Hort Update for March 17, 2015

Hort Update for March 17, 2015

henbit
Winter Annual, Henbit. Photo by John D. Byrd, Mississippi State Univ., bugwood.org
Lawns Major Symptom:
1. Late winter irrigation May be needed to prevent winter drying
2. Spring seeding Quality seed and good seed bed preparation keys to success
3. Fertilizer/herbicide timing Commercial lawn services compared to do-it-yourselfers
4. Vole damage Surface runway damage will repair itself without reseeding
5. Winter annuals To control or not to control during spring
6. Earthworm activity Collect and go fishing. Aerate or power rake to reduce bumps
   
Trees & Shrubs  
7. Emerald ash borer in the News Nebraska Forest Service resources to prepare for this pest
8. Oak tree pruning Do not prune April 1 to mid-July to reduce risk of oak wilt
9. Pruning spring flowering shrubs Wait until after blooming unless doing renovation pruning
10. ReTree Nebraska 15 for 2015 Hackberry and American Sycamore added to the ReTree list
11. Tree planting  Quality trees perform well only if planted correctly
   
Landscape Ornamentals  
12. Pruning roses Wait until mid to late April to prune roses
13. Cutting back herbaceous perennials Remove last years' tops before new growth begins
14. Bulb cold weather protection/ recovery Temperatures below 20 may cause flower & foliage damage
   
Fruits & Vegetables  
15. Fruit tree spray schedules Spray schedules for homeowners & commercial growers
16. Dormant oils/sprays Make applications in March to control mites, scale
17. Time for fruit tree pruning Best done from late February through March
18. Red raspberry pruning When & what to prune determined by raspberry type
19. Peach leaf curl/plum pocket control Dormant sprays must be applied before leaves begin to expand
20. Early season vegetable gardening Cold tolerant vegetable planting can begin soon
   
Miscellaneous  
21. Pesticide disposal Information available from Nebraska Department of Ag
22. Soil temperatures Monitor soil temperatures, not just air temperatures
23. Average last frost dates April 30 for southeast NE; May 21 for northwest NE

 

1. Late winter/early spring irrigation - It has been a fairly dry winter and recent warm temperatures have increased drying of turfgrass soils and plants. Irrigation when temperatures are above freezing can be beneficial in reducing dessication injury. However, irrigation in late winter or early spring can also lead to crown hydration injury where water taken up by the crown freezes, causing ice crystals that damage and rupture plant cells, ultimately causing tissue death. If irrigating in later winter, water only when air temperatures are above 40 degrees F. Apply water at mid-day so it has time to soak into soil before colder nighttime temperatures and potential freezing. Apply water slow enough for it to soak in and not run off.

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2. Spring seeding - Spring seeding of cool season turfgrass should take place as early as possible to take advantage of spring rains and cool temperatures, typically in April. Along with timing and use of quality seed, a key to success is seedbed preparation. Detailed information is available in the following publication on establishing lawns from seed:

Establishing Lawns From Seed, Nebraska Extension

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3. Fertilizer/herbicide timing - There is an ideal time to fertilize lawns and to apply preemergent herbicides. The ideal window is what UNL Extension recommends to do-it-yourselfers (DIYs). As a rule, that window is about April 20 to May 5 in eastern Nebraska and about one week later in western Nebraska. When lawn care professionals begin to make applications earlier than this, questions naturally arise from the DIYs and the customers of lawn care services.

For DIYs who are making an application to one or maybe two lawns, they have the ability to apply products during the time period research has shown to be ideal. However, depending on the size of business, a professional applicator may have up to 500 lawns that need applications within a given window. Thus, a lawn care company may need to start a little earlier than UNL recommends to apply the product to all of their customer's lawns before the "too late" date, especially for crabgrass control. To adjust for the earlier application of preemergent herbicides for crabgrass control, many professionals will use higher rates or split applications. For DIYs, this is not necessary.

Why Do Lawn Care Companies Maintain Lawns Different than Do-It-Yourselfers, Nebraska Extension

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4. Vole damage to turfgrass appears as surface runways. The one to two inch wide runways consist of closely clipped vegetation due to vole feeding beneath snow over. These areas will recover by themselves as turfgrass begins active growth. In most cases, overseeding is not needed to repair vole damage to turfgrass.

Vole Damage, Nebraska Extension

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5. Winter annual weeds like henbit and speedwell will soon be blooming with purple and blue flowers. The seed of most winter annuals germinated last September/October. These annual plants bloom in spring, produce seed, and then die.

Henbit is a good, early season nectar plant for pollinators. If control is not essential, leave these weeds for the pollinators. Where control is desired, preemergence herbicide applications are not recommended at this time. Hand-pull weeds if feasible. Applications of postemergence herbicides for broadleaf weeds can be used in areas where turfgrass will grow to fill in the area and compete with these weeds.

For long term control, determine why turfgrass is not competing with winter annuals and change cultural practices to promote grass density in the area. If the future, if herbicide control is needed, applying a preemergence herbicide in early September is most effective.

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6. Earthworms leave castings (small, hard mounds) leading to rough surfaces. While the mounds are a nuisance and create some walking/mowing difficulty, earthworms are beneficial by increasing air and water movement in soil and helping with thatch decomposition. Although some pesticides and fertilizers are known to have an impact on earthworm populations, none are recommended as controls. Core aerification, power raking and verticutting will break down some of the castings and reduce bumpiness. Use of a heavy roller is not recommended due to creation of soil compaction.

Earthworm and Nightcrawlers in Home Lawns, Colorado State University

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7. Emerald Ash Borer (EAB) has been and will continue to be in the news. While it has not yet been found in Nebraska, it could be found in the near future. To prepare for EAB, the Nebraska Forest Service has a number of resources for professionals and homeowners. Refer to this website for a listing EAB resources ranging from Identifying EAB to Frequently Asked Questions, Community Readiness, and Guidelines for Homeowners as well as Treatment Options.  For homeowners who choose to treat their ash tree, it is recommended to wait until EAB has been found within 15 miles. An alternative to treatment is to replant a dead ash tree with a new and different tree that adds diversity to landscapes and community forests.

Emerald Ash Borer Resources, Nebraska Forest Service

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8. Oak tree pruning is best not done after April 1 in areas with oak wilt disease. Oak wilt is fungus that is often carried by sap beetles who are attracted to fresh pruning wounds. It is lethal to oaks. The risk of infection can be avoided by not pruning oak trees from April to mid-July. Oaks in the red oak group (black oak, red oak and others with pointed leaf edges) are most easily infected. Oaks in the white oak group (bur, white, swamp white and others with rounded leaf edges) are less susceptible.

Diseases of Broadleaf Trees, Nebraska Forest Service

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9. Pruning spring flowering shrubs after the finish blooming. Spring bloomers, like lilac, forsythia, some Spirea, and mockorange, form flower buds the previous summer. Pruning during winter removes the flower buds to prevent or reduce blooming. If a shrub is in need of renovation pruning, where it is to be cut back close to the ground, this type of pruning should be done while the shrub is dormant even if it removes flower buds for that season.

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10. ReTree 15 for 2015 - For this year, hackberry (Celtis occidentalis) and American Sycamore (Platanus occidentalis) are the tree species added to ReTree list of trees to plant in Nebraska to increase diversity in our tree plantings. For information on these trees and a list of other trees to plant, see the ReTree Nebraska website.

ReTree Nebraska Planting Diversity, Nebraska Forest Service 

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11. Correct Tree Planting. Selecting and purchasing a top quality tree will only provide long term benefits if the tree is planted correctly. Here is our annual reminder of tree planting mistakes to avoid. Planting too deep, not taking care of girdling roots, and other mistakes will greatly reduce tree vigor and shorten its life.

Avoiding the Top 10 Tree Planting Mistakes, Nebraska Forest Service

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12. Pruning roses - While some of the hardier roses can be pruned in March, most rose growers wait until just before new growth begins to prune roses. This can help reduce the risk of additional cold temperature injury that may occur as a result of early pruning. On all roses, first prune out any winter killed canes by making an angled cut just above the nearest outward facing healthy bud. Shrub roses require very little pruning; thinning of canes smaller than pencil diameter, crossing canes, and canes too densely arranged in the crown should be done.

Shrub Rose Pruning, Nebraska Extension

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13. Cutting back herbaceous perennials and ornamental grasses in spring, before new growth begins, is an important management practice for pest control, creating an optimal environment for new growth and aesthetics. Last year's growth is dead and needs to be removed. It is fine to delay this practice until just before new growth begins as old growth does provide some protection from spring freezes. However, this practice needs to be done before much new growth occurs. Delay pruning on suffrutescent plants until new growth can be seen, including Caryopteris (blue mist spirea), Buddleia (butterfly bush), Lavandula (lavender), to better assess the amount of winter injury and to protect the crowns of plants from cold temperatures.

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14. Bulb cold weather protection/recovery - Early growth of spring bulbs may occur following warm periods in late winter. Leaf and bulb growth can be damaged when normal hard freezes occur.  Tulips and daffodils can survive freezing temperatures in the upper twenties without much damage, but colder temperatures can damage the plant's flowers and foliage.  Freeze damaged foliage turns white and limp. Little long term damage is likely to the plants. Do not cut back damaged foliage until it dies back on its own.

Continued growth of bulb shoots may be slowed by applying 3-4 inches of wood chip mulch to keep the soil cold.

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15. Fruit tree spray guides - Fruit trees & small fruits are susceptible to a number of disease and insect pests. Often, selection and planting of resistant cultivars will reduce the need for pesticides. When needed, timing of pesticide applications is critical to effectively controlling targeted pests. For recommended fruit spray schedules see the following publication.

Homeowners:

Commercial Growers:

  • 2015 Midwest Small Fruit and Grape Spray Guide - This guide provides pest management recommendations for commercial berry and grape producers in Arkansas, Indiana, Illinois, Iowa, Kansas, Kentucky, Minnesota, Missouri, Nebraska, Ohio, Oklahoma, West Virginia, and Wisconsin. These recommendations have been formulated to provide up-to-date information on pesticides and their application.
  • 2015 Midwest Tree Fruit Spray Guide - It contains a spray schedule and background information for commercial producers of apples, pears, cherries, peaches, and plums. Recommendations for herbicides and plant growth regulators are also included. It is a joint publication of Purdue University, University of Illinois, Iowa State University, University of Kentucky, University of Missouri, Missouri State University, Ohio State University, and University of Wisconsin.
  • 2015 Midwest Vegetable Production Guide for Commercial Growers is a great resource for best production practices, pesticide and cultivar recommendations.

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16. Dormant oils/sprays (raspberries, fruit trees) - March is typically the month to apply dormant oil sprays to fruit, nut and ornamental trees to kill insects and mites overwintering in cracks and crevices on trunks and branches. Temperatures need to be above 40° F when applying dormant oils. Pests controlled include aphids, scales, spider mites, insect eggs and some hibernating caterpillars. A few dormant oils are labeled for use on white flies, mealybugs and lacebugs.

Dormant oils kill by suffocating insects and mites. They are most effective if applied as late in winter as possible, but before spring growth begins. At this time, insects are weakened and easier to kill. Also, dormant oils can damage tender plant tissue and should not be used once flowers or leaves begin to grow. Follow label directions when using any pesticide.

For more information on horticultural oil and dormant oil applications, refer to :
Insect Control: Horticultural Oils, Colorado State University Extension

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17. Time for fruit tree pruning - Fruit tree pruning is best done from late February through March, before trees begin to break bud. Occasional summer and fall pruning may be needed, but keep it to a minimum to avoid spreading fireblight and creating wounds that can be invaded by other diseases.

Make proper pruning cuts and use sharp pruning tools. Do not use pruning paints or wound dressings on pruning wounds. If a fruit tree sustains storm damage, consider removing the tree if over 50% of the trees branches need to be removed due to breakage.

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18. Red raspberry pruning- When and what to prune on raspberries is determined by the type of raspberry. Everbearing red raspberries are typically pruned to the ground during March. This eliminates the summer crop, but results in an earlier, higher yielding fall crop. When pruning the one-crop type red raspberries in March, only prune winter killed tips back to live tissue. Also, thin the patch by removing weak, diseased and damaged canes at ground level. Leave vigorous canes spaced about six inches apart.

Pruning Raspberries Video, Backyard Farmer

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19. Plum pockets & peach leaf curl are caused by Taphrina fungus. Dormant sprays of fungicides are effective controls if applied in late winter before buds begin to swell and when temperatures are above 40° F. These diseases cannot be controlled once leaves have started to expand. Use the fungicides ferbam, chlorothalonil (Daconil), Bordeaux or liquid lime-sulfur. Do not add oil to lime-sulfur or spray oil treatments for three weeks after application of lime-sulfur. Lime-sulfur should not be applied to trees when temperatures are below 45 or above 80 F. Follow recommended label rates for all commercial fungicides.

Peach Leaf Curl, Nebraska Extension
Peach Leaf Curl and Plum Pockets, University of Kansas

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20. Early season vegetable gardening - Warmer temperatures mean many gardeners are anxious to start planting their vegetable garden. Gardeners need to be aware of the last average spring frost date for their area and until that date wait on planting of cold sensitive crops.  However, many vegetables are very cold tolerant and can be planted long before the spring frost date. The following is a partial listing of cold tolerant vegetables, with the potential spring planting dates for eastern Nebraska.

  • March 15th - Asparagus crowns, collards, onion sets, garden peas, radishes, spinach and turnips
  • March 30th - Leeks, mustard, potatoes and swiss chard
  • April 5th - Beets, cabbage, carrots, bibb lettuce and leaf lettuce

Making use of these cool season vegetables can provide an early vegetable harvest with extra sweet flavor. Some vegetables, like carrots and radishes, taste better when grown in cool weather and tend to get bitter or hot if growing temperatures are too warm. Most other vegetables including beans, cucumbers, eggplant, muskmelons, okra, peppers, pumpkins, squash, sweet corn, sweet potatoes, tomatoes and watermelon should not be planted until after the spring frost date, unless extra cold protection is provided.

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21. Pesticide disposal - The best way to "dispose" of a pesticide is to use it according to label direction. This is sometimes not feasible. The pesticide may have been banned, the label is missing, or it is an old or banned pesticide found in storage. For information on disposal, and about storage guidelines until disposal can be safely arranged, see the Nebraska Department of Agriculture, Container Recycling.

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22. Soil temperature monitoring. Even if air temperatures are warm, it is important to monitor soil temperatures. A minimum soil temperature is required for plant and weed seeds to germinate. A soil temperature of 40° F is needed for most plant roots to begin growth and functioning. Weed management, seeding, planting, transplanting and many plant care practices should begin after soil temperatures warm to at least the minimum if not the optimum temperature for that practice or plant.

Average Soil Temperatures, High Plains Weather Center

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23. Nebraska average last spring freeze - Average spring freeze (32° F) dates are a measure of when the average last spring frost will occur in a region. They indicate that half of all final spring freezes will occur before the dates shown and half will occur after, based on 47 years of data from 1949-1995. In southeastern Nebraska that average autumn freeze date is approximately April 30 and May 21 in the northwest corner of Nebraska's panhandle. These dates are guidelines only. Freezing temperatures may occur after the dates listed below. Also remember that local microclimate conditions can significantly affect the occurrence of frost in your landscape.

Nebraska Average Last Spring Frost Dates

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