Issue link: http://read.dmtmag.com/i/291333
F ruit growers are always looking for better, cheaper ways of controlling vegeta- tion under the trees in their orchards, but, in general, weed control gets more expensive and more complicated. That's partly because of the way they've managed their herbicide programs in the past. Either the weed spectrum shifted or weeds moved in that were tolerant to the herbicides they were using. So, they have to find other herbicides—newer ones, patented ones, that cost more. But it's also because of weeds, like horseweed, Palmer amaranth, and fleabane, that developed herbicide resistance on row-crop farms and blew into their orchards on the wind. Dwight Lingenfelter, a weed control specialist at Pennsylvania State University, spoke to fruit growers about weed management during the Mid-Atlantic Fruit and Vegetable Convention. He reminded growers that weeds that tolerate herbicides occur naturally. Some weeds just can't be killed by a given herbicide. So, growers should monitor orchards to identify problem weeds and see how herbicides are working. New weeds that appear may just be taking advantage of an open opportunity, meaning a different product needs to be added to the mix. Resistant weeds are different. These are mutated weeds that were once killed by a given chemical but can now survive. "Resistance drives up the cost of weed control," Lingenfelter said. Worldwide, 162 species of weeds have developed resistance to one or more kinds of chemicals that once killed them. Of these, 27 are orchard weeds, he said, but not all of them are in orchards in the United States. Worldwide, 142 weed species have become resistant to the ALS (acetolactate synthase) inhibitors, like Sandea (halosulfuron-methyl) and Matrix (rimsulfuron). Seventy-two species have become resistant to triazines and other photosynthe- 26 APRIL 15, 2014 GOOD FRUIT GROWER www.goodfruit.com SOILS & Weed Control K1075-24-115168-1 Get Ready for with Kubota! VISIT YOUR LOCAL KUBOTA DEALER FOR GREAT FINANCING OFFERS! BLUELINE EQUIPMENT Cle Elum 509-674-4544 BLUELINE EQUIPMENT George 509-785-2595 BLUELINE EQUIPMENT Pasco 509-544-6678 BLUELINE EQUIPMENT Sunnyside 509-839-2066 BLUELINE EQUIPMENT Walla Walla 509-525-4550 BLUELINE EQUIPMENT Yakima 509-248-8411 VALLEY TRACTOR & EQUIPMENT,INC. East Wenatchee 509-886-1566 M8540N UÊnx°xÊ iÌÊ*]Ê{ Þ`iÀ]Ê/ÕÀLV>À}i`ÊÕLÌ>ÊiÃiÊ}i UÊ1ÌÀ>ÊÀ>`Ê >LÊÛ>>LiÊÊUÊ{7Ê UÊ*iÀvÀ>Vi>ÌVi`Ê«iiÌÃÊÛ>>Li Managing orchard WEEDS Herbicide programs should aim to prevent shifts in species and weed resistance. by Richard Lehnert Ten important herbicide modes of action Number of resistant Mode of action WSSA group Key herbicides species ACCase Group 1 Poast, Select, Fusilade 44 ALS Group 2 Sandea, Matrix, Solida, Pruvin 142 7LSSXMRLMFMXSVW +VSYT 7YV¾ER4VS[P/IVF PGR Group 4 2,4-D, Stinger 31 PS II Group 5 Simazine, Sinbar 72 PSP Group 9 Glyphosate, Roundup, many others 25 PS I Group 22 Gramoxone 29 GS Group 10 Rely, Finale 2 PPO Group 14 Goal, Chateau, Treevix, Aim, Venue 6 Cellulose inhibitors Group 20/29 Casoron, Gallery, Alion 1 SOURCE: International Survey of Herbicide Resistant Weeds. At www.weedscience.com