How to Spot, Stop, and Prevent Spider Mites in Your Greenhouse

July 24, 2026

Since greenhouses remove the mortality factors that would suppress spider mites, growers are especially vulnerable to an infestation. These factors include predators, extreme temperatures, and volatile weather conditions.

“Greenhouses have suitable temperatures year-round and often ideal temperatures for the growth rate of insects,” says Laura Ingwell, Ph.D., associate professor of entomology at Purdue University. “Growers create a perfect mesocosm of a well-fed, ideal temperature food source that’s never being interrupted by predators or rain—spider mites flourish in that environment.”

Because growers control their environment so precisely, they often underestimate the conditions they create. There aren’t predators, temperature swings, or rain to keep spider mite populations in check.

Every grower could experience an infestation if they don’t take precautionary measures. Even if they do, they must know how to respond.

Considering a Greenhouse’s Vulnerability

The types of plants grown in a greenhouse have a direct correlation to spider mite infestations. This is true for both crop type and how long it’s been in the greenhouse.

“The longer a plant is in the greenhouse, the more likely it is to accumulate pests,” Dr. Ingwell says. “So your highest area of risk in the greenhouse is the older plants that are harboring mites.”

To reduce the risk of harbored mites spreading, Dr. Ingwell suggests considering the spatial organization of plants and the movement between older plants and plant starts. Movement especially, she says, is how pests tend to spread.

“Points of entry are usually going to be the origin of an infestation,” she explains. “So greenhouse growers should think strategically about the organization of their plants.”

Dr. Ingwell offers three specific recommendations for greenhouse growers:

Have protocols in place at the point of entry. This helps reduce the risk of workers bringing in a spider mite on their clothing, which is also known as a hitchhiker.
Consider how workers are moving through the greenhouse. Ensure your workers are going to the seedlings and young plants first, then go to the older plants last.
Be mindful of the crops you’re growing. While spider mites feed on thousands of host plants, there’s evidence that some crops are preferred and more likely to be colonized than others.

Growers cultivating susceptible crops should prioritize early detection and proactive prevention. That starts with knowing which crops are most at risk. To see how you can control spider mites check out this helpful guide.

Crops to Monitor Closely

Food crops are much more likely to attract spider mites, and it’s difficult to prevent them from entering the greenhouse altogether.

“Food crops have to be grown for a long time in a greenhouse for flowering and fruiting,” she explains. “I think cucumbers are at the top of the list for susceptible greenhouse crops. If you’re growing cucumbers in a greenhouse, you’re going to have spider mites.”

Cucumbers and tomatoes are especially vulnerable to mites because they’re vining crops that have thick leaves.

“They penetrate into the leaves of the plant, pulling the juices, photosynthesis, and sugars out of the plant material,” Dr. Ingwell says. “They don’t damage plant cells and they don’t leave holes in the leaf. Their mouth parts are very exact, and they can go in between cell layers to get the exact tissue they want to feed on.”

As time progresses and the spider mites continue to feed on the plant, chlorotic spots will start to appear due to the photosynthate loss in those cells. Experienced growers will notice those spots early on—but newer growers may not notice them until more severe warning signs emerge.
Knowing what to look for and when can be the difference between early intervention and a full infestation.

Spotting Signs of a Spider Mite Infestation

One of Dr. Ingwell’s biggest goals is teaching growers how to identify warning signs sooner. Here are the different infestation signs growers will encounter ranging from the least to most severe.

Spotted leaves. Distinct bleach spots on the leaves of the plant.
Mottled leaves. Larger bleach spots on the leaves that start to blend together—not distinct individual spots.
Webbing on leaves. When spider mite populations are high, webbing will be visible on the leaves of the plant. “Eventually, you will start to see spider mites crawling around on that plant material,” she adds.

To make sure they’re dealing with the two-spotted spider mite, she encourages growers to perform the “white paper test.” This test makes it easy to spot an infestation before the other signs start to appear.

“You hold a white piece of paper under the plant and tap it, which will dislodge the mites that are harbored in the plant,” she says. “Spider mites are almost translucent with two black dots on them. If you have mites, you’ll start to see little black dots crawling around on that sheet of paper.”

The faster a grower acts, the better their chance of containing it.

The Importance of Sanitation

Sanitation is the most effective weapon against a spider mite infestation.

“It’s really about starting with a clean environment,” she says. “That means having no weeds and clean benches in the greenhouse.”

This applies to plant material as well. Dr. Ingwell suggests finding a healthy seed source and ensuring the growing media entering the greenhouse is sterile and clean.

“That could mean physically inspecting all the plants that enter your facility,” she says. “It could also mean proactively releasing a predator to take care of anything that might be residing on those plants before you plant them in the greenhouse.”

But prevention doesn’t stop at planting in a clean greenhouse environment. Growers must maintain clean, sterile surroundings during and between growing cycles. This means removing all plant material from the greenhouse and cleaning as well as disinfecting all structures.

“If you can’t get a sanitizer on the surface, do a heavy hosing down,” Dr. Ingwell explains. “Dislodge them to the ground and wait as long as you can until planting again. This gives them time to starve.”

For Dr. Ingwell, preparedness is the bottom line.

“Growers have a balancing act of all the different things they have to manage in the greenhouse,” she explains. “They need to understand the biology of each potential pest they could encounter on their crops.”

In a greenhouse, the conditions are always right for spider mites. The question is whether a grower is ready for them.

One Engineer’s Fight for Energy Efficiency in CEA

July 15, 2026

Gretchen Schimelpfenig entered the energy space fighting climate change one utility bill at a time. As senior energy engineer at Energy Resources Integration, she aims to save energy and reduce the cost of operating buildings.

She originally started working on university buildings, data centers, and hospitals. Throughout those experiences she learned a lot about HVAC and lighting, which encouraged her to tackle the energy challenges plaguing the controlled environment agriculture (CEA) industry.

Since she first joined the industry in the 2010s, when CEA was picking up steam in the U.S., Schimelpfenig started creating policies and programs that aimed to make indoor agriculture more efficient.

“I didn’t realize how much energy was used in CEA until I started working in large-scale greenhouse construction,” Schimelpfenig says. “I wanted to look into how better HVAC and lighting solutions could keep that in check.”

This has been her primary focus for the last 10 years. In that time, she’s helped growers optimize their operations by making smarter energy-focused decisions.

Knowing What to Look For

When she first walks into a CEA facility to perform an energy audit, Schimelpfenig evaluates the organization, the control system, and the equipment installed.

Organization: Getting a feel for the facility’s overall health helps Schimelpfenig determine what the grower’s budget could be for improvements. “If it’s an older facility, for example, low-cost quick fixes that could make a big difference for them to keep equipment running efficiently,” she says.
Control system: How data is monitored and how many people are responsible for operating controls are also key. “Whether they use a tablet, central computer, or their phone, automation matters because it can save energy,” Schimelpfenig explains.
Equipment: Lastly, she looks at the unit heaters, boilers, lights, and other pieces of equipment that are high energy users. “I’ll look at the make and model to get an estimate of how much energy is being used by those systems,” she says. “Then I’ll go back to my desk and use that information to make some energy models to calculate potential savings.”

Once she completes her first walkthrough, Schimelpfenig addresses the most prominent energy opportunities in the operation.

Common Greenhouse Energy Opportunities

Here are the most common drivers behind energy costs that Schimelpfenig encounters across CEA operations:

High-pressure sodium (HPS) lights. Some growers still use HPS lights over LED lights, which can account for 75 – 90% of electricity bills for greenhouses.
Thermal Curtains. Growers may not use energy curtains or have ones that are outdated and in need of repair. By failing to use or upgrade them, they’re unknowingly driving up their energy costs. “The latest climate screens are a great way to save energy on heating,” she says. “Growers can tailor the environment for shade during the day and retain heat at night.”
Automation. Lighting controls are one of the main things Schimelpfenig focuses on when evaluating a CEA operation. Using sensors to automate supplemental lighting operation saves energy in every climate. “If growers are using timers for scheduled control, there is almost always savings if you move to a sensor-based system,” Schimelpfenig says.

While updating these parts of a CEA system is important, it can get expensive—and fast. For that reason, growers should take return on investment (ROI) into account before making any energy upgrades to make sure they tackle the right project first.

Taking ROI Into Account

The importance of ROI varies from operation to operation.

Larger greenhouse operations can tolerate longer payback periods, even if it takes seven to 10 years. However, that’s not the case for small growers with lower profit margin crops—they often need to see ROI within three to five years.

“When I do energy audits at greenhouses, I can usually get a sense of the payback period we’re talking about,” Schimelpfenig says. “If I see a lot of newer equipment, I might assume this facility has been able to do these replacements and they’re not deferring their maintenance.”

This indicates that the facility can schedule equipment replacements in advance instead of waiting for a failure to occur before replacing it.

For operations that can only afford to update their equipment when it’s absolutely necessary, Schimelpfenig encourages them to explore on-bill financing. This gives small-scale growers the option to pay energy upgrades off on their energy bill instead of putting capital into it.

“Some folks need loans, and they can’t make ROI work without one,” she explains. “This year, I’m looking at projects that have shorter payback periods because the cost of energy is only going up.”

Energy Efficiency in Action

Since 2024, Schimelpfenig has worked on a large energy efficiency greenhouse project in Idaho. Setting May 2026 as a completion date, the project will cost approximately $1.8 million. But, since it was built with energy efficiency in mind, it will receive about $200,000 in rebates.

Those rebates have helped shorten the payback period.

“My work is quantifying those energy savings because of the measures we took,” she says. “That’s what energy engineering comes down to sometimes—being the translator for energy upgrades, proving to the utility that they work, and making sure the grower gets the support they need to do the efficient thing.”

She set out to fight climate change one bill at a time. Ten years in, she’s still at it, and continues to make a difference with every grower she works with.

The Intersection of Horticulture, Hospitality, and the Culinary Arts

June 17, 2026

Jack Maruna has spent the last four years at the intersection of horticulture, hospitality, and the culinary arts. He dedicated most of that time to Auburn University’s Food U program, a campus-wide effort that brings locally grown food to students across campus.

Jack Maruna

He brought knowledge from that experience to his new role at Jones Valley Teaching Farm as the director of partnerships just a few months ago.

Similar to Food U, Jones Valley Teaching Farm is focused on education in the horticulture and culinary hospitality realm—just at the K-12 level. The nonprofit works directly with 16 schools across Alabama, though its level of involvement differs depending on how much help each one needs.

Understanding the Program Levels

Here’s a breakdown of Jones Valley’s different levels of involvement in Alabama schools.

Level 1: Hiring an instructor at a school. Jones Valley chooses the horticulture program instructor at the greenhouse, outdoor teaching farm, and culinary lab—it pays their salary, and they teach the lessons developed in house. “That’s the most intimate level of involvement,” Maruna says. “Often we are financing the design, materials, and construction of outdoor, indoor, and greenhouse teaching labs.”
Level 2: Co-developing an ag or culinary program with the school. The second level typically involves redeveloping the current curriculum. “We essentially help schools revamp their program,” he says. “Or they have an old, dilapidated greenhouse that we help them get back up to speed.”
Level 3: Finalizing details. The last level is the least involved of the three—Jones Valley refines the horticulture and culinary curriculum, ensuring it’s up to date. “We hone in on the specific, more granular details for the curriculum we’re assisting them in,” Maruna explains. “We’ll go into a greenhouse, recommend equipment, and make sure it fits into the current curriculum.”

But for Maruna, the levels are just the delivery mechanism. The real test is whether what’s being taught can keep pace with where the industry is actually going.

During his time in academia, Maruna discovered that universities could be up to three to five years behind private industry. “That defeats the purpose for me,” he explains. “What are we researching at university if growers are already ahead?”

Maruna sees similar risk in K-12 programs. If the curriculum isn’t closely tied to where the industry is headed, schools fall behind before the students graduate. That’s the main challenge he aims to address at Jones Valley Teaching Farm.

But staying ahead of industry trends only matters if kids are engaging with food in the first place. That fundamental connection is where Jones Valley’s mission really begins.

The Jones Valley Mission

One of Jones Valley’s most ambitious goals is to reconnect children with locally grown food.

“It’s a disservice if you go through grades K through 12 without ever talking about food,” Maruna says. “Then, you enter your adult life not understanding where our food is coming from and how.”

From there, it’s a trickle-down effect on health and making informed decisions about food. About 64% of the U.S. eats three meals per day. It’s very likely, Maruna says, that a majority of those people don’t think about those three meals or how they reached a dinner plate.

“It takes a lot of hands, states crossed, logistics, and trucking to get to the final consumer,” he explains. “When people always have food available to them and lack perspective for how it got to them, they take it for granted.”

The hands-on programming Jones Valley offers has already started making a meaningful difference. In one school that has both culinary and horticulture programs, the organization went through an entire lesson with cucumbers. Students grew cucumbers in a Dutch bucket system, harvested them, then pickled and canned them.

In Maruna’s words, the kids were obsessed with the finished product.

“Kids can’t believe that seeds turn into pickles. When they get into a program like this, they’ll be walking around with a foot-long cucumber eating it raw and loving it,” he says. “That connection afforded them the ability to try it, and I think they love it because they were intimately involved in the process.”

Introducing children to these concepts when they’re young opens their eyes to a future career path.

Planting the Seed Early

Jones Valley offers a two-year internship for high school juniors and seniors. It’s a personal and professional development internship, aiming to give these students direction after they graduate.

“The goal isn’t simply to create farmers. It’s to expose students to the entire food system, from production and distribution to culinary arts, business, education, and environmental careers,” he explains. “This is a human impact opportunity, we see leaders exiting our program no matter what next step they decide to take after high school.”

The program currently has 10 interns. That may seem like a small number, but the impact these 10 people can make is significant.

“You think about 10 interns and it doesn’t sound like a lot,” Maruna says. “But when they all graduate from an internship program and stay in the industry year over year, it ends up being pretty impactful for the state of Alabama.”

Jones Valley’s goal: growing that number from 10 to 50 within the next five years.

Great Lakes Growers’ Blueprint for Profitability

March 17, 2026

Take a stroll through Great Lakes Growers’ 2.75-acre greenhouse operation in Burton, Ohio, and it’s like walking through time. Managing facilities ranging in age from six to 13 years old, Director of Growing Renato Zardo doesn’t just grow lettuce. He fine-tunes a production strategy that adapts to each environment’s strengths to maintain consistent yield and profitability.

“I have five different growing environments that give me five different crops even though they’re the same variety,” he says.

Getting the best possible yield in all of his greenhouses is easier said than done. In addition to mastering the different growing conditions of each facility, Zardo must be intentional about upgrades as well as retrofits.

Production planning

To navigate these different growing conditions, Zardo has developed a strategic approach to production planning. The wide range of technology and equipment across Great Lakes Growers’ greenhouses means he must be especially careful when deciding where to grow each of his lettuce varieties.

The lettuces grown in each greenhouse are determined by the level of tech, light intensity, and glass used in the facility. “That’s the difference between finishing a crop in 35, 38, or 40 days,” Zardo says.

Crop placement is based on sensitivity. The most delicate and profitable lettuces are grown in the high-tech greenhouses while the hardier, less profitable varieties are grown in the low-tech facilities.

“Let’s say I have butter lettuce and cut lettuce growing together,” Zardo says. “The butter lettuce will drive the greenhouse because it’s sensitive to tipburn.”

While he can afford to have a smaller yield on cut lettuce, he cannot afford to lose his butter lettuce crop entirely. So, he must adjust the lighting recipe to be more suitable for butter lettuce than cut lettuce.

“Higher yield on the cut lettuce wouldn’t make sense if I lost the butter to tipburn,” he explains.

Be intentional with technology upgrades

Beyond deciding what to grow where, Zardo must determine the right time to upgrade his facilities with new technology and equipment.

Great Lakes Growers’ careful, strategic approach to production planning extends to technology upgrades. The operation has made minimal updates to each of its greenhouses, only investing in new tech when it makes sense. But when it builds a new greenhouse, it makes sure the structure has the highest level of tech available.

Problems tend to emerge when growers rush into expansion and invest in new tech without proving its value. This is another instance where Great Lakes Growers’ decision to grow slowly has worked in its favor.

“We have seen growers grow too fast in an industry that’s not doing that well,” he says. “We grow slowly, with certainty that our expansions will be very related to our market.”

But this decision hinges on how practical the upgrade is. When it comes down to it, Great Lakes Growers is a lettuce-growing operation. Leafy greens aren’t a high value crop, so the profit margins aren’t very high.

Ultimately, Zardo says, he needs to remember that his job is growing lettuce. Investing in expensive new tech rarely has a major ROI in greenhouse production.

Reading the Plant First

No matter how old a greenhouse is or advanced the technology inside of it, Zardo says success ultimately comes down to reading plants correctly.

“If a plant can’t handle your environment, it will let you know,” he says. “You have to learn how to read your plant. It will tell you if your environment is too much, not enough, or just right.”

There is no shortcut for grasping this concept. It takes time to figure out how a greenhouse works and what plants want – but every greenhouse and plant are different. Once a grower masters the conditions of their facility and how to grow their crops, that’s when the magic happens.

“You’re not going to get the hang of growing during your first or even second year of it,” Zardo says. “Growing is a science, and it takes time to understand it. There is no shortcut for experience.”

In the spring, Great Lakes Growers will add another acre to its greenhouse operation — the next chapter in its walk through time.

While this greenhouse expansion will be equipped with cutting-edge technology, Zardo’s approach remains the same: adapt to each greenhouse, prioritize the crop, and only expand when it makes sense. This plant-first strategy has kept Great Lakes Growers profitable while newer, tech-focused operations struggle to find their footing.

OHP Expands Sales Team with New Hire and Internal Promotion

March 12, 2026

RESEARCH TRIANGLE PARK, North Carolina | March 12, 2026 – AMGUARD™ Environmental Technologies (“AMGUARD”), the specialty markets division of AMVAC Chemical Corporation, a wholly owned subsidiary of American Vanguard Corporation (“AVD”), today announced two key additions to its OHP sales organization: the hiring of Alfredo Lara as Technical Sales Manager and the promotion of Joe Grippi to Key Accounts Manager.

Alfredo Lara joins OHP as Technical Sales Manager, covering California, Nevada, and Arizona. A native of California’s Central Coast and now based in the Central Valley, Lara holds a B.S. in Plant Health from California State University, Fresno. He brings extensive experience in field research, account management, business development, and independent consulting, with a career focused on market development, product launches, and customer support. In his new role, Lara will be responsible for building and maintaining customer relationships, driving demand with distribution and end-user accounts, and supporting OHP’s growth in the greenhouse and nursery segments across his territory.

“We are excited to welcome Alfredo to the OHP team,” said Frank, Director of Sales for OHP. “His deep roots in California agriculture and hands-on experience across multiple areas of the industry make him an ideal fit for this Western territory.“

Joe Grippi has been promoted to Key Accounts Manager, joining fellow KAM Duffey Clark in managing OHP’s national distributor relationships. Together, the two will divide responsibilities across key accounts, working to develop and execute strategic commercial plans that drive growth across OHP’s Nursery, Greenhouse, CEA, and Cannabis markets. Grippi joined OHP as Southeast Technical Sales Manager and has demonstrated a strong ability to build relationships and drive results. He brings a distinguished industry background, having previously served as Key Account Manager for Specialty Products at UPL Environmental Solutions and, prior to that, as Business Development Key Account Manager at Bayer Environmental Science / Envu, where he spent 22 years. He began his career at Elf Atochem and American Cyanamid.

“Joe’s promotion reflects both his exceptional performance since joining OHP and the confidence we have in his ability to strengthen our key distributor partnerships nationally,” said Frank Fornari, Director of Sales for OHP. “Together with Duffey, we now have a formidable KAM team that is well-positioned to accelerate OHP’s growth across our most strategic accounts.“

About OHP

OHP offers a comprehensive portfolio of conventional and biological solutions, including fungicides, insecticides, herbicides, plant growth regulators, and biosolutions, designed to meet the evolving needs of greenhouse, nursery, and CEA markets across the United States and Canada.