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May 2012


HEADS UP!   If you’re a cherry grower it’s time to think about Western Cherry Fruit Fly.


For the Palisade & Dominguez Canyon areas the degree day accumulation as of 5/11 (today) shows 1043.  At this total approximately 3% of the fly population has emerged.  Mature adults with egg laying capacity will be present within a few days!  It’s time consider your control measures.


I’ll post timings for the other areas in the weekly “Pest Alert” starting Monday.


Western cherry fruit fly has one generation per year. It spends the winter as a pupa in the soil.  Emergence of the adult fly usually begins about four weeks ahead of Bing cherry harvest, and continues for approximately 4 weeks after.  Adults can live from 15 to 40 days.  Adults mate soon after they emerge and will begin to lay eggs 5 to 10 days later depending on temperature.  Females oviposit (insert an egg) just under the skin of the cherry.  They seem to prefer straw colored or riper fruit, but will infest green fruit.  Females can lay 15 – 20 eggs per day for up to a month.  You do the math!  Once an egg is laid the female will “mark” that fruit with pheromone letting others know “this room is occupied.”  This ability to multiply quickly is why a few infested cherries one year can turn into a disaster the next.  Most WCFF will not travel far after emergence. Usually the first tree they come to.  An expert from the Northwest told me that trapping for WCFF is an example of natural selection at it’s finest.   Only the really dumb, blind, unlucky flies blunder into a “yellow sticky” trap.  If you can consistently catch flies then you’re an extraordinary trapper or have one heck of a population problem!  It’s still a good idea to hang a few traps around your cherry block.  Put them head high in an exposed sunny part of the tree.  I would bias them towards the border of the block and/or near a suspected source of infestation.


An insecticide control program should start a week to 10 days after the first catch. Guthion, Sevin, Diazinon, Advise, Success, Entrust and GF120 are all labeled for control.  The best program, both for conventional and organic growers seems to be GF120.  GF120 is a bait that uses molasses as a base.  It’s applied at very low gallonage with an ATV.  It’s the least expensive and by far the quickest to apply.  It’s the only material that has a PHI of 0 days to harvest.  This easily allows you to maintain coverage between pickings. Since it may take the fly several days to find it, start early with this material. Advise has some residual contact activity against adult flies (2-3 days) but will kill hatching larvae in the egg for up to 10 days.  Advise will also clean up any black cherry aphid present.  I would advise against using Advise more than twice in a season due to mite issues.  Give me a call if you need info on spray intervals, application methods and preharvest timing with the different choices.  One final thought, keep in mind that 25 – 40% of the population emerges after harvest.  Leaving unharvested (no one picks them all), unsprayed fruit in the orchard will guarantee an increased population next year!  Advise (post harvest) will kill larvae inside the fruit.


These two links provide great info on WCFF and the use of GF 120.


Want a test to determine if your cherries are infested (other than finding half a maggot in the remaining bite)?  Dissolve 1 – 1.25 lbs. of  brown sugar in 1-2 gallons of water and place 2-3 lbs of mashed (squashed) cherries in the bucket and stir gently.  Wait approximately ten minutes, any maggots will float to the surface.


A note on post harvest cherry handling.  THE QUICKER THE COLDER THE BETTER!  Info from a post harvest seminar.  Cherries one hour at orchard temps had a vapor pressure deficit of 29 mbars.  Vapor pressure deficit on cold fruit (mid 30’s) was only 0.5 mbars.  Moisture lost by leaving fruit one hour in the orchard is equal to the water loss of 58 hours in cold storage!  With cherries, EVERYTHING IS LESS IMPORTANT THAN TEMPERATURE!


Questions?    PLEASE call,

Larry 970-234-3424          Dan 480-254-3025

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