Rice Leaf Blast Gets Early Start, Arkansas Growers Should Scout Now

SARAH CATO

LITTLE ROCK, ARKANSAS

With early planted rice comes earlier-than-expected issues. Rice leaf blast, a fungal disease caused by the pathogen Magnaporthe oryzae, is most commonly observed during the late vegetative to early reproductive stages of the rice plant. This season, Arkansas rice is reaching reproductive growth stages very quickly, with blast reports beginning as early as the first week of June.

“We received reports of rice blast in Cross and Randolph counties earlier than usual this year,” said Camila Nicolli, extension plant pathologist for the University of Arkansas System Division of Agriculture. “Humid and wet conditions paired with early rice development fueled the early start.”

Because blast can lead to significant yield losses, Nicolli recommends scouting rice fields.

“Scouting is especially important in fields with a history of blast or with conditions that favor the disease like low-lying areas, areas surrounded by tree lines and fields with susceptible cultivars,” Nicolli said. “Focus scouting efforts on tree lines, dry field edges, levees and areas with greener, denser canopies due to excess nitrogen and double drilling.”

Symptoms can be found by opening the canopy to inspect lower leaves. Those scouting for leaf blast should look for small, diamond-shaped lesions with gray centers and brown margins. Early symptoms may appear as grayish-black spots.

As far as treatment options go, Nicolli recommends holding off on fungicides unless the disease is burning down areas of the field.

“We recommend increasing flood depth to 4 inches to suppress disease development until early heading stages,” she said. “At heading, a fungicide application may be considered for prevention of neck and panicle blast.”

Control options for rice blast can be found in the 2024 Arkansas Rice Management Guide.

Nicolli asks growers to alert her and her lab of leaf blast reports across the state. She can be reached at cnicolli@uada.edu or 870-830-2232. ∆

SARAH CATO: University of Arkansas