New online course on diagnosing herbicide injury now available 

—Petr Kosina, UC Statewide IPM Program

A brand-new online course on Diagnosing Herbicide Injury focusing on how an herbicide injury situation can arise, what information can help diagnose symptoms during field investigations, and what tools are available to you, is now available from the UC Statewide Integrated Pest Management program (UC IPM).

When unexplained damage is noticed on a crop or other non-weed plant, herbicides are often a primary suspect. That is no surprise because herbicides are very powerful and effective tools used to control weedy plants in a wide variety of locations. However, symptoms of many other plant stresses, such as diseases and nutrient deficiencies or toxicities, can closely resemble the injury symptoms caused by herbicides. Economic implications of herbicide damage can vary–in some cases visible injury may have very little direct economic effect while in others, even slight herbicide symptoms can affect the marketability of affected plants. In addition, the presence of an unregistered herbicide on non-target crops can result in illegal residues which could have both safety and legal consequences.

The new online course was developed by Dr. Brad Hanson and Dr. Kassim Al-Khatib from the Department of Plant Sciences at UC Davis, and UC IPM instructional designers. If you are a grower, pest control adviser, or pesticide applicator, then this course is a great opportunity to learn about how to approach crop injury investigation when herbicide is suspected cause. You will learn how herbicides injure plants, how long herbicide symptoms may last and factors that may influence the time that herbicide injury symptoms are visible, possible scenarios of herbicide exposure based on uniform and variable injury patterns observed in the field, how to prepare samples for the laboratory analysis and more. 

The course content is free to anyone who wishes to view it. For those requiring a certificate of completion and continuing education units (CEUs), the regular cost is $30, but we are offering a reduced price of $15 through October 31, 2021. Diagnosing Herbicide Injury course has been approved by the California Department of Pesticide Regulation (DPR) for 1.5 continuing education units (CEU) of Other, Certified Crop Advisor (CCA) for 1.5 units (IPM), and the Arizona Department of Agriculture for 1.0 Credit.

If you are a DPR license or certificate holder with a last name beginning with letters M through Z, then this will be your year to renew. Now is a good time to check out the other UC IPM online training courses offered. All are 50% off the regular price through October 31^st. DPR strongly suggests returning renewal packets back to them by October so that your license or certificate can be renewed before it expires. Many of our courses are accredited by DPR for continuing education hours and also by the California Structural Pest Control Board (SPCB), Certified Crop Advisor (CCA), the Western Chapter of the International Society of Arboriculture (WCISA), and the Arizona Department of Agriculture.

Oakleaf goosefoot a new weed concern in the Salinas Valley

Richard Smith, Farm Advisor, UCCE Monterey County

Oakleaf goosefoot (Chenopodium glaucum) is a new weed to the Salinas Valley that has become more prevalent. Its population has been on the rise for several years and it has become a significant weed in some parts of the valley. It ranges in vegetable production fields from Castroville to King City. High populations are still spotty in the valley, but in some fields it is one of the principal weeds.  

Oakleaf goosefoot is closely related to lambsquarters (C. album) and nettleleaf goosefoot (C. murale). A variety of oakleaf goosefoot is native to eastern California (C. glaucum var. salina). The variety that we have here in the Salinas Valley is not the native, but rather the non-native variety C. glaucum var. glauca which is widely reported as a weed in many parts of the United States.

Oakleaf goosefoot can be distinguished from the other Chenopodium species by the shape and texture of the leaves. The undersides of the  leaves are white-mealy (Photo 1), while the rest of the plant is glabrous or nearly so (Photo 2). The leaves tend to be thickened and the margins of the leaves can be coarsely serrated. The plant is more prostrate than lambsquarters or nettleleaf goosefoot and that is a good way to distinguish it in the field (Photos 3-5). The stems of oakleaf goosefoot tend to be reddish.

Oakleaf goosefoot can inhabit vegetable production fields as well as the margins of fields and ditches (Photos 6-7). At this point, it appears to be susceptible to the same herbicides as the other Chenopodium species. In one trial, it was shown to be highly susceptible to the combination of Kerb and Prefar. That is the good news. The bad news is that it is spreading and is taking full advantage of opportunities along field edges to set great quantities of seed. At this point, the populations of this weed have increased to the point that several growers and PCA's have commented about it and have expressed concern for its growing populations. It is good to recognize this weed and address it as you would the other Chenopodium species.

Photo 1. Oakleaf goosefoot: above and lower leaf surfaces shown

Photo 2. Oakleaf goosefoot seedling

Photo 3. Oakleaf goosefoot showing prostrate growth form and coarsely serrated leaves.

Photo 4. Oakleaf goosefoot in comparison with lambsquarter seedling (on right).

Photo 5. Oakleaf goosefoot just below nettleleaf goosefoot seedling

Photo 6. Flush of oakleaf goosefoot seedlings and more mature plants in a ditch

Photo 7. Flush of oakleaf goosefoot growing along the edge of a ditch

Compost for a climate resilient Salinas Valley 

Compost para un Valle de Salinas resiliente al clima