Biological control of two sugarcane stalk borers in the United States

Authors: Showler, Allan

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/15/2017
Publication Date: 3/6/2018
Citation: Showler, A. 2018. Biological control of two sugarcane stalk borers in the United States. In: Singh, P., Tiwari, A.K. Sustainable Sugarcane Production. 1st Edition. New York: Apple Academic Press. Book Chapter. 10:241-263.

Interpretive Summary: In the United States, two exotic stalk boring crambid moths, the sugarcane borer and the Mexican rice borer are the most economically important arthropod pests of sugarcane. Their behaviors are sufficiently dissimilar to present unique challenges to sugarcane production. The sugarcane borer is particularly important in "wet" regions like Florida and Louisiana, but the Mexican rice borer displaced the sugarcane borer in "dry" South Texas after its arrival in 1980. Because the sugarcane borer spends most of its life in unprotected places, it is more vulnerable to insecticide applications and to biological control agents than the more cryptic Mexican rice borer. Some exotic parasitoid wasps seem to have become established in Florida and Louisiana, their effects on the sugarcane borer are modest. The red imported fire ant was found to protect the crop against the sugarcane borer in Louisiana, and vegetational diversification using weeds increases red imported fire ant populations. While weeds can reduce sugarcane production, they are associated with heightened predator diversity and other predator abundances. The Mexican rice borer’s cryptic habits protect it from natural enemies and many insecticides. The pest is spreading from Texas to Louisiana and Florida. Because the Mexican rice borer prefers to lay its eggs on drought-stressed sugarcane, and because red imported fire ants are relatively sparse in South Texas, the pest has thrived there. It is not clear whether it will displace the sugarcane borer in "wet" regions. The effects of predators like the red imported fire ant on Mexican rice borers is also not yet understood, nor the effect of enhancing predators using vegetational diversification. Many parasites and parasitoids have been released for Mexican rice borer control in South Texas but to negligible effect. Despite consistent attempts to control the two stalk borers with biological control agents, including pathogens of insects, use of resistant cultivars is of greater value for protecting sugarcane. Biological control has value in some conditions as a tactic integrated into stalk borer control strategies.

Technical Abstract: In the United States, two exotic stalk boring crambid moths, the sugarcane borer, Diatraea saccharalis (F.); and the Mexican rice borer, Eoreuma loftini (Dyar), are the two most economically important arthropod pests of sugarcane, Saccharum spp. Although the two pest species are closely related, their behaviors are sufficiently dissimilar to present different challenges to sugarcane production. Diatraea saccharalis is the key pest in relatively wet sugarcane growing regions such as Florida and Louisiana, but E. loftini displaced D. saccharalis in the drier South Texas climate after it arrived there in the early 1980s. Because D. saccharalis undergoes its life stages in less protected places than E. loftini, it is more vulnerable to insecticide applications and to biological control agents. Although a few introduced parasitoid wasp species appear to have become established in Florida and Louisiana (releases have occurred since 1915), control of D. saccharalis through their action has been modest. Exclusion of predators using insecticides has resulted in increased D. saccharalisinduced injury to sugarcane in Louisiana, and enhancement of the red imported fire ant, Solenopsis invicta Buren, using vegetational diversification reduced injury to sugarcane. While the weed species that diversify sugarcane fields themselves can decrease sugarcane production, they are associated with heightened predator diversity and abundances. Eoreuma loftini is more cryptic than D. saccharalis, protecting it from natural enemies and many insecticides. The pest is spreading from Texas to Louisiana, and it has been found in Florida as well. Because E. loftini prefers to lay its eggs on water deficit-stressed sugarcane plants, and because red imported fire ants are relatively sparse in South Texas, it has thrived there. It is not yet clear whether it will displace D. saccharalis in wetter environments. The effects of efficient predators like the red imported fire ant on E. loftini populations is also not yet well understood, nor the effect of enhancing predator numbers using vegetational diversification. Many parasites and parasitoids have been released for E. loftini control in South Texas but to negligible effect. Despite consistent attempts to control the two stalk borers with biological control agents, including entomopathogens, use of resistant cultivars is of more value for protecting sugarcane from them. Insecticides are generally effective against D. saccharalis and less so against E. loftini. Biological control, however, has value in some conditions as a tactic integrated into stalk borer control strategies.