Hort Update for April 26, 2017

1. RoundUp for LawnsNot Glyphosate. May create confusion for homeowners. See Turf Info. 

Roundup ® for Lawns is a new product on the market this season. Roundup® for Lawns, which can selectively control weeds in lawns when used according to label specifications, is likely to create confusion because its name is common 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.

Be informed and read more about it in the Turf Info - Roundup® for Lawns

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2. MowingWeekly mowing in spring may not be frequent enough.

Mowing during spring growth flush is needed every 4 to 5 days. Following a weekly schedule may not be often enough. Mow at 2.5” to 3.5” for the entire growing season, returning clippings to the lawn. Do not remove more than 1/3 of the total canopy height at one time. Mowing at the shorter end of the recommended range will require more frequent mowing than mowing at the higher end. Mowing too infrequently – called scalping – accelerates growth rate, reduces quality and canopy density, and encourages weed invasion.

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3. Wateringcheck systems now for repairs. Only use system when soil is dry/turf wilted.

Watering is fine if conditions are dry, warm and windy; however, irrigation should only be done if soils have insufficient moisture.  As we begin the season, a reminder that more lawn problems arise from over-watering than under-watering. Lawns should be watered deeply with 0.5 to 1.0” of water (depending on soil type) only when wilt is observed. Common symptoms of minor drought include light blue-green color and lingering footprints. Automatic irrigation systems should be closely monitored, and be equipped with either a rainout or soil-moisture sensor to prevent irrigation when there is sufficient soil moisture.

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4. Fertilizingwindow for application remains April 20-May 5 or later.

Fertilizing established lawns is best started once the spring growth surge begins to slow and turfgrass color is off. Newer lawns may benefit from a little earlier fertilization. With above average temperatures this year, beginning fertilization in April instead of May could be needed. Fertilizer containing 50% each quick and slow release nitrogen sources are good choices.  

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5. Preemergent for CrabgrassAPRIL 20 TO MAY 5 REMAINS TARGETED TIME TO APPLY. 4" SOIL TEMPS ARE APPROXIMATELY 60F IN LINCOLN, STILL TIME TO APPLY.

Crabgrass, a summer annual, begins germination when soil temperatures reach 55 degrees F. at two to four inch depth for a few consecutive days. This typically does not occur until May in Nebraska making late April into early May the ideal treatment window for PRE products. April 20 to May 5 is holding true again this year.  While fertilizer/PRE products are popular, keep in mind most granular products tend to have excessive amounts of nitrogen; however, if the recommended rate is not used, then not enough herbicide is applied.  

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6. Powdery Mildewgrayish white growth on turfgrass blades in shady areas. 

Appears as a grayish-white growth on the surface of grass blades. It is common in shady areas with poor air circulation that is rarely more than an aesthetic concern. Cloudy, overcast weather and high humidity promote infection and spread of the fungus. Powdery mildew is managed by reducing shade and increasing air circulation to reduce leaf wetness. If this is not feasible, replace Kentucky bluegrass turf with tall fescue which is more shade tolerant. The disease typically dissipates with dry summer weather and treatment is generally not required. Under heavy pressure, fungicide treatment is an option. Applications need to be repeated as needed and treatments started prior to significant mildew development. Routine fungicide applications are not a long term solution. For a listing of fungicides, see NebGuide link below. 

Powdery Mildew in Turfgrass, Nebraska Extension

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7. Necrotic Ring SpotSpring/fall patch disease, similar to summer patch. Treat or not?

This fungal disease causes circular tan patches, sometimes with green tufts in the centers; usually in heat and drought stressed areas of lawns such as full sun locations and near pavement. Infected roots are black or brown. Symptoms are similar to summer patch disease, but appear in May and June (and again in fall) rather than July and August. Symptoms may persist through summer because of root decline.  Planting or overseeding with resistant cultivars and the use of cultural practices that enhance turfgrass health are best control measures. Fungicides are available; however application timing is mid to late April and mid to late May for this disease (3” soil temperatures from 60-75F). If fungicide treatment is used, the disease tends to continue reinfecting turfgrass. If left alone, the disease eventually disappears.

Necrotic Ring Spot and Summer Patch Disease, Nebraska Extension

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8. Earthworms & NightcrawlersHard lumps in lawns and thinning. Knock down mounds with rake, etc. 

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. Large numbers can thin turfgrass. 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.

While no product has earthworms listed as a pest controlled on the label, several have negative effects on them.  Carbaryl (Sevin) has been demonstrated to last 1-3 weeks against them and the same is true for combination insecticides (pyrethroid + neonicotinoid). Early Bird fertilizer is also known to have an impact on earthworm populations.

Controlling Earthworm Casts on Golf Courses, USGA Green Section Record

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9. Pear Bark BlastingLoss of bark on ornamental pear trees continues

Ornamental pear bark blasting is the loss of bark on the trunk, eventually leading to tree death. Most bark blasting can still be traced to the sudden cold spell of November, 2014 and/or other periods of extreme weather. Sudden weather changes damages or kills the cambium layer just beneath the bark if it is not yet dormant. One to four or five years later, the tree loses its bark. There is no treatment. Replace the trees as needed with a tree other than ornamental pear. These smaller trees have become over-planted and have other issues, such as fire blight. 

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10. Sirococcus Shoot Blight - SpruceNeedles turn brown on branch tips and drop off

Sirococcus appears on branch tips as reddish brown needles or bare tips that have lost needles. These symptoms appear similar to injury from winter drying or frost damage; however, shoots killed by Sirococcus are scattered throughout the tree rather than uniformly, such as being only on one side of the tree. Also, small black fruiting bodies called pycnidia, in which spores for the fungus Sirococcus strobilinus are produced, can be found on bud scales and dead shoots. These fruiting bodies can be seen with the naked eye or a 10X hand lens.

Infection of current year shoots occurs during spring once new buds begin to open. To control Sirococcus shoot blight, apply a fungicide such as chlorothalonil (Daconil, Bravo) when new shoots are ½ to two inches long, typically in May; and repeat every 3 to 4 weeks if frequent rains occur.

Diseases of Evergreen Trees, Nebraska Forest Service

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11. Yellowing of Spruce NeedlesLikely cause is a root related issue

Spruce needles with little browning is most likely due to a root related issue. Planting too deep, overwatering, poorly drained soils, root rot, soil compaction girdling roots, and transplant shock are some factors that negatively affect roots. Improve the growing environment for roots by applying a 2 to 4 inch deep layer of mulch in a 4 to 6’ diameter ring around the tree trunk. Avoid overwatering. Avoid overfertilizing with nitrogen. 

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12. Treating Tree StumpsKeep in mind that tordon is not labeled for use in landscapes

Tree issues will continue, and as EAB moves across Nebraska, more trees will be removed. If stumps are treated, rather than chipped out, it is important to read label directions. Tordon is labeled for use in treating stumps; however, it is NOT labeled for use in landscapes.  

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13. Euonymous scaleWhite waxy sap-sucking scale on leaves

Appear as tiny white and waxy, tear drop shaped scales on leaf surfaces. Beneath the waxy scale is a sap-sucking insect. Populations can become high and kill leaves. Prune and destroy heavily infested stems. Scales are best controlled with insecticides when in the crawler stage. They overwinter as eggs that hatch in May and early June. There may be a second generation in August. Crawlers resemble tiny yellow spots moving around on leaves and stems. To scout for crawlers, wrap a piece of black electrician's tape around a branch with the sticky side out. Crawlers become stuck to the tape as they crawl across it. Although there are several pesticides labeled for scale control, insecticidal soaps and horticultural summer oils are effective and have less impact on beneficial insects. Generally multiple sprays applied ten to twelve days apart are needed.

As with many insect pests, stressed plants are more susceptible. Keep plants healthy with correct watering and fertilizing. Use mulch to promote healthy roots. A variety of natural enemies, including parasitoids and predators like lady beetles, green lacewing, and predatory mites will help keep populations in check if insecticides are not used/overused. However, if an infestation is high, beneficials generally can't control them.

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14. Rose pruningMid to late April; prune to remove winter damage

Pruning roses after winter injury is needed following our cold, dry winter. Remove all winter killed wood back to healthy tissue, making the pruning cut just above on outward facing leaf or leaf bud. If tender roses were killed down to the graft, watch for regrowth occurring from below the graft. If this is the only growth that occurs, it is best to remove the entire rose. The growth is coming from the root stock rather than the desirable grafted portion and this growth is typically not desirable in the rose garden.

Roses- After Care Planting, University of Missouri Extension

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15. Dividing perennialsDivide summer and fall bloomers just as new growth begins

Dividing perennials is an important management practice for many species, helping to encourage vigorous growth and optimum blooming. As a rule, divide summer and fall blooming perennials during spring, beginning just before new growth begins. Many perennials benefit from division once every three to five years. Dividing is also a good way to propagate perennials. This year give special consideration to soil moisture and the possibility of dry summer conditions when deciding to divide.

Dividing Perennials, Iowa State University

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16. Rhubarb bloomingFlower stalk formation often caused by cold spring temperatures

Bolting, or seed stalk formation, happens to rhubarb plants for a variety of reason including physiological stress, age of planting and varietal differences.  Several environmental stresses can cause flower initiation, such as low fertility, excess heat, periods of hot or cold temperatures, shorter day length and drought. In spring, flower formation is often initiated by cold night temperatures.  Greater amounts of flower stalk development frequently appear on older plants, indicating overcrowded crowns and the need for renovation or division of plants. Variety differences also occur with green stalked varieties being more prone to bolting than red stalked varieties. Old fashioned varieties Victoria and MacDonald are heavy seed producers. Canada and Valentine are less likely to bolt.

Remove flower stalks as soon as possible to prevent plants from using energy on seed development. Removing seed stalks results in a larger amount of crown bud development and will increase harvest the following year. Bolting does not effect the edibility of rhubarb stems; they do not become poisonous and can still be harvested and eaten.

Rhubarb, Cornell University

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17. Planting warm season vegetablesWait to plant warm season vegetables - tomato, watermelon, etc.

Nebraska average last spring freeze (32° F) dates 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 the average last spring 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 these dates. Also remember that local microclimate conditions can significantly affect the occurrence of frost in your landscape. These dates can be used as guidelines for gardeners planting spring crops.

Warm season 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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18. MolesRaised tunnels caused by moles feeding on earthworms/insects

Raised tunnels across lawns are the feeding tunnels of moles, which feed on earthworms and insects. Moles are most effectively controlled by trapping. Two bait products, Kaput® and Talpirid®/Tomcat®, show promise. Castor oil and castor oil products, such as Mole-Med® or MoleChase®, have shown minor effectiveness in repelling the eastern mole. 

It does not work to apply insecticides to control moles by controlling their food source. It does not work to use toxic grain or poison peanuts. 

Moles and Their Control, Nebraska Extension

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19. Firewood InsectsInsects found in firewood rarely a concern indoors

Firewood can host a variety of wood-infesting insects, which occasionally escape into the home when firewood is brought indoors. Most of these pests are only a nuisance and will not hurt people nor damage furniture or the home. The moisture content in furniture and structural wood is generally too low to support insect infestation.

Continued

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