Its a busy time in the greenhouse, but our next topic is timely! Rot rots like Fusarium, Pythium and black root rot are often the bane of spring bedding crops. Dr. Mary Hausbeck, a Distinguished Professor from Michigan State University, is going to share her vast knowledge on this topic, including which fungicides work best. Check out the details below, and don’t forget to register!
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.
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, dipsandearly sprays to prevent key pests, as well as tips on where to spend your biocontrol dollars.
With the holiday season over, 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 has important tips on sanitation for common spring crop diseases, dipsandearly sprays to prevent key pests, as well as tips on where to spend your biocontrol dollars.
It’s that time of year again, when baskets of Million Bells (Calibrachoa) are going up in the greenhouse. Here’s how to deal with and prevent some of their most common issues.
From a nutritional standpoint, the best thing you can is keep the pH of your calibrachoa in its ideal range; between 5.5 and 6.0. A pH higher than this can inhibit nutrient uptake, especially micronutrients such as iron.
Iron deficiency can be difficult to distinguish from other issues (like Black Root Rot – see below), but 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.
Yellowed plant growth (yellow circle) and dead plugs (orange circle) on a plug tray of Callibrachoa from black root rot.
Million bells are also highly susceptible toBlack Root Rot (Thielaviopsis) – I’ve seen this take out a good chunk of a crop. Symptoms include:
Stunting of foliage and roots
Plants in a tray will have uneven heights
black areas on roots
yellowing of leaves
Prevention is worth a pound of cure with this disease, as it is difficult to eradicate once established. Important steps to take include:
Proper Sanitation. To avoid an issue with Black Root Rot year after year, immediately dispose of diseased plants, limit water splashing, and sanitize benches, floors and used pots/plug trays. Always physically wash surfaces with a cleaner to remove organic matter, then follow up with a disinfectant such as KleenGrow (ammonium chloride compound).
Consider prophylactic applications of fungicides onplug trays. Products include Senator (thiophanate-methyl) or Medallion (fludioxonil). Preventative applications are an especially good idea if you’ve issues in the past. Adding bio-fungicides containing Trichoderma harzianum(e.g. Rootshield, Trianum) may also help.
Lowering your pH. This diseaseis significantly inhibited by a lower pH – between 5.0 and 5.5.
Manage fungus gnats and shoreflies, since these insects can spread Black Root Rot between plants. Treatments include nematodes, Hypoaspsis mites , or applications of Dimiln (diflubenzuron) or Citation (cyromazine).
If already established, rotated applications of Senator and Medallion may limit Black Root Rot, but are unlikely to cure it.
Lastly, Million Bells are highly attractive to aphids. With baskets hung up in the greenhouse, they can be “out of sight, out of mind”, but regular monitoring is needed to prevent large aphid outbreaks. Place sticky cards directly in baskets, and routinely check plant material for aphid cast skins and honeydew.
Once aphids are detected (and they will be!), applications of Beleaf (flonicamid), Enstar (kinoprene) or Endeavor (pymetrozine) will usually take care of them. However, be aware that all of these insecticides take around 4-5 days to start causing aphid death.
Diagnosing a plant with vague symptoms likewilting, yellow and stunting is much like being a “plant detective”. First, you need to profile the “victim” — here, Callibrachoa plugs. Then, collect DNA evidence. Finally, use knowledge and instinct to narrow down your “suspects”. Only then can you come up with a plan to stop the assailant.
In this case, our DNA evidence (c/o UofG Lab Services) gave me 3 possible suspects: Pythium disotocum, Fusarium oxysporum and Thielaviopsis basicola. But which of these was the real culprit?
P. disotocum is rarely documented as an aggressive pathogen in flowers, so we can eliminate that. Similarly, Fusarium is often “around” at low levels without causing a problem. But, T. basicola, better known as Black Root Rot, is a common problem in Callibrachoa, specifically. Rotting roots are not always directly evident (even under a microscope), but severe discoloration of the foliage is a good clue, since this pathogen produces toxins that result in yellowing. Left unchecked, Black Root Rot causes severe stunting and plant death.
Luckily, there are treatments for Black Root Rot, and preventative measures that can be taken.
Drenches of Senator 70 WP (thiophanate-methyl) are the best option for dealing with an existing outbreak of Black Root Rot
Black Root Rot is often transmitted by fungus gnats and shoreflies. Management of these insects is key to prevention. They can be controlled with soil applications of nematodes, predatory mites (e.g. Hypoaspis), or insect growth regulars like Dimilin (diflubenzuron). These products are compatible with biocontrol programs for other pests, like thrips and aphids.
A high soil pH encourages the growth of Black Root Rot. pH should be kept below 5.6.
Bio-fungicides containing the beneficial organism Trichoderma harzianum (e.g Rootshield) can help protect plants from this Black Root Rot if applied at planting.