This post was jointly written by Dr. Chevonne Dayboll and Dr. Sarah Jandricic
It’s time to think about spring again! This post gathers some of the most important things to plan and prep for in the greenhouse before your spring production begins in earnest.
1. Make sure your inputs are ordered
We can’t emphasize this one enough. COVID-19 and container boat issues are still causing shipping delays that are affecting many industries including greenhouses. Make sure you order potting mixes, plastic trays and pots, fertilizers, and production inputs well ahead of when you will need them. If you are planning on doing greenhouse upgrades in between seasons make sure you confirm delivery and installation timelines with your contractors. Many of them are facing delays too!
2. Now is the time for preventative maintenance
Now is a great time to schedule preventive maintenance for your boiler, irrigation and shading systems. Make sure that all motors and alarms are working before you need to rely on them. No one wants to find out that their temperature alarm failed on a cold February morning! Ensure you are getting the pressure you expect all along your irrigation system. If you rely on propane heaters for early spring production make sure they are venting properly. Damage from improper venting can present as stunted growth or leaf burn.
Take some time to inspect the greenhouse for wear-and-tear. Repair cracked poly and broken glass to keep heat from escaping. Make sure old torn energy curtains are replaced. A heat sensitive camera can help to identify areas of energy loss and help you plan for energy efficient upgrades in the future.
3. Start with sanitation
Several key spring crops, like Calibrachoa, Pansy and Petunia are highly susceptible to black root rot (Thelaiviopsis), and we’ve seen more Fusarium pop up in the last few years on crops like salvia, gerbera, echinacea and lavender. These pathogens are everywhere in the environment and can easily be brought in by insects like 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:
- Scrub down your benches. This removes all the soil particles etc., where fungal spores might be hiding. It also allows sanitizers to work better, 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 peroxide (Virkon) or quaternary ammonium (KleenGro) products 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. This may be more costly, 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; 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.
4. Monitor pH for optimal nutrient uptake
Keeping the pH of your crops in an ideal range can help with a host of issues. To avoid common nutritional issues such as iron deficiency, it’s best to keep crops at a pH in the range of 5.5 to 5.8. Iron deficiency can be difficult to distinguish from other issues (like black root rot), but it typically leads to yellowing of new growth. Leaves may only show chlorosis between the veins, or it may be spread throughout the leaf. This is different from nitrogen deficiency where yellowing occurs in the oldest leaves. If iron deficiency occurs, adding a chelated form of iron is best for uptake.
A lower pH can also significantly inhibit black root rot. Aim for a pH between 5.0 and 5.5. Regularly monitor the pH and EC of your feed water and crops using the pour through method.
5. Prevent pests where possible
Dips aren’t just for whitefly on poinsettia! Research from the BioControl Lab at the Vineland Research and Innovation Centre has demonstrated dips can be an important weapon for reducing thrips, whitefly and spider mites in spring crops.
This video shows how to effectively use dips to reduce springtime insect pests.
The first step in successfully incorporating dips into your IPM program for spring is phytotoxicity testing. VRIC’s BioControl lab did some work on this in 2019 and they have generously shared it with us (Figure 1). 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). 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? VRIC’s BioControl lab also came up with a handy summary chart (Figure 2). 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.
The following products have dip applications on the labels, so use (and test!) them where appropriate!
6. Plan your Bio Program
Advance planning can help 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?).
This post will 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:
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 10°C 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.
As with thrips, aphids can be a major problem in hanging baskets, especially those containing calibrachoa or pansy. Recent work from Cornell University has demonstrated that parasitoids don’t control aphids on calibrachoa, which means 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.
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 application of Fujimite or Forbid may be the best option. Pylon or Avid are also effective options if spider mites are also a crop concern.