Study: Biological treatments in early production of tomatoes

At Vineland Research and Innovation Centre in Ontario, Plant Pathology Research Technician Travis Cranmer is working to analyze the efficacy of biopesticides against root diseases in hydroponic tomato production.

Cranmer’s objective is to imitate the production of a commercial grower. He uses both available biological products and those soon to be released in the early stages of grafted and nongrafted plants.

The study’s findings were released at the Canadian Greenhouse Conference in Niagara Falls in October 2016. Cranmer shares some of his conclusions below.

Produce Grower: Can you give us an overview of the bio-inoculant study?

Travis Cranmer: I’m looking specifically at microorganisms, whether they are bacterial or fungal — as well as microbial extracts — to see how they can suppress pathogen development. Our pre-commercial greenhouse mimics the same fertilizer, equipment, cultivar, media and growing practices that Ontario greenhouse vegetable growers would have. My experiment is also set up to test a wide range of products on the same crop at the same time, without contaminating plants on adjacent slabs.

We inoculated these products with biopesticides, as we know that plants actively respond to a variety of environmental stimuli. These stimuli can either induce or condition plant host defenses, to subsequently suppress infection from pathogens such as Pythium, or Fusarium, or other brute raw pathogens that hydroponic growers often have problems with.

My role is to see how they perform, so that a grower can make an informed decision when they select the product based on their growing practices, the media they use or the cultivar that they choose.

PG: Why did you decide to look at Pythium first?

TC: I wouldn’t say it’s the most severe pathogen, but a lot of growers struggle with it. It’s something that even a grower who is careful can sometimes have. It’s a relatively easy pathogen to inoculate and to monitor. We developed a [biological assessment] for it, and now we’re answering questions about Pythium with different media.

With Pythium, wilting occurs seven, 10, 14 days after inoculation. As those plants wilt following innoculation with Pythium, we record any symptom development. We take a height measurement at week 9 for the grafted, and week 7 for ungrafted plants. We do fresh weight, open up slabs, flip them over, look at root development and root rot, and we rate them on a 0 to 100-percent root rot scale. Then, we have a disease severity index that we also use.

PG: And what have you discovered about Pythium in tomatoes?

TC: We have found that we can see significant differences at the nine-week tomato harvest. It’s very likely that if we were to let the crop grow for another six months, the plants with poor root development would be stunted and have smaller yields. That’s why we test everything over so many weeks.

Our healthy controls had excellent root development, and they scored near 100 percent. And our infested controls, the grafted ones, really got swept off. But [with] the ungrafted, there were significant differences. Some of the products such as Trianum, Rootshield, BW240, had better root development and performed almost as well as the chemical control.

PG: What studies are on the horizon for hydroponic tomato pest and disease?

TC: We’re switching [the media] up. We’re basically using most of the products [from the first experiment], and a couple more. And instead of looking at grafted versus ungrafted, we’re looking at coco versus rockwool. We’re still trying to figure out which product works best for Pythium. We’d also like to know which product works best to cause suppression of whitefly or twospotted spider mite. And it’s tricky, because these biologicals don’t behave the same way in every growing media. I can’t say right now which product is our clear frontrunner, and which ones are runners up. But at the end of the day, I want to be able to help growers make informed decisions — to be able to pick the right bio-inoculant for their crop.

Editor’s Note: This interview was edited for length and clarity.