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With the holiday season almost upon us, it’s time to turn our attention to Spring bedding crops. Although here for a brief window, the diversity of these crops means you’re bound to encounter some sort of disease and insect problems.
One way you can head off issues is to plan and prepare now. This post from January 2020 has important tips on sanitation for common spring crop diseases, dips and early sprays to prevent key pests, as well as tips on where to spend your biocontrol dollars.
Hosing down saves Headaches:
Several key spring crops, like Calibrachoa, Pansy and Petunia are highly susceptible to black root rot (Thelaiviopsis), and I’m seeing more Fusarium pop up in random crops the last few years (e.g. salvia, gerbera, echinacea, lavendar). These pathogens are everywhere in the environment, and can easily be brought in by insects (fungus gnats and shoreflies), on worker’s boots or via equipment. Further, their spores can hide in nooks and crannies of benches while less-susceptible crops are growing, then pounce when conditions are right.
Once black root rot or Fusarium get hold, it can be almost impossible to control them with fungicides (AND we only have 2 registered for them!). When it comes to these diseases, a good clean out of your spring crop propagation and growing areas is as close to a “silver bullet” solution as we are going to get. This includes:
- Scrubbing down your benches. This removes all the soil particles etc., where fungal spores might be hiding. It also allows sanitizers (see step 2) to work better (see table below), since they can get trapped by organic matter. Use a hose, scrub brush and a product like Strip-It to make sure everything is as clean as possible.
- Sanitize benches AND drip lines, where organic mater, biofilm and disease spores can accumulate. Use products like Virkon or KleeGro at the recommended rates for the material you’re sanitizing. If cleaning drip lines, make sure to always thoroughly flush your watering system several times before plants go in to prevent any potential phytotoxicity.
- Use new plug trays. Again, this may be more money, but it’s something you’ll wish you did if you develop a problem. Pot/tray cleaners aren’t perfect, and trays can act as a ready source of innoculum for resting spores. If you are cleaning your trays, use the same process as for benches, i.e. first clean, then sanitize.
- . Control fungus gnats and shoreflies, as they can spread disease spores. Fungus gnat larvae can also chew on plant roots, making them more susceptible to disease.
Need more convincing that sanitation works? Check out this screen shot of a trial done by Plant Pathologist Ann Chase in the greenhouse. You can see here, regardless of your growing surface, there’s a combination out there of cleaners and sanitizers that can lead to COMPLETE eradication of Fusarium. Wouldn’t it be nice to start out this growing season free of disease?
Percent eradication of Fusarium depending on the combination of a) cleaning treatment and b) your growing surface. Using a cleaner (Strip It) followed by the right sanitizer for your bench/floor material can eliminate residual Fusarium spores in your greenhouse entirely. Image credit: Ann Chase Consulting Ltd.
I highly recommend that everyone watch the full webinar on Fusarium control in the greenhouse by Dr. Chase, as it it chalked full of helpful tips, including against other spring crop diseases like Botrytis. Just click here and sign up with your email address (it’s free!).
Preventing Pests Where you Can:
Dips aren’t just for whitefly on poinsettia anymore! More recent research from the BioControl Lab at the Vineland Research and Innovation Centre, run by Dr. Rose Buitenhuis, has demonstrated dips can be an important weapon for reducing thrips, whitefly and spider mites in spring crops.
Check out this video, housed on the Greenhouse Canada website, on how to effectively use dips to reduce springtime insect pests. A direct link to the video can be found here. Image courtesy of Greenhouse Canada Magazine / VRIC.
However, the first step in successfully incorporating dips into your IPM program for spring is phytotoxicity testing. Rose’s lab did some work on this in 2019 and has generously shared it with us (Fig.1).
As you can see in the figure below, different plants react differently to different products. Although Landscape oil at 0.5% is safe for crops like ivy geraniums, ipomea and impatiens (green boxes), it can cause significant phyto on things like zonal geraniums, petunia and mini roses (yellow and red boxes).
Fig. 1. Phytotoxicity results with various dip products on various spring crops. Rating scale: 0 = no or little damage (green boxes) to 5 = significant damage/dead (red boxes). Chart courtesy of R. Buitenhuis (Vineland Research and Innovation Centre).
Variety can also play a role, as seen with mum var. Ottawa, which could not tolerate Landscape oil, while other varieties could. This highlights why ON-FARM TESTING of a small batch of ALL VARIETIES should always be done before you incorporate preventative dips on a wide-scale.
So, just how well do dips work in reducing initial pest populations? Rose also came up with this handy-dandy summary chart (Fig. 2):
Figure 2. Efficacy of various reduced-risk products when used as cutting dips against various pests. Chart courtesy of R. Buitenhuis (Vineland Research and Innovation Centre). Green boxes indicate high efficacy of treatments against specified pests. Caution symbols containing plants indicate a significant risk of phytotoxicity.
As you can see, oils had the highest efficacy (>70%) against all 3 main greenhouse pests (thrips, whitefly and spider mite). Soaps were generally only effective for whitefly, whereas BotaniGard (by itself) was generally only effective for thrips. However, soaps and BotaniGard also pose the least risk to plants when it comes to phyto. Striking the right balance between efficacy and phytotoxicity is why testing is a must.
Here are the products with dip applications on the labels (see label links), so use (and test!) them where appropriate!
Planning your Bio Program:
Planning in advance helps you know where you’re spending your dollars, and where you can potentially cut back based on last years performance. It can also help you plan for contingency issues (i.e. what are you going to do if your planned biocontrol program isn’t working?).
I’ve blogged about spring bedding crops that are magnets for certain pests before. Read this post to help you know which plants are likely to get which pests, so you can target your biocontrol efforts. Here are other some general spring crop recommendations:
Hanging baskets can pose a challenge for pest control, as they tend to get forgotten about once hung above the main crop. Photo courtesy OMAFRA.
Thrips control:
- Thrips can be trickiest in hanging baskets, since they tend to get hung up and forgotten about. If the basket contains any thrips-magnet crops, then your best strategy is to use long-duration sachets, or even the new Ulti-Mite sachets. These products have a higher chance of ensuring mites are present in the baskets for 8-10 weeks, without needing to add a second sachet. For example, the Ulti-mite sachets are less dependent on ideal environmental conditions/placement, making them a good choice for hanging baskets above your regular crop.
- Using dips on both mums and gerbera will make your life easier, as these popular crops can arrive already infested with insecticide resistant pests that may move to other attractive crops.
- Use thrips-sensitive crops like verbena to assess whether your current strategy is working, or if you need to add things like twice-weekly sprays of Beauveria-containing microbial pesticides. BotaniGard and Bioceres are 2 different strains of Beauveria that are registered for floriculture crops.
- Mass trapping is your friend in the spring, as temperatures above 10C mean thrips can potentially fly in from outside (including the usual Western flower thrips AND onion thrips). Large sticky cards also help prevent thrips from migrating from source crops to sensitive crops.
Aphid control:
Green peach aphid are the most common species of aphid found in hanging baskets crops, like Million bells. Photo by OMAFRA.
- As with thrips, aphids can be a major problem in hanging baskets, especially those containing calibrachoa or pansy. Given that recent work from Cornell University has demonstrated that parasitoids don’t control aphids on Million bells, this is a time when pesticides are your best bet. Beleaf (flonicamid) has been the go-to for a while, but Altus (flupyradifurone) may provide an alternative if whitefly are also a concern. Beleaf works best when applied as a preventative drench sometime in early March.
Mite control:
- Although spider mites can generally be controlled with releases of Persimillis when outbreaks occur, broad mite and cyclamen mites are much harder. In some crops, high releases of Amblyseius cucumeris will keep populations in check enough to get you to sale. Where broad mites tend to be your only problem (and insecticide residues aren’t an issue) preventative applications of Fujimite or Forbid may be the best option. Pylon or Avid are also effective options if spider mites are also a crop concern.
What other spring crop issues are YOU concerned about? I’d love to hear from you and address your concerns in follow up blog posts. Shoot me an email at sarah.jandricic@ontario.ca or leave a comment at the bottom of this post!