Hort Update for July 14, 2014
|1. Little on "to do" list for July||Other than watering, little to do for lawns|
|2. White grubs||Preventive products best applied by mid-July|
|3. Post emergence crabgrass control||Quinclorac still industry standard|
|4. Yellow nutsedge control||Thriving in lawns now|
|5. Seed buffalograss ASAP||NebGuide says up to Aug. 15 but the sooner the better|
|6. Some disease beginning to appear in lawns||June rains promoted foliar fungal infections|
|Trees & Shrubs|
|7. Red maples - not leafing or poor canopy||Winter injury not improving|
|8. Iron chlorosis - River birch and others||Yellow leaves with darker green veins|
|9. Apple scab & cedar apple rust||Foliar lesions, yellowing and leaf drop on ornamentals|
|10. Hunting for Emerald Ash Borer||EAB infested trees likely infested by common borers, too|
|11. Budworm of petunia & geranium||Small green-to-brown colored worms; small holes in flower buds and leaves|
|Fruits & Vegetables|
|12. Codling moth (apple & pear)||"Apple worm" a serious pest of apples and pear; grayish brown moth, 5/16 inch length|
|13. Brown rot (peach, cherry, plum)||Infected fruits quickly rot and dry out, covered with masses of browish-gray spores|
|14. Fruit tree pruning||Stimulating new growth by heavy pruning is not recommended now|
|15. Powdery mildew (cucumber, squash, melons)||Whitish-gray talcum-like spots or patches on leaves|
|16. Blossom end rot (tomato)||Leathery, brown dry rot on base of the fruit|
|17. Bacterial leaf spot & speck (tomato)||Leaf spots and fruit spots with white or yellow halos|
|18. Tomato leaf distortion - herbicide, virus, leaf roll?||Several causes of tomato leaf distortion are possible|
|19. Weed control in the vegetable garden||Control weeds to improve harvest, and minimize weed seed for next season|
1. Little on lawn ‘to do' list for July - Correct irrigation and mowing are the most important lawn care practices for July and early August. Keep nitrogen fertilization to a minimum, if any, on cool season turfgrasses during the hot, dry summer months. Avoid applying herbicides for broadleaf weed control during this time to limit damage to non-target landscape plants. Don't change the mowing height, 3.0 inches and higher is perfect all year long.
2. White grub control - Adult beetles (masked chafers and May/June beetles) are now laying eggs which will hatch in early to mid-August. If a turf area had white grub damage last year, an insecticide application may be warranted this year. Preventive products such as imidacloprid (Merit) or halofenozide (Mach 2) needs to be applied by or shortly after mid-July, prior to egg hatch. A new insecticide on the market is chlorantraniliprole (Acelepryn). This insecticide provides season-long control of wide range of insects including white grubs, but should be applied earlier than imidacloprid or halofenozide. Correct application and irrigation is important to effectiveness. Read and follow all label directions.
For turf owners who choose not to apply a preventive grub treatment, the insecticides Dylox and carbaryl can be applied after egg hatch, typically in August and September, as a rescue treatment. Insecticide control is recommended at this time of year if 8 grubs are found per square foot in a turf area.
White Grub Management, University of Nebraska-Lincoln
3. Postemergence Crabgrass Control - While preemergence control of crabgrass is preferred, there are post-emergence herbicides available that will control crabgrass. Ideally, post-emergence herbicides should be applied when crabgrass is young, typically before mid-July. Quinclorac is the industry standard for postemergence crabgrass control. Tenacity is also effective and can be spot-applied in residential lawns. Once crabgrass matures beyond three to five tillers it becomes difficult to control and multiple applications seven to fourteen days apart are necessary. After mid-July, it is best to allow crabgrass to die out with frost rather than attempt herbicide control.
Crabgrass Control in Home Lawns, University of Nebraska- Lincoln
4. Yellow Nutsedge Common in Lawns Now - While hand pulling and herbicide applications are recommended prior to July, hand-pulling can continue and the following herbicide products can be used now. Postemergence herbicides include Basagran or SedgeHammer or ProSedge (formerly Manage), and FMC's Dismiss (sulfentrazone). Since yellow nutsedge can regrow from rhizomes or tubers that the plant begins to form after the summer solstice, multiple applications are usually needed. Even so, nutsedge will likely persist for multiple years. More information on nutsedge biology and herbicide control can be found at the link below.
Yellow Nutsedge Thriving, University of Nebraska-Lincoln
5. Seed buffalograss ASAP - Seeding buffalograss should have taken place earlier this summer to maximize establishment and survival before winter. Seeding buffalograss now can be done, but will require significant inputs of water, fertilizer, herbicides and mowing yet this summer and likely next summer. Sodding or plugging buffalograss may be a better option. So-called drop-dead dates for seeing buffalograss are no later than Aug. 15 in eastern Nebraska and Aug. 1 in western Nebraska.
Seedbed preparation and early-season weed control are important for success. If vehicles or extensive foot traffic have compacted soil, deep till or, preferably, chisel the site to a depth of 18 to 24 inches to promote deep rooting. Work the soil to a garden-like but firm condition before planting. The seedbed should be firm enough to walk on without sinking more than one-half inch into the soil. This can be accomplished mechanically by packing with a roller or culti-packer, or by irrigation.
Irrigation during germination and stand establishment enhances successful establishment. Without irrigation, stand establishment is slowed considerably and may take more than one growing season. Keeping the area damp the first few weeks following seeding will greatly increase the germination rate and stand establishment. This usually requires more than one sprinkling per day.
Weed control is also important and quincloarc-containing products are the industry standard. However, a number of other products including Tenacity (mesotrione) or SquareOne (carfentrazone+quinclorac) are safe on young buffalograss, based on UNL research. For information on seeding rates, seed placement and pre/post emergence herbicides, refer to the following publications.
Establishing Buffalograss in Nebraska, University of Nebraska-Lincoln
Buffalgrass Establishment with Pre and Post Emergence Herbicides, University of Nebraska-Lincoln
6. Turf diseases may be developing - Rainy June weather likely promoted foliar fungal diseases such as brown patch in tall fescue and Kentucky bluegrass as well as dollar spot in Kentucky bluegrass. For most home lawns, fungicide control is not recommended or needed. Most turfgrass will recover. Areas that are thinned can be reseeded in late summer.
7. Red maple winter injury - Poor leafing, or no leaf development, continues to be reported across the state in red maples and other maples. Red maples appear to have been hard hit by cold temperatures this past winter. The reason may range from 1) microclimates of specific growing sites, 2) a tree being from a southern seed source, 3) or other factors such as stress that may have set a tree up to be more cold temperature susceptible.
On affected maple trees, bare branches are best removed with proper pruning. This needs to be accomplished by mid-August. Pruning after mid-August and up until leaf drop can interfere with a tree hardening off for winter and lead to additional winter injury in the subsequent winter.
8. Iron chlorosis in River Birch and other deciduous trees appears as pale green to yellow leaves with darker green veins. Like pin oak and silver or red maple, the cause is typically iron chlorosis brought on by high pH or alkaline soils. In these soils, certain tree species have difficulty taking up iron that is in the soil. It is not due to a lack of iron in the soil. In river birch, chlorosis can also be compounded by growing them in poorly drained clay soils or in landscapes overwatered with automatic irrigation systems. Along with adjusting irrigation, treatment includes applying iron to the soil or via trunk injections. See link for treating trees in western and eastern Nebraska.
Chlorosis of Trees in Eastern Nebraska, Nebraska Forest Service
Chlorosis of Trees in Central and Western Nebraska, Nebraska Forest Service
9. Apple Scab & Cedar Apple Rust - June rains provided conditions conducive to fungal infections on susceptible crabapple and Hawthorne ornamental trees. Selecting and planting resistant cultivars is key to preventing and reducing damage. Trees that are highly susceptible may experience severe defoliation in wet years. It would require a number of years of defoliation to cause branch die back. It is too late in the season for fungicides to be applied. Replacement of these trees with resistant cultivars can be considered. If the tree is valuable, fungicides applied in early spring just as the tree begins to bud will reduce infection and subsequent leaf drop.
Apple Scab,University of Nebraska-Lincoln
Cedar-apple and Related Rusts of Apple and Ornamentals, University of Nebraska-Lincoln
10. Hunting for Emerald Ash Borer - While Emerald ash borer has not yet been identified in Nebraska, it has been identified in nearby states. This makes it important for us to be aware of signs to watch for to aid in EAB identification. A recent tour to Kansas City, where EAB has been found, made us aware of an interesting point for monitoring ash trees. We know that the EAB beetle emergence holes are D-shaped. However, observations of infested ash trees in Kansas City showed that while D-shaped holes were present in dying trees, round emergence holes of more common borers like lilac-ash borer and red-headed ash borer were also present. And they were often more numerous than the D-shaped holes.
These common borers attack stressed trees so it makes sense they would move into a tree that is stressed by EAB. The take home message is to do a thorough examination of ash trees for D-shaped borer holes. If mostly round holes are observed, do not assume there may not also be some D-shaped holes and continue a thorough examination for D-shaped holes and for other signs of EAB.
11. Budworm of geranium and petunia - Tobacco budworm feeds on flower buds and may cause petunias, geraniums and other annual flowers to stop blooming. The budworm's droppings, sometimes described as small black seeds, are often seen before the worms are noticed. On close inspection, small green-to-brown colored worms can be found nibbling small holes in flower buds and leaves. Treat with a Bt product (Bacillus thuringiensis) such as Dipel or Thuricide or carbaryl (Sevin) or permethrin (Eight).
Tobacco (Geranium) Budworm - Colorado State University
12. Codling moth is a non-native insect and a serious pest of apple, but also attacks pear, crabapple, quince, and English and black walnuts. Insects overwinter as fully grown larva inside a silken cocoon under flaps of loose bark, in brush, on posts, or other areas around the home orchard. Adults begin to emerge in spring, as the last petals fall from apple trees. They are a grayish-brown moth with a crisscross pattern of light gray lines on their forewings and a bronze or copper colored patch near the forewing tip. They are 5/16 inch in length with an 11/16 inch wing spread. Females lay eggs on fruits and leaves.
After hatching, larvae seek a rough patch on the apple skin, such as a scab lesion, wound, or calyx end of the fruit, to begin tunneling into the fruit. They spend about 3 weeks tunneling through the fruit and growing. At maturity the larvae are white or a pale pinkish color with a brown head. They leave the apple, fall to the ground to pupate, and reemerge as adults for a second generation or "summer brood" in July. Insect tunneling greatly reduces the appeal and marketability of fruits, as well as creating openings for rot fungi.
Codling moth attack often results in fruit drop. One important method to minimize insects is to pick up and destroy fallen fruits as quickly as possible throughout the summer. Chemical control involves applications every 7-14 days from petal fall to near harvest. For a complete schedule, including recommended pesticides, refer to the spray schedule below.
13. Brown rot is a very common fungal disease of peaches and other stone fruits, including plum, nectarine, apricot and cherry. The fungus begins infecting blossoms, small fruit spurs and twigs in spring. Trees wounds, such as hail damage, create many openings for brown rot fungus. Consequently home orchards that received hail this spring, may see large amounts of brown rot fungus in their trees this year. Infected twigs and branches develop cankers, resulting in branch dieback.
In summer, disease spores are mainly wind-blown, but can also be carried in rain splash or by insects. Healthy young fruits are fairly resistant to infection, but as fruits mature they become more susceptible even in the absence of wounds. Infected fruits rot very quickly and are covered in masses of browish-gray spores. Fruits quickly dry into mummies and continue to hang onto the tree or fall to the ground. Harvested fruits quickly rot if not cooled and stored properly.
Sanitation is very important. Remove all dropped and infected fruits as quickly as possible and destroy them. Prune out infected branch cankers. Control insects to minimize disease spread and prevent insects from wounding fruits. Fruits should be cooled and refrigerated (as close to 32 degrees F as possible) after harvest. Improperly stored fruits can rot within a few days. Use a fungicide spray program to minimize infection.
14. Fruit tree pruning from mid-summer through fall is discouraged. Only minimal maintenance pruning, such as removing suckers is recommended. If trees suffer wind damage, prune out damaged sections, making clean cuts. No other pruning is recommended. It is important that fruit trees begin to harden off during late summer and fall. Heavy pruning at this time would cause the initiation of new growth in trees, which might not have time to harden off properly before cold weather arrives.
15. Powdery mildew infection of cucumber, squash and melons results in grayish white powder-like spots or patches on upper leaf surfaces. It is promoted by warm temperatures and high humidity. Quality of produce on infected crops is reduced due to low vigor of plants and reduced photosynthesis. Premature leaf death, reduced fruit size, poor fruit storage, poor flavor, poor rind color and fruit sunburn are common symptoms seen on heavily infected plants. Older plants are infected first, so removing them and planting a new fall crop is one method of control.
Control by selecting resistant varieties, planting in areas with good air circulation and avoiding overhead irrigation and excess nitrogen fertilizer that promotes succulent growth. If needed, fungicides labeled for use on vegetables can be beneficial if applied early as soon as symptoms appear.
Powdery Mildew of Cucurbits, Cornell University
16. Blossom end rot is a common problem of tomatoes, but also affects peppers, eggplant, squash and watermelon. It appears as a flat, dry, sunken, brown rot on the blossom end of fruits caused by a calcium deficiency in the fruit. In Nebraska, rarely is there a lack of calcium in the soil. Blossom end rot occurs when plants cannot pull calcium up quickly enough for developing tissues. Calcium must be dissolved in water to move within a plant, so dry soils can increase the problem.
Drought stress, low daytime humidity, high temperatures, and rapid vine growth favor blossom end rot. Applying calcium to the soil or to the plant is not beneficial. Instead, maintain a consistently moist but not saturated soil; use organic mulch near the base of plants; and avoid excess nitrogen fertilization with ammoniacal nitrogen sources.
Often the first ripe fruits are affected. Remove them and later ripening fruits will usually be normal.
17. Bacterial leaf speck and spot diseases on tomato are common during wet summers. Bacterial speck and spot cause small (1/8-1/4 inch) black lesions, usually with a yellow halo, on leaves. Bacterial spot causes small, slightly raised, water-soaked spots on the fruit which may enlarge to 1/4 inch in diameter and become very rough and cracked. Bacterial speck fruit lesions are also slightly raised but typically smaller (1/16 inch). Bacterial speck lesions do not crack or become scaly.
To control, use a 3 year crop rotation, practice good sanitation, and select bacteria free seed/transplants. Copper-based fungicides may be effective in suppressing bacterial speck and spot if applied at the first sign of leaf spotting or at the time of first blossom and applications continued at 7 to 10 day intervals.
18. Tomato leaf distortion can have several causes, the most common of which are herbicide damage, virus infection and a condition called physiological leaf roll. The publications below contain pictures of typical damage. Virus infection often creates more subtle symptoms that herbicide or leaf roll.
Why the Heck Are My Tomato Leaves Curling?, University of Illinois Extension
Physiological Leaf Roll of Tomato, Pacific Northwest Extension Publication
Disorders of Tomato, University of Minnesota Extension
Glyphosate Damage on Tomatoes, Clemson Cooperative Extension
Banvel (Dicamba) Injury on Beans, Tomato and Muskmelon>/a>, University of Missouri Extension
19. Weed control in the vegetable garden- The vegetable gardener's biggest problem is usually not bugs, plant diseases or weather. It's weeds. And the best time to deal with weeds is early, while they're still small. It's important not to allow weeds to develop seeds, which will make future weed problems worse than ever. For example, one shepherdspurse plant produces 38,500 seeds in a single growing season, while a single redroot pigweed can produce 117,400 seeds! Mechanical and chemical control, along with the use of mulch, may all be needed for a good level of control.
In a large garden, or a small one where weeds have gained a foothold, gardeners may have to resort to mechanical cultivation to control weeds. Rotary hoes, wheel hoes and powered garden tillers do a good job between rows, but hand tools or hand pulling are often necessary close to crops.
To halt a weed takeover, you may even need to use your lawn mower. Close mowing between the rows on a hot sunny day sets weeds back and may even kill them. It will at least give you time for some hand weeding and an application of mulch to regain control.
Mulch is a very helpful tool in the vegetable garden to slow the germination of weed seeds and conserve soil moisture. Common organic mulches commonly used in the vegetable garden include compost, old hay, straw, leaves, shredded or whole newspapers and grass clippings. But be aware that straw, hay and lawn clippings can contain large numbers of weed seeds so choose your mulch carefully. When using coarse materials, like straw, hay or grass clippings, apply a 3-4 inch layer of mulch.
Once the current weeds are controlled, apply a preemergent herbicide to kill additional weed seeds as they germinate, which they will continue to do throughout the summer. Only use this method, however, if you do not plan to seed any additional vegetables in your garden since preemergent herbicides will kill your germinating vegetables, too.
Products labeled for use in the vegetable garden include trifluralin (Preen Garden Weed Preventer) and corn gluten meal (Preen Vegetable Garden Organic Weed Preventer). Trifluralin provides approximately 9 weeks of control, while corn gluten meal provides 4-6 weeks of control. For the best results, apply the product to weed-free areas and top with mulch. Then water the product into the soil.
Chemical weed control of existing weeds in a vegetable garden is risky. he chances of damage from drifting spray or movement of chemicals through the soil often outweigh the potential benefits.