PCC MarchApril Final Draft
Plastic Mulches Reduce Spotted-Wing Drosophila Infestation in Fall-Bearing Raspberry By HANNA MCINTOSH | University of Wisconsin, Madison CHRISTELLE GUÉDOT | University of Wisconsin, Madison AMAYA ATUCHA | University of Wisconsin, Madison Spotted-wing drosophila (SWD), Drosophila suzukii, is an invasive vinegar fly and a major pest of softskinned fruit crops. The fly was first detected in the continental U.S. in 2008 1 and has quickly spread from its native range in Eastern Asia throughout the U.S. and into most major fruit-producing regions of the world 2 . For smallscale fruit growers, damage from this pest substantially reduces the yield of marketable fruit, making susceptible crops challenging to grow economically and sustainably 3,4 . For large-scale growers, the presence of SWD can lead to complete crop loss due to processors’ zero-tolerance policies for insect infestation 5 . Spotted-wing drosophila life cycle (courtesy Jana Lee, USDA-ARS.) Biology Vinegar flies typically lay their eggs in damaged or rotting fruit, but female SWD have a highly serrated ovipositor that allows them to saw through the skin of undamaged, ripening fruit 6,7 , which makes SWD an especially detrimental pest. Larvae emerge inside of and feed on the fruit, making it mushy and unmarketable. Recent research showed that around 80% of larvae drop from the fruit to pupate in the top layer of soil and that they are more likely to drop from the fruit if the fruit is overcrowded 8,9 . Larvae and pupae can also reach the ground when damaged fruit becomes mushy and falls to the ground. SWD has a quick generation time, with many generations per year in most regions. The fly develops fastest in temperatures between 68 to 83 degrees F, but is unable to develop at temperatures above about 87 degrees F 10,11 . In temperate regions like the Upper Midwest or Pacific Northwest, SWD populations are highest during summer months. In hotter regions like California or Florida, fly populations are highest in the spring and fall and are much lower during their hot and dry summer months 12 . SWD thrives in high humidity, developing fastest around 94% humidity 13 . Researchers found that females laid more eggs in the inner canopy of blackberry and blueberry plants, likely because the environment is more humid, cooler and darker 14,15 . Fruit crops that are the most susceptible to SWD include raspberries, blackberries, blueberries, strawberries, sweet and tart cherries, and some cultivars of wine grapes 16-18 . However, SWD can survive on alternative hosts like wild blackberries and apples, buckthorn and honeysuckle. It remains largely unknown how SWD survive in the winter and spring before fruit is available in the landscape and on farms, but one study found that SWD can develop on non-fruit hosts like mushrooms and bird manure 19 . Traditional Management Pest pressure from SWD is often very high due to the fly’s fast development time, optimal development conditions in the summer and high availability of host plants and food in the agroecosystem. Management relies heavily on chemical control in organic and conventional systems, which is costly to growers. In California, chemical controls for SWD cost around $470/ acre for conventional and $1,210/acre for organic growers 3 . Only a few insecticides approved for use in organic systems are effective at controlling SWD, limiting organic growers’ options for control 20 . Unfortunately, recent reports show evidence of insecticide resistance developing 18 Progressive Crop Consultant March / April 2021
(Left) Spotted-wing drosophila adult female and male on a raspberry. Male flies are easy to identify by the large black spots on their wings. (Right) Spotted-wing drosophila females have a serrated ovipositor that allows them to lay eggs in undamaged, ripening fruit (photos courtesy Agri-Mag and Chris Thomas.) for some active ingredients in some regions, including spinosad (the main insecticide used to control SWD in organic systems) 21,22 . Cultural practices can help reduce the fly’s population and are often used in tandem with chemical controls. Such practices include harvesting fruit promptly (every one to two days), frequent field sanitation, burial or composting of infested fruit and exclusion netting 23,24 . However, these methods are labor-intensive and expensive. Since SWD is sensitive to temperature and humidity, cultural practices that modify the crop canopy microclimate have the potential to reduce infestation by deterring adults from laying eggs or disrupting larval development inside of fruit. Management strategies for SWD typically target adult flies in the canopy, but since the majority of SWD larvae fall to the ground before pupation, ground-based cultural management practices could also be important for reducing populations. Growers have used plastic mulches since the 1960s to modify the microclimate in fruit and vegetable agroecosystems. Plastic mulches are commonly used for weed control, promoting earlier ripening, improving fruit quality or color and increasing yield 25,26 . Different colors of plastic mulches have also been shown to successfully control Pippen Robin Luigi Spock EVEN THE GREATS NEED HELP BEING GREAT. 51% Improved conventional herbicide performance* 79% Increased organic herbicide performance* ® Ampersand adjuvant 85% Increased insecticide performance* Ampersand ® adjuvant works differently than other surfactants to maximize the potential of your herbicide or insecticide’s chemistry, even at low use rates, to levels never seen before. Ampersand® Continued on Page 20 *compared to active alone Learn more about our technology at www.attuneag.com March / April 2021 www.progressivecrop.com 19
- Page 1 and 2: March / April 2021 A Review of Pyth
- Page 3 and 4: 4 8 12 18 24 IN THIS ISSUE A New Ge
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- Page 7 and 8: Because protection requires great p
- Page 9 and 10: Average Yield (lb/ac, 12% protein)
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- Page 13 and 14: THE BEST WAY TO MANAGE PATHOGENS BE
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- Page 24 and 25: New Findings on Limb Dieback of Fig
- Page 26 and 27: Figure 3. Left, pycnidia protruding
- Page 28 and 29: Figure 4. Susceptibility of various
- Page 30 and 31: Enhancing Diamondback Moth Manageme
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- Page 36 and 37: Vegetable Growers Express Impressio
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- Page 45 and 46: everything at fall pre-plant with P
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(Left) Spotted-wing drosophila adult female and male on a raspberry. Male flies are easy to identify by the large black<br />
spots on their wings. (Right) Spotted-wing drosophila females have a serrated ovipositor that allows them to lay eggs in<br />
undamaged, ripening fruit (photos courtesy Agri-Mag and Chris Thomas.)<br />
for some active ingredients in some<br />
regions, including spinosad (the main<br />
insecticide used to control SWD in<br />
organic systems) 21,22 .<br />
Cultural practices can help reduce the<br />
fly’s population and are often used in<br />
tandem with chemical controls. Such<br />
practices include harvesting fruit<br />
promptly (every one to two days), frequent<br />
field sanitation, burial or composting<br />
of infested fruit and exclusion<br />
netting 23,24 . However, these methods are<br />
labor-intensive and expensive.<br />
Since SWD is sensitive to temperature<br />
and humidity, cultural practices that<br />
modify the crop canopy microclimate<br />
have the potential to reduce infestation<br />
by deterring adults from laying eggs or<br />
disrupting larval development inside of<br />
fruit. Management strategies for SWD<br />
typically target adult flies in the canopy,<br />
but since the majority of SWD larvae<br />
fall to the ground before pupation,<br />
ground-based cultural management<br />
practices could also be important for<br />
reducing populations.<br />
Growers have used plastic mulches<br />
since the 1960s to modify the microclimate<br />
in fruit and vegetable agroecosystems.<br />
Plastic mulches are commonly<br />
used for weed control, promoting<br />
earlier ripening, improving fruit<br />
quality or color and increasing yield 25,26 .<br />
Different colors of plastic mulches have<br />
also been shown to successfully control<br />
Pippen<br />
Robin<br />
Luigi<br />
Spock<br />
EVEN THE GREATS<br />
NEED HELP BEING GREAT.<br />
51%<br />
Improved conventional<br />
herbicide performance*<br />
79%<br />
Increased organic<br />
herbicide performance*<br />
®<br />
Ampersand<br />
adjuvant<br />
85%<br />
Increased insecticide<br />
performance*<br />
Ampersand ® adjuvant works differently than other surfactants to maximize<br />
the potential of your herbicide or insecticide’s chemistry,<br />
even at low use rates, to levels never seen before.<br />
Ampersand®<br />
Continued on Page 20<br />
*compared to active alone<br />
Learn more about our technology at<br />
www.attuneag.com<br />
March / April 2021 www.progressivecrop.com 19
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