Increasing Grower Involvement

Pine Tree Apple Orchard is on the shores of Pine Tree Lake near the town of White Bear Lake in Washington County. The orchard was originally planted in 1904. John Jacobson’s father came to work as a foreman for the orchard’s owners in 1950. In 1957, when the owner retired, John’s parents bought the orchard and expanded the farm which now includes 400 acres of apples, strawberries, alfalfa, and fallow fields. In 1963 John’s father, looking for a different microclimate to spread his risk and expand his apple variety options, purchased a 90 acre orchard near Preston in southeastern Minnesota. All told, Pine Tree markets apples and apple products from approximately 150 acres of productive apple orchard. The farm is now run by the second generation of Jacobsons with some assistance from the senior Jacobsons. John manages apple production.

Spraying techniques have changed since John was a boy. “When I sprayed with my Dad in the mid-70s, he would spray as a form of cheap insurance,” John remembers. “He’d spray eight cover sprays of insecticide and four or five disease sprays and he’d do it every two weeks. At first, I did the same and then people started to look at using less inputs. Dad was a real nervous guy when I started to get into IPM (integrated pest management) and once we started to look at spore maturity tests it was hard for him to watch it rain for three or four hours and not spray right away.”

One of the diseases that IPM has caused John to look at differently is apple scab. Scab is the primary disease needing control at Pine Tree’s White Bear Lake orchard. The first part of John’s new thinking on scab has to do with scab spore maturity.

“The Apple Grower’s Association funds a program where we monitor for spore development,” John says. “We have three sites around Minnesota that have leaves in corrals on the orchard floor. In late April, I’ll collect seven leaves from each site, send them to a plant pathologist friend of mine and she’ll look at them under a microscope. She’ll look for a percentage that are ready to mature. The action threshold that we work with is five percent. If we have it that means we only have the potential for infection.”

The pathologist posts the level of spore maturity onto a telephone answering machine recording that farmers can call. Some orchardists spray a pre-infection protective fungicide when the 5% threshold is reached. Protection is good for five to seven days, according to John. Since the development of post infection sprays, John has decided to wait to spray until moisture and temperature conditions are right for an actual infection. The end result of the careful monitoring is often reduced spraying levels.

Computers and answering machine recording aren’t actually what makes IPM work, though “Part of the IMP process is for a grower to get a good feel for what’s in the orchard,” John says. “You should spend time out there to determine what conditions were last fall and look at the apples that the pickers were picking. You can watch them run through the sorting equipment and you can see what the scab level was. Then you’ll know what your inoculant levels are in the orchard right now. You’ll know what your potential ascospore discharge rate is. We call that ‘PAD.’ We are running some research on PAD to see if we can read the leaves in the fall and determine the PAD.”

“Once they’re through the primary season and you don’t have apple scab on your leaves, you don’t have to spray anymore,” John said. “Before, when we were spraying heavily, we sprayed for apple scab the entire season.” John also has a summer spraying program for fungal pests such as sooty blotch and fly speck. He says he sprays for them about once a month.

Pine Tree Orchards uses an IPM monitoring system for major insect pests as well. “We put out red spheres that we bait with an apple essence so that they are a little bit more desirable,” he says.

Each orchard has different pest problems. Pine Tree’s orchard near White Bear Lake regularly has apple maggots but they are rare at the Preston orchard, according to John. As he’s worked with IPM, John’s learned more about the insect pests in his orchard. And while he’s been learning which chemicals to treat with, the pests have been changing.

“It’s always dynamic,” John says, “and you’ve got to be flexible. You need to identify your main disease and insect threat and set up a program that will deal with those and then keep an eye open for minor pests or diseases that may become a problem because of how you’re reacting to your major one. We work with the Minnesota Department of Agriculture and have traps out for minor pests such as red banded leaf roller and white apple leaf hopper. When you get into an IPM program and don’t spray as much, minor pests might build up.”

John says the major goal of IPM isn’t necessarily to save money. “We go in with the idea that we are going to try and spray less,” he says. “If that translates into saving money, that’s all well and good.” But with IPM, you could end up spraying just as much as with the old spray-by-the-calendar approach. A wet year with high potential for apple scab would keep the spray rig rolling an awful lot, for instance.

“With IPM there’s a lot more grower involvement,” John says. “You have to be knowledgeable about what’s going on in the orchard. Getting more involved in this way kind of recharged my batteries about this whole thing.”

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This article is one in a series which can be found in “A Bountiful Harvest: Minnesota Fruit and Vegetable Growers Manage Pests,” Sept., 2002. The publication was produced by the Minnesota Department of Agriculture (MDA) with funding provided by the U.S. Environmental Protection Agency, Region 5, Chicago, IL. For the entire article please go to the MDA’s web site at:
http://www.mda.state.mn.us/ipm/fandvipm.html