Hort Notes 2024 Vol. 35:6

A monthly e-newsletter from UMass Extension for landscapers, arborists, and other Green Industry professionals, including monthly tips for home gardeners.

Click on the headings below to jump to that section of the newsletter.

 

Registration for our 2024 Green School has Begun!

UMass Extension’s Green School is a comprehensive 60+ hour certificate short course that offers fundamental horticultural training in a compact time frame.

Who Should Attend? Professional practitioners such as landscapers, lawn care providers, nursery operators, sports field managers, public and private grounds managers, DPW, professional gardeners, landscape and garden designers, and others in the green industries. Both experienced individuals, as well as those aspiring to be, will benefit from this course.

Where? Entirely virtual in 2024, taught by UMass Extension Specialists, UMass faculty, and distinguished guest instructors. 

When? Tuesday, Wednesday and Thursday afternoons 1:00 to 4:30 pm from 10/29/2024 thru 12/19/2024.  

How? The curriculum emphasizes a systems-based approach to plant and land care based on current research and is built on a framework of Best Management Practices (BMPs) and Integrated Pest Management (IPM). 

Choose from two specialty tracks: 

• Landscape Management
• Turf Management 

For complete information, detailed schedules and registration options, go to https://ag.umass.edu/greenschool

Why Choose Green School? 

• A robust alternative or a stepping stone to a more involved degree program.
• Convenient yet rigorous remote learning from the comfort of your home or office.
• In-depth, research-based training for skills that are in high demand, and are applicable to active and engaging outdoor work.
• Two educational track options to fit your personal goals.
• Structured interaction with University educators and researchers.
• Competitive fees and tuition assistance options.
• An established program with a 30+ year history and a certificate that carries weight in the industry.

Move your career or business forward, and achieve better results with a smaller overall impact!

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Are Microbial Probiotics Worth Adding to Your Soil?

• Other than rhizobia for legumes, soil inoculants aren't yet reliable soil amendments.
• Use reduced tillage, compost, and ground covers to encourage the growth of existing beneficial bacteria and fungi.

Bacteria and fungi play a large role in the health and productivity of soil. The plants we grow need these microbes for soil fertility, protection from disease and other stresses, and good soil structure. Unfortunately, we all know about microbes that compete with plants for soil nutrients and cause plant disease. This means that having the "right" microbes is important for plant and soil health.

But how do you know if you have the right ones? And enough of them? While a lot of pathogens cause recognizable symptoms, sometimes plants just don't look "great." In these cases, it's hard to know if a soil microbiological imbalance could be part of the reason. However, this topic is different than soil fertility, where there are reliable and accessible soil tests which easily identify issues and solutions. Unfortunately, we don't have reliable tests for soil microbiology yet. In the meantime, growers should follow best practices to encourage healthy bacterial and fungal ecosystems in the soil. These are tried and true growing methods, but sometimes it seems like maybe that's not enough and many microbial probiotics or soil inoculants are available to supplement the organisms already in your soil.

So does it make sense to add beneficial bacteria and fungi to your plantings? The short answer is "no." The slightly longer answer is "the effects of soil probiotics usually aren't reliable enough to bother with." Of course, that's still a pretty short answer! So let's dig into it a little more.

What beneficial microbes do: Bacteria and fungi are the core of the soil ecosystem. Without them, the soil would not be fertile or have structural integrity. They can make phosphorus and nitrogen available, alleviate drought and salt stress, reduce pest and disease pressure, generally promote plant growth, and reduce greenhouse gas emissions. Despite this diversity of function, soil probiotics fall into only three main types: mycorrhizal fungi, "plant growth promoters," and rhizobia.

Mycorrhizae: Their name means "fungus root" for a reason. These symbiotic fungi intertwine with plant roots and vastly expand the effective size of the root system. Mycorrhizae are particularly good at collecting phosphorus from minerals and trade it and water to the plants in exchange for photosynthetic carbon.

Plant Growth Promoters: This is a catch-all group which includes some members of many groups like Trichoderma, Pseudomonas, and Bacillus. Individual types of bacteria can do many different things in laboratory and greenhouse research trials and have improved plant performance by stimulating the plants' immune systems, making phosphorus available for plants, and reducing environmental stress in some controlled conditions.

Rhizobia: Leguminous plants (like clover, beans, indigo, and wisteria) create root nodules for rhizobia bacteria. In these nodules, the rhizobia take nitrogen out of the air and give it to the plants in exchange for carbon resources. This means that healthy legumes generally need no added nitrogen fertilizer. Most legumes require specific strains of rhizobia to perform at their best.

All of these organisms are great for plants in the right circumstances! All of them have the potential to make useful additions to garden and landscape toolkits someday. Unfortunately, while these microbes are starting to show real promise in lab and greenhouse studies, most of them aren't yet performing reliably in real-world settings. Rhizobia are the exception that proves the rule. Landscape-scale use of rhizobia has proven to be highly effective as a seed inoculant when the right strains aren't already in a particular soil. While it's not needed for common weedy legumes like red and white clover, adding a rhizobia strain that works with your legume plants is definitely an important seed treatment.

But other than rhizobia, you're better off simply following soil health principles and ignoring the microbial content of potting mixes and soil amendments. More reliable microbial strains and application methods to add mycorrhizae and "plant growth promoter" bacteria to plantings may arrive in coming years. But until then, reducing tillage, adding organic matter like compost and mulch, and using groundcovers to protect the soil are still the best ways to encourage the growth of beneficial bacteria and fungi already in the soil.

Arthur Siller, UMass Extension Soil Health Educator

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Trouble Maker of the Month

Surfactants with Landscape and Turf Herbicides

Herbicide performance is the primary goal with any herbicide application. When developing a weed management program for landscape or turf, we should first focus on correctly identifying the target weed and its growth stage. The next step is to determine the herbicide and formulation that will result in the best control. Lastly, focus should be shifted to abiotic factors such as soil moisture and air temperature that might impact overall herbicide performance.

With these initial tasks completed, it is then time to explore whether the addition of a spray surfactant is required to achieve the best herbicide efficacy. Spray application is often considered the weakest link in the herbicide effectiveness from its initial synthesis, testing, product registration, and final use. In other words, you can have a great herbicide, but if you cannot get it into the plant it is of little or no value. Surfactants can strengthen or eliminate this weak link in performance.

A surfactant is a material that is added to a spray solution to modify its physical characteristics and/or to aid the action of an herbicide. The word surfactant is derived from the term “surface-active agent."  Surfactants increase herbicide performance by solubilizing spray materials, reducing surface tension, increasing spreading, improving spray retention, and increasing leaf penetration. While all of these functions are important, the reduction of surface tension rises to the top of the list.

The unit traditionally used to measure surface tension is dyne per centimeter (dynes/cm). The surface tension of distilled water at 25°C (77°F) is 72 dynes/cm. With a surface tension of 72 dynes/cm, a reduction of herbicide activity can be observed as the spray droplets sit on leaf hairs or the leaf surface with minimal leaf surface contact. Surfactants typically reduce surface tension to 20-40 dynes/cm and provide broader leaf contact by increasing leaf contact by spray droplet spread over the leaf surfaces and penetration of hairy leaf surfaces. This increase in spray coverage directly improves herbicide activity and performance. Surfactants used with postemergence herbicide applications increase the amount of herbicide entering the plant and reaching the targeted site of action in the weed.

There are many types of agricultural surfactants used when preparing a spray solution for an herbicide application. The most common types of surfactants used with landscape and turf herbicides are non-ionic (NIS), crop oil concentrate (COC), and methylated or modified seed oil (MSO). The herbicide product label will state if the addition of a surfactant is required. The simple rule is that if the product label calls for a specific surfactant, then that type of surfactant should be used.  If the product label does not call for a surfactant, then one is not needed and should not be added. Different herbicide products require different surfactants. Your pesticide distributor will be able to assist you in the selection of the correct surfactant. An overview of the surfactant type needed with some key landscape and turf herbicides is shown below in Table 1.

Table 1. Surfactant type needed with some landscape and turf herbicides (The information in this table is not meant to replace label instructions.)
Herbicide (active ingredient)	Trade name (example)	Surfactant type	Comment(s)
clethodim	Segment IITM	methylated/modified seed oil (MSO) or crop oil concentrate (COC)	Non-ionic surfactants (NIS) or blends are not recommended as weed control may be unsatisfactory.
fenoxaprop-methyl	Acclaim ExtraTM	specific type not stated	Specific type not stated but label states the addition of a surfactant will improve coverage.
glyphosate	RodeoTM	non-ionic surfactants (NIS)	Nonionic surfactant (NIS) containing 80% or more active ingredient; using this product without surfactant will result in reduced performance.
glyphosate	Round Up ProTM	not required	Surfactant added by manufacturer; consult label of generic glyphosate formulation for surfactant requirements.
halosulfuron	SedgehammerTM and Pro SedgeTM (surfactant type and comments same for both products)	nonionic surfactants (NIS) that contain at least 80 percent active material	Use 0.25-0.5 percent v/v of a nonionic (NIS) surfactant (NIS) at (1-2 quarts per 100 gallons of spray solution) for broadcast applications. For high volume applications, do not exceed 1 quart of surfactant per acre.
mesotrione	TenacityTM	non-ionic surfactants (NIS)	Required for postemergence applications; not required for preemergence applications of this product.
quinclorac	Drive XLR8TM	methylated or modified seed oil (MSO)	Methylated or modified seed oil (MSO) is preferred for postemergence applications; however, if an MSO is not available the use of a crop oil concentrate (COC) or another high-quality surfactant must be used. Required for postemergence applications; not required for preemergence applications of this product.
topramezone	PylexTM	methylated/modified seed oil (MSO) or crop oil concentrate (COC)	Methylated/modified seed oil (MSO) or crop oil concentrate (COC) at 0 5 to 1% volume/volume (v/v) (2 to 4 qt./100 gallons of spray) or 30 ml per 1000 sq. ft. Nonionic surfactants (NIS) or blends are not recommended as they may provide unsatisfactory weed control.

In summary, surfactants are materials that are added to a spray solution to modify its physical characteristics and/or aid the action of an herbicide. Surfactants will increase herbicide performance and provide economic benefits. Remember this simple rule about surfactants; “if the product label calls for a specific surfactant, then that type of surfactant should be used; if the product label does not call for a surfactant, then one is not needed and should not be added."

Randy Prostak, UMass Extension Weed Specialist

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Q&A

Q: I have a glut of zucchini and eggplant. Are there creative ways to store these vegetables for winter use?

A: One of our favorite ways to preserve these “meaty” vegetables is to slice them lengthwise into 1/4” thick slices, brush with olive oil and season, then roast them in the oven at 425^ºF for 5-10 minutes per side, cool, and freeze. These are great stand-ins for lasagna noodles and are easy to layer in a variety of casseroles. Another way to use up quantities of zucchini is by making a green pasta sauce. Chop 2 to 3 lbs of zucchini roughly and mix with sauteed onion and garlic in a slow cooker with 1 to 2 cups of chicken or vegetable broth. Allow the mixture to cook 4 to 5 hours on low. Cool and portion out into containers for freezing. 

Q: Can you recommend seeds I can sow now to maximize my vegetable garden’s productivity through the fall months?

A: Many of the fast-growing, cool-season crops sown early in the season can be sown again in August. Leafy greens such as spinach, arugula, Swiss chard, kale, and mustard greens are good candidates for direct seeding, as is lettuce, although if it is sunny and hot (daytime temperatures consistently in the 80s and 90s), you will want to provide a shade cloth for sun protection over tender seedlings, along with straw mulch around them and plenty of water. Root crops to sow direct this month include beets, radish, turnip, and carrots (especially shorter-rooted cultivars, e.g. ‘Little Finger’, ‘Short N Sweet’).

Herbs to sow for fall harvest include basil (early August); cilantro (later in the month, sown in small batches every 3 weeks or so for continuous production); and dill (later August).

Pea harvest may be modest from a late summer sowing since peas perform best in the cooler temperatures of late spring and early summer, but the flavor of fresh peas is worth tossing some leftover podded, snow, or sugar snap seeds in the ground if space allows. 

Q: As spaces open in the garden after harvest, I would like to suppress weeds and improve the soil. Which cover crops are best for sowing this time of year?

A: The following cover crops will tick the boxes for late summer weed management and soil organic matter accumulation. Seed of most of these species is available in smaller quantities from online vegetable seed suppliers, if not from your local garden center or farm supply store.

• Buckwheat — sow 2 to 3 lbs per 1,000 square feet; grows rapidly which makes it an excellent weed suppressor; flowers attract pollinators; easy to kill by mowing down before seeds mature (otherwise may re-seed itself) or killed by frost.
• Sudangrass — sow 1 to 2 lbs per 1,000 square feet; grows rapidly which makes it an excellent weed suppressor; extensive roots break up compacted soils; killed by frost.
• Oats — sow 2-3 lbs per 1,000 square feet; grows rapidly and suppresses weeds via competition; an easier grass to work into the soil than annual ryegrass prior to spring planting since oats are winter killed.
• Berseem clover — sow 1 lb per 1,000 square feet; grows rapidly; excellent nitrogen fixer and biomass producer; can be used in mixes with grasses such as oats; killed by frost.
• Mustard — sow ¼ to ½ lb per 1,000 square feet; grows rapidly and suppresses weeds through competition and inhibiting weed seed germination; may act as a biofumigant against soil borne diseases; mow down before seeds mature (otherwise may re-seed itself).

An excellent resource for home gardeners and professionals alike is the cover crop species selector tool from the Northeast Cover Crops Council. Users input their location and cover cropping goals, which the tool then uses to identify site conditions and generate a list of appropriate cover crops along with recommended planting dates. Choices can be narrowed down by selecting filters adjacent to the list, including ease of establishment, drought/heat tolerance, methods for killing, etc. Clicking the name of an individual species on the list takes users to a fact sheet about that plant and its pros and cons.  

Jennifer Kujawski, Horticulturist

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Garden Clippings Tips of the Month

August is the month to . . . .

In the Vegetable Garden

• Don’t let summer squash, zucchini and cucumbers get too large. Allowing fruit to get large repeatedly will reduce total yield.
• Sow cool season crops like beets, carrots, greens and lettuce for a fall crop.
• Harvest onions when the tops start to fall over. Harvest after several days of dry weather and don’t wash. Air dry onions for several days to several weeks. Remove tops only when necks are paper dry.
• August showers often create perfect conditions for tomatoes to crack. Harvest tomatoes susceptible to cracking such as heirlooms at about 50% color and shelf ripen for better quality and to reduce post-harvest rot.

Lawns - Prepare for lawn renovation. Late summer and early fall is a crucial time to support the lawn for a healthier, denser lawn next year.

• Test your soil. Fall is an excellent time to amendments to adjust soil pH. A soil test by the UMass Soil and Plant Nutrient Testing Lab will provide nutrient and pH recommendations. Fertilize and lime according to your soil test results.
• Aerate. Heavily trafficked lawns should be aerated every one or two years. Aerating equipment works best when the soil is slightly moist, not dry or wet.
• Select grass seed based on needs and conditions. Species selection has a big impact on overall quality.
• Overseed with a high quality seed.

Containers

• Tired of watering containers or looking at wilty plants? Install drip irrigation using a timer, filter, backflow preventer, and drip tubing so you can set it and forget it.
• Repot houseplants that have been outside for the summer and destined to go back inside. Repot when there are still several weeks of good growing conditions available so the plants root into the new soil before returning inside.
• Renovate mixed containers by giving overgrown plants a haircut, pulling out plants that aren’t doing well, and filling in with something for fall color. Heuchera and summer bunch grasses make for stunning fall containers. 

In the Landscape

• A year of seeds is ten of weeds. Lots of annual and perennials weeds set seed in late summer, so be vigilant and don’t let weeds go to seed.
• Investigate trees and shrubs which show signs of early fall foliage coloration. Early fall foliage coloration is often related to chronic stresses and injuries.
• Concerned about jumping worms? Jumping worms have an annual lifecycle and are hard to identify before reaching adulthood in mid to late summer, making now is the best time to identify them. See UMass Extension's Checklist of Characteristics for Jumping/"Crazy" Earthworm Identification.
• Spring planted shrubs and trees still require watering attention. Make sure they receive a deep watering at least once a week if there isn't sufficient rain.

Russell Norton, Horticulturist, Cape Cod Cooperative Extension

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Increasing Chinch Bug Populations in New England and Approaches to Their Management

Chinchbugs (Blissus spp.) are one of the most destructive insect pests of turfgrass. There are several species of chinch bugs, which look very similar and differ mainly in their geographical distribution and respective hosts. For example, southern chinch bugs (Blissus insularis) are problem in the southern United States and their preferred host is warm-season St. Augustine grass. Common chinch bug (Blissus leucopterus leucopterus) occurs mainly in western and mid-western states, the Northeast, and some southern states, but mostly prefers grain crops such as sorghum, corn, and wheat, and occasionally infests turfgrasses such as Bermudagrass, fescues, Kentucky bluegrass, perennial ryegrass, zoysiagrass, and crabgrass. In New England, hairy chinch bugs (Blissus leucopterus hirtus) are the most common chinch bug species affecting different species of cool season turfgrasses. 

Adults of this species are small (only 1.6” long, Fig. 1), and have distinct contrasting black-and-white coloration with an “X” -pattern and black marking on the wings. Nymphs are very small when eggs first hatch and are bright orange and initially have a white band across their bodies (Fig. 2). They look like smaller, orange, and wingless versions of the adults. Older nymphs become darker, and black wing pads can be distinguished on their backs; the lighter band remains noticeable across their body.

In New England, two generations occur per year. Adults overwinter and become active in the spring, depending on the temperatures. This year, adults were noticed in the beginning of May and by the end of May, eggs and nymphs were observed. In mid-July, most of the specimens collected were adults and nymphs appeared by the end of July. These second-generation nymphs will develop into adults and these adults are not likely to produce any progeny before seeking shelter for overwintering. 

 

 

 

 

 

 

Despite being relatively small, hairy chinch bugs can cause significant damage (Fig. 3). Populations are often overlooked and their feeding damage is often confused with turfgrass dormancy or drought stress, until it is too late. If densities are high and damage is severe, even with additional irrigation, turfgrass fails to recover. Chinch bug feeding is easy to confuse with drought symptoms because, unlike other turfgrass pests (white grubs, billbugs, caterpillars), they do not chew the grass blades. Their piercing-sucking mouthparts are modified to pierce the grass tissues and suck up the juices. Thus, grass will look dry, with no chewing signs present. Dry and hot conditions benefit this species and exacerbate the damage, therefore dry, well drained and sunny areas of the lawn are most commonly affected by this pest.

Previously, damaging high-density populations of chinch bugs were not common. The main recommendation was to irrigate affected areas to provide enough resources for turf to tolerate and recover from the chinch bug feeding. This approach remains effective if chinch bug density is low. Chinch bugs have a complex of natural enemies, such as the big-eyed bug (Geocoris spp., Fig. 4), an egg parasitoid small wasp (Eumicrosoma beneficum), and the naturally occurring fungus Beauveria bassiana which can help to keep populations at bay. When conditions are conducive to growth and development, however, these are often not capable of keeping chinch bug densities below damaging levels and intervention is necessary to avoid damage. Unfortunately, the frequency of high-density populations occuring is on the rise and now chemical intervention is often necessary to avoid significant turf loss. 

A changing weather pattern with rising temperatures and erratic rainfall is one of the factors that can explain the recent increase of chinch bug densities. Some changes to management of turf pests, such as introducing new insecticide chemistries and restricting/banning use of older insecticides, can also be a factor in increased reports of high densities of chinch bugs. For instance, the new class of insecticides used for grub management, anthranilic diamides (chlorantraniliprole), that came to replace the neonicotinoids (imidacloprid, clothianidin) can only provide suppression of chinch bug populations (according to the label).

Chinch bugs are traditionally targeted by pyrethroids (bifenthrin), insecticides that stay in the thatch, act on contact, and are relatively fast-acting. However, this insecticide class, if overused, tends to lead to resistance. Chinch bugs in New England were managed by pyrethroids for many decades, and even though we have not yet documented any resistant populations in our region, the risk is high, especially if the frequency of high-density populations increases. Another active ingredient used for chinch bug management is clothianidin, a neonicotinoid. Because of its harmful non-target effects, neonicotinoids have become a restricted-use insecticide class in Massachusetts with an uncertain future in the turf industry. Considering the increasing risks of chinch bug damage, risk of resistance development, and lack of tools to manage them, the need for alternative management solutions is a high priority. 

Our lab conducted research on the efficacy of different management strategies against chinch bugs this season. In the laboratory studies, we discovered that commercially available formulations of the entomopathogenic fungus Beauveria bassiana can cause 98-100% of chinch bug mortality within 72 hours. However, in the field study, only the pyrethroid bifenthrin, the neonicotinoid clothianidin, and the combination products containing both bifenthrin and clothianidin provided a 95-98% reduction of the chinch bug population. Unfortunately, Beauveria bassiana was not effective in the short term (at evaluations conducted 1 and 2 weeks after application); nor was it effective one month after application under field conditions. According to our preliminary data, the efficacy of bifenthrin declines over time and we observed similar chinch bug densities as in the untreated plots, although the population remained below the damage threshold. 

The applications in the study were done in late May, as soon as adult activity was detected. This timing is generally recommended as the optimal timing for chinch bug management because the populations are weaker after overwintering and densities are lower than during the summer because of winter mortality. According to the results of our study, applications of bifenthrin, clothianidin and in combination, using this timing, can reduce chinch bug population densities below the damaging levels without the need for additional applications later in the season. Next season, we plan to conduct additional studies to determine the optimal conditions for Beauveria bassiana efficacy and the efficacy of other new chemistries against chinch bugs that could help to replace the use of pyrethroids and neonicotinoids against this emerging pest.

Olga Kostromytska, Stockbridge School of Agriculture, University of Massachusetts Amherst

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Upcoming Events

For more details and registration options for upcoming events, go to the UMass Extension Landscape, Nursery, and Urban Forestry Program Upcoming Events Page.

• 9/1/2024 - Enrollment scheduled to open for the UMass Winter School for Turf Managers
• 09/15/24 - End of early-bird rate for Green School registrations. For complete details and registration options, go to http://ag.umass.edu/greenschool.
• 10/18/24 - Deadline to register for UMass Extension's 2024 Green School.
• 10/29/24 - Green School begins!

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Additional Resources

For detailed reports on growing conditions and pest activity – Check out the Landscape Message

For professional turf managers - Check out our Turf Management Updates

For commercial growers of greenhouse crops and flowers - Check out the New England Greenhouse Update website

For home gardeners and garden retailers - Check out our home lawn and garden resources

TickTalk webinars - To view recordings of past webinars in this series, go to: https://ag.umass.edu/landscape/education-events/ticktalk-with-tickreport-webinars

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Diagnostic Services

Landscape and Turf Problem Diagnostics - The UMass Plant Diagnostic Lab is accepting plant disease, insect pest and invasive plant/weed samples. By mail is preferred, but clients who would like to hand-deliver samples may do so by leaving them in the bin marked "Diagnostic Lab Samples" near the back door of French Hall. The lab serves commercial landscape contractors, turf managers, arborists, nurseries and other green industry professionals. It provides woody plant and turf disease analysis, woody plant and turf insect identification, turfgrass identification, weed identification, and offers a report of pest management strategies that are research based, economically sound and environmentally appropriate for the situation. Accurate diagnosis for a turf or landscape problem can often eliminate or reduce the need for pesticide use. See our website for instructions on sample submission and for a sample submission form at http://ag.umass.edu/diagnostics. 

Soil and Plant Nutrient Testing - The lab is accepting orders for Routine Soil Analysis (including optional Organic Matter, Soluble Salts, and Nitrate testing), Particle Size Analysis, Pre-Sidedress Nitrate (PSNT), Total Sorbed Metals, and Soilless Media (no other types of soil analyses available at this time). Testing services are available to all. The lab provides test results and recommendations that lead to the wise and economical use of soils and soil amendments. For updates and order forms, visit the UMass Soil and Plant Nutrient Testing Laboratory web site. 

Tick Testing - The UMass Center for Agriculture, Food, and the Environment provides a list of potential tick identification and testing options at: https://ag.umass.edu/resources/tick-testing-resources.