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Hort Update for July 18, 2016

Major Symptom:
1. Welcome Cole Johnson New UNL Turfgrass Specialist
2. Summer annual grassy weeds Crabgrass, yellow foxtail, goosegrass, barnyard grass

3. Curative grub control

Too late for preventive grub products
Trees & Shrubs  
4. Japanese beetles High numbers feeding in Omaha area; reports in other areas
5. Emerald ash borer (EAB) quarantine

Information related to quarantine areas

6. Tree sucker control Prune, pull (rip out) and products to use
7. Fungal leaf rusts Orange spots on crabapple, Hawthorne, pear and ash
8. Euonymous scale White waxy sapsucking scale on leaves
Landscape Ornamentals  
9. Deadheading perennials Encourage additional flowers by removing spent ones
10. Division of perennials Fall ideal time to divide and transplant
11. Aster lacebug Yellow to brown scorched leaves caused by insect feeding
12. Mushrooms and molds in the landscape Several mushrooms and molds are common in landscape; control usually not necessary
Fruits & Vegetables  
13. Spotted wing drosophila Monitor for insect presence; male fruit fly with red eyes and one dark spot on wing tip
14. Poor fruit set in heat Weather conditions affect flower pollination and fruit set
15. Sudden death of cucumber, squash and melons Common culprits - squash bugs, squash vine borer, bacterial wilt
16. Blossom end rot Leathery to soft brown rot on the blossom end of tomatoes and other vegetables
17. Chiggers Immature harvest mites; causing itchy bumps
18. Ticks Numbers remain high this summer
19. Digging wasps Cicada killers, sand wasps and others active now
20. Poison ivy, Boston ivy and Virginia creeper Identification key to Poison ivy control 

1. Welcome Cole Thompson - Dr. Cole Thompson eagerly joins the Department of Agronomy and Horticulture faculty this July as the new Integrated Turfgrass Management Specialist. Cole comes to UNL after working for two years as an Assistant Professor of Turfgrass and Landscape Physiology at California Polytechnic State University-San Luis Obispo. In this previous position, Cole had a primary teaching role, but is excited to get back to his extension and research roots. His expertise in applied turfgrass pathology and weed science compliments the existing skills of the UNL Turf Program.

A native of Beloit, KS, Cole received his advanced degrees from Kansas State University. His Master’s Degree research focused on silvery-thread moss control on putting greens and creeping bentgrass cultivar susceptibility to dollar spot. His Ph.D. research focused on management and control of rough bluegrass (Poa trivialis), a challenging weed to control in turf. Cole’s applied industry experience comes from his previous work as an Assistant Golf Course Superintendent and an internship with the USGA. Cole has a positive, resourceful, and congenial attitude and will be a great addition to the UNL turf program. We are very excited to have him at UNL where he will jump right in and make a positive impact on our turf extension, research, and teaching programs.

Please join us in welcoming Cole to Nebraska this summer. Cole officially starts July 1, so you’ll have the opportunity to meet him at Field Day on July 20th.


2. Summer annual grassy weeds like crabgrass, yellow foxtail, goosegrass and barnyard grass are growing in thinned turfgrass areas. As annuals, these grass plants will flower, seed and then die. The best means of control is with preemergence products applied in late April to mid-May. If a control method is used at this time of year, the goal is to help reduce weed seed build-up in the soil and kill the weeds so turfgrass can better fill in bare areas to compete with summer annuals next season.  Products containing the herbicide quinclorac provide effective postemergence control of summer annual grasses. They are most effective on young plants and older plants; less effective on “middle age” plants. Other control options are hand-pulling before seed production. Also, good fall management practices need to be used to increase turf density for better competition against these grasses. Summer annual weeds tend to be a sign of poor turfgrass growth rather than a problem in and of themselves.   


3. Curative (post egg hatch) control of white grubs usually occurs in late August or early September, but only if needed. When about 8 white grubs per square foot can be found feeding in turf in mid-August to mid-September, a curative insecticide application may be warranted. Products containing carbaryl (Sevin) or trichlorfon (Dylox) are applied after egg hatch. These products must be watered in for acceptable control. Moving the insecticide into the root zone involves applying ½ inch of water immediately after application. Other control options are using good fall management practices to aid root recovery from white grub feeding.

White Grub Management, Nebraska Extension Turf iNfo
Improving Turf in the Fall, Nebraska Extension Turf iNfo


4. Japanese Beetles feed on leaves. The injury is referred to as skeletonizing since they tend to eat green tissue and leave behind a network of veins. Heavy feeding is reported in Omaha on linden, birch, apply and other fruit trees as well as on roses. The majority of damage is in the top tree canopy. Japanese beetle feeding is also being reported in Lincoln, South Sioux City, Aurora, Grand Island and North Platte, but in fewer numbers with less damage occurring.  

To control, commercial applicators can by Acelyprin. Homeowners can apply Permethrin or the organics Neem or Pyola. Acelyprin, Neem and Pyola will have less of an effect on pollinators than Permethrin or Sevin. Hand-picking or cover plants with row cover fabrics are other options of control. If Japanese beetle traps are used, place them away from targeted plants since they attract beetles; typically more than they trap.


5. Emerald Ash Borer (EAB) Quarantines: Nebraska Department of Agriculture (NDA) has issued a quarantine prohibiting ash nursery stock from leaving the quarantine area. The quarantine also regulates the movement of hardwood firewood and mulch, ash timber products and any living, dead, cut or fallen ash material such as logs, branches, and roots.  These regulated materials must not be moved out of the quarantined area without a compliance agreement.  The quarantined counties are Douglas, Sarpy, Cass, Washington and Dodge.  Following the quarantine will help prevent the human-assisted spread of EAB into un-infested areas. For information about EAB quarantine regulations, see the following links:

Emerald Ash Borer, Nebraska Department of Agriculture
EAB Quarantine Regulations and Ash Wood Product Treatments, Nebraska Forest Service


6. Tree basal suckers often grow at the base of trees such as crabapple and purple-leaf plum or Canada cherry. These are root suckers, often referred to as basal suckers. On other trees, basal suckers may be a sign of stress or wounding. It is not possible to stop sucker growth on trees that naturally sucker. The best method is to stay on top of the suckers and pull or cut them off below ground level when they are small. While they can be pruned off, they will return quicker than if ripped or cut out when small. There is a product called Sucker Stop. This has been shown to slow the return of suckers, but it does not stop them. Herbicides are best not used as they will be translocated from the suckers into the tree itself to cause damage.


7. Fungal Leaf Spots: Spots of many colors are appearing on leaves and fruits, along with brown or blighted leaf areas. In most cases, these are some type of fungal leaf spot disease that has been promoted by rainfall and high humidity. Key points about fungal leaf spot diseases are:

  • Most are a minor problem for otherwise healthy trees and shrubs. Other than some leaf spots, leaf yellowing and leaf drop, they do not harm trees and shrubs in the long run.
  • Most fungal pathogens are host specific; meaning they will only infect one type of plant or plant family. There is no need to be concerned that they will spread to other types of landscape plants.
  • Once a plant’s leaves are infected, fungicides will not cure the infection or kill the fungus. Fungicides will prevent new infections. If used, they are best applied prior to infection beginning in the spring.
  • And most important is that the best means of control is planting resistant varieties. This is especially important with roses and fruiting plants like apples, strawberries or grapes.


8. Euonymus scale 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.


9. Deadheading ornamentals - Cut back spent flowers and discolored or tattered foliage of late spring and early summer blooming perennials. This practice is referred to as deadheading and dead-leafing. Some perennials will produce a second flush of blooms. If they do not, they still produce new foliage that is more ornamental. Do not cut back the leaves and stems of peony and Hosta. Only remove spent blossoms and flower stems on these plants.


10. Division of perennials - Most perennial plants need periodic division to maintain their vigor and achieve maximum flower production. This may need to be done annually, as with 'Stella d'Oro' daylilies, but is usually only necessary every three to four years. Some perennials, such as babys breath,Gypsophila paniculata, should never be divided.

  • Summer and fall bloomers, like chrysanthemum, aster, or coneflower, are best divided in the early spring, just as new growth begins.
  • Spring and early summer bloomers, such as peony or creeping phlox, should be divided in the fall, or after the foliage dies.
  • The exceptions to this rule of thumb are iris and daylilies, which should be divided immediately after flowering.

The time of year when perennials are divided is a major factor in determining the success of this procedure. Summer conditions have gotten too warm for successful division to be done now.  Instead, gardeners should wait until September to divide spring-blooming perennials. 

Dividing Perennials, Backyard Farmer on YouTube


11. Aster lacebug - Lacebugs are very small, flattened insects with ornate, lacy membranous wings.  Approximately 160 species of lacebugs occur in North America.  They are highly host specific, meaning each species of insect feeds only on one type of plant or a few closely related plants.  They have piercing-sucking mouthparts, and can often be found on the undersides of leaves of trees and shrubs.  Lacebugs damage plants by sucking plant sap from the leaves, resulting in yellow or white stippling of the leaves. Lacebug excrement is seen as small black tar-like droppings on the undersides of leaves.

Severe infestations can occur on asters, causing leaves to turn completely turn brown and decrease plant vigor. Monitor plants for signs of damage, but insects are usually are kept in check through natural predators.  If control is needed, try washing the insects of plant leaves with a strong jet of water several times per week. If chemical control is needed, heavily infested plants may be treated with carbaryl, bifenthrin or insecticidal soap.

Lace Bug on Deciduous Woody Ornamental Plants, PennState


12. 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


13. Spotted wing drosophila -  is active now attacking the soft fruits of brambles (raspberry, black berry), strawberry, blueberry, grape, cherry, plum, peach and many small wild berries. Adult females make a slit through the fruit skin and insert eggs inside. Larval feeding inside the fruit causes fruits to become wrinkled and dimpled and they are prone to fungal infection causing decay and rot. In its native range in Japan roughly 13 generations occur each year.  Upwards of 10 generations are predicted in the United States depending on climate.

Monitor for SWD through trapping to distinguish it from native fruit flies. Fruit growers especially need to be monitoring frequently, but also to be checking for evidence of ovipositional or early larval damage. Traps do not always keep in real time sync with what is going on in the field.

Treatment is warranted immediately once one or more SWD flies are discovered, or if larvae are found in fruit. Remember to take notice of PHI's for whatever insecticide is used. Sanitation is also important as a means of helping to minimize fly numbers, and consequently, yield losses.

If SWD occurs, manage it through sanitation including prompt remove of infested fruits and insecticide applications.

Spotted Wing Drosophila in Home Gardens, University of Minnesota Extension


14. Poor fruit set and flower drop in heat - is being seen 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.


15. Sudden wilt and death of cucumber, squash and melons - Sudden wilting and death of cucumber, squash and melons in the late summer garden is a pretty common problem with three common culprits - squash bugs, squash vine borer and bacterial wilt. Symptoms of these three pests can be similar at first glance. Initially plants wilt during the day, but recover at night. Eventually plants don't recover so well, stay wilted and develop yellow or brown leaves. Then plants completely wilt, turn brown and die. Often this process happens very quickly, in only a matter of days.

Three common causes of these symptoms include squash bug, squash vine borer and bacterial wilt. For more information, refer to:
Sudden Wilt and Death of Cucumber, Squash and Melons in the Vegetable Garden, Nebraska Extension


16. Blossom end rot (BER) - is a 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, University of Nebraska - Lincoln Extension


17. Chiggers - Chiggers are the larval state of harvest mites. In early spring, adults lay eggs in the soil that hatch in June. Adults are harmless, but the tiny, six-legged larval stage is parasitic on animals and humans. On hosts, chiggers move about until reaching a confined place, such as around ankles, under socks, waistbands or arm pits. Chiggers do not burrow into the skin, but pierce the skin and inject a fluid that causes tissues to be inflamed and itchy. Once fully fed, chiggers drop from hosts and enter the ground. In the fall, it becomes the bright red overwintering adult.

To monitor for chiggers, place six-inch squares of black paper vertically in the grass. If chiggers are present, they will climb to the top of the paper. Because several hours elapse before chiggers settle down to bite, bathing soon after exposure to chigger-infested areas may wash chiggers off the body and prevent feeding. Clothing should also be washed. Insect repellents containing "DEET" (diethyl toluamide) are effective in reducing chiggers.

Where chiggers are a problem in landscapes, keep lawns and shrubbery well manicured and mowed, especially in areas adjacent to dwellings.

Chiggers can also be reduced by treating turf with insecticidal sprays. UNL Extension Entomologist Fred Baxendale found a liquid treatment of bifenthrin reduces chiggers 75-95 percent for several weeks. Use 0.2 pounds active ingredient per acre. To escape the highest chigger populations, your first treatment should be early- to mid-June.

Itchy Chiggers, Nebraska Extension


18. Ticks - Larger numbers of ticks are being reported early this year. For information on control and/or bite prevention refer to the Tick Control Resources by Nebraska Extension.


19. Digging wasps - Some folks are finding high numbers of digging wasps in their lawns, sand traps, and playgrounds this summer. Digging wasps are parasitoid insects, meaning that they will capture and sting another insect (like a cricket or a cicada) and then drag their immobilized body to a small hole in the ground. These insects do not have a colony or hive like other wasps and bees and this results in them being far less aggressive than insects like honey bees or yellowjackets. Some of the more famous representatives of this group are the cicada killer wasp (Figure 1) and the sand wasp (Figure 2), both of which can be large and in places where humans often visit. Cicada killers are the largest, usually reaching about 1.5 - 2 inches in length, while the sand wasp is around an inch long.

While these insects are not a sting hazard, they do frighten some people. The males in particular can be territorial and fly towards your face. In years with high numbers they may also do some damage to lawns as they dig their tunnels. If control is desired there are very specific methods of achieving it. Applications of carbaryl dust (Sevin) or cyflutrhin (Tempo) made directly into the burrow entrances are effective.  Broadcast sprays over the area where digging wasps are nesting will be unlikely to reduce their populations. Applications should be made at dusk, when the wasps are the least active. Physical control by swatting with a tennis racket is also effective. 

Stinging Wasps and Bees NebGuide, Nebraska Extension


20. Poison ivy, Boston ivy and Virginia creeper - These three common vines are often confused by homeowners and professionals alike. Correct identification is an essential first step for poison ivy control. September through mid-October is the best time of year for poison ivy control.

  • Poison ivy, Toxicodendron radicans - Leaves alternate, compound with three leaflets; rarely 5-7 leaflets. The middle leaflet is larger with a long stalk, compared to the two side leaflets which are smaller and attached directly to the central petiole. Leaflet margins may be smooth, lobed or toothed. Plants grow as upright woody shrub, trailing shrub or woody vine. Young growth greenish-red, dark green throughout summer; fall color red, orange or yellow. Cream to yellow flowers produce 1/4" cream to light brown berries produced in small clusters in the leaf axils. Many aerial roots produced on vines allowing them to climb trees.
  • Boston ivy, Parthenocissus tricuspidata - Leaves alternate, simple with three coarsely serrated lobes. Young plants and basal shoots may produce compound leaves with 3 stalked leaflets. Fruits bluish-black berries, 1/4-1/3" diameter, on terminal panicles. Tendrils ending in adhesive tips, shorter than those of Virginia creeper.
  • Virginia creeper, Parthenocissus quinquefolia - Leaves alternate, compound palmate with 3-5 leaflets. Each leaflet has a 1/3" stalk. Young growth bright waxy bronze to red; fall color purple-red to crimson-red. Fruits bluish-black berries, 1/4" diameter, on terminal panicles. Grape-like tendrils ending in adhesive tips.

Poison Ivy: Identification and Control, University of Missouri Extension