1. Drip Irrigation in Potatoes to Control Silver Scurf
(Helminthosporium Solani)
Donald McMoran donaldm@co.skagit.wa.us
Agriculture & Natural Resources Extension Educator / Director
WSU Skagit County Extension, Burlington, Washington
Viva Results
Abstract The trial located at Viva Farms in Burlington was desiccated and topped on Sept 16.
WSU NWREC
The WSU NWREC trial consisted of plots with four rows at 38-inch row spacing, ten feet
Four 10‟ rows were harvested at random of Drip Irrigation, Non-Irrigated, Reemay long, with ten feet of separation between plots. The plots were planted with the common
As farms in western Washington have changed the products they grow to higher application of 60 days, Reemay application of 60 days with drip and a Reemay
value cash crops, irrigation has become more vital to their cropping systems. „Chieftain‟ variety red potato with a mean average of 79% incidence of silver scurf. The
application at 45 days with drip. Commercial harvest of the field took place October 25. trial was planted on May 20 due to a very wet spring in Skagit County and consisted of
Reduced rotation variables combined with depletion of the agricultural land mass Each tuber was washed, weighed and graded. Commercial yield data was recorded
has created the perfect storm for an increased incidence of silver scurf four replications of drip irrigation, drip irrigation with chemigation, non-irrigated control
(figure below). There appear to be very little statistical difference between the untreated and big gun irrigation in a split replicated design. Drip application treatments included
(Helminthosporium solani). Field surveys of all of the commercial specialty potato check, drip irrigation and long season Reemay applications; however, the short season
growers in western Washington have consistently ranked silver scurf as the most chemigation with a rotation of a new DuPont fungicide called “Vertisan” (penthiopyrad)
Reemay treatment did have a substantial effect on tonnage due in part to an increase in created specifically for drip irrigation. Irrigation set times were recorded to determine
difficult disease to manage in potato production in western Washington, followed by A-sized tubers.
a solid top ten need for increased awareness in regard to irrigation watering. This total applied irrigation water and chemigation.
poster presentation focuses on the implementation of drip irrigation in potato fields
in western Washington to provide water to the crop and the use of chemigation to Viva Farms Yield Data WSU NWREC Yield Data
reduce the incidence of silver scurf. The poster highlights two fungicides that were b b b b a b b b b
applied via chemigation in the 2011 trial: “Vertisan” (Penthiopyrad) 24 oz/acre 30 30
produced by DuPont on station at WSU Mount Vernon Northwestern Washington
Research & Extension Center (WSU NWREC), with a 100% silver scurf infected
seed lot and “Quadris” (Azoxystrobin) at 9 oz/acre produced by Syngenta at an on- 24 24
TONNAGE-US YIELD
farm commercial potato field, Viva Farms. Both trials indicated a higher yield and
reduced incidence of silver scurf with a chemigation application of fungicide at 60
TONNAGE-US YIELD
days after planting (DAP). This study indicates that there is a statistical difference in 18
18
the amount of silver scurf disease that is present on the control relative to the
potatoes grown under drip irrigation with an application of fungicide. Once adopted,
this technology will reduce irrigation water usage by up to 30% over current Big-Gun 12
irrigation while producing higher quality potatoes with less incidence of silver scurf. 12
6
Viva Farms 6
A commercial drip irrigation in potatoes trial was created at Viva Farms in Burlington, 0
WA in cooperation with Tony Wisdom of Valley Pride Farms. Tony prepped, cultivated Untreated Check Drip Irrigation Gun-Irrigation Vertisan
and harvested the commercial trial in accordance with Valley Pride‟s commercial 0
agricultural practices. WSU Skagit County Extension provided the time slip labor for Drip Non Ree Ree Ree
-Irrig may may may
assisting with the installation of the drip tape, irrigating and chemigation. Rather than do ated Drip 45D
ayD
a commercial pack out on 6.5 acres it was determined early on to select samples out of rip The trial located at WSU NWREC in Mount Vernon was desiccated and topped on
the field and rate them including pounds of number 1 A‟s, B‟s and C‟s, number 2‟s and August 25. Harvest took place October 7 to ensure the maximum exposure to silver
culls. scurf and black dot pathogens in the soil. Each tuber was washed, weighed and
At Viva Farms the 60 DAP application of Quadris had a slight reduction in silver scurf graded. Twenty-five potatoes out of each plot were evaluated post harvest for silver
Viva Farms‟ plot size consisted of 6.5 acres; 4.5 acres were prepared for drip irrigation (figure below). The data is more difficult to quantify due to the low rate of silver scurf scurf and black dot. A commercial yield (figure below) and pack out of each irrigation
in potatoes planted with a six-row planter at 36-inch row spacing without the closing present on the sample; however, the growers have expressed an interest in silver scurf system treatment was completed. Please note, the Vertisan treatment did have an effect
disks. A smaller cultivator tractor was used to insert the drip tape and cover the rows. readings of zero in the 60 DAP chemigation application. on the seed tubers that were infected with silver scurf due in part to an increase in A
This practice could be avoided if the drip tape insertion shanks were inserted directly on sized tubers and a reduction in silver scurf.
the planter; however, the stakeholder was not interested in modifying his planter for a
4.5 acre field of drip irrigation. Approximately 1.5 acres of the trial plot was a control Silver Scurf Evaluations Viva Farms Silver Scurf Evaluations WSU NWREC
planted and cultivated using Valley Pride‟s commercial potato standards. The trial was a a
0.04
planted with the common „Chieftain‟ variety red potato. Due to a limited supply of b a
7
irrigation water, the drip irrigation field was split in half, 2.25 acres to the North and 2.25
acres to the south. Drip application treatments included chemigation with azoxystrobin
0.032
(Quadris) at 60 DAP at 11 oz/acre. Applied irrigation water was estimated using the
5.6
emitter flow rates and spacing as well as drip tape spacing to calculate an application
Percent Symptomatic
rate. Irrigation set times were recorded to determine total applied irrigation water and
Percent Symptomatic
chemigation. 0.024
4.2
Silver Silver
0.016 Scurf Scurf
2.8
0.008
1.4
0
0
Drip Non-Irrigated
Drip Non-Irrigated
Conclusion
Potato farmers in Skagit County appear to be irrigating more frequently using big gun systems in western Washington. By investigating new irrigation technology (drip irrigation), area
growers are given the ability to increase irrigation efficiencies and include controls on major disease issues like silver scurf. This research gives growers access to the latest irrigation
technology along with helpful hints that go a long way to using our natural resources more effectively while providing better results to the grower.
Funded by The Washington State Potato Commission