North American Fruit Explorers mailing list at ibiblio

[<dmnorton@royaloakfarmorchard.com>]

Alan,

 

I know you asked about Imidan, specifically, but during May and June I use the fungicide tables as a guide when spraying all products.  We are typically spraying the scab fungicides around the same time as Imidan for PC so I put the fungicides as the higher priority.  A general rule-of-thumb for the effect of rain on washing-off protectant fungicides is as follows:

_ Less than one inch of rain since the last spray will not
significantly affect residues.

_ One to two inches of rain will reduce the residue by one half.
Reduce the number of days until the next spray by one half.

_ Over two inches of rain since the last spray will remove most of the
spray residue. Renew the fungicide deposit as soon as possible.

 

The residual effect of any spray is usually on the label and can be different for each product.  So if  Imidan typically lasts for 14 days, let's say, and you get 1 inch of rain within a day after application, that Imidan spray will now only last 7 days and you would need to re-apply within 7 days instead of 14.  After 2 inches of rain its gone.  The use of a surfactant or sticker will increase the residual effect.  Hope this helps!

Dennis Norton
Royal Oak Farm Orchard, Zone 5
http://www.royaloakfarmorchard.com
http://www.theorchardkeeper.blogspot.com
http://www.revivalhymn.com

----- Original Message -----

From: Alan Haigh

To: nafex@lists.ibiblio.org

Sent: Sunday, May 25, 2008 6:28 AM

Subject: [NAFEX] required time to set Imidan before rain

This question is addressed to the experienced applicators out there.  Unusually cool spring weather has altered and extended bloom period considerably here in Z.6, SE NY.  It creates quite a dilemma on the decision of when to put down first insecticide application when the first apples to set on a given tree are being ravaged by curculio while there are still unopened blossoms on the same tree.

 

In the past I've been able to wait until the latest flowering apple varieties drop their petals to make first Imidan application to all species in mixed fruit orchards and have avoided serious curc damage even on the earliest plums.  To further complicate matters, frequent showers are limiting the opportunity to set spray.  I need at least an hour of good drying conditions following spray to have any confidence of adhesion. 

I'm not even sure this is enough time and I'm interested in the experience of some of you veterans on this issue.  How much setting time before rain seems to be required for Imidan?  How heavy a rain will erase the application before it sets?  I already know that mist and drizzle are fine but a specific number like 1/8th an inch would be useful. Thanks