[IN1341] Stem Borers (Lepidoptera: Crambidae) in Florida Rice

Three stem borers, the sugarcane borer, Diatraea saccharalis (F.), rice stalk borer, Chilo plejadellus Zincken, and Mexican rice borer, Eoreuma loftini (Dyar), infest rice in the southern United States. They occur in Florida, with the Mexican rice borer being an invasive species recently introduced into the state. This publication briefly describes stem borers and sampling methods and reports results of the first extensive survey conducted to measure their occurrence in Florida rice.

Diatraea saccharalis (sugarcane stalk borer).

D. saccharalis is generally considered to be a pest of substantial economic importance. The extent of economic losses may vary depending on factors such as environmental conditions and sugarcane varieties. Losses to the sugarcane borer often vary across geographic regions (e.g. crop losses to the borer in Louisiana), USA may range from 4-30% annually, possibly twice as high as in Florida (Ingram et al., 1951).

Eldana saccharina (African sugarcane borer).

E. saccharina is the most serious sugarcane pest in tropical and sub-tropical Africa, and in situations of high pest pressure total crop failure can result.

Population Trends of the Sugarcane Borer (Lepidoptera: Crambidae) in Louisiana Sugarcane

The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), is the primary pest of sugarcane, Saccharum spp., in Louisiana. Spring populations are not considered economically damaging, but quantifying infestations can provide an indication of the spatial and temporal character of the damaging summer populations. Statewide surveys quantified the density of sugarcane tillers killed by D. saccharalis (deadhearts) from sugarcane fields across the state in spring from 2003 to 2020. Deadheart density varied greatly among years with a high of 1,318/ha in 2003 to a low of 0/ha in 2018. Linear regressions of the 3-yr rolling average showed declines in spring D. saccharalis populations and the percentage of acreage treated with insecticides over 17 yr. Weather factors including minimum winter temperatures and average spring temperatures were poor predictors of D. saccharalis populations. Only total precipitation in the month of April was positively correlated with numbers of deadhearts per hectare. Results suggest overwintering mortality is not a key factor influencing populations of the first generation of D. saccharalis in Louisiana. Total precipitation in the month of July was positively associated with percentage of treated acreage. Spring deadheart density was directly related to percentage of acreage treated with insecticides during the summer. Quantifying first-generation D. saccharalis populations by recording deadheart density can aid in predicting pest pressure later in the growing season.