Today, the pear orchard in Wenatchee Valley, Washington, looks very "clean." This is how many growers and field representatives describe the recent low pressure from pests (i.e. psyllids).

Some of them suspect that integrated pest management or IPM work on research projects over the past four years has begun to pay off. Growers now usually take measures such as using kaolin and overhead washing. So far, they like what they see.

"Last year was a real home run," Dryden grower Josh Hill said. As of late July, he said that this year looks good.

Psylla pear is a major destructive pest in the Washington pear industry. It destroys the fruit with honeydew, which is a sticky by-product that can cause scars and rust spots. Since 2017, a group of colleagues from Washington State University entomologist Louis Nottingham and Wenatchee has been exploring IPM strategies to control psyllids.

Research continues, but Nottingham and his team have identified recommendations to reduce the use of pesticides. Psyllids have been building resistance: kaolin, reflective coverings, nurturing predators, and overhead washing.

All these methods will be tested with the confidence of growers in early August. By then, the third generation of adult psyllids had begun to appear, but so did the predators-if the growers had played their cards before then. It's easy to say; it's a heartbreaking trust.

"We ask people to believe that these predators will appear, which is a leap of faith," Nottingham said.

Nottingham said that the traditional mode of operation is to let growers spray the harvest in their own way, hoping to keep the third generation away for a long enough time. However, if they do not succeed, the psyllid population will explode and destroy their fruit. By that time, the trees were so dense that the spray was not effective, and the growers had rotated their way of action, and the time interval before harvest hindered their progress. Even if the growers are able to harvest, they will make the problem even bigger next year-use additional spray to kill all beneficial insects.

Nottingham says that alternative IPM methods are effective in Hood River, Oregon and Northern California, where researchers sometimes cannot even find psyllids for bioassays.

"This is not a theory," Nottingham said. "This has been proven."

The Nottingham laboratory is exploring how different predators react to different chemicals. Tianna DuPont, WSU's horticultural extension expert, is studying pest thresholds. Pullman's WSU PhD student is studying vibrational mating interruption. Researchers at the U.S. Department of Agriculture in Wapato are identifying attractants for pests and predators, and studying the rate, methods, and other best practices for releasing natural enemies. 

According to DuPont's investigation, so far, Wenatchee Valley growers seem to trust IPM at least to some extent. She calls these methods biological-based IPM because these strategies are designed to enhance biological control, such as predators, and use selective chemistry and cultural control.

"In fact, I am very encouraged by the adoption of IPM practices," DuPont said.

Her survey told her that a total of 94% of the growers and consultants surveyed reported using at least one bio-based IPM practice, affecting more than 11,000 acres of land. 

At the same time, her experiments showed that compared with the land under standard management, the population of natural enemies in the biological IPM land is more similar to the organic land, and the biological IPM treatment keeps the psyllid and honeydew levels at a relatively low level at the end of the season. Low level. In addition, the overhead washing test reduced the honeydew and fruit marks in the test block where the pressure of the psyllid caused the obvious stickiness.

Ray Schmitten, the orchard owner and director of agricultural services at Blue Star Growers, is a believer.

"This year, the pest control of Psylla sylvestris has progressed smoothly, some of the best I have seen in the area," he said. In fact, many growers do not need to open the overhead cleaning before mid-July because the orchard is very clean. 

The grower has precisely mastered the spraying time and allowed the population to develop some to see where the hot spots are. He agreed, it was difficult.

"For us growers, it is difficult to push the limits of our trees to become sticky to the point where we learn something," he said.

Hill of Dryden has been using IPM on a 6-acre plot of Anjous and Bartletts, which is usually not one of his strong. Last year, he saw for the first time that the results of IPM blocks were similar to his traditional blocks. The pressure is low and the return of the packer is high. 

"Last year was the first year that things were put in place," he said.

Maybe it was just luck, so his farm invested in an overhead washing machine and made a backup plan for himself. 

Overhead washing has a long history.

According to Kameron Miller, a grower in the Kashmir region, tree washing in Wenatchee Valley was popular in the 1960s, when growers used galvanized pipes to erect an overhead sprinkler system. A few years later, when PVC became more readily available and growers were more worried about fire blight than washing off sprays, they fell out of favor. 

Now that the spray options are limited, the residual span is shorter, the psyllids have developed resistance, and washing is making a comeback. Miller and his twin brother Kerry came up with an affordable farm project that uses sprinklers under the canopy. Some growers have followed suit. After three years of overhead cleaning, they believe that their packaging has increased by 3% and saved them one round of spraying every year.

To avoid the risk of fire blight, WSU recommends limiting overhead cleaning to one or two times per season, specifically for removing honeydew, rather than simply irrigating from above.

Other IPM methods also have a long history.

"We have been spraying kaolin," Miller said. It works, but it is too close to the harvest and it will turn off the picker. The WSU team does not recommend spraying kaolin close to harvest, it is also a sunburn protector. 

Miller said that today, traditional growers have no choice but to adopt IPM. Sprays are not as effective as before. But predators are also unpredictable. For example, last year, ladybirds swarmed in his orchard like bees and suppressed Tetranychus urticae. This year, not so many.

"If you rely on predators, they are the least reliable thing ever," he said.

Nottingham agreed. The number of predators changes every year. The same is true for pest populations. But the IPM strategy should not be foolproof. They gradually lower the curve, especially if everyone is involved.

"Those ups and downs are still happening, but at a much lower level," he said. 

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