Richard Smith, Vegetable Crops Advisor; Kirsten Pearsons, Entomology Advisor; and Yu-Chen Wang, Plant Pathology Advisor, UCCE Monterey, Santa Cruz and San Benito Counties
This is just a reminder of the need to control weeds on ranches this winter to reduce the overwintering habitat for Impatiens Necrotic Spot Virus (INSV). In the absence of lettuce fields during the winter, INSV survives in winter weeds. Daniel Hasegawa has identified the top ten weed hosts for INSV (Table 1) from survey work conducted over the past three years. Seven of the ten are common winter weeds that can be found along roadsides and in equipment yards, ditches, around valves, on banks and other areas on ranches. The winter provides an excellent opportunity for us to strike a blow to the survival of INSV in these and other key winter weeds.
Table 1. Top ten weed hosts of INSV and their seasonality (from Daniel Hasegawa)
In addition to controlling weeds on ranches, it is important to look at areas surrounding your farms. Weed hosts commonly occur around industrial and commercial sites. In early 2022 we observed an outbreak of INSV that was traced to patches of weeds in an industrial site that escaped everyone's attention. This winter, it is important for growers to pay attention to weeds on properties that are adjacent to their farms. Talking with neighbors and getting them to control weeds in areas that may seem unimportant is critical to curbing early-season outbreaks of INSV. Most neighbors are probably more than willing to control weed host plants if asked. But on properties where the property manager is uncooperative, an infestation of weeds that harbors a pest that threatens lettuce can be deemed a nuisance and be subject to a weed abatement order by the County Agricultural Commissioner.
The Grower Shipper Association (GSA) has been working with the Monterey County Dept. of Public Works and the Board of Supervisors to streamline the process controlling weeds along county road right-of-ways. The process involved a modification of an encroachment permit to allow growers to treat weeds on the county right-of-way that boarder their ranches. Below is a description of the process provided by Chris Valadez, President, GSA:
The County of Monterey recently adopted an urgency ordinance authorizing a temporary encroachment permit (permit) to Grower-Shipper to eradicate weeds on County rights-of-way, namely along County roads, as a new tool to protect against the spread of INSV.
How this Works:
(1A): A farm, licensed pest control advisor, or contracted licensed advisor (inc. pest control business) must complete and return this use 'agreement' and request a unique copy of the permit from Grower-Shipper, by email: joann@growershipper.com. The agreement must be completed and returned to joann@growershipper.com after which a copy of the permit will be issued.
If a farm intends to conduct weed abatement in a County right-of-way adjacent to their farm property, they must contact the Monterey County Ag Commissioner's Office to add adjacent, off-farm areas to their permit and subsequently follow pesticide use reporting requirements.
OR:
(1B): If you intend to eradicate weeds in areas either adjacent to a farm, in a County right-of-way (along a County road), or areas not adjacent to a farm but are in a County right-of-way along a County road, the farm, licensed pest control advisor, or contracted advisor (inc. pest control business) must complete and return this use 'agreement' and request BOTH a unique copy of the permit and a copy of Grower-Shipper's Operator ID documentation, by email: joann@growershipper.com. The agreement must be completed and returned, after which a copy of the permit and Operator ID information will be issued. Here, instead of performing the abatement under a farm's permit, the abatement would be conducted under Grower-Shipper's Operator ID. You are responsible for pesticide use reporting under this Operator ID.
Once you have a completed use agreement, a unique permit copy, and Grower-Shipper's Operator ID documentation (if applicable), you may proceed by giving a minimum 48-hour advance notice or Notice of Intent, indicating the anticipated date, time, and location of where the abatement will be conducted. Please include your permit copy with your advance notice in an email to Encroachment@co.monterey.ca.us, copying/cc: joann@growershipper.com.
If you have a question about whether a certain area is in fact along a County maintained road, visit maps.co.monterey.ca.us/wab/parcelreportwebapp/ to identify the area in question and to find if it is a County 'maintained' road.
To discuss this further, contact chris@growershipper.com.
In summary, INSV is at its most vulnerable state during the winter and efforts that we take to control them can help reduce problems later. For the most part, INSV is surviving in the winter weeds and efforts to control the weeds can go a long way to reduce the loads of the virus for the start of the 2023 lettuce production season.