Hurricanes Increase the Need for Insecticides in Louisiana Sugarcane Fields

Fire Ant Killing Sugarcane Borer

Fire Ant Killing Sugarcane Borer

Louisiana is the top producing sugarcane state accounting for 40% of the nation’s sugarcane production. Approximately 3 billion pounds of raw sugar are produced annually by Louisiana sugar mills. The sugarcane borer is the most damaging insect pest of sugarcane in Louisiana. The larvae bore into the plant where they feed on the central tissue. Borers make tunnels up and down the stalk. The size and weight of the stalks are decreased. Sugarcane borers in Louisiana are controlled by an integrated system that consists of spraying insecticides, planting varieties with some resistance and by natural enemies of the borer. The most important natural enemy of the borer is the red imported fire ant. Typically, the predation of fire ants contributes an estimated savings of two insecticide sprays. However, when the sugarcane fields are flooded by hurricanes, the fire ants are negatively affected and insecticide use has to increase.

“On 24 September 2005, Hurricane Rita made landfall on the extreme southwestern coast of Louisiana near the border with Texas as a Category 3 hurricane.

Twelve thousand to 16,000 ha of sugarcane produced in south Louisiana were flooded by saltwater from Hurricane Rita storm surge.

During spring 2006, sugarcane growers and contracted agricultural consultants began observing that flooded areas seemingly had more [sugarcane borer] infestations, which might require earlier and more frequent insecticide applications for D. saccharalis control.

This study showed that growers had to treat more (2.4-fold increase) in zones impacted by the hurricane storm surge.

S. invicta [red imported fire ant] seemed to be negatively impacted 10-12 mo after the areawide habitat disruption caused by the storm surge flooding. When plunged into freshwater, S. invicta individuals gather and form floating clusters that can drift for more than a week without drowning. However… S. invicta is susceptible to saltwater, sinking within 30 min when in 3.5% saltwater (approximately equal to seawater), and within 48 h in 1% saltwater. …Susceptibility to saltwater flood and limited dispersal abilities may explain why S. invicta was negatively impacted by the storm surge and slow to recover back to prehurricane population levels.

This study suggests that Hurricane Rita disturbed the pest management stability between beneficial and pest anthropods for the subsequent production season, requiring additional insecticide applications…”

Authors: Beuzelin, J.M., et al.
Affiliations: Department of Entomology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center
Title: Impacts of Hurricane Rita storm surge on sugarcane borer (Lepidoptera: Crambidae) management in Louisiana.”
Source: Journal of Economic Entomology. 2009. 102[3]:1054-1061.

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