Hort Update for August 4, 2017

1. Caring for new sod in heatUse Correct Irrigation

Moisten the soil before laying down sod; but avoid overwatering. Make watering after installation a priority. During the first two weeks, sod requires daily watering. During warm weather, sod may need to be lightly watering during mid and late afternoon. After 7 to 10 days, check for root development by firmly grasping the grass blades with both hands and lifting. When the sod resists being lifted, usually within 10 to 14 days, the frequency irrigation should be reduced but the amount of water applied during each irrigation increased. 

Establishing Lawns from Sod, Nebraska Extension Turfgrass Science

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2. Managing Kentucky bluegrass in dormancyAvoid traffic and irrigate 1/4" every 4-5 weeks

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3. Annual white grub rescue treatmentneeded if grub numbers are greater than 5-8 per square feet

White Grub Management, Nebraska Extension Turfgrass Science

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4. Japanese beetle larvae controlno control now; apply products in May or June next season

The larvae of Japanese beetle is a type of white grub. If grub numbers are high enough in a lawn, damage can occur. To control Japanese beetle larvae in a lawn that had a history of damage the previous year, a preventative treatment in May or June with chlorantraniliprole ensures little to no grubs in the lawn that year. It does not ensure there will be no adult beetles as these canb fly in from quite a distance. 

Dealing with Japanese Beetles, Nebraska Extension

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5. Windmill grass controluse Tenacity (mesotrione)

Windmillgrass can be controlled selectively with the herbicide Tenacity (mesotrione). Several applications, usually at least 3, should be made on 3-4 week intervals for the best control. Susceptible grasses will turn white following the application, as chlorophyll in their leaves breaks down. Tenacity is labeled for use on Kentucky bluegrass, tall fescue, fine fescue, perennial ryegrass, and buffalograss. It should not be used on zoysiagrass unless damage or grass death can be tolerated. Tenacity can be applied by commercial pesticide applicators, or purchased online by homeowners.

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6. Sudden limb drop Tree limbs suddenly drop for no apparent reason

Reports of tree limbs that appear to be strongly attached and have no obvious issues suddenly dropping have been made. Sudden limb drop is basically a tree’s response to very hot, dry conditions. Within arborist circles, there is a lot of discussion on how and why this actually occurs. One thought is that “the wood becomes dry, dry wood is weaker, the limb fails”.  Another explanation is that it is the tree’s response to a hot, dry environment where transpiration needs exceed vascular capabilities. When it gets too hot to keep all tissue properly circulated, the tree responds with auto-amputation, letting go of a limb. Eric Berg, with the Nebraska Forest Service, recommends:

• Be cognizant of the property and potential targets under ash trees that are on your property. For example, if you typically park under a large tree you might consider other location options until at least the weather cools and / or we get more moisture.
• Move potential targets such a picnic tables etc. and or limit access to areas directly under the canopy
• If you are a commercial arborist, take extra precautions of what you are tied into and what you are lowering from.

Sudden Branch Drop, Urban Forest Pro

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7. BagwormControl now if insects are still feeding; infestations quite high this year

Bagworm infestations have been high this year. As long as bagworms are still actively feeding, insecticides will reduce damage and overwintering populations. While damage has already occurred (bagworm eggs hatched in June and larvae have been feeding since then), insecticides like bifenthrin applied now can still help. June remains the ideal time to begin insecticide control on conifers. Once the larvae, inside their needle camouflaged bags, firmly attach to twigs and pupate, sometime in late August or early September, insecticide control will no longer be effective. See our NebGuide for bagworm information and control recommendations.

Bagworms, Nebraska Extension

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8. Japanese beetlesNebraska Forest Service Resource Helpful

Japanese beetles use their sharp mouthparts to eat the green tissue between the veins of leaves. This results in “skeletonization” where leave take on a lacy appearance.  Control in June, July and August consists of collecting beetles and placing them in a bucket of soapy water or using plant covers to exclude them where feasible. Treating leaves with Carbaryl or bifenthrin, or organic products like neem or pyola will provide some relief from Japanese beetles. Damage can be prevented with a preventative systemic insecticide treatment around the base of plants in April or May. Imidacloprid is most common systemic used. This product cannot be used on Linden trees; but most other plants can be treated.

Dealing with Japanese Beetles, Nebraska Extension

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9. Watering trees and shrubslate summer and fall water very important to preventing winter injury

Some parts of the state have abnormally dry conditions. Trees and shrubs need late summer and fall watering to prep them for winter survival. This is a critical time for watering trees and shrubs to prevent winter injury. Moisten the soil around trees and shrubs, and just beyond the dripline, to a depth of 8 to 12”. Avoid overwatering; but continue to water well into fall as long as dry conditions persist. 

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10. Stress colorationtrees develop earlier than normal fall color

Stress coloration (early fall color) is developing in some trees. Other trees are showing yellow leaves and early leaf drop (i.e. hackberry around Grand Island). Stress coloration this year is likely to the week of extreme heat we had in July; combined with drought conditions in some areas of the state. Provide adequate irrigation and correctly mulch trees to help reduce stress.

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11. Stop rose fertilization and pruningLate summer pruning & fertilization may delay hardening off and development of winter hardiness

Avoid pruning and fertilization of roses and most other woody plants from now until they are dormant in November. Using these practices after early August promotes growth that will not harden off before winter, increasing the risk of winter injury and death of late season growth shoots.

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12. Stop pinching fall bloomersLet fall bloomers, such as mums and asters, develop for fall color

The rule of thumb for gardeners is to pinch fall bloomers until July 4th to encourage bushiness, stem strength and control plant height. After July 4th, allow plants to grow naturally so flowers develop for fall color. Pinching longer into fall will delay flower development and could result in flowers damaged by frost. 

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13. Japanese beetlesExtensive leaf feeding damage to plum, peach and other fruits

Japanese beetle feeding damage has been severe in some parts of Nebraska and will likely continue into August.  Favored plants include grape, plum, peach, and rose. They also feed on overripe and fallen fruits.  

Do not use the Japanese beetle traps found at some hardware stores in clients landscapes. They tend to attract more insects to the landscape, resulting in heavier damage.

Keep in mind that trees and shrubs tolerate damage with little significant impact on the plant's health, even severe defoliation, if it only occurs a few times. Repeated defoliation several years in a row is a greater concern for long term health of the plant.

If Japanese beetle damage becomes an annual event in landscapes you manage, consider swapping out the plants they feast on for less preferred ornamentals. Take a look at the publication Japanese Beetles in the Urban Landscape from Purdue University Extension for a list of resistant plants.

The organic pesticides Neem and Pyola will give some control of the adult beetles, but only for about 3-7 days. Other insecticides, including carbaryl, bifenthrin, cyfluthrin, permethrin and lambda-cyfluthrin provide about 2 weeks of control following a thorough application.

Commercial fruit producers refer to the following publication for pesticide ratings and recommendations. 

Midwest Fruit Pest Management Guide, 2017 (page 35)

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14. Blossom end rotLeathery to soft brown rot on the blossom end of tomatoes and other vegetables

Common problem of tomatoes, but also affects peppers, eggplant, summer squash, zucchini and watermelon. It appears as a flat, dry, sunken, brown rot on the blossom end of tomato and pepper fruits. On squash and watermelon tissue at the blossom end may first turn yellow, then brown, feeling wilted or shriveled. Blossom end rot is caused by a calcium deficiency in the fruit. In Nebraska, rarely is there a lack of calcium in the soil. Blossom end rot occurs when plants cannot pull calcium up quickly enough for developing tissues. Calcium must be dissolved in water to move within a plant, so dry soils can increase the problem.

Drought stress, low daytime humidity, high temperatures, and rapid vine growth favor blossom end rot. Applying calcium to the soil or to the plant is not beneficial. Plants do not take foliar applied calcium in through leaf tissues. Instead, maintain a consistently moist but not saturated soil; use organic mulch near the base of plants; and avoid excess nitrogen fertilization with ammoniacal nitrogen sources. Often the first ripe fruits are affected.  Remove them and later ripening fruits will usually be normal. 

Blossom End Rot of Tomato, Kansas State University
Special Tomato Problems, Nebraska Extension

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15. Vegetable garden pollinator problemsPoor fruit set and flower drop in heat

This common summer problem is being seen now in the vegetable garden on tomatoes, peppers and zucchini, and is likely weather related. Daytime temperatures above 90 degrees, and/or nighttime temperatures above 70 degrees interfere with pollination.  Ideal conditions for pollination are moderate temperatures, 59-68 degrees. Plants receiving excessive fertilization and abundant moisture often produce excessive foliage growth that inhibits flower formation.  However, very low fertility levels, substantial damage from insects or diseases, and inadequate moisture can also inhibit flower development.

Provide plants with good basic growing requirements, without over or under fertilizing, so that flower clusters are produced.  In small gardens, hand pollination can be done to encourage fruit formation.  If the lack of fruit set was due to high temperature conditions, plants should begin to set fruits again now that temperatures have cooled.

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16. Squash bugsFlat, brownish-black, shield-shaped insects attack cucurbits; cause leaf yellowing, sudden wilting and plant death

Squash bug adults are flat, shield-shaped, brownish-black and congregate on leaf undersides and fruit. Young nymphs are tear-drop shaped and gray with black legs. Yellowish to brick red, oval shaped eggs are laid in groups, usually in the V made by veins on leaf undersides. Squash bugs feed on plant sap and inject a toxin which causes wilting known as Anasa wilt of Cucurbits. Because of an extended egg laying period, all life stages occur together throughout the summer. Inspect leaves for egg masses and crush them when found. Row covers can protect plants until blooming and pollination begins. Apply carbaryl (Sevin) or permethrin (Eight) according to label directions when bugs first appear to control nymphs. Repeat applications as recommended and needed for control.

Squash Bugs in Home Gardens, University of Minnesota Extension
Common Vegetable Garden Insects, Backyard Farmer on YouTube

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17. Blister beetlesSudden vegetable leaf defoliation damage; slender black, gray or striped beetles present

Blister beetles are a sporadic problem in vegetable plantings, but have a wide range of host plants, including bean, beet, carrot, cabbage, Chinese cabbage, corn, eggplant, melon, mustard, pea, pepper, potato, radish, spinach, sweet potato and tomato. Weeds, like pigweed, are also a preferred food host for adult blister beetles. They often congregate into large mating and feeding groups; their voracious feeding activity can cause sudden defoliation injury in vegetable plantings. Several species of blister beetles are found in Nebraska, including black, gray and striped blister beetles. Each adult insect has a long, slender, 3-segmented body, approximately 1/2 to 3/4 inch in length with long legs, allowing them to move quickly when disturbed. Immature stages are beneficial biological control agents of grasshoppers. If control is warranted, carbaryl or pyrethroids (bifenthrin, lambda-cyhalothrin or permethrin) can be used.  

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18. Colorado potato beetleFeeding damage on potato, tomato and eggplant

The potato is a favorite crop for these beetles, but they will feed on other vegetable crops in the same family such as tomatoes and eggplant.  In Nebraska, beetles overwinter as adults in the soil, emerge in the spring and begin feeding.  Beetles mate, and then the females lays her eggs on the undersides of leaves, and when the larvae hatch and emerge, they begin feeding on the crop foliage.  This stage in the life cycle is the most damaging to the vegetable crop.  Unfortunately, Colorado potato beetle has developed resistance to many insecticides, so it is imperative that chemical rotation, as well as other IPM techniques, are utilized for successful control.

Colorado Potato Beetle Management, University of Kentucky
Colorado Potato Beetles in Home Gardens, University of Minnesota Extension

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19. Tomato foliage disease controlEarly blight, septoria and bacterial leaf spot, common diseases on tomatoes are active now

Tomato leaf spots, such as the fungal diseases early blight and septoria leaf spot, and bacterial leaf spot are appearing now in tomato gardewns. These diseases often begin as leaf spots on lower leaves, then work their way up the plant causing leaves to die; often leading to fruit sunscald. Tomato leaf spot diseases can be managed with regular applications of fungicides labeled for use on tomatoes. For best results, applications need to begin as soon as symptoms first appear on lower leaves and applications made about every 7 to 10 days. Avoid overhead irrigation and increase air circulation around plants with proper spacing and caging. Mulch the soil around tomatoes to reduce soil splash of fungus onto lower leaves. Plant resistant varieties and avoid planting tomatoes in the same area each year. Severely infected plants are best pulled and destroyed. Use fall sanitation to reduce the amount of overwintering fungus.

Common Vegetable Diseases, Backyard Farmer on YouTube
Tomato Leaf and Fruit Diseases & Disorders, Kansas State University

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20. Cucubit foliage disease controlAnthracnose, downy mildew common fungal diseases on cucurbits are active now

Anthracnose of cucurbits and melons is a destructive disease that occurs during warm, moist seasons. Significant damage can occur to cucumber, muskmelon, and watermelon unless resistant varieties are grown. All aboveground plant parts can be infected. Symptoms vary somewhat among the cucurbits. On watermelon, leaf spots are irregular and turn dark brown or black. On cucumber and muskmelon, leaf spots are brown and can enlarge considerably Stem lesions on muskmelon can girdle the stem and cause vines to wilt. The most striking symptoms are on the fruit and appear as circular, black or brown, sunken areas. A combination of crop rotation and fungicide applications are necessary for controlling this disease on susceptible varieties. Protective spray applications should be made when vines start to run and continue at 7 to 10 day intervals during periods of humid or rainy weather.

Powdery & Downy Mildew can also be problems in Cucurbits.  Powdery mildew appears as a white flour-like dusting growing on leaf surfaces. Downy mildew first appears as pale green areas on upper leaf surfaces which change to yellow irregular shaped spots. A fine white-to-grayish downy growth soon appears on lower leaf surfaces. Infected leaves generally die but may remain erect while the edges of the leaf blades curl inward. Usually, the leaves near the center of a hill or row are infected first. The infected area spreads outward, causing defoliation, stunted growth, and poor fruit development. The entire plant may eventually be killed. Spores are carried by wind so crop rotation is not as effective. Plant resistant cultivars. Avoid overhead irrigation. Space correctly. Improve air circulation. Copper based fungicides are recommended for mildew in cucurbits, but can damage plants. Read and follow label directions.

Managing Downy Mildew in Cucurbits, Cornell University
Powdery Mildew of Cucurbits, University of Minnesota Extension
Anthracnose of Cucurbits,University of Minnesota Extension

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21. Watch for spider mitesYellow stippling on the leaves of tomato, watermelon & muskmelon

Spider mites on tomatoes can cause problems in the late summer garden, particularly on tomato, watermelon and muskmelon growing in light or sandy soil.  Damage symptoms progress from stippling to yellowing, wilting, browning, and eventually to death of the leaves or whole plant. Mites may move from soybean fields into vegetable gardens, as the soybean plants begin to turn yellow and dry out. To check for spider mites, place a white piece of paper beneath the branch or leaves and tap several times. The mites will appear as very small, bits of dust that are crawling across the page.

Controlling spider mites is difficult because they reproduce so rapidly. One method to try involves spraying the plant with a strong jet of water once or twice a day to dislodge some of the insects and to create an environment that is cooler, more humid and less favorable for spider mite reproduction. Several days or even weeks of this treatment will be required to make a noticeable difference in spider mite populations.

In the late summer garden chemical control may not be needed as plants near the end of their harvest season. Removal of infested plants may be the best option.  Refer to the publications below for additional chemical control options. Be sure any chemical you use is labeled for use in the vegetable garden.

• Spider Mites, Colorado State University Extension
• Spidermites and Their Control, The Ohio State University

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22. Swallowtails laying eggs on dillProtect caterpillars to encourage butterfly development

Several species of swallowtail butterflies rely on plants in the parsley and dill families as food sources for their immature caterpillar life stage, including black, anise and Indra swallowtails. Don't mistake the immature caterpillar stage of these beautiful butterflies as a pest and kill them. For more information on Nebraska butterflies, including pictures of the adult and immature life stages of those butterflies mentioned above, check out:

Butterflies and Moths of North America 

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23. Solitary waspscidada killers, sand wasps and cricket hunters; large solitary wasps active now

Midsummer is the season of solitary wasps. These wasps are called solitary because they do not build large colonies like paper wasps or yellow jackets. They are predators and prey on spiders, crickets, cicadas and other insects. Solitary wasps paralyze their prey and drag it to a burrow. They lay an egg on the paralyzed prey, which hatches into a larva that feeds on the paralyzed insect. Solitary warps are not aggressive and would only sting someone who is foolish enough to handle the live wasp.

While these insects are not a sting hazard, they do often frighten people. The males in particular can be territorial and fly towards your face to discourage you from coming close to their nests, but males lack a stinger so can't sting. Females do have stingers, but prefer to avoid people.

In years with high numbers they may do some aesthetic damage to lawns as they dig their nests. Adult wasps may be found feeding on flower nectar. They do no damage to flowers, so can be ignored.

Three of the most common types of solitary wasps are the cicada killer wasp, steel blue cricket hunter and sand wasps. Cicada killer wasps are the largest wasp species in Nebraska. They are up to two inches long and boldly marked with yellow stripes on a black body. Females are larger than males.

Cicada killer wasps create underground burrows. These burrows can be found near walks, driveways, and retaining walls and can usually be identified by the presence of fresh soil around the 1/2-inch entrance hole. These wasps can create clusters of nests within a preferred area.

It makes sense that cicada killers are most abundant during midsummer when their prey - cicada, grasshoppers and crickets - are active. Each individual nest is provisioned with 2-3 cicadas for the developing wasp larva to feed on, then sealed. Larvae will develop in the soil until they emerge as adults next summer.

Steel blue cricket hunter is also a large wasp, about 1 to 1 1/4 inch long. Sometimes called thread-waist wasps, this group of insects have a thin structure connecting their thorax and abdomen. Look closely at the steel blue cricket hunter and you'll see their body is a dark steel blue metallic color with dark smoky wings. As their name implies, their larvae are fed primarily with crickets.

The sand wasp is around an inch long. They have large eyes, with black and white striped abdomens. Although they are considered a solitary wasp, several females may join together to create individual nests in the soil and discourage invaders. Backyard sandboxes are a prime nesting location for sand wasps. Their larvae are fed primarily with flies.

Control Is Usually Not Needed
Due to their docile nature and the fact they are beneficial predatory insects, solitary wasps should be tolerated as much as possible. They are active for only a short time in mid to late summer, then will be gone again for another year.

Ground nesting wasps prefer to dig in areas of dry soil. If their nest building is a problem in some areas of your landscape, one way to discourage them is to run a sprinkler where they are trying to nest. You may have to do this a couple times a day to keep the soil moist until they find another location.

If control is desired an application of carbaryl dust (Sevin) or cyflutrhin (Tempo) made directly into the burrow entrances is effective. If you're nervous about approaching the nests, put the carbaryl dust on a shovel and sprinkle it over the holes.  Applications should be made at dusk, when the wasps are the least active.

Don't broadcast applications of liquid insecticide over the area where solitary wasps are nesting. This method of application is unlikely to reduce their populations.

Stinging Wasps and Bees, Nebraska Extension

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24. Nuisance fungi identification & controlPuff balls, stick horns and slime molds appearing in landscapes

Mushrooms and molds in the landscape- Fungi are a wonderfully diverse part of our natural environment. Many are decomposers, breaking down organic matter such as dead leaves or woody stems, so are beneficial in the long run. Mushrooms and fungi lack the green chlorophyll found in plants, so cannot photosynthesize and create their own food as plants do. Instead they absorb nutrients from soil, manure or organic matter they decompose, such as wood or leaves. The mushrooms we see are actually fruiting structures produced by a vast underground network of hyphae, or fungal roots. Three types of fungi commonly found in landscapes include mushrooms, puffballs and slime molds.

Mushrooms and toadstools both have a structure similar to an umbrella, with a cap and a stalk (called a stipe). Common mushrooms found in landscapes include inky caps and stinkhorns.

• Inky caps decompose into a dark liquid resembling ink shortly after they appear in the lawn, which gives them their name.
• Stinkhorns resemble fingers sticking up from a landscape bed or lawn. Their head is covered with a gooey slime, which smells really bad, attracting flies and other insects to spread spores hither and yon.

Puffballs are similar to mushrooms but lack a stalk, consisting of a round or pear-shaped ball, often white in color, growing from the soil surface. They range in size from less than 1 inch up to 1 foot in diameter.  If cut open before they are mature, puffballs have a solid white fleshy structure throughout the ball, but in late summer or fall when they reach maturity the ball splits open to release thousands of black spores.

Slime molds are also common in landscapes, but many are small enough they go unnoticed. They are not true fungi, but are primitive organisms found in similar environments. Slime molds have the ability to move up to several feet a day. They occur in lawns, but more commonly grow on the mulch in landscape beds. In appearance, they can be white, gray, yellow or shades of red. Gardeners usually spot slime molds after they shift into their reproductive phase, as a dried mass of spores. 

Common slime molds belong to the Physarum and Fuligo species. 

• Physarum slime mold can be seen as tiny dark gray to black grain-like structures growing on grass leaf blades. From a distance, they give small patches of turf a black or dark gray appearance. Closer inspection reveals the slime mold fruiting structures.
• Fuligo slime molds are often white or yellow and are often given the very descriptive common name “dog vomit fungus.” 

Control - These mushrooms and slime molds are not damaging to lawn grasses or landscape plants. They can be ignored them, for the most part. Once they have broken down all the organic matter they are using as a food source, they will disappear on their own. Tenacity will reduce mushroom growth but not eliminate it completely.

However, if young children or pets are present and might accidentally eat them then it’s best to remove them by hand when they appear. Removal will also help reduce their numbers over time, preventing the spread of additional fungal spores. Slime molds on grass leaves can be removed by raking the area to knock them off or by spraying them off the leaf blades with a jet of water.

Mushrooms, Fairy Rings and Other Nuisance Fungi in the Landscape, Nebraska Extension

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25. NNLA Field Day August 4, Doane University, Crete, NE

The Nebraska Arborists Association (NAA) and the Nebraska Nursery and Landscape Association (NNLA) are co-hosting the 2017 GREAT PLAINS Summer Field Day on Friday, August 4 at Doane University in Crete, Nebraska. We are excited to offer a great line-up of educational sessions and activities for this year’s event. Connect with other professionals while enjoying the arboretum, gardens, trees, trails, and lakes on the Doane University campus.

The event includes a keynote address on Diversity: Think Genera, Not Species by Dr. John Ball; and breakout sessions on topics ranging from climbing techniques to rain gardens. Demonstrations on the latest products and services will be done by industry representatives.

We hope you can join us for this educational opportunity at the 2017 GREAT PLAINS Summer Field Day on the beautiful campus of Doane University (1014 Boswell Avenue) in Crete, Nebraska!

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