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Hort Update for April 18, 2018

Nebraska Extension Hort Update for April 2018,
The shoot on the right is dying back from infection by Diplodia tip blight fungus, compared to the healthy shoot on the right.
Serious ConcernsMajor Symptom:
1. Roundup™ for lawns This is not Glyphosate and may create confusion for property owners
2. Fireblight Complete annual pruning before blooming begins; prune only to remove infected branches in spring; streptomycin applications
3. Sawflies Large groups of light to olive green caterpillar-like insects; defoliate evergreens
Minor IssuesMajor Symptom:
4. Evergreen diseases Plan for control of Diplodia tip blight, Dothistroma needle blight, and Rhizosphaera needle cast
5. Cedar-apple rust control Start fungicide applications at bud break on susceptible trees; multiple applications required
Timely topics
6. Bagworms Monitor evergreens; hand pick old bags now; apply controls in June
7. Crabgrass preventer Still too early apply preemergence herbicides to control crabgrass
8. Evaluating 4-step lawn programs Timing of application for each product, when needed, is essential
9. Spring seeding of lawns The sooner it can be done the better; or wait until late summer
10. Plant problems & soil testing Soil testing will not often provide an answer; use a plant diagnostic strategy instead
Product UpdateNotes:
11. Mesotrione Provides preemergent systemic weed control and contact post-emergent control. Labeled for use on cool season grasses and buffalograss. 

1. Roundup™ for lawnsThis is not Glyphosate and may create confusion for property owners.

Roundup® for Lawns was a new product on the market last season. Roundup® for Lawns selectively controls weeds in lawns without damaging turfgrass when used according to label specifications. It is likely to create confusion because its name is so similar to Roundup (from Roundup Weed and Grass Killer). Those without knowledge of herbicide nomenclature may consider the terms synonymous, but they are not.  

Roundup Weed and Grass Killer is the brand name of an herbicide that contains the active ingredient glyphosate, which nonselectively kills most plants, including turfgrass.

Round for Lawns® is the brand name of an herbicide that does NOT contain glyphosate or other nonselective herbicides. Rather, it contains the active ingredients MCPA, quinclorac, dicamba, and sulfentrazone, each of which are selective herbicides that control various weeds without harming Kentucky bluegrass, perennial ryegrass, or tall fescue lawns.


2. FireblightComplete annual pruning before blooming begins; prune only to remove infected branches in spring; streptomycin applications

Fireblight is a bacterial disease that can kill branches and entire plants. It attacks plants in the rose family, including apple, pear and crabapple. Symptoms include dead branches, water-soaked blossoms, light brown to blackened leaves, discolored bark, black "shepherd's crook" twigs, and dried fruits.

Management includes resistant varieties, cultural practices, pruning and preventive chemical sprays. Ideally major fruit tree pruning for size and structure was completed in March. Now, as trees begin to bloom, pruning should only be done to remove branches infected with fireblight. Cut each branch eight to 12 inches below the canker to be sure all infected growth is removed. Clean pruning equipment between each cut to avoid spreading infections throughout the tree. Dip tools in a 10% bleach solution or ethyl alcohol. Chemical controls are best applied during blooming. Streptomycin applications should begin when 25% of flowers are open, and be repeated at 4-5 day intervals until petal fall.

Fire Blight of Apples and Pears, Ohio State University
Fruit Spray Schedules for the Homeowner, University of Missouri Extension


3. SawfliesLarge groups of light to olive green caterpillar-like insects; defoliate evergreens

Sawflies are the immature, larval stage of tiny, non-stinging wasps.  They are a common pest of evergreen trees and can seriously damage conifer trees through defoliation. There are many different species of sawflies, each with a preferred host. Several species of sawflies are present in Nebraska, including the European pine sawfly, yellowheaded spruce sawfly and larch sawfly. Most commonly damage is seen on Scotch, Austrian, Ponderosa, Jack and Mugo pine, along with spruce and larch. White pine is rarely damaged.

Adults resemble small non-stinging, wasps or flying ants. Females cut slits in evergreen needles with a saw-like apparatus and insert eggs. A new generation of immature insects begins to hatch out from late April through May, and will feed on evergreen foliage until mid-June. The larvae resemble a caterpillar and are light to olive green with a reddish-brown to black head. Larvae usually have several darker green stripes longitudinally down their bodies. There is only one generation of this insect per year. 

After hatching out in spring, the larvae feed in large groups on the branches of affected trees. At first the larvae eat only the outer portion of the pine needles, leaving behind the stringy, tough, central needle vein, which dies and turns brown. As the insects mature, they begin consuming entire needles. Due to the coloration of the insects, which blends in well with the color of the needles, the insects are often not noticed until considerable defoliation has already occurred. When disturbed, larvae rear back into a defensive "S" position.

If you're working with a small tree, or only a few larvae are present, then simply knock them off the tree either by hand or with a garden hose. They seldom find their way back up onto the tree and are very susceptible to predators such as birds, rodents and predatory insects. 

Large populations should be treated as soon as possible.  Several chemical controls can be used, such as insecticidal soaps, horticultural oils, permethrin, bifenthrin, malathion or orthene, but all controls are most effective when the larvae are small.  Dipel, or Bacillus thurengiensis, is NOT effective against sawflies because they are in the Hymenoptera family (ants & wasps), not the Lepidoptera family (butterflies & moths).

Insects of Evergreen Trees, Nebraska Forest Service


4. Evergreen diseasesPlan for control of Diplodia tip blight, Dothistroma needle blight, and Rhizosphaera needlecast

Diplodia Tip Blight is a fungal disease that commonly infects older Austrian, Ponderosa and other pines causing new growth to be stunted, black pycnidia to develop on the bottoms of cones and entire branches to die with needles turning brown and hanging straight down as if wilted.

This disease can be controlled with fungicides. The first application is made at budbreak (around the third week of April), a second just before needle emerge, and a third 7 to 14 days later. The active ingredients of Thiophanate-methyl, Propiconazole, Copper Salts of Fatty & Rosin Acids, or Bordeaux mixture are recommended fungicides.

Diplodia Tip Blight of Trees, Nebraska Forest Service

Dothistroma  Needle Blight is also a fungal disease, causing the greatest amount of damage in Austrian and Pondera pines. Older needles are infected and fall from the tree prematurely, resulting in a thin tree canopy. Lower branches in trees are most heavily infected. 

The first application should be done in mid May, and protects the existing needles from infection. The second application, which protects the current season's new growth, is made after considerable new growth has taken place, usually around mid June. This spring's new growth is initially resistant to infection and will not become susceptible until midsummer, around July.

Dothistroma Needle Blight of Pine, Nebraska Extension

Rhizosphaera needle cast is a common fungal disease affecting Colorado blue spruce and other spruces.  Trees in eastern Nebraska are more commonly affected than those in the west. Needles are infected in spring, but symptoms do not become evident until a year later when the needles turn yellow, then a reddish brown which is being seen in trees now.  Older needles on the interior of the branch are affected.  Black fungal fruiting structures can be seen with a hand lens protruding from the stomata of infected needles. 

Infections can be high due to extended wet weather last season and now this spring. Saturated soils increase air humidity around the tree's lower canopy and also contribute to good conditions for disease development.   The disease can be controlled with an application of chlorothalonil in spring when new growth is one-half to two inches long.  Follow-up applications should be made every 3-4 weeks if frequent rains occur during spring and early summer.

Rhizosphaera Needle Cast of Spruce, Iowa State University


5. Cedar-apple rustStart fungicide applications at bud break on susceptible trees; multiple applications required

Cedar-apple and cedar-hawthorne rust are similar but different diseases. Cool, moist conditions this spring increase the potential for infections on susceptible apple, crabapple and Hawthorne trees. Both diseases cause yellow spots on upper leaf surfaces and raised orangish-pustules on leaf undersides. Infected leaves drop resulting in unsightly trees and poor fruit production in apples. Repeated yearly infections can weaken trees and lead to other issues.

The best control of rust is selecting resistant trees. On susceptible trees with a history of infection, fungicides need to be applied starting at bud break, petal fall and 3-4 additional applications at 7-14 day intervals.

Cedar Apple Rust and Related Rusts of Apples and Ornamentals, Nebraska Extension
Diseases of Broadleaf Trees, Nebraska Forest Service


6. BagwormsMonitor evergreens; hand pick old bags now; apply controls in June

Check evergreens, especially spruce, Juniper and Arborvitae, for overwintering bagworms. As many as 500 to 1000 eggs can overwinter in one female bagworm. Removing and destroying bagworms from now until May 1st can help reduce the bagworm population. Destroy bagworms by crushing or immersing in soapy water. If bags containing eggs are discarded on the ground, eggs may still hatch and larvae return to the tree.

It is too early to apply insecticidal products to evergreens for bagworms. Wait until after egg hatch. Products are most effective in reducing damage if applied during the early stages of bagworm development. Insecticides, as well as Bacillus thuringiensis, are best applied from mid-to late- June. They can be applied up until about mid-August, but increased damage will occur the later they are first applied.

Bagworm, Nebraska Extension


7. Crabgrass preventerStill too early apply preemergence herbicides to control crabgrass

The seed of crabgrass, a summer annual, begins germination when soil temperatures reach 55 degrees F at a two to four inch depth for a few consecutive days. In most years, this typically does not occur until May in Nebraska. The targeted window to apply preemergence herbicides for crabgrass in eastern Nebraska is April 20 to May 5. This year, with continuing cold temperatures and cold soils, delaying application until May will likely be ideal.

Crabgrass Control in Home Lawns, Nebraska Extension Turf iNfo 
Lawn Care Pro Series: Crabgrass and Other Summer Annual Grassy Weeds, Nebraska Extension Turf iNfo


8. Evaluating 4-step lawn programsTiming of application for each product, when needed, is essential 

While these products are convenient for homeowners, and often a better price than buying separately, it is important to explain to the customers who are buying them the purpose of each step, how to apply the product correctly, and the timing for each step. Timing is often essential to success. Providing customers with this information increases a store’s/company’s level of professionalism and respect from their customers. Refer customers to, or provide customers with the publication linked below to assist them in decision-making on application timing. Also, avoid selling products that are not needed. If the four-step program contains an application for white grubs, but the lawn does not have a history of white grub damage, this would not be responsible selling and recommendation of a pesticide.

Cool Season Lawn Caendar - Eastern Nebraska, Nebraska Extension


9. Spring seeding of lawnsThe sooner it can be done the better; or wait until later summer

Fall remains the best time to seed cool season turfgrass. If spring seeding needs to be done, the sooner seed bed preparation and seeding can be done, the better. There are challenges to spring seeding. This year, we may go from cool conditions to hot weather very quickly which will make seedling survival tough.

One of the largest issues with spring seeding is weed pressure. UNL Turfgrass Specialist, Bill Kreuser, recommends the use of Scott’s Turf Builder Starter Food for New Grass. It contains mesotrione which provides PRE and POST control of weeds. While Siduron has been the recommended in the past as a preemergence to use on new seedings, this product can be difficult to find and has no post emergence control of weeds.


10. Plant problems & soil testingSoil testing will not often provide an answer; use a plant diagnostic strategy instead

When a plant or lawn has a problem that is not readily identified as an insect or disease, the soil often gets blamed and a soil test is recommended. While it is a good idea to have a basic soil test taken, know that soil testing will not often provide the answer to plant problems. Basic soil tests test for macronutrients, organic matter content, pH and a few other components. If there is a specific soil concern, such as high sodium levels, then a request would need to be made to have sodium levels tested and the price of the soil test would increase. A soil test does not test for every possible soil issue. Unless you suspect what the issue is and ask the soils lab to test specifically for that, a basic soil test is not likely to provide an answer to many plant issues.

Incorrect planting, watering problems, environmental or mechanical issues, allelopathy, etc. are not identified by soil tests. There are a number of resources that can be used to assist with plant diagnostics. These include the resource linked below from Virginia Tech and provides a systematic approach to plant diagnostics. Extension Specialists and Extension Educators are available to assist with plant diagnostics; and the UNL Plant Diagnostic Clinic is a great resource for sending samples to for a minimum fee.

Plant and Pest Diagnostic Clinic, Nebraska Extension
Plant Problems, Virginia Tech


11. MesotrioneProvides preemergent systemic weed control and contact post-emergent control. Labeled for use on cool season grasses and buffalograss.

Mesotrione is most commonly sold as Tenacity, by Syngenta, and can be used on cool season grass and buffalograss lawns to control both broadleaf and grassy weeds. It is available this spring to homeowners in a granular form, as Scotts Turf Builder Starter Food for New Grass. 

Apply it as a preemergent herbicide at grass seeding on tolerant turfgrass, except fine fescue. (Mesotrione may reduce density of fine fescue seedings. Fine fescues include red, sheep and hard fescue - Festuca rubra, F. ovina and F. trachyphylla, respectively. Turf-type tall fescue, F. arundicacea, is not considered a fine fescue. )

Avoid spraying on newly germinated turgrass; if grass has germinated, wait until it has been mowed two times or four weeks after emergence (whichever is longer) before making a postemergence application. 

Use to spot treat for broadleaf weeds, annual bluegrass, crabgrass, nimblewill, creeping bentgrass, windmill grass and goosegrass. Most effective on young, actively growing weeds. Herbicide group 27. 


Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Nebraska Extension is implied. Use of commercial and trade names does not imply approval or constitute endorsement by Nebraska Extension. Nor does it imply discrimination against other similar products.