June 2005

 

 

The crew at Grand Mesa Discount has switched cell phone providers (with a few hicups along the way) from Clear Talk to Sprint.  All of our numbers remain the same.  If you get a message stating that the number has been disconnected, it’s false!  Please call the office (835-3335) if you can’t get through on our cell phones. 

 

The first catch on Western Cherry Fruit fly (wcff) in Mesa County occurred on May 16th at 717 degree days which was 232 degree days ahead of average.  If you raise cherries and haven’t put a trapping and treatment program in place, today would be a fine day for the task!       

 

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, Provado, Spintor, 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. Provado has some residual contact activity against adult flies (2-3 days) but will kill hatching larvae in the egg for up to 10 days.  Provado will also clean up any black cherry aphid present.  I would advise against using Provado 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!  Provado (post harvest) will kill larvae inside the fruit.

 

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! 

 

The timing for Peach Twig Borer cover sprays are just a few days away.  Here’s a few thoughts about material choices.  If damage from stink bug and lygus bug have been impacting your packouts consider using Thiodan.  It has good efficacy on both, as well as good control of PTB.  The softest (least disruptive to predators) choice is one of the materials containing spinosad, either Spintor or Entrust.  You may want to consider Guthion for the last time on peaches.  The registration is scheduled to be pulled as of Dec. 31st.   If mites have been an ongoing battle at your orchard it’s a good time to add to the tank a miticide with a long residual.  This also is a good opportunity to apply a shot of Calcium.  No matter what material you choose, keep in mind the re-entry and pre-harvest intervals.   

 

So what’s my spray date?  That’s a question I get asked often.  How do I know the answer for your orchard?  Biophenometers, traps, experience and a knowledge of the entire region.   Every year in February, I place  biophenometers in Palisade, Olathe, Eckert, Paonia, Rogers’ Mesa and Cedaredge.  A biophenometer is a self-contained device that works around the clock keeping track of temperature data.  This data is used to track development of your favorite pests.  I also have a network of pheremone traps for each pest, in each of these areas.  Once I obtain a biofix (the start of continuous trapcatch) I will note the biophenometer reading and start accumulating degree days.  Each pest has a threshold (a start time) unique to it.  The decision is further refined by pest populations in your block, daily temps just prior to spraying and the choice of materials you plan to use.  For example, if the population in your orchard is low, it may be advisable to delay a bit, if you farm at the lowest elevation in the area you may want to be a few days early.  If you use GF 120 for WCFF, you’ll need to start a few days early.  If Spintor is your choice for PTB, make sure you’re applying it in the proper window and so on and so on.  As new materials become more pest specific and active on a particular life stage, timing becomes more critical.  Every year I work at refining my pool of knowledge that I use to determine spray timings.  I make notes of who suffers pest damage and why.  Damage is not always the result of poor timing.  It can be insufficient spray coverage or the wrong material.  If all the other factors are properly in place then I take a look at adjusting the spray timing.

 

Well, we’re hot into the season.  Most areas have started treatment for codling moth, PTB sprays are not far off and Western cherry fruit fly is out and about in Mesa county.  I’m still waiting to get a biofix on a Worker Protection Standards EPA agent.  Their emergence pattern is varied, and completely unpredictable.  Usually a grower will only see one generation per year.  It’s the next year’s emergence that requires preventative treatment.  As most of you know the threshold for this encounter is very low, one agent can cause extensive damage.  At this point in time the only program that I know of to prevent damage is complete adherence to the WPS standards.  If you need help with your on farm compliance, give me a call!

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