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Hort Update for July 5, 2023

Hort Update for July 2023 - Tomato early blight leaf lesions.
Serious ConcernsMajor Symptom:
1. Correct watering techniques Turf, ornamentals, vegetables, woody plants - recommendations for clientele
2. July 2nd growing degree days (GDD) Several Nebraska sites below. Understanding Growing Degree Days
3. Pest update Pests to watch for based on Growing Degree Days (GDD).
4. Magnolia scale Prepare for crawler control in August. GGD 1925-1950.
5. Zimmerman pine moth Pinkish pitch/sawdust masses at branch junction with trunk; ultimately results in branch death or breakage. GGD 1700, adult flight.
6. Japanese beetle control Strategies for homeowners. GGD 950-2150, adult emergence.
7. Poison ivy, poison hemlock, yellow nutsedge Weeds of serious concern due to difficulty of control or human health impact.
Minor Issues
8. Cicada killer wasps Huge yellow and black wasp or small mounds of soil near pavement.
9. Turf dormancy Kentucky bluegrass vs. tall fescue.
10. Tree leaf-feeding insects Control usually not needed unless very heavy infestations occur.
11. Mid-summer vegetable garden problems Many maladies appearing now; symptoms and link to additional information available.
12. Geranium budworm Flower loss on many common flowering annuals including geranium, petunia and nicotiana.
Timely Topics
13. Chiggers Immature harvest mites; active now; cause itchy bumps.
14. Ticks Identification and protection strategies.
15. Mosquitoes Eliminate stagnant water in pools, tires; control adult mosquitoes.
16. Slime mold Yellow, white, gray growths appearing in turfgrass and mulch beds.
Heads Up: For Your Information
17. Cool Season Lawn Calendar - Eastern Nebraska New publication for use with clientele.
18. Commercial/Non-commercial pesticide applicator certification Obtaining a new license or updating an expired license.
19. Digital Diagnostic Network - Need help with diagnostics? Submit pictures and questions for diagnosis by Nebraska Extension experts.

1. Correct watering techniquesRecommendations for clientele

Clients often ask how frequent to water plants and how much water to apply. There is not a "one size fits all" answer. It depends on many factors including soil and plant type, differences in sites like wind exposure, slope and shading, the irrigation method used and homeowner preferences.

Correct watering is a challenge for property owners and there are misconceptions about plants and water needs. Too much and too little are both harmful. Overwatering - often by watering too frequently, not just too much water total - is a common mistake leading to water waste, unhealthy root systems and drought stress in plants.

Results of Too Frequent Watering
Clientele know water is critical to plant growth. Many do not realize soil oxygen is also critical, especially to roots. Without sufficient soil oxygen, roots stop growing or may even begin to die back. Without a vigorous root system, plant growth and function are decreased and a plant's ability to efficiently use soil moisture and nutrients hindered.

With drought conditions in many areas of the state, a common issue will be automatic irrigation systems running too frequently and keeping the upper few inches of soil too wet while soil lower in the profile is too dry. The wet layer decreases oxygen recharge of soil and dry soil lower in the profile leads to drought stress for deeper rooted plants.

When asked about landscape watering, the basic answer is to apply enough water to moisten the soil to the depth of plant roots; then wait to water until soil begins to dry or plants show signs of needing irrigation.

Average rooting depths:

  • Turfgrass – 2 to 6 inches
  • Ornamental annuals & perennials – 6 to 10 inches
  • Vegetables – 6 to 36 inches (Deeper roots are found on hardy perennial vegetables like asparagus and rhubarb.)
  • Woody plants – 90% of water absorbing roots are in the top 24 inches of the soil.

Misconception #1 - Roots will "go in search of water". Roots only grow where there is available soil water and oxygen.

Misconception #2 – Tree roots go as deep as the tree is tall. Yes, trees do have some deep anchoring roots, but they do little to absorb water. If the top 24 inches of soil is dry, the tree is functioning at a water deficit.

Assessing Soil Moisture
A simple long-bladed screwdriver or other metal probe can be used to estimate soil moisture levels and depth of water penetration after irrigation.

To assess current soil moisture, push the screwdriver into the soil, pull it out and feel the blade. If the blade penetrates the soil with little resistance, there is plenty of soil moisture. If wet or muddy soil is on the blade, there is plenty of soil moisture and watering is not needed. When it becomes harder to push the blade into the ground, the soil is drying out and irrigation may be needed especially if additional drought stress symptoms, listed below, are seen in the turf. Test the soil in several locations.

After irrigation, use the blade to determine water penetration. Push the blade into the soil until it reaches a layer of increased resistance. Pull the blade out and measure the depth of penetration, which will correspond to the depth of water penetration. Measure the soil in several areas.

Watering Recommendations
To conserve water and reduce water related issues, here are recommendations for property owners.

Trees and Shrubs:

  • Tree and shrub roots grow outward 2 to 3 times a tree's height with the majority in the upper 12 to 24 inches of soil.
  • Moisten soil to a depth of 10 to 12 inches minimum. Begin about one foot away from the trunk and deeply moisten soil as far beyond the plants drip line as feasible.
  • Use an automatic irrigation system, sprinkler or soaker hose.
  • Avoid setting a garden hose at the base of the trunk and letting it run, because a majority of water absorbing roots will not get any water.
  • When watering newly planted or young trees, be sure to also moisten the soil outside the planting hole to encourage root growth into surrounding soil.
  • Allow soil to begin to dry before watering again. The upper few inches should be dry.


  • The rooting depth of most cool season grasses is usually 2 to 6 inches deep. Kentucky bluegrass has shallower roots than tall fescue.
  • Moisten soil to a depth of 4 to 6 inches; then let soil begin to dry or turfgrass to show signs of needing irrigation before watering again. Signs include footprints or wheel tracks remaining in grass after being walked on or mowed, a darker cast to the turf and rolled grass blades.
  • Kentucky bluegrass lawns can be allowed to go dormant. Irrigate dormant turf ¼ inch every two weeks to prevent death of the dormant crowns. Keep foot traffic to a minimum on dormant turf.
  • Tall fescue is deep-rooted and requires very little irrigation in years with normal rainfall levels. However, it's drought survival is poor and should be watered enough to prevent "dormancy" during extended droughts. Tall fescue turf does not go dormant. If the grass is turning brown, it's dying.

Vegetables and Flowers:

  • Root depth varies with plant type.
  • Moisten soil to 6 to 8 inches deep; then wait for soil to begin to dry before irrigating.
  • Vegetables need a uniformly moist soil for quality produce.
  • Place organic mulch on bare soil to conserve soil moisture.

Irrigating Home Lawns, Nebraska Extension
Water Wise: Vegetable and Fruit Production, Nebraska Extension


2. July 4th growing degree day(GDD)

Location Accumulated Growing Degree Days
Grand Island, NE - Airport 1478
Lincoln, NE - Airport 1592
Omaha, NE - Airport 1580
Norfolk, NE - Airport 1448
North Platte, NE - Airport 1153
Scottsbluff, NE - Airport 1056


3. Pest updatePests to watch for based on Growing Degree Days (GDD)

GGD (base 50) InsectLifestage present at this GGD
850-900 Mimosa webworm 1st generation egg hatch
850-900 Fall webworm Egg hatch
930 Lilac borer 1st generation hyaline stage
950-2150 Japanese beetle Adult emergence
1000-2000 Emerald ash borer Peak adult emergence
1200-1800 Fall webworm Caterpillars feeding
1250 Codling moth 2nd generation control stage
1375 American plum borer 2nd generation
1500 Pine needle scale 2nd generation control stage
1700 Zimmerman pine moth Adult flight
1800-2200 Banded ash clearwing adult emergence
1850-2025 Fall webworm Tents become apparent
1925-1950 Magnolia scale Egg hatch

For a more complete list, visit Michigan State University GGD of Landscape Insects or GGD of Conifer Insects.


4. Magnolia scalePrepare for crawler control in August. GGD 1925-1950.

If clients have a saucer or star magnolia in your landscape, one insect to watch out for is magnolia scale. August through September is the time crawlers emerge and are susceptible to control. It's worth your time now to scout for potential problems.

Magnolia Scale, Nebraska Extension


5. Zimmerman pine mothPinkish pitch/sawdust masses at branch junction with trunk; ultimately results in branch death or breakage. GGD 1700, adult flight.

The first signs of infestation is the appearance of soft, pinkish pitch masses on the trunk or branches. These pitch masses, which form where larvae are feeding beneath the bark, may be found anywhere on the tree. After larvae finish feeding, pitch masses dry and become light yellow to cream colored, hard, and brittle. Mostly affects ponderosa and Austrian pines.

Signs of damage are broken or dead branches or tops of trees may be broken or dead. Larvae hatched last fall and spent the winter under loose bark scales or in old tree wounds and are now susceptible to control.

To control, spray bark with a drenching spray of permethrin or bifenthrin the second week of April and the second week of August, or at the growing degree days listed below. Remove heavily infested trees.

  • 1st larve - 25-100 GDD
  • Adult flight - 1700 GDD

Insect Pests of Evergreens, Nebraska Forest Service
Zimmerman Pine Moth, Backyard Farmer


6. Japanese beetle controlStrategies for homeowners. GGD 950-2150, adult emergence.

A new season of Japanese beetle control will begin this month. Growing degree day (GGD) models target adult emergence from 950 to 2150 GGD (base 50). Emergence timing varies across the state based on location and yearly weather variations, but an emergence estimate for several locations are below. Adult feeding damage will occur during this entire period and for several weeks afterward, as the last adults complete their lifecycle.  More details.


7. Poison ivy, Poison hemlock, Yellow nutsedgeWeeds of serious concern due to difficulty of control or human health impact

Poison ivy - The old saying tells us, "Leaves of three, let it be." This refers to the structure of a poison ivy leaf, which consists of three leaflets, however the leaves can be quite variable in appearance. Each leaflet is 2-4 inches long, and dull or glossy green in color with point tips. The middle leaflet is generally larger than the two side leaflets, and the leaflet edges are quite variable, being either lobed, toothed or completely smooth.

Plants can grow as an upright woody shrub, a trailing shrub that grows along the ground, or as a woody vine. Vines climb trees quite high and develop a mass of aerial roots along the stem, resulting in the appearance of a "fuzzy rope" growing up the tree. Poison ivy produces yellowish-green flowers in the leaf axils, which later develop into waxy, white, berry-like fruits. Birds love these berries and after eating them, spread the seeds hither and yon. In fall, leaves turn a beautiful orange-red. Control

Poison hemlock - Leaves have alternate arrangement on stems, although they may be oppositely arranged on the upper stems. The foliage is bright glossy green and finely divided (bipinnately compound) similar to carrot foliage. Leaves are smooth and hairless. On the lower leaves, petioles are long and their bases wrap around the main stem. Upper petioles are shorter and may not sheath the stem.

Three main identification characteristics – stems are hairless, hollow between nodes, highly branched, with reddish-purple streaks or splotches. Stem coloration is often very faint in young first year plants, so inspect non-blooming plants carefully.

Blooms are composed of many clusters of tiny 5-petalled white flowers, creating showy flat-topped flower heads. Control

Yellow nutsedge - Yellow nutsedge is a member of the sedge family although it closely resembles a grass. In fact it is frequently called nutgrass or watergrass. It is a common weed in lawns and landscapes, and can often be found in areas with moist soil. The leaf blades are light green and are "V" shaped with a prominent ridge down the center of the leaf blade. Leaf arrangement on the plants is called 3-ranked, meaning the leaves originate from the base of the plant giving the lower stem a distinctive triangle shape.

The leaf blades always seem to grow faster than surrounding grass, sticking up above the turf only a few days after mowing. The root system is shallow and fibrous and produces small nut-like tubers that serve as food storage organs. Each of these small tubers can sprout and form a new plant. Yellow nutsedge is a perennial, meaning each individual plant can live for many years if not controlled. Control


8. Cicada killer waspsHuge yellow and black wasp or small mounds of soil near pavement

Cicada killer wasps 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 near sidewalks, driveways, and retaining walls, creating small mounds of soil around a 1/2-inch entrance hole. Cicada killers are most abundant in midsummer when their prey - cicada, grasshoppers and crickets - are active. They paralyze their prey and drag it to a burrow, then lay an egg on it. After hatching, the larval wasp feeds on the paralyzed insect. Larvae develop in the soil until they emerge as adults next summer.

These wasps are solitary but will create clusters of nests in preferred areas. Solitary wasps are not aggressive and would only sting when handled or accidentally caught in clothing. Male cicada killer wasps will sometimes aggressively fly towards people to defend their territory, but males cannot sting. Females, which do possess a stinger, are docile in nature. Due to this and the fact they are beneficial predators, solitary wasps are best tolerated when possible. They are only active for a short time in mid- to late-summer. Since they prefer to dig in areas of dry soil, homeowners can discourage their nest building by running a sprinkler where they are trying to nest. This may have to be done a couple times a day to keep the soil moist until the wasp finds another location.

If control is necessary, an application of carbaryl dust (Sevin) or cyflutrhin (Tempo) made directly into the burrow entrances is effective. Make applications at dusk when 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.

Remain Calm, It's Just a Cicada Killer Wasp!, UNL GRO Big Red Blog


9. Turf dormancyKentucky bluegrass vs. tall fescue

A tall fescue lawn should NOT be allowed to go dormant as it is not likely to recover.

Kentucky bluegrass (KBG) can be allowed to go dormant for a short period to conserve water. Why the difference? KBG physiologically has the ability to go dormant (turn brown but still be alive) to escape drought conditions during hot, dry summers. On the other hand, tall fescue tolerates drought due to a much deeper root system but cannot physiologically go dormant to avoid drought. If tall fescue turns brown, it is likely dead. Due to a deeper root system that uses soil moisture deeper in the profile, tall fescue does require less frequent irrigation than shallow-rooted Kentucky bluegrass.

If a homeowner chooses to let KBG to go dormant, remind them that during very hot, dry conditions, the lawn may need about ¼" of water a week to moisten crowns; and KBG can remain dormant for about 4 to 5 weeks only. If fall conditions remain hot and dry, irrigation should resume.

If lawns have thinned excessively, late August into early September is the ideal time to seed the cool season turfgrasses tall fescue and Kentucky bluegrass. For success, make plans to finish seedbed preparation before August 15th. Early seeding allows more growing time for new seedlings.


10. Tree leaf-feeding insectsControl usually not needed unless very heavy infestations occur


11. Mid-summer vegetable garden problemsMany maladies appearing now; symptoms and links to additional information available

Unfortunately vegetable gardens can be affected by many disease problems. Below are symptoms and links to additional information for the most common problems.

  • Bacterial wilt of cucurbits - Plants wilt and over night my recover. But eventually plants wilt completely and die. 
  • Squash bug - Sudden yellowing and death of plants. 
  • Squash vine borer - Sudden wilting/death of vines and/or plants.
  • Tomato blossom end rot - Leathery to soft brown/black rot on the blossom end of tomatoes.
  • Tomato spotted wilt virus - Upper young leaves bronze and develop small dark spots or flecks; fruit lesions develop unique concentric rings. Transmission by thrips.
  • Tomato mosaic virus - Green mottling of leaves; yellowing and stunting of plants; fruit lesions with yellow halos.
  • Tomato early blight - Starts with small brown spots on lower leaves. Lesions develop a "bulls-eye" pattern of concentric rings. Infected leave yellow and die. Infection progress up the plant.
  • Tomato bacterial spot/speck - Begins as very small black spots on leaves and fruits. Severe infection causes leaf loss and unmarketable fruits.
  • Tomato wilts - Several wilt disease affect tomatoes including Fusarium, Verticillium and walnut wilt. Symptoms of each can be very similar, starting with leaves turn yellow, often on one side of stem or branch. Symptoms get progressively worse and whole plant wilts. Eventually plant dies.


12. Geranium bugwormFlower loss on many common flowering annuals including geranium, petunia and nicotiana

Tobacco (geranium) budworm, Chloridea virescens, is a serious pest of tobacco and cotton in the south, and also attacks the flowers of Solanaceous plants in Nebraska gardens such as petunia and nicotiana. It also feeds on geranium, rose and many other flowering plants. Moth larvae are quite variable in color - nearly black, pale brown, green, reddish - partly based on the flowers they eat. Caterpillars reach 1.5 inches in length at maturity. 

Tobacco (Geranium) Budworm, Colorado State University Extension


13. ChiggersImmature harvest mites; active now; cause itchy bumps

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. Former 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.

Chiggers, Nebraska Extension
Itchy Chiggers, Nebraska Extension


14. TicksIdentification and protection strategies

High tick season in Nebraska is generally April through June, but ticks can be active all year round when temperatures are above freezing. With the arrival of spring and an increased involvement in outdoor activities, Nebraskans must be prepared to practice tick safety to prevent tick-borne illnesses.

Tick Time - Check Yourself!, Nebraska Extension GRO Big Red
Ticks, Nebraska Extension
Tick Tag Go, University of Nebraska - Lincoln Dept. of Entomology


15. MosquitoesEliminate stagnant water in pools, tires; control adult mosquitoes

Mosquito numbers are on the rise. Mosquito control involves:

  1. Applying larvicides, such as Bactimos or Vectobac which contain BTI (Bacillus thuringiensis israliensis) to stagnant water pools.
  2. Spraying grassy areas and shrubbery with insecticides such as permethrin or malathion (check label for use on the landscape plants to be sprayed.
  3. Preventing water from standing in containers such as flower pot basins, children's wading pools, bird baths, clogged roof gutters.
  4. And using personal repellents containing DEET (diethyl toluamide).

Mosquitoes, Nebraska Extension
Residential Mosquito Control, Nebraska Extension
Flies, Gnats & Mosquitoes, Nebraska Extension


16. Slime moldYellow, white, gray growths appearingin turfgrass and mulch beds

Slime molds can appear suddenly on any turf species or in mulch beds during warm, wet weather (especially in shaded or overcast conditions). The fruiting bodies of these organisms grow on turfgrass stems and leaf blades. They are gray to black but may be white, yellow, or pink to purple. They do not infect the turfgrass to cause a disease. They only use grass plants for support to grow on. Dense slime molds may cause some yellowing of turfgrass as the fruiting structures can last a few weeks if not removed from turf with mowing, brushing, raking, or by running water over affected areas.

Slime Mold in Turf, NC State Extension
Slime Mold, Colorado State Unviersity Extension


18. Commercial/Non-commercial pesticide applicatorsObtaining a new license or updating an expired license

If you have a pesticide applicators license which expired in April 2023 or you need to get a new license, testing options are listed below. 

Testing-only Options

  • Closed-book exams are given by the Nebraska Department of Agriculture (NDA). Preregistration is not required an there is no cost. Visit the link below for a list of available test-only dates, times and locations -
  • NDA computer-based testing is provided through the Pearson-Vue company. Click here for a list of testing sites, categories available, dates, and registration information. Cost $55 per exam. (For applicators with multiple categories on their license, each category is charged the full testing fee.)

Commercial/noncommercial applicators are professionals who apply restricted-use pesticides for hire or compensation. Anyone who applies pesticides to the property of another person, either restricted- or general-use products, for control of pests in lawns, landscapes, buildings or homes must also have a commercial pesticide applicators license. Public employees (those employed by a town, county, state) applying mosquito control pesticides whether restricted- or general-use, must also hold a commercial or noncommercial certification.


19. Digital Diagnostic Network - Need help with diagnostics?Submit pictures and questions for diagnosis by Nebraska Extension experts

Do you or your clients have questions you need help answering? Maybe you are a lawn care person and they're asking about trees, shrubs, or flowers? While you can refer them to their local Extension office, another option is Digital Diagnostic Network. Homeowners, lawn care professionals, pest control operators and others are invited to submit questions and photos through this website or with the assistance from an Extension professional at any Nebraska Extension office. All offices are equipped with high-resolution digital image capturing technology. Whether the question is about a lawn weed, insects on a plant, diseases in a shrub border or other, an expert panel of Extension professionals will review and respond to the question. To get started, create an account so the question can be reviewed and responded to via email. For more information and to create an account, go to Digital Diagnostic Network.

Bugging Out With Your Camera Phone - Tips on how to get a good picture.


Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Nebraska Extension is implied. Use of commercial and trade names does not imply approval or constitute endorsement by Nebraska Extension. Nor does it imply discrimination against other similar products.