Chipped, shredded, or fiberized, wood was once thought to be a possible alternative to peat moss, and is now a reality. Commercially available wood-based substrates are becoming more commonly trialed among greenhouse growers or implemented in greenhouse production (Fig. 1). While there are a handful of commercialized wood-based substrates available to greenhouse growers, smaller localized substrate producers and growers have begun formulating their own mixes with wood materials. Whether you purchase a pre-formulated wood-based substrate or incorporate wood materials as components or extend your peat supply with a pre-formulated wood-based substrate, success and challenges with the substrate will vary.

Consistency

Considering making the switch or trialing a wood-based substrate? Before making the plunge, it’s important to keep in mind that not all wood-based substrates or components are produced the same. Research and development of wood components as a replacement or alternative to "traditional" greenhouse substrates and components has been the forefront of Dr. Brian Jackson and Dr. William Fonteno’s research at North Carolina State University, which you can read at bit.ly/2hKRLKp

Much of their research is to understand wood as a substrate component, how to consistently and repeatedly produce wood materials for substrates, and use of wood materials in greenhouse plant production. From the many research experiments and trials, there seems to be an overall theme for wood-based substrates — consistency. Consistency of wood materials or components, type of wood, availability, and the production method in which the wood material will be used are all important points to consider. These considerations should be addressed before making the switch to pre- or self-formulated wood-based substrates.

Wood materials

Wood materials that are used to formulate a wood-based substrate vary in physical and chemical properties. For instance, wood materials to be used as substrates or components can be produced from various hardwood and softwood trees and may be chipped (Fig. 2A), shredded (Fig. 2B), or fibrous/ground (Fig. 2C). Physical properties such as the particle size and shape of the wood materials will directly influence the substrate and how it performs during production. For instance, chipped wood such as those I reported on at bit.ly/2i3LSb9, is blockular and can be used as an alternative to perlite in greenhouse substrates, while a fibrous wood material mimics many properties of fluffed or expanded peat moss. This fibrous wood material is one of the most popular materials being commercially produced as a peat moss alternative or replacement. To produce the various physical properties of either chips or fluffy fibers is no easy task, but a science that Drs. Jackson and Fonteno are becoming closer to understanding during processing of raw wood. In addition, chemical properties such as pH, electrical conductivity (EC), phytotoxicity, and the efficacy of applied plant growth regulator drenches of wood materials are of interest and have been previous explored for pine wood chips that I reported on. Additionally, these properties may vary among tree species, time of the year trees were harvested, and age of the wood materials (fresh vs. aged).

Commercially available wood-based substrates

There are a few commercial substrate producers developing and marketing wood-based substrates. Overall, these substrates vary from shredded and pulverized wood to fibrous peat-like doppelgänger materials. Interestingly these products are handled similarly to peat and coir, meaning they are also compressed for ease of shipping and storage, but require fluffing prior to use. While there may not be an answer of which producers’ wood-based substrate is better than another, it is recommended that growers perform in-house trials of various wood materials and mixes to determine which works best for your greenhouse operation, equipment and production method. 

While visiting greenhouse growers around the U.S. and in Europe, I have seen some of the challenges of wood-based substrates. The most common challenge is the substrate mixing equipment and flat or container fillers. The most common problem is that free-flowing wood fiber high in moisture content can build-up on the side of mixing equipment, and thus, causing clogs and producing clusters of un-fluffed balls of fibrous wood. However, I have also seen this similar challenge with peat moss and coir that was either shredded or chipped/chunked respectively. Regardless, each substrate material has its own production challenges but one thing is certain, wood-based substrates will change how the industry thinks about growing media.

Garrett is a Floriculture and Greenhouse Outreach Specialist at Michigan State University. wgowen@msu.edu

For the past three years, Dr. Tim Rhodus, a professor at Ohio State University’s Department of Horticulture and Crop Sciences, has assisted his colleague, Dr. Claudio Pasian, in running Ohio State’s annuals trial. To help attendees better interact with the trial, Rhodus developed an app that allowed visitors to walk through the gardens and evaluate the trial from a smartphone or tablet.

“They could go through the gardens and just tap, tap, tap and record the scores, transfer it to a website we were keeping,” Rhodus says. “[Claudio] had a pencil-and-paper approach that took more effort and was more expensive.”

For this year’s trial, Rhodus wanted to take digital interaction with the trial to a new level. During OSU’s spring semester, he was teaching his students about virtual reality (VR) using Google Street View. In his class, students had to create 10 VR tours consisting of photos of Ohio State’s campus and campus locations they consider important. Then, the students had to make an introductory video for their virtual tour and package the entire project on YouVisit.com, a cloud-based virtual reality hosting website.

It was this project that spurred Rhodus to develop a VR trials tour. Work started in the middle of May and was completed by summer when OSU’s trial was opened to the public.

“Even though you could have a wonderful close-up shot of the nicely new colored foliage or the ruffled edge of the flower, it doesn’t put you there,” Rhodus says. “I think particularly in full screen, this approach of VR really lets you feel what the place is like on that day.”

A career in innovation

As an undergrad at Bowling Green State University in Bowling Green, Ohio, Rhodus received a business degree. From there, he worked in a commercial greenhouse for four years before receiving his master’s degree and Ph.D. from Ohio State’s Agricultural Economics Department.

After receiving tenure in 1994, Rhodus switched his entire focus to websites and utilizing the internet.

“I decided I wanted to go in a new direction and that was the time that the worldwide web was being developed, as were virtual browsers and then setting up a server,” he says.

He and a team built PlantFacts.osu.edu, which Rhodus says is the first internet search engine strictly for horticulture in the U.S. Extension communication websites were indexed, as was an early image database. Both projects were funded by the United States Department of Agriculture’s (USDA) higher education challenge grants — a program that “involves a creative or non-traditional approach toward addressing that need,” according to the USDA.

In his classes, Rhodus aimed to show his students that there was more than just word processing and PowerPoint on computers, particularly in horticulture. When he was interested in a new development, he’d find a way to work it into the class.

VR also happens to be a longtime fascination for Rhodus. In 1996, using QuickTime VR 1.0 software from Apple, he made a VR with 50 cultivars in it. It was not until recent technology improvement that VR could be used beyond the original endeavor.

How it was made and how it works

Rhodus used his class’ project as a trial to see if creating a VR could work for tours. What he found was that he could, but that it would require using different software. So, instead of using YouVisit, the trial VR was put on its own server and built using software to digitally stitch photos together and another program to build navigation tools.

The trial itself took four or five days to build — one to take all the photography, another three or four to construct the VR. After some adjustments, the VR trials were made headset-friendly just before it was launched.

The entire trial consists of over 400 cultivars with 224 available in the VR trials. When using it, viewers can rotate the screen 360 degrees to see the entire garden. And when a specific plant appears on the screens, its genus, name and its breeder are shown. In short: The entire VR trial garden is accessible to anyone anywhere in the world, so long as they have access to the internet.

There are aspects of the VR trial garden Rhodus wants to improve — namely, he’d like to speed up the building process and then showcase different days of the trial — but he sees this year as the first step towards something new.

“These are real photographs, real plants and real flowers versus the 3D drawings that you would get in a computer game,” Rhodus says. “That’s the goal — to let you feel and see the look of the trials.”

The VR trial gardens can be viewed at bit.ly/2fvBich

Alternaria leaf spot is one of several fungal diseases that can pounce on your poinsettias when your attention is diverted. The pathogen, Alternaria euphorbiicola (or certain other Alternaria species) most likely travels along with poinsettia cuttings, and attacks when the environmental conditions favor infection.

Susceptibility to this poinsettia disease varies from one cultivar to another; in the past, some of the V-14 types were seen to be particularly susceptible in comparison to the Heggs, which developed only tiny leaf spots. Unfortunately, modern cultivars have not been trialed for their relative susceptibility. This leaf spot problem is most likely to appear on outdoor grown crops in hot, humid environments, but there have been several outbreaks in greenhouses in the Northeast in recent years.

Because the disease is unfamiliar, there is a chance that it will be mistaken for Botrytis blight. Especially on the less-susceptible cultivars, the symptoms could be confused with those of bacterial leaf spot caused by Xanthomonas axonopodis pv. poinsettiicola, or with poinsettia scab caused by Sphaceloma poinsettiae. The large, brown, multi-celled Alternaria spores can be moved on air currents or splashed to nearby plants by overhead watering.

Wet leaf surfaces, high humidity and warm temperatures are needed for infection. The symptoms appear not only on leaves, but also on stems, petioles, cyathia and bracts, so that the disease quickly has an impact on saleability of a crop.

Alternaria leaf spot is not often mentioned as a propagation disease, where it might be mistaken for Botrytis blight; it tends to be noticed in late summer or early fall. Alternaria leaf spot is obvious on a highly susceptible host: spots are purplish-black and become irregularly shaped as they expand to become an inch across or more. Leaves can be distorted if infections land on veins, and there may be yellowing and leaf drop. Spots on stems are elongated and sunken, up to an inch long.

Fogging equipment for ornamental crop production has come a long way over the last decade or so. Ultra-low volume foggers can now spray up to 2 million square feet as growers have pressed for machines that are bigger and faster. Also, some foggers are capable of doing double and even triple duty in the greenhouse: sterilizing, humidifying and cooling, giving growers a little more bang for their buck.

Yet, not all growers need a fogger with all these capabilities. Like any tool in your arsenal, foggers and sprayers are just another tool — an important one — to get the job done as efficiently as possible.

“It’s a really nice tool to have in your IPM toolbox,” says Tim Reusch, Western Technical Representative with Dramm Corporation. “[But] it’s not an end-all silver bullet where you’ll never have to use a wet sprayer again.”

Reusch says the main advantages of some of the modern fogging equipment are the increased efficiency of application and labor cost savings. Prices range from $3,500 to $15,000 for these machines, so it is important to select the right fogger to meet the needs of your greenhouse. Consider these points when investing in fogging equipment.

High volume hydraulic sprayers

The standard hydraulic sprayer may be what you initially started out using in your greenhouse. Like a hammer that you keep in your tool box even after upgrading to a nail gun, a hydraulic backpack sprayer is a tool that is still handy to have within reach in a greenhouse. Hydraulic sprayers can be effectively used to spot treat infestations before they get out of hand. A typical hydraulic sprayer operates between 100-300psi with an output between two and four gallons per minute with average particle sizes between 200 and 400 microns. When shopping for a hydraulic sprayer, Reusch suggests choosing a spray gun that allows for easy pattern adjustment and multiple nozzle choices.

Targeted low volume sprayers

The targeted low volume sprayer can do what the high volume hydraulic sprayer does only faster. These sprayers produce smaller particle sizes and lower flow rates, allowing for spot treatment and focused application in targeted areas where insect populations are running high. And because the particle sizes aren’t too small, they can be used in shade houses and even outdoors on a calm day. With low volume sprayers there’ll be little to no run-off.

Growers have several types of low volume sprayers to choose from, including high-pressure cold foggers, electrostatic sprayers, mist blowers and rotary disk sprayers. High pressure sprayers, such as the Dramm Coldfogger, working at 3,000psi will create fine droplets with high velocity, which results in good coverage to the undersides of leaves.

Not all foggers are created equal

Growers should do their homework before investing in fogging equipment. Ask other growers what has worked for them. Look at white papers and reviews of the different products on the market. There are different kinds of fogging equipment that can be used for different purposes and even ones that can multi task. There are likely advantages and disadvantages to each one.

“Know the structure where you’re going to be setting up the foggers,” says Reusch. “If you have a series of hoophouses, 20 to 30, a cold fogger or thermal fogger is a faster way to do it.” He says stationary equipment applies the product at a slower rate, but the automation saves on labor and it gets the job done effectively.

Fan-based foggers are an option for growers as well and can perform multiple functions in a greenhouse, according to Dana Pack, Vice President of Sales at Fogco Systems, Inc., based in Chandler, Ariz.

“We have a couple different product lines of fans, the Revolution and an Evolution.” says Pack. “Basically, what it does is fog comes out of a nozzle ring, airflow from the fan will either distribute it horizontally 360 degrees like an umbrella from top down; then we have fans that are more directional that send it horizontally.” He says an injector injects solution into the water supply that then runs through a high pressure pump, which atomizes into a fog. He says the particle sizes by this method is 10 microns or less, which allows for good distribution in the houses.

A good investment for growers

Given the cost of labor, which ranges from about $10-15 an hour, fogging equipment can be a good investment. With just 400 hours of manual labor at $10 an hour, a grower could break even with an entry level fogger quickly. If properly maintained, the equipment will last for years.

“We have some equipment that has been around over 20 years,” says Reusch. “The No. 1 thing is keeping the equipment clean and doing annual maintenance — change the seals and rings — [to] prolong the life of the equipment.”

If your fogging equipment works well but you’re thinking of upgrading, there are plenty of reasons to do so. The manufacturers of this equipment have added features and capabilities to these machines, mostly responding to grower input, to make them bigger, faster and smarter.

“The machines have gotten bigger, growers want something bigger and faster,” says Reusch. “That’s why we want a machine that treats 2 million square feet at a given time, that was unheard of 10 years ago.”

New technology also provides applicators important information that not only prolongs the life of the equipment, but can alert the applicator to halt fogging operations if something is going haywire.

“One of the biggest changes is with our custom high-pressure pumps,” says Pack. “We now build them with a PLC option, which controls several features in the pump. It allows for a high-pressure safety switch so if there is a breach in the line the pump will automatically sense it and shut down; it will also log hours of operation and indicate when maintenance is needed on the pump. In addition, it includes indicator lights that will illuminate and will track normal run operation and illuminates green light, normal operation; yellow for maintenance, red for a fault — high pressure fault or low water fault — and it will track and store that info as well. So, if there is any problem with the pump, it is much easier to troubleshoot.”

A fogging unit should also be able to apply any of the biological insecticides currently sold on the market. Food crops, in particular, require these products. However, many growers of ornamental crops are turning towards organic-based insecticides as well.

The bottom line in any pesticide applicator program is, of course, worker safety.

“Make sure you check with your state agriculture regulatory agency to see if you’re meeting drift compatibility requirements, if there is any for worker safety,” says Reusch.