FAQ

Captan is a fungicide and primarily for control of apple scab, black rot, lotch, Botrytis blossom infection.  Malathion is one of several
insecticides used for control of codling moth.  So they have very different functions - malathion is not a fungicide.  I have copied a section below about Captan which states it should not be used with lime or other alkaline materials or with oil within 4 days.  Malathion is often prepared in an oil solution so caution should be used if timing is too close to last Captan spray.  My question for you is what are you treating your fruit trees for??
It is best to use an appropriate chemical when you have identified the pest, generally we do not recommend spraying as a preventative.

For more information on apple codling moth, here is the link to USU Fact
Sheet on codling moth
http://extension.usu.edu/files/publications/factsheet/ENT-13-06.pdf

There also is information at USU Extension website for more information on Integrated Pest Management is a strategic approach to plant and animal care that seeks to suppress pest populations while minimizing pest control costs and environmental disruption.
http://utahpests.usu.edu/ipm/


Captan 50W or 80W formulations are used at 6.0-8.0 lb/A of Captan 50W or 3.75-5.0 lb/A of Captan 80W, for control of diseases on apple; other formulations should be used according to label direction. On apples Captan has proven effective in the control of apple scab, black rot, Brooks spot, Botryosphaeria rot, blotch, bitter rot, Botrytis blossom infection, fly speck, and sooty blotch. Captan=s residual life is  elatively short, consequently, sooty blotch, fly speck, and fruit rot control may not be satisfactory where sprays are discontinued more than 3 weeks prior to harvest. The higher indicated rates are for severe summer disease pressure.
Captan may produce frogeye-like spotting of the foliage of Delicious, Stayman, and Winesap early in the season. The small spots do not enlarge and are no cause for alarm. The inclusion of sulfur in the spray mixture may increase this type of injury.

Captan should not be used with lime or other alkaline materials. Do not use it with oil or within four days of an oil spray. Do not use in
combination with EC formulations of parathion. Captan should be used with caution in bloom sprays, especially on varieties which are hard to pollinate (e.g. Red Delicious). Captan has been shown to severely reduce pollen viability for 24 - 48 hours after application.

Although new Captan labels permit application to apples up to the day of harvest, Captan has a 4-day re-entry interval which makes pre-harvest application more restrictive. A label exception is made for the last 48 hours of the re-entry interval during which workers may enter the treated area to perform hand labor or other tasks involving contact with anything that has been treated, without time limit, if they wear  ll of the following: coveralls, waterproof gloves, shoes and socks, and protective eye wear. http://www.caf.wvu.edu/kearneysville/profile/critfung.htm