Agdia Immunostrips for Diagnosing Phytophthora in the Field

The following article is a discussion of Agdia Immunostrips (photo 1 below) for making diagnoses of Phytophthora from plants.

The idea with the strips is sort of what most of us have already experienced with the Covid test kits - basically you get a sample, process it in some way (swirling a Q-tip around in your nostril for Covid or crushing up suspect root tissue with the Agdia test - see photo 2 below) and then you get a result of one or two lines (one the control on top, and a second stripe appearing when you have the disease and no stripe appearing if you don't).  An example of a positive read which was subsequently verified as positive with a highly reputable plant disease diagnostic lab is shown on the third photo below.

Do they work consistently would be the next question, and our own little bit of experience now, together with the experience of other researchers in our industry, says that yes they do.

Last year, the berry industry experienced more than significant amounts of flooding, which presented us with a tremendous opportunity to test these strips for the water loving Phytophthora. Two tests were done side by side with samples submitted to Trical Diagnostics, a local lab recognized for accurate diagnosis of plant diseases.  In this very small sample, one trial out of strawberry tested positive with the Agdia strips also came out positive at Trical Diagnostics for Phytophthora, and another sample which Mark swore up and down would test positive for Phytophthora (very early in the season, cool weather and excessive moisture at the bottom of the hill), did not test positive with the strips and this was substantiated by a diagnosis not of Phytophthora but of Fusarium oxysporum f.sp. fragariae.  

This year, Mark was called out to field suffering a great deal of wilt in raspberries, prompting yet again a test with the Agdia strips, and ALL FIVE samples tested positive for Phytophthora (see photo 5 below), a result which was confirmed by in-house testing by that company's research support of plants from the same field.

The thought is then at this point to share that these testing strips can be useful to the grower in diagnosing Phytophthora and Phytophthora like species.  Since these strips DO NOT diagnose down to the level of species, which while for most field management decisions is ok, those desiring an understanding of a problem down to that level still must do at a reputable plant diagnostic laboratory.

 

 

Photo 1. A package of Agdia test strips, there are 25 strips per tube and together with the bags of buffer cost is a bit over $100.

Photo 2. Suspect root samples laid out ready for insertion into the bags of buffer solution in the hinterground and subsequent maceration.

Photo 3. A positive read of a sample, notice the lighter line 2/3's of the way down the strip, this is an indication of positive.

Photo 4. Five in a row, all positive - later confirmed by grower support research lab as Phytophthora.

Photo 5: One of the Phytophthora affected raspberry plants in the field.

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