If late blight is detected or suspected on your farm, and you cannot get a sample to a Cornell Vegetable Program staff member in a day or two, you should submit your sample to Chris Smart's lab at Cornell. Following are instructions for reporting, collecting and mailing samples to his lab.

From usablight.org:
Samples must be reported online and a form that is generated from your submission must be included with the sample. You will receive a sample number (which should be written on the sample bag when it is sent to the lab), and this number can be used to track your sample. 

Report online and fill out a form. (If you are new to the system you must Register for Sample Submission BEFORE Reporting.)

When sending late blight samples it is better to send leaf tissue rather than fruit or tubers. If you do send fruit or tubers send them in a separate bag or shipment -- so they do not crush the leaf tissue in transit. What to send:
1. A minimum of 5 fresh turgid leaves with actively sporulating lesions. Smaller lesions are best. Collected from several locations when possible.

2. Place the foliage in an air-tight dry plastic (Ziploc) bag with a cushion of air - so the foliage doesn't get crushed. Use a small shipping box rather than an envelope. PLEASE write the sample number on the bag.

3. Send the sample immediately upon collection. If you must "hold" the sample overnight, keep it at 40 - 50 F.

4. Include the completed sample submission form (see instructions for reporting sample online) in the box with the sample.

5. Mail the sample via overnight mail to:

Cornell AgriTech
Attn: Colin Day / Chris Smart
630 West North St, Barton Laboratory
Geneva, NY 14456

E-mail: cds14@cornell.edu
Phone: 315-787-2441