An unusually mild winter has brought on an early uptick in the thrips populations across the U.S. Many growers are surrounded by open fields or they are in agricultural areas. This is true whether it’s cotton in Florida, hay in Colorado, or a different crop in California.
When those crops are cut, the wind moves the thrips onto another food resource and cannabis is a very attractive alternative. High-level screening is expensive and with any opening such as a roof vent or a sidewall, they’re going to get in as the wind moves them.
The importance of constant monitoring
Alison Kutz is a growing consultant and President of Sound Horticulture. Much of her practice is advising clients with the various pathogen and pest infestations on how to avoid and eradicate problems when they inevitably occur.
“Scouting and monitoring are extremely important, especially on the windward side of the greenhouses,” stated Alison. “Growers who know the history of the crops around them are particularly aware of when the hay is cut or when the cotton is being harvested. To be prepared and ahead of the ballgame is critical for these growers.”
For some species of thrips and for growers who know that this is the time when thrips are most likely to invade, Alison often recommends high-pressure nematodes. “That will catch the end start of the thrips larvae in the soil, before they actually hatch into the adult stage and move up into the canopy to start feeding on plants and laying eggs.”
Early detection and identification
It’s often not enough just to deal with one stage of a pest such as thrips, which has both a below the ground as well as an above the ground life cycle. Alison preaches that early detection and identification are critical. You have to know exactly what type of thrips you have.
“Some species like chilli thrips, don’t have the below the ground stage whereas the western flower thrips, you have to be more aggressive with predator mites. We advise to deploy them as early as possible in the vegetative cycle. It’s applied as a loose broadcast and as early as the grower can put it into the greenhouse without, of course, killing it with the spray, is a good option.”
Knowledge is paramount
As pests developed resistance and consumers balked at the use of chemical crop protection, growers moved away from toxic approaches. Alison’s advice is the reason we read trade publications and attend conferences: education.
“The best investment from a managerial perspective is investing in the training of those growers in your system,” Kutz explains. “It’s common for infestations to be greatly aggravated due to lost time, and a misdiagnosis of the problem is a major contributor. Confusing thrips feeding damage for the damage that spider mites cause, for example, could lead to missing an opportunity to stop the true problem. Your results are only as good as your diagnosis.”
For those battling thrips right now, it is probably too late for extensive training and education. Keeping detailed records of what worked, when it worked, what failed, and why it failed are critical to maintaining the institutional knowledge that someone experienced at the facility may know, but a grower new to the facility will not.
Ms. Kutz echoed that sentiment. “We’re training a new generation of growers. They have to put their time and energy into learning how to scout and monitor, record-keep and record, from week to week, month to month, and year to year.”
Larger facilities are already rapidly moving towards technology platforms that use optical scanners and AI to put early detection and data on a laptop or a cellphone app. As one grower said, “the days where you keep your records in notebooks or basic Excel spreadsheets are inconsistent with the responsibility a grower has for millions of dollars of cannabis. There’s too much money involved not to have every single plant in your house getting the most light possible or worse, losing part of your crop because you didn’t catch a disease soon enough.”