Frequently Asked Questions - QuickStix Kit for Soybean Rust



Do the strips detect “New World” soybean rust (Phakopsora meibomiae)?

The QuickStix Kit is specific to Asian Soybean Rust (Phakopsora pachyrhizi). Based on current research data, the strips do not detect New World soybean rust (Phakopsora meibomiae).



Do the strips detect the soybean rust mycelium?

Yes, we have laboratory-based evidence that the antibodies used in our test kits react with antigens produced by mycelia developing inside the leaf tissue.



Are the strips validated? Have they been tested in the field? Are there any diagnostic labs or companies using the test strips?

Please check here for validations and testimonials. Our current customers include industry, government and university users.



How should I scout for soybean rust?

There are numerous sources and suggestions for sampling frequencies and plans. Depending on risk factors (i.e. SBR found nearby, climatic conditions, plant growth stage) you should be scouting visually about once a week. Walk in a “w” pattern and look low in the canopy every ten paces for rust symptoms. Two good publications with recommendations for scouting come from South Dakota State University and University of Illinois Extension .

According to the 2006 Indiana Soybean Rust Wrap-Up published by Purdue University Extension, “We have also learned how difficult it is to detect rust at very low incidence. To make timely fungicide applications we need to detect rust when it first appears.” It goes on to explain the difficulty in finding rust symptoms among the look-alikes and minor wounds.

With QuickStix Strips on hand, these questionable spots can be tested immediately and with confidence that they will detect SBR at even the earliest stages.

QuickStix Strips are not meant to replace scouting in any way, but as an adjunct to good crop management.



How many tests should I run to determine if my field is contaminated by soybean rust?

Best practice suggests that you scout your field as recommended by the USDA or Extension specialist, and keep tabs on weather, predictive models, and scouting reports in your area. By running a QuickStix test on any suspicious-looking leaf, you will increase your chances of detecting the disease early in its cycle, which makes your fungicide decisions more effective. Because of the impact of proximity/environmental factors, along with variable numbers of suspicious-looking symptoms, there is no statistically valid number of tests that can be recommended.



How much leaf material is needed for testing?

Approximately 1” x 1” square, or about the size of a quarter (or the cover from the canister of strips is a good measuring guide).



Does this test cross-react with any other plant pathogens?

The kit does not cross react with several other rust infections caused by Uromyces, Puccinia and Melampsora species.

No cross reactivity was observed with other common fungal genera including Aspergillus, Cercospora kikuchii or C. sojina, Fusarium, Penicillium, Peronospora mansurica, Pseudomonas savastanoi pv. Glycinea, Septoria, Rhizoctonia, Rhizopus, and Xanthomonas campestris pv. Glycinea.

No cross reactivity has been observed with similar-looking diseases such as frogeye leafspot, powdery mildew, downy mildew, brown spot, bacterial blight, bacterial pustule.



Does the strip detect soybean rust following fungicide application?

The strip will not distinguish between “old” lesions and “new” ones. Both dead and live mycelia may be detected following a chemical treatment. When scouting for rust some number of days following an application, it is important to observe new, unprotected leaf tissue that may present symptoms. The presence or absence of old or new lesions will be influenced by type of fungicide used and the method of application, as well as weather conditions. Across all possible scenarios, the strip test should complement other rust-management approaches and the advice of a crop-management specialist.



Does the condition of the leaves affect test results (i.e. dried material)?

Condition of the leaves affects the test results slightly; however, extent of rust contamination affects the test more. Because the QuickStix Kit is sensitive enough to distinguish Soybean Rust at very early stages, later-stage heavily contaminated samples may overwhelm the strip and make the test line appear light. Because heavily infected leaves are quite easy to distinguish from so called “lookalike” diseases, this is not deemed any sort of problem. The most valuable use of the QuickStix is its ability to distinguish SBR from look-alikes very early in the disease process, when visual differences are less noticeable and when fungicide application decisions are critical.



I tested a leaf sample that was confirmed SBR positive with heavy infection and received a very light test line result, is the strip functioning properly?

QuickStix Strips are designed to detect very low levels of soybean rust antigen or protein in a sample extract. The test (antibody-antigen reaction) can be overwhelmed with heavily contaminated samples, resulting in a light positive signal (Test Line); this is referred to as the “hook effect” and is a phenomenon seen in many immunoassays. Any pink Test Line, no matter how light, is interpreted as positive for soybean rust.






If I receive a green or gray test line does this indicate a positive result?

Only a pink test line indicates a positive result. A gray or green test line could indicate an improper sample extraction, improper test procedure, or invalid strip. Please call Tech Service for troubleshooting if this result is reached.



How sensitive are the strips?

In terms of the type of lesions that can be detected, inoculation studies have shown that the strip detects the presence of SBR in chlorotic lesions, at about five days after tissue infection occurs, when symptoms first start to appear (covering less than 0.5% of the leaf). At this stage, it is difficult to distinguish soybean rust from a number of other foliar diseases. Further, when leaves were inoculated with a high level of spores, the strip detected rust as early as 24 hours after infection – before symptoms were visible. This suggests the strips can be used for sampling in field situations where heavy deposition of spores is expected (e.g. after a rain).

In terms of the number of lesions that can be detected, the same inoculation studies showed that as many as 4-5 pustules on the suggested sample size can be detected with the strips. For a lower level of infection (fewer pustules per leaf), there is an alternate protocol taking a smaller tissue sample size, which reduces the potential for overdilution of the inoculum.

In terms of the number of spores that can be detected, laboratory studies have shown that as few as 3000 spores can be detected with the strips.



What is the sensitivity difference between the QualiPlate ELISA plate kit and the test strips?

The QualiPlate Kit is 10 times more sensitive than the test strips. However, even the test strips are sensitive enough to detect SBR at a very early stage (before pustulation or sporulation in many cases).



Do the strips expire? How long do they last?

QuickStix Strips for Soybean Rust have a shelf life of 6 months when stored at room temperature, or 18 months when refrigerated. Please remember that if refrigerating your kits, let the canister of strips and buffer warm up to room temperature before using. We recommend transporting the strips in a small, portable cooler when used in the field.



What is the price and packaging?

Kit sizes are 25 tests for $110 or 50 tests for $200. Everything you need is included.











Have a question that’s not answered here? for our comment form and ask!


Click here to return to the QuickStix Kit for Soybean Rust product page.











Email Page Print Page

PDF files, where provided, require Adobe Acrobat Reader.

- up -

Home  |  Glossary  |  Shipping  |  Precautions &Warranty |  Related Websites  |  Privacy  |  Security  |  Employment