David Doll0 commentsApril 17, 2020Weeds

Herbicide Drift: PPO Herbicides

Protoporphyrinogen oxidase (PPO) enzyme inhibitors are a common class of herbicides used within almonds. They include the active ingredients oxyfluorfen and carfentrazone-ethyl. These compounds are reasonably effective in managing broadleaf weeds. Due to their limited translocation within the plant, they are often referred to as contact herbicides even though they can also provide residual control at higher rates. Off-target drift by these herbicides can damage almonds. Generally, however, the effects are more short-term due to the contact nature of these products on foliage. The reduced medium- to long-term effects of herbicide drift is useful when utilizing these chemistries on young trees. Even so, drift should be avoided as this can cause leaf spotting and loss, reducing photosynthetic area. More information on PPO herbicides and drift can be found here. PPO herbicides have a distinctive pattern when drifted onto almond leaves. At the location where the droplet lands, syptoms occur relatively rapidly. The lesion typically has a yellow outer-halo, a purple middle-halo, and a brown lesion in the center. These lesions fall out of the leaves in 2-3 weeks, giving the appearance of shot-hole fungus.

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David Doll0 commentsDecember 14, 2013Weeds

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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Brand Hanson4 CommentsOctober 29, 2012Weeds

Glyphosate-Resistant Weeds in Orchards – Recent UC IPM Publications

Last winter, I particpated in a series of seven half-day workshops in California, Oregon, and Washington on herbicide-resistant weeds.  These workshops were organized by Kassim Al-Khatib from the Univeristy of California Integrated Pest Management (IPM) Program and had a special focus on glyphosate-resistant weeds in tree and vine crops. In preparation for these workshops, we wrote a series of extension publications that I wanted to share today.  The publications and resulting presentations were prepared by weed scientists from various Universities, Cooperative Extension, and USDA-ARS and included various aspects of herbicide resistance in permanent crops.  Even as somone who thinks about herbicide resistance every day, I found the bulletins and presentations to be tremendously informative.  These included: Selection Pressure, Shifting Populations, and Herbicide Resistance and Tolerance by Brad Hanson, Albert Fischer, Anil Shrestha, Marie Jasieniuk, Ed Peachey, Rick Boydston, Tim Miller, Kassim Al-Khatib. PPT slide handouts available here: Glyphosate Stewardship: Keeping an Effective Herbicide Effective by Tim Miller, Brad Hanson, Ed Peachey, Rick Boydston, Kassim Al-Khatib Preventing and Managing Glyphosate-Resistant Weeds in Orchards and Vineyards by Ed Peachey, Rick Boydston, Brad Hanson, Kassim Al-Khatib Managing Glyphosate-Resistant Weeds in Glyphosate-Resistant Crops by Kassim Al-Khatib, Brad Hanson, Tim Miller, Ed Peachey, Rick Boydston These bulletins are being published by UC-IPM and the near-final versions are available right now  at this link.  Or at: http://www.ipm.ucdavis.edu/IPMPROJECT/glyphosateresistance.html. Take care, Brad Read more orchard weed management blog posts at UC Weed Science

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