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Posts Tagged: Drosophila
Two Webinars on Spotted Wing Drosophila Management
Readers might be interested in attending either or both of the following webinars coming up in the next few weeks:
Making the Most of Your Insecticide Toolbox to Manage SWD: Jan. 25, 2017, at 8:30 9:00 am PST
Will provide recommendations for growers to prepare for the 2017 growing season.
Registration is free, but you must register: https://msu.zoom.us/webinar/register/5c0227f576a61869d746f627e8486654
Organic Management of SWD: February 1
Join eOrganic for a webinar on organic management of Spotted Wing Drosophila on February 1, 2017, at 2PM Eastern Time, 1PM Central, 12PM Mountain, 11AM Pacific Time. The webinar is free and open to the public, and advance registration is required.
Registration is free, but you must register: https://attendee.gotowebinar.com/register/8379387290681616900
Efficacy and Phytotoxicity of Biopesticides for Management of Spotted Wing Drosophila (SWD) in Raspberries.
JUSTIFICATION AND OBJECTIVES:
IR4, the branch of the USDA focused on speciality crops, identified research on SWD as a priority need. The purpose of this efficacy and crop safety trial was to determine the level of SWD control by organically registered biopesticides in caneberries to determine the impact on plant and yield variables.
TEST SYSTEM DESIGN and STATISTICAL METHOD:
The test site consisted of three replicates of each treatment in Table 1 below. Plots in the active organic raspberry ranch were arranged in a randomized complete block design. Since SWD is a mobile pest, the 3 replicate plots of each treatment (see Table 1 below) were large, consisting of three raspberry hedgerows across, being 54 ft long and 14 feet wide (756 ft2). Statistical analysis was done on ARM, version 9.
TEST SUBSTANCE APPLICATION:
All test substances were applied with a motorized Maruyama 058 backpack sprayer with a hand gun at a pressure of approximately 120 psi. Each material was mixed in a water carrier rate of 75 gpa. Three total applications were done; beginning 9/17/2015, 9/25/2015 and 9/30/2015. Because of excessive residues for the Cimexa Gel material and request of the collaborating grower that this material no longer be applied, no applications of any treatment of Cimexa Gel were made on the last date.
INSECT AND YIELD EVALUATION:
One day prior to the first application of September 17, samples of 10 marketable fruit were collected from each replicate plot and further a section of 18 ft long from the center hedgerow was vacuumed with a Bug-vac for adults. Fruit were held for several days and then each evaluated under the dissecting scope for SWD larvae and eggs. The vacuum sample was evaluated for female and male SWD, along with other insects taken in the sample.
Subsequent sampling and evaluation dates were Sept 22 (pre-sampling), Sept 28, Oct 5 and Oct 16. The sampling date for October 5, taking place after full application of all treatments and thereby likely to give the most meaningful results, is given below. Note that no evaluations were done of treatments containing Cimexa Gel on the last sampling date.
SUPPLEMENTAL CROP TREATMENTS:
No supplemental treatments of any kind were made to the crop during the course of this study.
DISCUSSION:
While there was a tendency for treatments containing Entrust to have lower numbers of larvae found in fruit as other treatments after completion of all three applications on the Oct 5 sampling date, none of these differences are statistically significant and as such regarded with caution.
Furthermore, the residue of CimeXa Silica Gel Dust on leaves, canes and fruit of plants subjected to its application was unacceptable and as such this material is not recommended for further study.
Hat tip to research assistants Don Yoshimura and Monise Sheehan, without whom I could not have possibly done this trial.
Treatments 1- 7 for 2015 SWD Biopesticide Trial
Treatments 8-14 for 2015 SWD Biopesticide Trial
October 5 Results of 2015 SWD Biopesticide Study.
A Few Observations on Vinegar Flies in Strawberries
As any grower knows, vinegar flies, Drosophila spp., have been a major deal in strawberries the last few years. It seems the slightest delay in picking (especially in the fall) is met with an onslaught of vinegar flies followed by a huge loss of fruit.
I have the good fortune to be funded this year by the North American Strawberry Growers Association (NASGA) on a study looking at predaceous nematodes as a way of controlling vinegar flies. More on that at a later date, but having my research assistant Monise Sheehan and I spend some time looking closely at vinegar flies in strawberry brings up some observations that I would like to share here.
First of all, regular vinegar flies, as opposed to the spotted wing drosophila, Drosophila suzukii, do not oviposit in fruit, rather they oviposit on the surface. I am going to underline that this doesn't at all mean they won't damage the fruit, since it is only 24 hours each one spends in the egg stage before becoming an active larva fully capable of penetrating into the fruit.
It is interesting to see where the egg laying is taking place. It's uncommon to see eggs just deposited on a healthy fruit (Photo 2); it is rather in wounds (Photo 3) and cracks (Photo 4), bruises and any other kind of damage which softens and compromises the integrity of the fruit where the bulk of the eggs are found.
I think the take home message for strawberry growers and supporting professionals is to know how very fast the life cycle of vinegar flies goes and the big role that damage, be it wounds, cracking, bruising or general softness has in promoting their development.
Photo 1: Vinegar fly eggs under the microscope. Long fibers are respiratory tubes.
Photo 2: Mass of vinegar fly eggs on an ostensibly healthy fruit. The immaturity of this fruit is notable.
Photo 3: Mass of vinegar fly eggs in fruit wound, rendering it totally unmarketable.
Photo 4: Vinegar fly eggs nicely lined up in crack under calyx. This fruit is lost.
Management Tips for Spotted Wing Drosophila on a Small Scale
I've been getting a number of calls lately concerning spotted wing drosophila in caneberries and strawberries, especially from growers on the smaller scale – in most cases organic operations.
Let's do a brief review what the best way to manage this will be:
One should take a two pronged approach. First the use of Entrust (spinosad) as a spray is recommended, while at the same time, to the extent possible, one should be removing the cull fruit (rots and over-ripes) from the field and burying them or throwing them away. For strawberry growers running the tractor over the culls in the furrow can be useful - not so much because it crushes the larvae, but because the flattened fruit dries out quickly and loses its property as a suitable food source. The spray is reducing the number of adults, while at the same time all routes of maturation are no longer available to the fly. Harvested fruit is removed and sold, and cull fruit is removed or destroyed, so there is no way for the larvae to complete their life cycle and turn into more flies.
That said, two years of research tells us to recognize that removal of cull fruit alone will not be enough to bring the population down to acceptable levels. There will always be the one fruit that is missed but yet contains the propagation potential in it to re-infest your field. That is why the best route for you is to spray along with practicing good sanitation.
Final word would be to take note of what is around your field. Are there any patches of uncontrolled spotted wing drosophila next door or wild blackberries? Both of these areas are serving as hosts and it will benefit you to get some control there also.
There is a pesticide mentioned in this article for control of spotted wing drosophila on the small scale. As always, before using such a pesticide, refer to the product label for directions on use.
Male spotted wing drosophila.
Organic management of spotted wing drosophila - Webinar
Those of you interested in organic management of spotted wing drosophila might want to catch this one.
It's planned for February 11, 2014:
