SWD Berry Management Programs 2015
Bev Gerdeman, Lynell Tanigoshi and Hollis Spitler
WSU Mount Vernon Northwestern Washington Research & Extension Center
SWD Control Strategies:
• In blueberry, an initial application of a product with long residual (e.g., Danitol® 2.4 EC) provides a >2 week boost in activity for subsequent applications of less residual products.
• Carryover effects (layering of insecticides) increase protection as the season progresses, coinciding with increasing SWD populations.
• Current small fruit SWD programs also provide protection from most other pests.
Skagit Valley along with the rest of Washington State experienced its warmest year on record in 2014 and its warmest winter this year. Bellingham’s average temperature was on average 6.2°F higher than the average normal temperature for February, according to the Office of the Washington State Climatologist. Fruiting crops are on average 2-3 weeks early and SWD adults are already being trapped in high numbers along field borders. It could be a very interesting year for pests like spotted wing drosophila.
An early SWD season in blueberry will not be as big a challenge as that in red raspberry, because hives are pulled in blueberry well before ripening berries become susceptible. While ‘Duke’s have been able to skirt economic damage from SWD in the last couple of years, an early SWD season this year may result in higher than normal pest pressure for early season varieties. The current industry program of rotation between a pyrethroid and an organophosphate (OP) should remain effective against SWD. Danitol® exhibits the longest residual of any pyrethroid we have tested and growers are limited to two applications/season. We suggest using Danitol as the leadoff spray for the blueberry season, which is comprised of rotations primarily between pyrethroids and organophosphates. Pyrethroids degrade more slowly over time than organophosphates, which experience a precipitous drop in residues and efficacy after three days. Normally in a 6-7 day rotation, an OP application would leave berries susceptible for a period of 3-4 days before another insecticide is applied, but Danitol extends the residual efficacy of the OP.
Optional programs could include:
1. Danitol - malathion - Mustang Maxx® - malathion - Danitol – malathion.
2. Danitol - Imidan® - Mustang Maxx - Entrust® - Danitol – Imidan.
The second program includes a lesser residual product Entrust, but not scheduled until after a safe layer of pyrethroids and OPs have been applied to supplement its efficacy.
Challenges to an early SWD season in red raspberry:
For the past couple of seasons, ‘Meeker’s have not exhibited much SWD damage until about half way through the season in mid-July. An early SWD season in red raspberry however could create a larger pest reservoir than usual from the trickle of ripening fruit prior to harvest. Typically, quality of first pick is not the best and this situation could be worsened if SWD invades and infests fruit earlier than usual. Unlike blueberry, honey bees are pollinating up until the hives are pulled just before the Brigade® cleanup spray, three days before first pick. To decrease the toehold by SWD and minimize bee poisoning, growers can apply malathion in late evening near the end of bloom. At that time flowering has diminished and fewer bees are working the field. An application in late evening, after foraging, better ensures residues are dry by morning, however be aware heavy dew can rehydrate dried residues. Honey bees are killed if directly treated by malathion and by contact with wet residues. Bees are flying by sunrise the next morning after temperatures reach 50°F. A late evening application of malathion can be made five days prior to the Brigade cleanup spray. That means berries are protected eight days prior to the first pick instead of just three days. If berries require approximately five days from first color to ripe, a large portion of the crop can be protected which should decrease the economic damage in that first pick due to an early SWD season.
Sample programs for red raspberry could resemble these:
1. Malathion at night, 5 days before cleanup spray -
hives pulled - Brigade, cleanup spray -
malathion - Mustang Maxx - malathion - Danitol.
2. Malathion at night, 5 days before cleanup spray -
hives pulled – Brigade, cleanup spray -
malathion - Mustang Maxx - Assail® - Danitol.
To maximize residual carryover of pyrethroids, a less residual product such as Assail is not applied until the fourth rotational position.
To minimize economic injury from an early SWD season:
• Continue with a pyrethroid/organophosphate rotation for both blueberry and red raspberry.
• Blueberry - lead off with Danitol.
• Red Raspberry - apply malathion in the evening, late bloom 5 days prior to the cleanup spray.
• Blueberry and Red Raspberry - work in less residual products no earlier than the fourth rotational position.