Issue link: http://read.dmtmag.com/i/114539
Pollination CONSERVING wild pollinators C ornell University has a new publication called Wild Pollinators of Eastern Apple Orchards and How to Conserve Them, compiled by Cornell's Mia Park with seven coauthors from Cornell, Penn State, and the Xerces Society. The 20-page publication describes the habits of major wild bee species (more than 80 species pollinate fruit crops in the eastern United States). The five most important are small mining bees, hornfaced bees (often called orchard bees or mason bees), blue-green sweat bees, large mining bees, and bumblebees. Many of them, the publication reminds growers, are much more effective pollinators than honeybees, so a few can go a long way. The bees are classified as ground nesters, cavity nesters (like bumblebees), and tunnel nesters. Many of these bees don't build their nests from scratch, but use existing cavities like rodent holes and plant stems. Carpenter bees, which tunnel into structural wood and are sometimes considered pests, are rated as effective apple pollinators. Part of the publication is devoted to advice on creating and conserving nesting sites. These bees are in the apple orchards at bloom time, but need alternative sources of food both during and after the apple bloom. Part of the booklet is devoted to the planting or encouragement of forage plants. A short section addresses pesticides and their toxicity levels to bees. Paraquat was cited as toxic to ground-dwelling bees and glyphosate as less so. The publication can be downloaded at www.north eastipm.org/park2012. —R. Lehnert pesticides. Both honeybees and native bees are being exposed to and need protection from pesticides. "Growers should not apply insecticides or fungicides during bloom," she said. "It's known that growers don't think fungicides are a problem, because they have low toxicity, but we and others have found that they can synergize and increase the toxicity of certain insecticides by as much as a thousandfold." If pesticides were the single major problem, the links would have been made by now, Frazier said. "Thinking now is, it's not just one thing acting independently to cause colony collapse disorder or the overall decline of pollinators—not pesticides, not mites, not diseases and viruses, not nutrition. It's likely a number of these things interacting. For instance, mites, pesticides, or poor nutrition can suppress the immune function of bees so they can't fight off the challenges of viruses or other disease." Provide a refuge. Growers can be misled into thinking that their orchards, with those billions of blossoms, are like candy stores chock-full of pollen and nectar. "Both honeybees and most native bees need a diverse source of pollen," Frazier said. "Our studies have shown that even during apple bloom, bees collect pollen from other plants." Bees in almond orchards have exactly one food source— almond flowers growing in an otherwise plant-free desert. Pollinators need places of refuge that are both free of pesticides and provide a source of pollen. The dilution effect of a source of pesticide-free pollen can reduce the impact of pesticides bees might pick up in the orchard or elsewhere, Frazier said. Studies are underway to identify the best mixture of plants, and there is some technical advice and government money available to orchardists who plant them. 5 Stay in the Pink: Use Centaur for Early Control of Scale Hood River pear grower, Larry Martin, learned the hard way the damage San Jose scale can inflict on pears. For two years in the mid-2000s, Martin's pears suffered what he characterized as "severe damage" after he stopped using the organophosphate insecticide, Imidan, in his early-season treatment program. Used to control early instar nymphs of pear psylla, the Imidan, Martin surmised, was picking up the scale. His solution: Use Centaur from Nichino America around the pink stage. ® "I've seen it as bad as to where packing houses have decided not to run them as U.S. No. 1, but run them as lower grade, because there have been that many scale marks on them," he said. "It can do quite extensive damage," Kiyokawa said. Scales can impact an orchard in two ways, according to university scientists. Bark infestations of San Jose scale can result in a decline in tree vigor, growth and productivity. Fruit infestations can result in small, deformed fruit and dark red discoloration around feeding sites. The early-season application of Centaur provides control of San Jose scale and helps control early instar pear psylla nymphs. Centaur is an insect growth regulator from Nichino America that is highly effective when applied to insects that are in their nymph Bark infestation of San Jose scale. stage. Researchers have also found some reduction in egg laying and viability of eggs from adult insects that come in contact with the active ingredient in Centaur, buprofezin. "Centaur is a good material, particularly for grape mealybug, pear psylla and San Jose scale," said John Dunley, a Wilbur-Ellis fieldman based in Wenatchee, Wash., who also uses Centaur at the pink stage. Scales overwinter usually as black caps on tree trunks and scaffolds and remain at that susceptible nymph stage until around petal fall, when they become adults. Adult female San Jose scale giving live birth to crawlers. "We get better control early in the season, because we can get better coverage, which is critical when targeting San Jose scale," Dunley said. Coverage is critical when targeting San Jose scale, as crawlers reside under the bark, and can be difficult to reach with an insecticide. Because Centaur is a contact material, it takes effect faster than products that translocate through a tree. And because Centaur is an insect growth regulator, it is easy on beneficial insects, which works well in Martin's mating disruption program, where beneficial predators are vital. "Centaur helps me with pear psylla, and it is very effective on San Jose crawlers," said Bruce Kiyokawa, a fieldman for Chamberlin Distributing in Hood River. "Centaur is also not disruptive. It doesn't seem to disrupt any beneficial that I have going on out there," Kiyokawa said. Healthy bark of apple tree. After mating, adult females produce crawlers for several weeks at a rate of about 10 per day. A single female can produce 150 to 500 crawlers during this first generation, again showing the benefits of targeting the pest early in the season, before the pest experiences its rapid population buildup. Martin has been using Centaur for "five or six years now," he said. And he plans to continue using it, "until the next magic bullet comes along." Dunley, too, said he plans to continue using Centaur. "It is an effective material," he said, "particularly when used in an early-season program." "San Jose scale is frowned upon by packing houses because it tends to be a quarantine pest in certain countries," Kiyokawa said. "They will isolate a grower's fruit if they see much of it in the packing line and not ship it into certain countries." ! 888-740-7700 www.nichino.net • www.goodfruit.com GOOD FRUIT GROWER March 15, 2013 19