Monitoring Nurseries Key to Preventing the Spread of GWSS
Nursery stock is a high-risk commodity for spreading the glassy-winged sharpshooter (GWSS). Approximately 53 percent of California’s 13,000 licensed nurseries are located in GWSS-infested counties. Many of these nurseries ship to the non-infested areas of the state.
The CDFA’s Pierce’s Disease Control Program coordinates county activities throughout the state to mitigate the risk of moving the GWSS on nursery stock. These activities include:
1. Inspection of nursery stock in infested areas prior to shipping to non-infested areas
2. Treatment of nursery stock when necessary
3. Certification of shipments
4. Inspection of nursery stock at receiving nurseries prior to sale
5. Trapping in and near nurseries in infested and non-infested areas.
In 2017, there were 36,700 shipments of nursery stock from infested areas to non-infested areas. Viable life stages of GWSS were discovered at destination in only six of these shipments. Origin county inspectors stopped 108 egg masses, nine nymphs, and six adult GWSS from moving in nursery stock shipments.
Nursery Regulatory Program Update
From January 1, 2018 through March 31, 2018, there were 8,546 nursery stock shipments from the GWSS generally-infested areas to non-infested areas of the state. Shipments were down by approximately 649 compared to the first three months of 2017. No regulatory actions have needed to be taken so far this year.
During outgoing inspections from January through March 31, 2018, origin county inspectors stopped 14 egg masses from moving in nursery stock shipments.
Nursery Stock Approved Treatment Program (ATP)
From January 1, 2018 through March 31, 2018, there were 3,235 ATP shipments consisting of 892,656 plants. The number of ATP shipments and plants for the same time frame in 2017 were 2,847 and 991,437, respectively. No regulatory actions have been necessary this year.
The “100 Days War”
Right now there’s a war going on in California. It’s not your typical war, but it happens every year from the end of January into June.
“The ‘100 Days War’ is how the nursery industry refers to this period, because that’s when many of them ship roughly 70% of their nursery stock production for the entire year,” said David House, President of Village Nurseries. “Some of the nurseries that ship to the big retailers are operating 24 hours a day, six days a week during this time,” added House.
During this period major holidays, including Valentine’s Day, Easter, Mother’s Day and Father’s Day, take place, all of which involve giving flowers. Then, to top it all off, it’s also when people look around their yards and decide to do some spring landscaping and plant vegetable gardens. As a result, some nurseries are shipping as many as 20,000 plants a day during this time.
Right in the middle of this “war” is when the first glassy-winged sharpshooters (GWSS) of the season begin to emerge as well. With over half of California’s nurseries located in Southern California’s GWSS infested areas, the challenge is to keep plant shipments free of GWSS. During the first two months of 2018 there were 5,207 shipments from GWSS-infested areas to non-infested areas of the state. That’s up by 456 loads, or over nine percent, compared to the first two months of 2017.
With the GWSS populations increasing during this period, there’s an added chance of egg masses being present on nursery stock. Plants that have been identified as hosts for GWSS receive extra attention and efforts by nurseries, which trap, treat, inspect, and safeguard plants to make sure they are free of GWSS.
Plants shipped to non-infested areas must be certified as GWSS-free before being shipped and may be inspected once again when they arrive at their GWSS-free destinations before they are released for sale at local outlets. “The county teams that provide inspection and certification services have been very cooperative despite their workloads,” said Robert L. Crudup, Jr., President and CEO of BrightView Tree Company. “It requires a working partnership to smooth out any bottlenecks and to keep the lines of communication open.”
All this effort by nurseries and county agricultural staff really pays off. In 2017, GWSS were found in only six of 36,700 shipments, a success rate of 99.98 percent.
And what happens in the rare event that GWSS adults, nymphs, or egg masses are found in a shipment at their destination? The shipment may either be destroyed, returned to origin, or rendered pest-free and released.
With the increase over last year’s numbers, this year’s “100 Days War” looks to be a busy one. All the troops, from nursery workers to county agricultural commissioners’ staffs, stand ready to once again help stop the spread of GWSS.