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Hort Update for March 17, 2020

Hort Update for March 15, 2020, Nebraska Extension,
Diplodia Tip Blight infects new shoots as they emerge in spring, killing them. This branch has one dead shoot, one in the process of dying, and two healthy shoots.
Serious ConcernsMajor Symptom:
1. Pruning roses Early to mid-April, just before or as new growth begins
Minor Issues
2. Evergreen blights Prepare now to treat common evergreen diseases in April & May
5. Pear rust Reddish-orange leaf spots on ornamental & fruiting pears
Timely Topics  
6. Lawn care timing Recommendations for do-it-yourselfers
7. Wild cucumber control Fast growing warm season, annual vine
8. Soil samples A starting point for good soil management
9. Cleaning landscape beds Rake leaves off of lawns, but keep mulch in place on ornamental plants

1. Pruning rosesEarly to mid-April, just before or as new growth begins

Early to mid-April, just as or before new growth begins or when winter protection is removed from roses like Hybrid teas, floribundas, and grandifloras, is the ideal time to prune out winter killed wood on roses. Pruning roses earlier than this can increase the amount of winter injury to roses.


2. Evergreen blightsPrepare now to treat common evergreen diseases in April & May

Diplodia (Sphaeropsis) blight and Dothistroma needle blight are two common fungal diseases of pine, especially Austrian and ponderosa, for which timing of fungicide applications is approaching.


  • Diplodia - dead and stunted needles on branch tips, black fruiting bodies (specks) on the bottoms of pine cones, and entire branches dying.
  • Dothistroma - dark spots or bands on needles and needles turning brown from the tips back to a lesion. Branches near the lower half of the tree are usually infected first.

While neither disease rapidly kills a tree, repeated infections in consecutive years will affect aesthetics, windbreak value, and likely shorten a trees life. Now is the time to prepare to treat trees infected with either of these diseases. Positively identify a disease on a plant, and know when timing of fungicides will be effective, prior to treating. For timing of fungicide sprays to control these two diseases, view the publication below.

Diseases of Evergreen Trees, Nebraska Forest Service


5. Pear rustReddish-orange leaf spots on ornamental & fruiting pears

For trees that were infected last year, and for clients who choose to control since this disease is more of a nuisance than one that causes significant harm, fungicide applications should begin when trees are in green tip stage (leaf buds just beginning to show green color, which is typically in mid-April. Myclobutanil (Immunox, Immunox Plus or Fertilome F-Stop Lawn and Garden Spray) is a good fungicide to use.  There are other fungicides that work but those with myclobutanil have the advantage of providing some control shortly after infection.


6. Lawn care timingRecommendations for do-it-yourselfers

For do-it-yourselfers, lawn care should not begin until after the grass breaks dormancy and begins to grow and soils have warmed. Mowing is not needed until after the grass begins to grow and requires mowing. Then maintain the same height of 3 to 3.5 inches from the first to the last mowing of the season.

Preemergence herbicides targeted at controlling crabgrass and other warm season annual weeds should not be applied until soil temperatures reach 50 degrees Fahrenheit. Soil temperatures across the state can be found at:

Fertilization should not begin until soil temperatures are even warmer, ideally sometime in May. A well-timed fertilizer application supplies the turf with nutrients when they are needed by the plant and when the soil isn’t already supplying the nutrient. Cool Season Lawn Calendar - Eastern Nebraska. 


7. Wild cucumber controlFast growing, warm season annual vine

Wild cucumber is a fast growing, warm season annual vine. This is the one that seems to take over trees in shelterbelts in late summer. As an annual, it dies each fall and comes back from seed which germinate and begin growth after soils warm, typically May. When you are dealing with only a few vines, snip the plant off at the base and it will die. Do this before it blooms and goes to seed to reduce a seed bank in the soil. In large shelterbelts, if needed, Simazine (Princep 4L) is labeled for preemergent control in shelterbelts to kill weed seeds as they germinate. Do not apply more than 4 qt. Princep 4L per acre (4 lb. a.i./A) per calendar year. Do not apply more than twice per calendar year.

Wild Cucumber Identification, University of Wisconsin - Madison
Controlling Weedy Vines, Nebraska Extension


8. Soil samplesA starting point for good soil management

A basic soil sample is good to have to know the basics about a soil, such as pH, organic matter content, and more. This can lead to good soil management practices which are the foundation of plant health. The University of Nebraska no longer provides soil sampling for a fee. Instead, we provide information on private labs soil samples can be sent to. Some of these include:

Midwest Laboratories, Inc. - Omaha
Ward Laboratories, Inc. - Kearney
Ag Source - Lincoln
Servi-Tech Laboratories - Hastings
American Agricultural Laboratory, Inc. - McCook 


9. Cleaning landscape bedsRake leaves off of lawns, but keep mulch in place on ornamental plants

Wait until weather is consistently warm to clean up landscape beds from the winter. If already cleaned up, homeowners should be prepared to cover plants again when cold weather threatens. Winter mulch, the tops of plants and leaves that blow into landscape beds in fall often do one of the most important jobs in late winter - keeping plants dormant as long as possible. The main purpose of winter mulch is protecting plants from extremes, and keeping plants dormant. Don’t remove mulch too early, instead let mulch do its job of keeping plants dormant until the risk of very cold temperatures is past. Warm sunny weather causes plants to break dormancy early and they become more susceptible to cold temperatures. Rake leaves off of lawns, but keep mulch in place on ornamental plants.


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