F. P. F. Reay-Jones

Integrated Tactics for Managing the Mexican Rice Borer (Lepidoptera: Crambidae) in Sugarcane

Abstract A 2-yr field study conducted in Texas to evaluate the effect of several management strategies on the Mexican rice borer, Eoreuma loftini (Dyar), in sugarcane, Saccharum spp. hybrids, showed that irrigation reduced injury in both susceptible (LCP 85–384) and resistant (HoCP 85–845) cultivars by 2.5-fold. Cultivar LCP 85–384 was more susceptible than HoCP 85–845 based both on injury and moth production. Irrigation, host plant resistance, and insecticide applications of tebufenozide decreased injury from 70% bored internodes to <10% during both years. The use of multiple control tactics was substantially better at suppressing E. loftini in sugarcane than solely relying on insecticide applications. In addition to accumulations of proline, several free amino acids (histidine and isoleucine) essential for insect growth and development were increased in sugarcane leaves by drought stressed conditions, which exacerbated E. loftini infestations. Modifying the suitability of the crop by reducing water deficit stress makes rational irrigation input a key component in the integrated pest management of E. loftini, in addition to other tactics such as cultivar resistance and insecticide application.

Role of oviposition preference in an invasive crambid impacting two graminaceous host crops.

Abstract Oviposition preference studies of the Mexican rice borer, Eoreuma loftini (Dyar), on sugarcane, Saccharum spp., and rice, Oryza sativa L., showed that drought stressed sugarcane was 1.8-fold more attractive based on egg masses/plant than well watered sugarcane. The E. loftini susceptible sugarcane cultivar LCP 85–384 was 1.6-fold more attractive than HoCP 85–845 based on numbers of eggs per egg mass. Egg masses were 9.2-fold more abundant and 2.3-fold larger on sugarcane than on rice. Rice, however, was preferred to sugarcane on a plant biomass basis. Oviposition on sugarcane occurred exclusively on dry leaf material, which increased under drought stress. Egg masses per plant increased on drought stressed sugarcane and were correlated with several foliar free amino acids essential for insect growth and development. The more resistant (based on injury) but more attractive (based on oviposition) rice cultivar XL8 had higher levels of several free amino acids than the susceptible cultivar Cocodrie. The association of host plant characteristics to oviposition preference is discussed. Projected oviposition patterns relative to sugarcane and rice production areas were estimated for Texas and Louisiana based on the availability of each host in different regions of each state. These results suggest that, where sugarcane and rice co-occur, the majority of eggs would be found on sugarcane early in the season, because of this crop’s substantially greater biomass compared with rice. Abundance later in the season would also favor sugarcane; however, the abundance on rice would be greater than expected solely based on host availability, largely because of the greater preference per gram of rice plant dry weight.

Movement of Mexican Rice Borer (Lepidoptera: Crambidae) Through the Texas Rice Belt

Abstract Pheromone-baited traps were used to monitor the movement of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), through the Texas rice belt from 2000 to 2005. Based on location of discovery in each county and year, the average rate of spread from 1980 to 2005 was 23 km/yr. From 2000 to 2005, the leading edge of the infestation has moved 16.5 km/yr toward Louisiana. The 1.8-fold increase (99% confidence interval) of the area occupied from 2000 to 2005 in the Texas rice belt indicates an expansion of the distribution of E. loftini. If movement continues to occur at similar rates, E. loftini will reach Louisiana by 2008.

Resistance to Stem Borers (Lepidoptera: Crambidae) Among Texas Rice Cultivars

Abstract A 4-yr field study was conducted to assess the resistance of rice, Oryza sativa L., cultivars to injury from the sugarcane borer, Diatraea saccharalis (F.), and the Mexican rice borer, Eoreuma loftini (Dyar) (both Lepidoptera: Crambidae). Several cultivars showed reduced levels of injury (‘CLXL8’, ‘XL8’, ‘Wells’, ‘Cheniere’, and ‘XP710’ in 2003; CLXL8, XP723, Cheniere, and ‘CL161’ in 2004) and lower stem borer yield loss (CLXL8 in 2004) than the more susceptible ‘Priscilla’. The resistant CLXL8 also had less injury and yield loss in 2004 and higher yield in 2003 than ‘Cocodrie’, currently the most popular rice cultivar in Texas and Louisiana. Linear regression analyses between whiteheads and main crop rice yield showed steeper negative slopes for the more resistant cultivars than the more susceptible cultivars, indicating a greater yield loss per whitehead on the resistant cultivars. Compensation from insect injury likely explains the positive associations established in our study between main crop yield and whiteheads for some cultivars. Cultivar resistance is anticipated to become a major control tactic in reducing infestations of E. loftini and D. saccharalis in the Texas and Louisiana rice industries.