You may or may not know that before Tech On Demand, I hosted another podcast called STEM: Insider Tips for Greenhouse Pros and although the technology was different (Skype and clunky editing tools), the topics were important and the guests were top-notch. Come to think about it, between Tech On Demand, STEM, GH Squad and our church podcast, I think I’ve now hosted more than 400 podcasts—but who’s counting …

Anyways, I jumped back in time and re-released a STEM episode with Dr. Todd Cavins (formerly a Ball Seed tech expert and now with PanAmerican Seed) who joined me to finish up a two-part episode on poinsettias. Part 1 focused on prop and transplant with deep dives into the five factors of plant growth impacting the crop, but THIS EPISODE—SUCCESS WITH POINSETTIAS (technically part 2) wrapped the topic up by covering tools for height measurement and management, as well as pest monitoring and control strategies.

Somewhere around week 40 (this week …) is a critical juncture for this important crop and as Todd tells us, it’s transition and adjustment time.  He shared past experiences working with hundreds of growers producing poinsettias, tips and tricks to help you make the most of your poinsettia crop, how to use graphical tracking tools, determining your optimal PGR regime and even some postharvest tricks to maximize sell through at retail.

And if you finish this podcast and still have time for more, check out POINSETTIAS, THE FINAL STEP—SHIPPING, the audio version of an article from GrowerTalks.

Usually, I work with my buddy Nick Flax, a technical services expert at Ball Seed, to share a concern that’s come up during one of his numerous calls with growers across North America. This week, it’s Josh Henry’s turn, and he’s leaning into his expertise in nutrition and tackling some fall crop issues that our tech team dealt with in late-August and September.

PROBLEM: Over the past several weeks, our tech team has received numerous questions involving distorted growth in common fall crops such as pansies, kale and mums. While the symptoms have varied by crop, many of the affected plants share a common set of characteristics including stunted growth, distorted or “clubby” new leaves, marginal necrosis on young foliage, leaf curling and tip atrophy.

JOSH’S TIP: These symptoms are consistent with both calcium (Ca) and boron (B) deficiencies but can also be mistaken for broad mite feeding or herbicide injury. Under the microscope, none of the samples have shown presence of broad mites, and while herbicide is hard to rule out, there have not been any obvious sources of contamination or drift in any of these cases. However, a common thread has emerged this season: the growers reporting these issues have also experienced prolonged periods of rainfall and unusually high humidity throughout August and September.

The explanation lies in plant physiology. Both Ca and B move through the plant primarily via transpiration. When humidity remains high, especially overnight, transpiration slows dramatically. Even when adequate levels of Ca and B are present in the substrate, plants struggle to move sufficient quantities into the youngest developing tissues where demand is highest.

As a result, plants can develop symptoms that closely resemble calcium or boron deficiencies despite having acceptable substrate and tissue test results. In fact, by the time symptoms are observed and samples are collected, tissue analyses often show Ca and B levels that are low but technically adequate. This occurs because the environmental conditions that limited nutrient movement may have happened days or even weeks earlier during a critical stage of leaf or flower development.

This type of issue is most likely to occur during extended periods of cloudy, rainy weather when relative humidity remains elevated for much of the day and night. Crops with rapidly developing growing points, flowers and young foliage tend to be the most susceptible since those tissues rely heavily on a continuous supply of Ca and B. Supplying adequate B (0.5 to 1 ppm total at every irrigation) in the plug stage and fertilizing with a high rate (e.g. 200 ppm) of a soft feed like 20-10-20 immediately prior to transplant can help prevent this issue from occurring in finished production.

While it can be difficult to grow out of once symptoms develop, growers can reduce future risk by promoting transpiration whenever possible. Good air movement, horizontal airflow fans, strategic venting and moisture management practices that prevent crops from remaining excessively wet overnight all help maintain nutrient movement during prolonged periods of humid weather.

As mums and pansies continue to head out the door, poinsettias still have several weeks to go. That means it’s not time to relax on crop management. One problem that can still sneak up on growers this time of year is cool-season Pythium root rot.

As temperatures drop and days get shorter, the environment changes. Your cultural practices need to change, too.

Photo: Premier Tech

Plants use water more slowly in fall because light levels are lower and transpiration decreases. Monitor media moisture closely and adjust irrigation accordingly. Saturated media and prolonged wet conditions create an ideal environment for root rot pathogens.

Lower water uptake can also lead to fertilizer salts building up in the root zone. Poinsettias are heavy feeders, but elevated EC levels can damage roots and make plants more vulnerable to Pythium infection. Regular substrate testing can help you stay ahead of potential issues.

Disease pressure can increase as crops remain in production longer and media stays wetter for extended periods. Review your root rot prevention program and consider tightening reapplication intervals within the label range during cool, wet conditions. For example, if a product allows reapplication every four to eight weeks, a five-to-six-week interval may provide more consistent protection.

Biological products can be effective tools for managing root diseases, but their success depends on maintaining strong populations of beneficial microbes in the root zone. Because of that, they often require timely reapplications to remain effective. If this is your first season using biologicals, review the label carefully and follow the recommended application schedule to maximize disease suppression through finish.

Find more details and info HERE.

Here are a couple quick pieces of advice from Nick Flax for those of you who sometimes run into stretch issues as you finish poinsettia crops. PGRs can definitely help but there are some cultural and environmental tricks that keep crops under control, too.

Allowing the canopy to fill in after pinch and before initial spacing helps encourage a tight, upright V-shaped habit, but spacing your crop at the right time is critical. If plants are grown too tight approaching finish, internode stretch pressure throughout the canopy will be a persistent challenge. Though allocating additional labor to poinsettias is not ideal, giving your crop some additional room on the bench can be a good alternative height control strategy if you’re nervous about late-applying PGRs like paclobutrazol. 

Like with most crops, overwatering and high relative humidity will encourage stretch in poinsettias. Don’t get lazy at the end of the hose and “water for the weekend” too often, especially with dropping temps and lower light levels. Reducing the amount of moisture applied when crop demand for water is low is a solid 2-for-1 to reduce stretch (not to mention reduce disease and pest pressure). 

If you’re battling Thrips parvispinus, understanding how this pest behaves may be just as important as knowing how to control it. If you’re not dealing with these thrips yet, you might very well be in the future as this pest continues to expand its geographical reach.

Research reports, blogs and a video miniseries, researchers from Vineland Research, OMAFA and AAFC shared the latest findings to help you improve monitoring and management strategies. (I honestly think the work this team does and the way they promote findings and share content for growers at all levels is phenomenal—I can’t say enough about the resources from ONFloriculture!)

The research shows that Thrips parvispinus behaves very differently from western flower thrips (WFT). It favors certain host plants and often targets young growing tips first, making scouting location critical. Researchers also found that parvispinus can be more defensive against biological control agents, tends to be most active in the late afternoon and responds especially well to dark blue sticky cards rather than the yellow ones you probably use for WFT.

Research from the experts sharing content in the ONFloriculture blog also highlights the strengths and limitations of different monitoring methods. While sticky cards provide a simple way to track adults, plant washes remain the most accurate method for assessing overall populations and detecting larvae. The findings are already helping researchers refine recommendations for scouting, monitoring, mass trapping and treatment timing.

There’s so much more to this research and finding summary. Here’s a LINK TO THE FULL REPORT from Jessie deHaan, a research technician in the biocontrol lab at the Vineland Research and Innovation Centre.

If you missed the three webinars in this series, they’re well worth watching. As a trio, they provide an up-to-date look at parvispinus biology, behavior and monitoring practices.

• FCG Parvi Webinar 1: Dip, cool or steam? Cutting treatments for Thrips parvispinus to Start Clean
• FCG Parvi Webinar 2: Getting to Know Thrips parvispinus to Better Control This Pest
• FCG Parvi Webinar 3: The Road to Thrips parvispinus Biocontrol

I talked to a lot of growers over the summer and heard from plenty of readers (and podcast listeners and video viewers) that Tech On Demand resources are very beneficial and timely. As a communicator, it’s always cool to learn that content is hitting home. In the past couple months, I’ve seen posts in our Greenhouse Tech Team Facebook Group from members who’ve produced “first crops” of different species and some have encountered issues and others have turned out beautifully.

It’s fun to see so many constructive comments and positive feedback from the peer-to-peer community—helping with tips and advice for identifying and controlling disease, battling insect and mite pests and especially suggesting nutritional changes and applications. I’ve followed along with some of these posts and read all sorts of comments with specific applications and rates, as well as cultural controls and ways to avoid challenges on future crops. As I’ve said before when talking up the Facebook group, it takes a village ... And this summer, the village stepped up and helped out a lot of peers.

(The post shown on the right was seen by more than 2,600 members in mid-September and 33 peers commented with advice to help a fellow grower!)

If you’re already a member of the GREENHOUSE TECH TEAM group, thank you. Don’t just be a lurker, jump into the conversation with questions, answers or ideas. If you’re not … now’s the time to join. It’s a private group, so all you need to do is answer a couple simple questions to prove you’re a greenhouse professional (not a hobbyist or spammer) and I’ll let you right in.

And please answer the questions—I do approve folks with clear industry affiliations who don’t answer but I do NOT approve about 20% of requests and that’s usually because they leave the questions blank. I don’t want to risk the integrity of the group so I have a pretty tight filter. That said, membership is now up to just about 6,400!

Talk to you next week …