Hort Update for June 3, 2014

Hort Update for June 3, 2014

dandelion
In This Issue:Major Symptom:
1. Crabgrass, foxtail germinating Past the ideal window; use other herbicide choices
2. Sandbur control Preemergence applied in June
3. Mild frost damage Tips damaged; turfgrass will grow out
4. New seedlings damping off Issues on golf courses seeded to repair winter injury
5. Too late to seed cool season grass Still time to sod if needed
6. Seed buffalograss now Ideal time to seed buffalograss
7. Weed control in buffalograss Careful of 2,4-D on hot days or will have burn issues
8. Broadleaf weed control Hold off until fall with most herbicide products
9. Follow 1/3 rule for mowing With frequent rains, mow as often as needed
10. Winter kill report on trees & viburnums Trees that did well, those that didn't, those recovering
11. Recommended trees for Nebraska Avoid problem trees
12. Bagworm treatment timing When young bagworms are about ¼" long; typically in early June
13. Shade tree borer treatments Positive I.D. and proper timing of application important
14. Avoid Emerald Ash Borer treatment for now Wait until EAB has been identified 15 miles from tree site
15. Winter kill on ornamentals Still seeing the effects of winter on a number of plants
16. Phlox plant bug Stippling, discolored spots on leaves and stems
17. Winter and freeze effects on tree fruits and grapes Reduced or delayed fruit production
18. Winter and freeze effects on brambles May delay fruit production until next year
19. Squash bug control Proper ID, especially of eggs to avoid issues later on
20. Fruit spray schedules and rain events Read and follow label directions for safe storage conditions
21. Swarming bees Naturally swarm; will disperse in a few days. Preserve these pollinators.
22. Early summer replacement planting Select quality plants, plant correctly, provide adequate irrigation

 

 

Articles
1. Crabgrass and foxtail are germinating - We are past the recommended window to apply preemergence herbicides for control of these annual warm season grasses. Unusually cool spring soil temperatures did delay crabgrass and foxtail germination a little depending on location. Products applied now will control seedlings yet to germinate, but usually have limited effect on seedlings larger than the two-leaf stage. Products containing Dithiopyr are the exception to this; it will control crabgrass up to the one-tiller stage. Visible crabgrass plants can be hand pulled, or herbicides like Tenacity or quinclorac (i.e. Drive) can be used to provide some post emergence control of young plants.

2. Sandbur control - Sandbur is a warm-season annual grass. It is mainly a problem on sandier soils and areas where turfgrass is sparse. Competition from a dense, vigorous lawn is the best management method. Sandbur germinates later than crabgrass and the timing for control with preemergence herbicides is in June. Pendimethalin is the preemergence herbicide of choice. Post emergence control with Drive or Acclaim is possible; however, only very young plants are controlled and sandbur matures rapidly making it easy to miss the proper application time. When possible, hand-pull and destroy plants prior to seed (bur) production.

Sandbur control on sandy beaches poses an issue due to herbicide use near water. Prior to seed production, repeated tillage with a garden tiller will kill existing plants. For post emergence herbicide control prior to seed production, use an aquatic glyphosate product, such as Rodeo, on young plants. Read and follow all label directions. Repeated applications through the growing season will likely be needed. To clean up burs later in summer, wrap a piece of pipe with carpet and roll it over the plants to trap burs. Remove and dispose of the carpet and burs.

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3. Mild frost damage on buffalograss is being seen. Following the freezes of May 11-17, buffalograss exhibited brownish tips and turf areas took on a brownish-gray cast. Turfgrass will grow out of this damage and mowing will remove the damaged tips.

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4. New turfgrass seedling damping off is being seen now on golf course areas reseeded this spring due to winter injury. Damping off is a fungal disease that typically becomes on issue once daytime temperatures are in the high 80ºs F, nighttime temperatures in the high 60ºs F, with high humidity. Damping off disease can be a problem in residential lawns as well. This disease requires preventative control. On new seedings, monitor rooting depth and reduce irrigation frequency once the seedlings are mature. While it is too late to seed cool season turfgrasses now, in the future, preventive fungicide applications, applied when conditions are conducive to damping off, can help reduce this disease.  

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5. Too late to seed cool season grasses now. Sodding can still be done if needed. Prior to sodding, good soil preparation is essential to increase rooting success. Late August into September is the ideal time to seed Kentucky bluegrass and turf-type tall fescue. Spend the summer improving soils in preparation for late summer seeding.

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6. Seed buffalograss now - Late spring is the optimum time for establishing buffalograss, but it can be established successfully until mid-August if adequate irrigation is available. Seeds will not germinate until soil temperatures reach 60°F, usually after May 15 in eastern Nebraska and May 31 in western Nebraska. For Nebraska as a whole, June 1 is a good target date if the goal is to have a full stand by September. For best results, buffalograss should not be seeded after Aug. 15 in eastern Nebraska and after 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 cultipacker, 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.

For information on seeding rates and seed placement, refer to the following NebGuide:
Establishing Buffalograss in Nebraska, University of Nebraska-Lincoln

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7.  Broadleaf weed control with 2,4-D in buffalograss risky - Broadleaf products cleared for use in buffalograss include a number of 2,4-D-containing products. However, do not apply products containing 2,4-D if you expect temperatures higher than 75°F on the day of application as damage to the buffalograss could occur. Damage symptoms are a yellowing of the grass and stunted growth that could last weeks or season-long. The following NebGuide provides information on weed control options in buffalograss.

Management of Buffalograss in Turf in Nebraska, University of Nebraska-Lincoln

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8.  Avoid broadleaf weed control at this time of year. The risk to nontarget plants (trees, shrubs, ornamentals and vegetables) is too great. At temperatures higher than 80°F, many herbicides volatize (change into a gaseous state) and rise or move on air currents to damage nontargets. Hand-pull weeds before they go to seed during the summer. When temperatures moderate in early September and October apply herbicides at that time for the most effective control of broadleaf weeds.

Lawn Care Pro Series: Broadleaf Weed Control, University of Nebraska-Lincoln

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9.  Follow one-third rule for mowing. Fertilization, especially with fast release nitrogen sources and rainfall promotes rapid, succulent turfgrass growth. For overall turf vigor, and to reduce susceptibility to diseases and heat stress, mow the lawn as often as needed to avoid removing more than one-third of the grass blade during any one mowing. This might require mowing every four to five days. Removing more than one-third of the leaf blade robs the plant of long-term food storage, making it more difficult for the plant to tolerate summer heat stress. Also set the mower as high as feasible, use sharp mower blades and return clippings to the lawn. Mowing at a 3- 3.5 inch height maintains a healthy lawn and helps reduce weeds. 

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10.  Winter injury/kill update - We are beginning to have a little clearer picture of which trees and shrubs are showing dieback from winter injury and which ones are recovering. Reports are of red maple dying but 'Fremontii' doing fine; the tops of birch trees being killed; oak trees being late to leaf but now leafing fine; elms being late to leaf and having a heavy seed crop but now leafing; and red buds being very slow to leaf and in some cases suffering dieback. Although Arborvitae was hard hit, we have heard reports of a cultivar called 'Brandon' that appears to be doing fine.

There are reports of severe dieback in Viburnums. Gary Ladman's of Classic Viburnums in Upland, NE has experienced serious loss of container stock and also found dieback in older, established field plantings.

Severely damaged plants, like holly, are just now beginning to send out new growth from the base.  Once new growth has begun, brittle dead branches can be removed.

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11. Recommended trees for Nebraska - When selecting trees to plant, avoid those known to have issues or expected to develop serious issues such as ash trees, and plant for diversity. From a list of recommended trees, or trees available at reputable nurseries, select those that have the characteristics you need and like and then be sure you can live with any bad points the trees might have. For pros and cons, visit with your nursery, a UNL Extension horticulturist, or a Nebraska Forest Service forester. For a listing of trees for Nebraska, see the following lists developed by the Nebraska Statewide Arboretum. Avoid any that are overplanted in your area; and check out the pros and cons of any that you select.

Trees for Eastern Nebraska, Nebraska Statewide Arboretum
Trees for Western Nebraska, Nebraska Statewide Arboretum

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12. Bagworm treatment timing - Bagworms can kill evergreens when populations are high. Begin monitoring for bagworms in early June. Insecticides are most effective when applied during early stages, typically from mid to late June. When bagworms are small, one-fourth to one-half inch long, the organic Bacillus thuringiensis is effective as is spinosad, neem oil and insecticidal soaps. Repeated applications will likely be needed; but these products have minimal impact on beneficials. Other insecticides for bagworms include acephate, bifenthrin, cyfluthrin and permethrin. Insecticidal spray applications require thorough coverage to penetrate the canopy and contact the feeding bagworms. When making an application, be certain the product is specifically labeled for both the target pest and plant species. Some products can injure ornamental plants.

Bagworms, University of Nebraska-Lincoln

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13. Common shade tree borer treatment timing - Several wood boring insects can damage trees and shrubs in Nebraska. Many of these require carefully timed insecticide applications to minimize damage. Insecticide applications are either topical or systemic. Topical applications with permethrin or bifenthrin are applied to the trunk and lower branches to the point of runoff. Concentrate applications on exit holes and wounds. Timing of the application is extremely important (see link below for this information), and multiple treatments may be necessary to cover the entire period of adult emergence, egg laying, and early larval activity. Systemic treatment with Imidacloprid has been shown to be effective against specific borers. This product is applied as a liquid or granule to the soil around the base or drip-line of a tree or shrub according to label instructions. As it takes time for uptake of imidadacloprid by the host plant, applications are usually made several weeks before pest activity is anticipated. Systemic control will usually provide season-long control.

The following publication covers the biology, life history, and management of the key wood borer species in Nebraska. Page 8 of this publication states when insecticides need to be applied for common borers.

Insect Borers of Shade Trees and Woody Ornamentals, University of Nebraska-Lincoln

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14. No need to treat for Emerald Ash Borer yet - Below are recommendations from the Nebraska Forest Service and the University of Nebraska-Lincoln Extension:

  • Treatment is recommended when EAB is known to be within 15 miles of a location.
  • Treating trees beyond 15 miles will likely provide little or no benefit to the trees and will result in unnecessary exposure of the environment to pesticides.
  • State and federal agencies monitor EAB infestations and will provide updates on infestations in Nebraska.
  • Visit the Nebraska Forest Service for information about when to begin treatments.

For people concerned EAB might already be here, but has gone undetected, it is important to know that trees already infested with EAB are treatable if the damage is not yet severe.

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15. Winterkill of ornamentals- Just as trees are showing signs of winter desiccation and dieback, perennials are as well.  Perennials that were not well watered in the fall may not have survived the cold, dry winter we just experienced.  Desiccation on perennials can be a serious and costly issue if the plants were allowed to dry out completely.  Plants that survived might show signs of stress, be additionally susceptible to pests and disease, or be slow to emerge in the spring.  Encourage the homeowner to water deeply when precipitation is lacking and maintain a mulch layer of 2-3" around perennials.

Roses and miscanthus grass are two ornamentals that seem to have been hit the hardest.  Make sure homeowners are removing only dead branches from roses, and if they have a grafted rose with new growth, make sure it's from the top, not the rootstock.  If the top (scion) rose died, it's best to remove that rose and replace it with another.  Emerging miscanthus grasses have shown sparse growth, with dead clumps in the crown.  Grasses can be dug and split to remove the dead material.

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16. Phlox plant bug is a true bug with piercing sucking mouthparts.  The insects suck the plant juices out of new leaves and stems of the phlox plant, leaving behind white spots, stippling, or lesions that eventually brown and die.   The insect feeding usually doesn't kill the plant, but can drastically reduce the aesthetics of an otherwise attractive landscape plant.  Phlox plant bugs will lay their eggs in the stems of their targeted plant in the fall, and the eggs hatch in the spring and begin to feed.  An important step in control is cutting plants down in the fall and destroying them, so eggs can't overwinter.  In the spring when the insect nymphs emerge, horticulture oil or insecticidal soap are control options for small populations.  For control of adult insects, or larger outbreaks, chemical use may be warranted, and permethrin or pyrethrin products should be used.

Plant Bugs on Perennials, Ohio State University
Landscape Diagnostic Guide - Phlox, University of Nebraska Extension

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17. Winter and freeze effects on tree fruit and grapes - Freeze damage to flower buds and young fruits on fruit trees, grapes and strawberries was high following the freezes of May 11-17.  Cherry and peach have had a large amount of flower and small fruit death.  Damage to strawberry flowers was also severe.  This will have a significant affect on production this year, resulting in smaller harvests.

Grape varieties marginally hardy in Nebraska experienced the most damage in vineyards. Grape plants that died to the ground will return from the base, but those plants will lose a year or two of production.  Grafted grapes should be observed to ensure that new growth comes from the scion or top cultivar.  If plants only sprous from the base or rootstock, they should be removed completely.

Assessing Spring Freeze Damage to Apples, Purdue Extension
Assessing Spring Freeze Damage to Peaches, Purdue Extension
Assessing Spring Freeze Damage to Grapes, Purdue Extension
Assessing Spring Freeze Damage to Strawberries, Purdue Extension

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18. Winter and freeze effects on brambles - In addition to other fruits, brambles experienced large amounts of winterkill.  Many canes of blackberries died to the ground.  Unfortunately, many blackberry varieties produce fruit on canes that are in their second year of growth (floricane).  New canes produced this year are called the primocanes.  A few varieties such as Prime-Jim and Prime-Jan will fruit on this new growth, but for growers with floricane varieties such as Apache, Natchez, and Triple Crown, fruiting will be delayed as the plant recovers, sends out the green vegetative shoots this year, and will produce fruit next year.

Assessing Spring Freeze Damage to Blackberries, Purdue Extension

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19. Squash bug control - Squash bugs are one of the most damaging insect pest of pumpkins and winter squash. The adult is a brownish, shield-shaped bug about 5/8 inch long and 1/3 inch wide. Adults are very difficult to control; hence plants must be monitored closely for squash bug eggs and young nymphs to effectively control this insect. Eggs are brick red and found on leaf undersides in the V made by veins. Young nymphs are gray and tear drop shaped. Scout plants often for adults, eggs and young nymphs. Hand-pick adults and squish egg masses. When nymphs are present, carbaryl (Sevin) or permethrin can be applied for control in home gardens.

Squash Bug Control on Melons & Cucumbers, UNL Extension

Lincoln University in Missouri has been doing research on utilizing trap crops as a way of reducing squash bug populations in vegetable production.  Some of their research results can be found in this presentation.

Using Trap Crops to Minimize Insect Pest Damage to Organic Vegetables, Jaime Pinero, Lincoln University

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20. Fruit spray schedules and rain events - Rain can interfere with fruit growers spray schedules.  For every ¼" rain, it is recommended to spray two days sooner than normally schedules.  Many fruit tree growers spray every 14 days.  If you have just sprayed your trees then receive a ¼" of rain, you would need to respray again in 12 days instead of 14. If 1/2" of rain occurs, then you would need to spray at 10 days instead of 14.  And if a full inch of rain occurs, you need to respray right away.    Continuous, or heavy rains can wash away residual pesticide coverage, increasing the need to spray again sooner. 

Home Growers:
Spray Schedules for the Homeowner, University of Missouri

Commercial Growers:
2014 Midwest Tree Fruit Spray Guide
2014 Small Fruit and Grape Spray Guide
2014 Midwest Vegetable Production Guide for Commercial Growers 

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21. Swarming honeybees create concern and unfortunately beneficial but harmless honeybees may be destroyed when it is not necessary. Swarming honeybees are a natural phenomenon. Swarming typically occurs in May and June and honeybees are not dangerous while swarming since they have no hive to defend. A swarm may contain from 1,500 to 30,000 bees. Swarming is instinctive. Overcrowding and congestion in the nest are factors which predispose colonies to swarm. When honey bees swarm they settle on a tree limb, bush, or other convenient site. The cohesiveness of the swarm is due to their attraction to a pheromone produced by the queen. The swarm will send out scout bees to seek a cavity to nest in and will move on when a suitable nesting site is found. When encountering swarming bees, leave them be. They will typically move on within a few days.

Why do Honeybees Swarm?, UNL Department of Entomology

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22. Replacement planting - If a plant does not produce new growth by June 1st, it is dead and needs replacement. However, this is not the ideal time to plant due to heat stress. If it is possible to wait until late August into September to plant, this is a better time to plant most trees, shrubs and many perennials. If replanting needs to be done now, the sooner the better. Check the root systems of plants when purchasing them. They need to be well established in the container but they should not be pot bound. Pull the plant out of the container or ask a nursery person to do this for you so the root system can be inspected before purchasing it. Plant correctly (wide hole, but not too deep); keep the soil consistently moist but not too wet; avoid nitrogen fertilization; and place a two to four inch layer of organic mulch over the roots of the plants to maintain a cooler soil and conserve moisture.