Orchard Weed Management Challenges For 2013
January 7, 2013 
The latest invasive insect, whether it be spotted wing drosophila or brown marmorated stink bug, gets all the attention, but it’s the pests that raise their ugly heads just about every year that cause most of the problems. Plain old weeds might not take a bite out of your crops, but they sure can take a bite out of your yields. They gobble up fertilizer and wash it down with water, growing bigger and stronger all the while.
In this, the first installment of American/Western Fruit Grower’s annual four-part Crop Protection Series, we’ll look at weeds. As always, the format is question-and-answer. We asked five questions of two industry experts, Deb Shatley, field scientist, Dow AgroSciences; and Nevada Smith, product manager – BioLogics and Alion, Bayer CropScience Company; to provide a little insight on how you might be able to better cope with weeds. Here are their answers.
Have any weeds emerged in recent years that have proved especially problematic for fruit growers?
Shatley: Yes, horseweed (marestail) and hairy fleabane.
Smith: There are numerous weeds that compete with fruit trees for resources such as water and nutrient management, and can complicate harvesting. The most challenging are those that have become resistant or have been selected due to their inherent tolerance to common herbicides.
What are the biggest weed challenges fruit growers will face in 2013?
Shatley: Completing their applications of pre-emergent herbicides before winter rains.
Smith: Hairy fleabane and horseweed (also called marestail), which are resistant to glyphosate (Roundup), are the biggest challenge. In some vineyards, willowherb seems to be increasing and is a big concern due to its impact on wine quality if not controlled.
Does glyphosate resistance continue to be a problem? With what weeds? What can growers do?
Shatley: Glyphosate resistance is an issue. Resistant fleabane and horseweed are problematic, making it key that residual herbicide programs are used rather than just a “see and spray” approach.
Smith: Resistance is continuing to increase not only in the area affected but also in the number of species that are no longer controlled. In addition to glyphosate-resistant horseweed, hairy fleabane, junglerice, and two species of ryegrass, glyphosate-resistant Palmer Amaranth has recently been documented in the Western U.S. Resistance to glyphosate is significant but certainly not the only herbicide resistance challenge that we face in orchards and vineyards. Hairy fleabane has also become resistant to paraquat, and many other weeds are now resistant to ALS-inhibiting herbicides. The most effective thing that growers can do to delay or manage resistance is to rotate herbicide modes of action or use multiple modes of action.
Has your company come out with any new herbicides and/or label additions? Growers of what crops would be interested?
Shatley: Trellis is now approved for use in bearing nuts and grapes in addition to non- bearing tree fruit, nuts, and grapes. Pindar GT starts its third season in tree nuts. Both are residual herbicides.
Smith: Bayer CropScience launched Alion herbicide in the fall of 2011 for use in tree nuts, pome fruit, stone fruit, and citrus. Since that time, we have experienced excellent weed control and grower satisfaction. We are now expanding the label to allow use in vineyards and olives so that those growers can also benefit from the long-lasting residual control and alternative chemistry that Alion provides.
Ground water contamination has become a huge issue, especially in the West. Are you taking those environmental concerns into account? How so?
Shatley: At Dow AgroSciences we recommend approaches that result in tree vigor. Stressed trees can result in over-use of agricultural products which could lead to
environmental concerns.
Smith: Environmental stewardship is very important to us at Bayer CropScience and we have taken those concerns into consideration as we were developing and now selling Alion. Based on the low use rate, the chemical properties, and what we have measured during the development of Alion, we anticipate very little movement into the soil profile when used as directed, resulting in an excellent environmental profile.
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