Utah Pest News Spring 2011

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Attract-and-Kill Stations for Management of Cherry Fruit Fly

 

Killing station treated with GF-120 bait spray attract cherry fruit flies, which then feed on the bait, and are killed.
 
 
 

Effect of GF-120 residue age applied to killing stations for attraction of cherry fruit fly adults: 0, 7, and 14 day-old residues compared to fresh 20% sugar water.  Data for morning (am), afternoon (pm), and total fruit flies per 1 hour observation period.
   
 



Killing stations for cherry fruit fly may allow expansion of organic cherry production.

   
Western cherry fruit fly, Rhagoletis indifferens, is the key insect pest of cherries in Utah and western North America.  Processed tart cherries have a zero tolerance for fruit fly larvae, and so strict prevention of fruit infestation must be maintained.  Use of a reduced-risk bacterial insecticide, spinosad, formulated with a feeding attractant, GF-120 Naturalyte, has proven effective in suppressing cherry fruit fly populations in Utah tart cherry orchards; however, the bait-insecticide is susceptible to ultraviolet light degradation and is not rainfast, and so must be reapplied every 5-7 days or immediately after a rain event.  GF-120 is registered for organic production (OMRI approved). 

In collaboration with Dr. Jaime Pinero (now located at Lincoln University of Missouri, Jefferson City, MO), and based on previous research from Pinero and a team of entomologists at the University of Hawai’i, we proposed that killing stations could protect GF-120 droplets from sunlight and rain, and yellow color could enhance attraction of fruit flies to the bait droplets. 

We constructed killing stations from 36 inch-diameter plastic plant pot saucers.  Saucers were hung inverted from tree limbs or posts and GF-120 sprays were applied to the underside.  Stations were painted green or yellow.  We found that both male and female flies were attracted to killing stations treated with GF-120, but females preferred yellow to green-colored stations. 

In experimental orchards with moderate to high cherry fruit fly populations, killing stations deployed at 18 and 30 per acre kept fruit infestation at or below 0.3%.  Killing stations extended the efficacy of GF-120 droplets up to 14 days as compared to fresh residues.  Interestingly, reproductively mature cherry fruit fly females (ovaries contained mature eggs) were more attracted to less concentrate GF-120 dilution (1 part GF-120 to 5 parts water) and GF-120 with the standard ammonium acetate concentration (1%) than to the more concentrated GF-120 (1:2.5 and 1:1.5) and GF-120 with 2% ammonium acetate.  In contrast, immature females (without mature eggs) were equally attracted to all GF-120 and ammonium acetate concentrations tested. 

These results suggest that reproductively mature females looking for egg-laying sites in fruit can be repelled by ammonium acetate concentrations higher than about 1%.  This finding bodes well for attempts to extend the longevity of GF-120 in the orchard through killing stations. 

Once placed in an orchard, killing stations are relatively easy to maintain with targeted GF-120 sprays every 1-2 weeks.  Sprays can be applied with a directed nozzle, such as from a hand-pump or electric sprayer mounted on an ATV.  Yellow killing stations show promise as a technology to increase female fruit fly response to bait-insecticides, and could help expand organic cherry production.



 

-Diane Alston, Entomologist