The spread of Phakopsora pachyrhizi spores, causal organism of soybean rust, continues to be the topic of interest for southern soybean-producing states. As I write this, several counties in Florida (Figure 1) have been confirmed to have active spore-producing pustules on kudzu leaves (an aggressive weedy species that’s also susceptible to the disease, Figure 2) and, as of June 29, the disease has been identified on soybean plants in a Marion county, FL sentinel plot. According to Jim Walker, Pest Survey Specialist, disease is reportedly localized in hot spots within the plot area and can be found in the lower to mid-canopy of plants approaching the pod fill stage (R5-7).

Earlier, one county in southern Georgia had volunteer soybean plants confirmed positive for the disease. Soybean plants at that location were destroyed in an effort to contain the disease. No other counties have been confirmed in that state.

Elsewhere, researchers in Louisiana and Alabama recently detected Phakopsora-like spores from spore traps. The number of spores that were collected fell short of the total needed to confirm the identity of the fungus using molecular protocols. Meanwhile, diseased soybeans were identified last week from sentinel plots in Alabama. This creates an increased level of awareness for producers in all Gulf Coast states.

Some speculate that tropical storm Arlene may have spread spores in its path. Disease in affected states has not been confirmed.

Northwest Red River Valley soybean growers are faced with more than enough cropping issues this year without adding soybean rust to the list of problems. I’ve got my fingers crossed that this won’t be the year that we have to deal with soybean rust.

INFORMATIVE SOYBEAN RUST WEBSITES:

North American Plant Disease Forecast Center
http://www.ces.ncsu.edu/depts/pp/soybeanrust/

Plant Management Network Soybean Rust Information Center
http://www.plantmanagementnetwork.org/infocenter/topic/soybeanrust/

Soybean Rust Pest Tracker
http://ceris.purdue.edu/napis/pests/asbr/index.html

USDA Soybean Rust Public Information
http://www.sbrusa.net/

Charla Hollingsworth
Extension Plant Pathologist