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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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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