MCP treatments can be tricky

D’Anjou pears from the 2015 harvest being packed in Peshastin, Washington. (TJ Mullinax/Good Fruit Grower)

It’s no secret MCP treatments on pears can be a highly complicated business that affects fruit quality, ripening and, ultimately, consumer satisfaction.

But in what may be among the largest trials ever done in the postharvest world, a recent study by AgroFresh Inc. using two of its products shows what many have long suspected: It comes down to the details. More specifically, one rate at one time cannot be used across all crops.

The study marks another step in the process of trying to better understand the relationship between MCP (1-methylcyclopropene) — both in the orchard and in the packing house — and the end product.

“They basically learned there’s some sweet spots for utilizing these products, and you can’t use any of them one way and expect them to work in all situations,” said Bob Gix, horticulturist for Blue Star Growers in Cashmere, Washington, which collaborated on the study.

“There’s some good fits, depending on a warehouse’s marketing program and depending on a grower’s harvest timing and schedule. It’s a very good tool,” he said. “But I think individual warehouses and individual growers need to figure out how it fits for them, and the most critical postharvest use of the product should be targeted to your market.”

The pear problem

The speed at which fruit loses quality and freshness is determined by the rate and amount of a natural hormone the plant generates internally: ethylene.

For growers and packers who want to sell fruit outside of its normal growing season, ethylene plays a key role in how successfully they can store and transport it. Many have increasingly turned to MCP to suppress ethylene production and the ripening process.

It’s worked well for apples. AgroFresh Inc., the Collegeville, Pennsylvania-based developer of MCP products including SmartFresh and Harvista, has created extensive use recommendations and protocols for growers since MCP was approved for use in the U.S. 15 years ago.

However, pear growers have been waiting for more precise recommendations.

The company has done MCP trials on pears across the world, including the United States, Chile and the Netherlands, but the results and recommendations differ by variety and region, said Fernando Edagi, former AgroFresh technical manager who led the study.

He has since moved to Apeel Sciences, a company that develops plant-derived products for shelf-life extension, but presented findings of the study at the Washington State University Fruit School in March.

“Here in Washington or Oregon, we don’t treat pears with over 300 parts per billion. It doesn’t go over that, because we know that if you go over that, you’re not going to ripen them. It’s impossible,” Edagi said. “But if you go to California — it’s not that far — you can treat to 600, 900 parts per billion and the fruit will ripen. Of course, it’s weather related; same variety, Bartlett.”

Meanwhile, the standard rate for apples in the Pacific Northwest is 1,000 parts per billion.

The trial was not intended to examine what happens to the fruit in the warehouse, but rather to explore the condition of the fruit under various treatments when it goes to the consumer, Edagi said.

And as trials go, it was big. Blue Star harvested 144 bins of fruit for the study in 2016, which evaluated fruit based on low and high rates of MCP applications, both in the orchard and in the packing house, regular atmosphere and controlled atmosphere storage and timings, and various ripening protocols on three different pear varieties — Bartlett, Bosc and d’Anjou — for a total of 1,944 combinations (including the control). Overall, more than 213,000 pieces of fruit were evaluated for firmness, color, sugar and acids and weight.

So what’s the verdict?

As expected, the results varied, and Edagi stressed that they were specific to the Cashmere area in North Central Washington. How pears would have fared in Oregon’s Hood River Valley, for instance, in a dissimilar growing environment, or even in Cashmere in a new year with different weather conditions, would be hard to say.

Blue Star harvested at least 24 bins for two blocks each of each variety — one control and one treated with Harvista (60 grams/acre, targeted at about 10 days before harvest) — with each then further divided by a grower-selected commercial harvest date and a delayed harvest date (seven days later), by low and high rates of SmartFresh at postharvest (varied by variety, 150 parts per billion and 300 parts per billion for Bartlett, 100 and 200 for d’Anjou, and 200 and 300 for Bosc), and by regular and controlled atmosphere with ordered removal dates.

They repeated the study in 2017 to similar results.

For Bartletts, generally, Edagi said, if growers and packers want to sell fruit in September or October from regular atmosphere storage, they don’t need to apply MCP in the orchard or the packing house.

If they want to sell fruit in November or December, then they need to consider using Harvista or SmartFresh or a combination of both. They also need the products if they want to sell fruit from controlled atmosphere storage January through April.

“We understand it’s very challenging in August and September, and you don’t know when you’re going to sell that fruit,” he said. “That’s why I think the combination of Harvista and a low rate of SmartFresh gives you the biggest flexibility, because if you want to sell the fruit in November or April, you can. You just need to work on the right ripening protocol for that.”

Bartlett growers, in particular, could hit the market in February successfully with that strategy, he said.

In addition, delaying harvest a week by applying Harvista increased yields overall by 17 percent, and even improved size for Bartletts and didn’t sacrifice color, Edagi said.

“If I’m a grower and I’m a packer and I have a budget and I need to treat something with MCP, I’ll definitely spend my money on Harvista, not SmartFresh,” Edagi said. “That will dramatically increase our chances of success.”

But it’s complicated, he noted, because if a d’Anjou grower wants to sell in June, Harvista alone is not going to cut it. “You’re going to have to have a postharvest application of SmartFresh to have that scald control.”

However, the study showed that growers and packers who use both Harvista and SmartFresh and/or want to sell fruit November through March should be using reduced rates.

The challenge is that few growers have solid blocks of just Bartletts or d’Anjous, Gix said. “It’s a little harder to find, in some of the traditional growing areas, the perfect Harvista fit to spray in on blocks,” he said. “But AgroFresh has really stepped up to the plate and been a really, really good partner with the pear industry to better understand how their product impacts pear ripening.”

Does the study solve all of the pear ripening issues? No. Only about a quarter of Northwest pears are treated with MCP and the industry still faces hurdles getting pears to ripen for consumers, Edagi said. But growers should work with AgroFresh to ensure the best use of the products following the results of the study.

Like anything, MCP is a tool, Gix said. “Tools, when used well, can be beneficial to the industry. It’s a tool when not used well that can be detrimental to the industry,” he said. “Through their study, we have some targeted rates and ways to utilize that product in a way that will deliver a better product to the consumer.” •

—by Shannon Dininny