Brand Hanson0 commentsSeptember 30, 2014Weeds

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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Brand Hanson6 CommentsOctober 11, 2013Weeds

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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Franz Niederholzer3 CommentsDecember 21, 2012Horticulture, Insects, Weeds

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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David Doll0 commentsJanuary 12, 2010Weeds

Organic Weed Control in Almond Orchards

Weed control within organic blocks is more critical than in conventional blocks. Weedy orchards can compete for the high value organically certified nutrients, decreasing yields and/or increasing fertilizer input costs. Organic weed control methods are also not as effective and more costly than conventionally available materials. Therefore it is important for growers to use multiple strategies to reduce weeds to a level that is economically acceptable. This entry will focus on several methods available for organic almond production weed control. These methods may also be useful in conventional orchards that have multiple areas of herbicide resistant weeds. Mulches: Plastic or fabric mulches block light, preventing weed germination or growth. These materials are often placed in the row strip before planting. Upon planting, a hole is made at the planting location so that the tree can be planted. Placing the mulches post planting can also be done. These materials control most weeds effectively while they are still intact. Materials do degrade over time due to UV light and temperature. Weed seeds that land on top of the mulches can germinate and grow. These types of materials are expensive ($250-$300 treated acre) and post-use disposal can be problematic since they are currently are not able to be recycled. Organic mulches (straw, newspaper, wood chips) can be used for early season weed management, but often interfere with harvesting practices. Organic mulches are most effective when they are at least four inches thick. Use on non-bearing age trees may be feasible. Remember, these mulches MUST be organically certified to be used. Cultivation: This is the most widely used organic weed control method. Cultivation uproots and buries weeds. This tends to work better on smaller, shallow rooted weeds. Deep cultivation is not advisable since it can damage tree roots. Usually, a mix of a tractor

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David Doll4 CommentsDecember 28, 2009Weeds

Managing Resistant Weed Populations

Over the next couple of weeks, I will be presenting information regarding weed control in an orchard system. Since herbicide resistant weeds are becoming more prevalent in the San Joaquin Valley (think Hairy Fleabane, Horseweed/marestail), it is becoming more important for growers to utilize practices that reduce the chance of herbicide resistance. Herbicide resistance is defined as the inherited ability of a plant to survive and reproduce following an exposure to a dose of herbicide that would normally kill the wild type (Think: “We used to get good control of this weed with this herbicide…”). This is different than herbicide tolerance, which is the ability of a species to survive and reproduce a herbicide treatment with no implied selection or genetic manipulation that would make the plant tolerant (Think: “We’ve never gotten dependable control of this weed with this herbicide…”). Since 1980, cases of herbicide resistant weeds within California has increased from 0 to 21 reported cases. This is mainly due to the change in tillage and herbicide use practices within agriculture. In perennial crops, growers have shifted away from orchard tillage and have become more reliant on herbicide “burn downs” to control weeds in the tree rows. Glyphosate is one of the most widely used herbicides for this practice, and, until recently, has provided good control. The formation of herbicide resistant weeds is an evolutionary process that occurs due to the application of herbicides. Since most herbicides are reliant upon a single site mode of action, it only takes a minor mutation within the plants genome to become resistant. Furthermore, the high genetic diversity of weed populations provides the opportunity for weeds to contain a mutation, thus yielding an “escape.” Once the weed is unable to be controlled by the herbicide, it produces progeny that is also resistant. These

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