Processed kaolin clay, commonly known as Surround, is non-charged, non-toxic, and best of all, has an organic label. Originally used as an insect deterrent for pear psylla, recently it has been found to lower plant and fruit temperature resulting in lower sunburn rates in apples. Permeable to gas and liquid, Surround claims it keeps fruit as cool as silicon oxide (SiO2), improves the quality of the fruit, and works better than overhead cooling.
For the past two years, Jim McFerson and his team at the Washington Tree Fruit Research Commission in Wenatchee, Wash. have done on-orchard trials to see if Surround really does do as good a job as over-head cooling or if the reduced sunburn rate was a fluke. The answer is: Mostly.
According to the published results, treated fruit appeared to have less sunburn and a better fruit finish. The Surround is also easily cleaned off the fruit. On average in 1999, only about 1.5 percent of the treated fruit was sunburned when Surround was applied every two weeks. About 2.1 percent of the fruit was sunburned when applied every four weeks. When no fruit was treated, about 6.5 percent were sunburned.
On most orchard trials, the long rows treated with Surround were random. Control rows were next to over-head cooled rows or treated rows to make sure results were accurate.
Generally, Laurie Wishkowski of Wishaven Ranch in Finley, Wash. loses about 10 percent of her crop due to sunburn but last season she only lost four to five percent and she attributes that drop to Surround. "Any time you can cut your cullage rate, it's worthwhile," she said.
On a number of the green cultivars, especially the Granny Smiths, Surround prevented blush on the fruit. Mario Martinez of Washington Fruit and Produce in Mattawa, Wash. said it kept his Grannys greener and less sunburned.
Rather than averting just sunburn problems, which Wishkowski feels isn't much of a concern with Pink Ladies, she says it improved the fruit's finish. She applied Surround to two acres of Pink Ladies in 1999.
One of the most consistent comments about Surround as a product is that is was "easy" to use. Easy to mix, easy to use, easy to see where it had been applied and easy to clean off.
Having used Surround for the first time during the 1999 growing season, Wishkowski agrees it is easy to us. "It dissolves well and no one minded applying it. We could use long-sleeved shirts rather than the heavy spraying gear that can be so hot in the middle of summer," she said.
Wishkowski also liked that there was no temperature limitation and only the wind kept them from spraying when they wanted to. She felt many had the wrong impression when they first looked at the treated fruit because it looks like it is covered in chemical pesticide, but once she explained what it was their fears were dispelled. Initially Wishkowski was concerned that the product would cause mite problems but she didn't experience any.
"One of the great things about this product is that you can put it on and ignore it. It's a lot easier than having to worry about turning the micro-jets on and off," Wishkowski said.
In addition to its ease and comparable results to over-head cooling, Wishkowski believes that having a comparable alternative to over-head cooling is a necessity because the amount of water needed for over-head cooling will soon become a luxury. In addition to reducing water costs, using Surround eliminates problems with fungus, bacteria and rots that result from using so much water.
However, all the results weren't great ones. In Martinez's experience, he felt the fruit tended to be smaller. Wishkowski also felt there was a slight delay in maturity but did not think it was enough to make a significant difference. Martinez feels the Surround may not have been as good at reducing sunburn as the over-head cooling but this year he will try heavier rates to see if it makes a difference.
Surround also makes color picking more difficult for the pickers because of the slightly opaque film left on the fruit. Martinez said his pickers left more fruit on the tree where Surround was applied than on areas where it wasn't. Mike Clayton of Clayton Orchards in Orondo, Wash. felt the only drawback to the product was how difficult it made color picking and sorting. Dave Putnam of Indian Cliff Orchards in Palisades, Wash., on the other hand, said color picking was difficult at first but the eye gets used to the film and color picking becomes as easy as without the Surround on the fruit.
Pickers, at least on Wishkowski's orchard, asked for masks during the first round of picking because the Surround "fluffed" off and was really dusty. She doesn't know whether to attribute the dustiness to the intense heat at the time or whether the pickers just weren't used to the product, but she says the workers didn't ask for masks during the second picking.
On varieties with sensitive skin colors, like Galas and Jonagolds, the Surround left blotchy spots on the skin. Imagine putting sun block on your stomach, but not everywhere. When you look at your skin, some spots are light and the others dark. This is the same effect the Surround had on the colors of more sensitive varieties. One of the assumed reasons for the blotchiness was the surfactant mixed in with the clay.
Wishkowski said she was more hesitant to use the product on her Galas unless the surfactant was changed to diminish the blotchy effect. Though Putnam didn't like the blotchy effect on his Galas, he feels the product is good enough to try this year on his Granny Smiths.
"It wasn't a good year to test for sunburn because of the weather [in Palisades]," said Putnam. "It didn't make much difference one way or the other."
Another reason the tests may not have gone as well as hoped is because the manufacturers did not deliver the product early enough in the season. Most of the growers received the Surround in early July, which in many parts of the state is too late to prevent sun damage. Both Martinez and Wishkowski think the product may work better this year if they can begin applying in early June.
Martinez also plans to use larger amounts of the product to see if the dosage increase makes a difference, but still on a small scale. He wants to wait until there is more definitive information before he uses it on more trees than his original trial area.
At about $40 per acre per application, with an average of 4 applications per summer, the input costs can pile up. "The Surround is pretty pricey," said Clayton. "I would use twice as much if it was half as expensive. I would be really aggressive with it if was $20 per acre."
"It is expensive but you have to counterweigh against the costs and benefits. Returns are a big consideration of economics until results are more determined," said Martinez.
Even if he doesn't use Surround consistently on an annual basis, Clayton thinks Surround is a great way to tell how well his sprayers are working. "If I don't do a whole block with Surround, I'll at least buy a bag to check how my sprayers are doing every year."
But Wishkowski has much more faith in the product. "We're limited as far as how much we can over-head cool at onc time and this gives me another tool to use," she said. "The industry as a whole has gotten a lot better about being specific with where plant varieties do best and not fighting so much with Mother Nature. Water has become such a precious commodity, programs like this should be explored."