue to ripen. Be patient and allow peaches to ripen on the tree before harvesting.
16. Heat and tomatoes- If tomatoes, or other vegetables, are not setting fruit it is likely due to hot night temperatures and humid days. Tomatoes are wind, not insect pollinated. Tomato plants shed the most pollen between 10:00 a.m. and 4:00 p.m. when days are dry and sunny. Optimum fruit set in tomatoes occurs when night temperatures are between 60 and 70 degrees F. When night temperatures are lower than 55 degrees or above 75, this interferes with the growth of pollen tubes and fertilization. High daytime temperatures or prolonged humid conditions also reduce tomato fruit set. If humidity is too low, pollen will be too dry to stick to flower stigmas. If humidity is too high, pollen will not shed readily and pollen grains stick together, resulting in poor pollination. Once night temperatures cool and humidity levels lower, fruit set increases.
17. Sap/picnic beetles are small black beetles that infest fully ripen, over-ripe or damaged fruits such as raspberries, strawberries, tomatoes and sweet corn. The best way to reduce sap/picnic beetles are to be prompt in harvesting fruit once it ripens and remove and destroy over-ripe or damaged fruit as soon as possible.
18. Tick & chigger populations have been fairly high. It is important to identify ticks if one is found embedded in the skin and to correctly remove ticks to reduce the risk of disease transfer. See linked NebGuide for information. Controlling tick-infested vegetation around the home and using contact residual insecticides on the fringe areas of the yard when ticks are most abundant reduces ticks. Insect repellents for humans and shampoos or collars containing insecticide for pets can help or reduce tick infestations. Chigger are a major nuisance when they bite. Preventing bites by staying out of chigger infested areas and bathing soon after being outdoors is the best way to prevent chigger bites.
19. Cicada killer wasps are up to 2” long and black and yellow. They dig nests, creating small soil mounds; then sting and drag paralyzed cicada to the nest and deposit an egg on it. The larval wasp uses the cicada for food. This wasp is solitary (one wasp per nest) and does not defend the nest. They are unlikely to sting humans unless provoked.
Stinging Wasps and Bees NebGuide, University of Nebraska- Lincoln
20. Bats in houses may be common at this time of year as young bats begin to leave roosts to feed at night and accidentally find their way indoors. Because bats can be carriers and transmitters of rabies and histoplasmosis, they must be dealt with safely. See NebGuide for information on safely handling bats inside of a building.
Bats in and Around Structures, University of Nebraska-Lincoln