Preemergence herbicide concepts for orchard crops

Cross post from the UC Weed Science blog 11-24-14. It’s that time of the year when we’re planning preemergence (aka “residual”) herbicide programs for orchard and vineyard crops in California.  Typically, these are the herbicides that are applied in the fall, winter, or early spring BEFORE weeds emerge (preemergence) and they usually affect weeds as they germinate or are just beginning to emerge from the soil. [often, people mistakenly think these herbicides kill seeds or sterilize the soil which is not actually the case]. As you’re planning the specific program for the weed problems in your orchards and vineyards (or any site, really), I thought it would be a good time to review some of the concepts of residual weed control with preemergence herbicides.  Hopefully the concepts and ideas presented in the following line drawings will help us think about what PRE herbicides can and can’t do, and how to best use them in the orchard and vineyard production system.

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Alion label changes for California orchard/vineyard crops

Cross post from the UC Weed Science blog 11-21-14 Effective this fall (2014) there will be a fairly significant change to the Alion herbicide label for California orchard and vineyard crops.  Growers and PCAs will want to be aware of this as you’re planning your dormant-season herbicide programs now that many areas of the state are getting some rain. The use patterns for Alion (active ingredient: indaziflam) has been modified for tree nuts, grapes, stone fruit, pome fruit, and olive (citrus uses were not changed).

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Managing junglerice in tree nut crops – a summer grass weed resistant to glyphosate

Cross posted from the UC Weed Science blog and originally written for the California Weed Science Society Research Update and News. -Brad Managing Junglerice in Tree Nut Crops – a summer weed resistant to glyphosate Marcelo L. Moretti1, Seth Watkins1, Bill Gary2, and Brad Hanson1 1University of California – Davis, CA; 2Mid Valley Ag – Linden, CA Junglerice, or Echinocloa colona, is a summer grass commonly found in orchards, annual crops, and roadsides of California. This weed germinates in early spring and throughout the summer and can grow and reproduce quickly. Junglerice commonly is identified by purple bands on the leaves.  However, in some populations or environmental conditions these stripes are less visible; thus a lack of banding should not be used as a definitive means of identification. In recent years, the feature that makes this summer grass really stand out in California fields is the discovery of glyphosate-resistant populations.

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Dormant Weed Control in Tree Nut Crops 2014

by Mick Canevari, Brent Holtz, and Brad Hanson Current dry weather has preempted most normal winter weed germination and growth while prolonged periods of dry soil has caused some early weeds to desiccate and die.  In most tree and vine herbicide trials conducted so far this winter–the untreated controls look similar to herbicide treatments, very clean and without weeds.  What to do at this point poses some interesting questions.  Will it rain? Most of us are worrying more about irrigating our almond trees this summer than controlling weeds right now. If you have some weed growth that germinated with rain our one December rain, or with fall and winter irrigations, you may want to apply a post-emergent herbicide now in order to prevent hard to kill weeds from becoming established.  The warm weather could allow these weeds to establish and become more difficult to control, impacting the success of later herbicide applications by increasing trash on the berm and reducing coverage. 

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Pre-emergent herbicide use in perennial crop orchards.

With the emergence of herbicide resistant weed populations, several spray programs now incorporate the use of pre-emergent herbicides. The use of these types of products provide the ability to control weeds for an extended period of time – sometimes into the late spring or early summer. In order to maximize the efficacy of these products and prevent drift, they must be applied correctly.

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Goosegrasses in nut orchards

Cross-post from UCWeedScience In the past couple of years, I’ve gotten a lot of questions about goosegrass in orchard production systems, particularly about suspected glyphosate-resistant biotypes. From a California orchard standpoint, we have two main goosegrasses (Eleusine spp) to deal with; these are goosegrass (Eleusine indica) and threespike goosegrass (Eleusine tristachya).  These species are fairly similar but have quite different flowers (see the photo below).

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Performance of Alion and Matrix combinations in 2013 trials

Repost from UCWeedScience blog One of the major research and extension areas in my program is weed control efficacy in orchards and vineyards.  During the 2012-13 growing season, we conducted about 50 herbicide efficacy trials in commercial orchards or research station sites.  Today I thought I’d share some data from 2012-13 orchard weed control efficacy experiments comparing various tank mixtures and sequential applications of Matrix (rimsulfuron) and Alion (indaziflam).  This work was primarily funded by the Almond Board of California, Bayer CropSciences, and DuPont.

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Dormant Weed Control in Tree Nut Crops 2012-2013

 Written by Mick Canevari and Brent Holtz, UCCE San Joaquin. Weeds have a tremendous capacity to spread within an orchard.  The first line of defense is  identifying the weeds you need to control, and selecting the best herbicides or cultural practices to control those weeds.  If you use the same herbicide(s) each year, a shift to tolerant weed species will ultimately take over and a loss of herbicide effectiveness will occur.  Alternating products with different modes of action at least every couple years will improve results and insure herbicides long term viability.  The UCIPM web site has charts that show which weeds are controlled by what herbicides, and an excellent weed photo gallery that includes many weed species commonly found in California for easy identification and reference http://www.ipm.ucdavis.edu/.      

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What did I learn at the Almond Board’s annual conference?

The Almond Board of California’s annual conference is a chance to connect with others in the almond industry, listen to world class researchers talk about their work, and check out a huge almond-focused trade show all at one event. The 2012 meeting was last week (Dec 11-13).  Here is a quick review of some of the things I picked up from researchers and informed industry members at that meeting…

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Rely 280 herbicide scarce for California almond market in the coming year – plan ahead

Over the past few years, herbicides with the active ingredient glufosinate (Rely, Rely 200, Rely 280) have become very important in California almonds as well as other tree nuts and grape vineyards. Glufosinate is classified as a “Group 10, or Group B” herbicide an inhibits an enzyme important in the production of the amino acids glutamine in plants.  Although it sounds similar to another amino acid inhibitor, glyhosate (the active in Roundup and others) glufosinate works quite differently than the Group 9 herbicide glyphosate.  Click here for more mode of action information from WSSA.

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