Shallow flooding reduces a major rice pest, researchers find

UF Institute of Food and Agricultural Sciences researcher Ron Cherry and his team discovered that shallow flooding of rice fields can help reduce rice water weevil populations during Florida’s growing season, between April and September. Previous studies of the effect of flood depth on the pest have been inconsistent.

“Application of this permanent flood is the most important external influence on the interaction between the rice water weevil and rice,” said Cherry, a professor of entomology and nematology.

As they feed, rice water weevils create translucent scars on rice plant leaves. Those scars predict future larval infestations (grubs) feeding on the roots, which damage the rice plant.

On April 14, 2014, Cherry and the team planted eight research plots, half with the Taggert variety of rice and the other half with Cheniere. All plots were flooded on May 5; four were continuously flooded at a depth of 15 centimeters (nearly six inches) and four plots were flooded at a depth of 5 centimeters (nearly two inches). Leaf scar samples from randomly selected plants were then taken every two weeks from May 7 to June 17.

“There were significantly fewer leaf scars in the shallow flood than deep flood,” Cherry said. “This shows that shallow flooding reduced rice water weevil populations, a significant find that suggests rice farmers could use water depth as a cultural control technique.”

Their finding could also impact rice growers in other states.

The group also tested for populations of damselflies, leafhoppers, spiders and stink bugs and found water depth had no significant effect.

The study was published recently in the Journal of Entomological Science. Other members of the research group are: Mohsen Tootoonchi, a UF graduate research assistant; Jehangir Bhadha, a UF post-doctoral associate ; Tim Lang, a UF graduate research associate ; Michael Karounos, a UF biological scientist; and Samira Daroub, a UF professor of soil and water science.