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Archive for July, 2011

Photo courtesy of Alison O'Connor

Several years ago a friend gave me hops plants, encouraging me to grow them, not because I love beer, but because I love bugs.  Each year, she assured me, her bines are crawling with ladybugs and lacewings feasting on the aphids that load the leaves. 

 The prospect of such a scenario won me over, and the hops have a home in the garden.  I’ve watched and waited for the insects, but the outbreak of historic proportions never arrived.  Until now.

Cleaning up and trellising the overgrown mass, I got up close and personal with more aphids than was comfortable.  True, they’re soft bodied and not aggressive, but the sheer numbers on the hops is alarming and the longer I worked with the bines, the more aphids I had crawling on me. 

Eventually I had to get the hoard off of me, and the stamping legs, shaking arms, and head flipping made my spouse think my iPod must be playing a rocking tune.  But soon he noticed the moving mass of pale green slowly engulfing me, the fence, and everything else in their path, and rescued me with a series of well aimed thwacks from his gloves. 

We fled the area, telling ourselves that the ladybugs have it under control, but in truth those plants are on their own.  A quick poll of gardeners this season shows many are fighting the same battle against that pear-shaped menace, which are rapidly turning our gardens into the Year of the Aphid.

Aphids are small, soft bodied, sap-sucking pests, and Colorado has several hundred species in a variety of sizes and colors, from green to black, purple, and red.  They feed by treating plants as their own personal big gulp, sucking the sap and reducing the plant’s vigor.  Aphids are born pregnant, and reproduce so quickly they rapidly build up on the plant. 

 But being soft bodied they’re easy to control.  Grab the hose and attach a nozzle that can direct a strong jet of water onto the plant.  The stream rips aphids from the stems.  If they aren’t crushed by water pressure, at least they’re flung to the ground, and due to very poor eyesight, can’t find their way back. 

 Insecticidal soap is excellent, provided the formula is made for the plant it’s sprayed upon.  Always read the label of any spray to see if your plant is listed.  Your plant must be mentioned on the label or chances are something about the spray will harm the plant.

Leaf curl aphids pose a different problem by stimulating the leaf to form a protective tent around the aphid colony.  This is a common problem on ash, plums and viburnums. Within the leaf, the colony is protected from water sprays and insecticidal soap, but there are a few beneficial insects can wriggle in and wreak havoc on leaf curl aphids. 

If you’re brave enough, grab one of the leaf curls and unroll it, ignoring the sticky sap and crushed insects that coat your hands.  Look for lady bug and lacewing larvae, or young syrphid flies, which are maggots.  Not all beneficial insects look cuddly like the ladybug, and learning to recognize pest predators is a must for savvy gardeners.  Check out the photos and information on Colorado State University Extension’s fact sheet .  To encourage beneficials, avoid spraying broad-spectrum insecticides that kill both good and bad bugs.

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Today’s post can be heard on the public radio show Crop to Cuisine, hosted by Dov Hirsch.

Crop To Cuisine

On the outskirts of Minneapolis, in a town called Eden Prairie, a vegetable patch is growing. This is not an average kitchen garden; the corn, beans, melons and tomatoes have a mission greater than feeding their gardener. Instead of filling plates with salad and side dishes, the plants here serve as canaries in a coal mine, providing early warning for problems cropping up on nearby grass.

Known as indicator plants, the vegetables are part of a holistic approach to turfgrass management on the professional practice fields of the Minnesota Vikings football team.

“The public thinks we practice at the Metrodome (inMinneapolis); they don’t know we have fields,” says Grant Davisson, Head Sports Turf Manager for the Vikings, who play in an indoor stadium. “But we have a lot of activity all year on this turf, from the end of March through the end of the season.”

With higher humidity and rainfall – they receive 30 inches per year – disease poses a challenge for managing the 210,000 square feet of turfgrass the Vikings practice on. Leaf spot, pythium, pink snow mold and Brown Patch are chronic problems.

Many high-use sports fields rely on a combination of play rotation and pesticides, but this facility is next to a riparian area protected by law. Because all of the runoff dumps into the wetland, Davisson is conservative in his turf treatments and prefers alternative means to controlling problems. “We don’t want any runoff, and we want as few applications as possible.”

That’s where the vegetables come in. In a 10-foot wide swath, watermelons, corn, tomatoes and soybeans act as sentinels for conditions that spur disease, succumbing to sickness a few days before the problems show up on the turf.

Rooted in the knowledge that disease outbreaks require the right environmental conditions to thrive, Davisson watches his vegetables for signs of oncoming turf problems. “Watermelons get hit by pythium, and though it’s not the same pythium that affects turf, they both need the exact same conditions,” he said, speaking of the disease that sends chills through turf managers’ spines due to its rapid destruction.

“It’ll hit the watermelons on the third hot, humid day and they’ll get killed, often by July 1. But once it shows up on the watermelons, I have a day or two lead time to spray the turf.” That’s all the time he needs to target his controls, knocking the dread fungus back behind scrimmage lines to keep it in check.

“Then we get cloudy days and the tomatoes get leaf spot. I’ve tracked it – three to four days later the turf gets leaf spot.” Affecting crown, rhizomes and roots in addition to leaves, in the heat of summer it kills the turf, leaving bare spots. “I hate leaf spot. It’s a bigger problem on rye than bluegrass.”

Replicating his plots in full sun and part shade, Davisson mimics the variable conditions on his fields, which receive differing amounts of sunlight. Applications of fertilizer are made at the same time to keep turf and vegetables even.

In addition to watermelon and tomatoes to watch for pythium and leaf spot, Davisson has corn and soybeans for rust. The peppers and peas are “because I like to eat them.” Harvested produce goes to coaches and staff.

Following a set schedule for fungicides calls for applications to be made every 90 days, and on fields this size, every application cost $35,000 to $40,000. But through this vegetable sentinel system, Davisson has been able to stretch out applications to 142 days between applications, saving money and lowering the impact on the environment. “It’s easily to most successful means to gauge disease,” he said, “and I save two applications per year. That’s a lot of money.”

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