T. E. Reagan

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.

Predicting economic losses from the continued spread of the Mexican rice borer (Lepidoptera: Crambidae).

Abstract The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), is an invasive species that originated from Mexico, and it is threatening to cause major economic losses to sugarcane, Saccharum spp., and rice, Oryza sativa L., industries in Louisiana. The insect is expected to reach sugarcane and rice production areas in Louisiana by 2008, and infest all of Louisiana sugarcane and rice industries by 2035. When all sugarcane in Louisiana becomes infested, annual yield losses of

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

220 million would be expected for a cultivar of comparable susceptibility to LCP 85-384 (assuming this cultivar is planted on 100% of the production area). This also assumes the use of the current practice of rainfed production and one application of insecticide, which is presently used by farmers in Louisiana. Irrigation with 30 cm of water is predicted to reduce estimated losses by 29%, whereas four applications of a biorational insecticide such as tebufenozide are expected to reduce the loss in revenue by 53%. The use of the resistant ‘HoCP 85-845′ would reduce the projected loss in revenue by 24%. Combining all three management tactics on sugarcane, anticipated net loss in revenue would decrease by 66%. The rice industry in Louisiana is projected to suffer from a loss in revenue of

Refuge Releases of Cotesia flavipes (Hymenoptera: Braconidae) into the Louisiana Sugarcane Ecosystem

45 million when the entire state is infested. A 77% reduction in loss in revenue is expected with one application of lambda-cyhalothrin. A quarantine on east Texas sugarcane is estimated to save the Louisiana industry between

Selection, egg viability, and fecundity of the sugarcane borer (Lepidoptera: Crambidae) with tebufenozide.

1.1 billion and

Effects of Diatraea saccharalis (F.) (Lepidoptera: Pyralidae) damage and stalk rot fungi on sugarcane yield in Louisiana

3.2 billion (depending on management) during the time needed for the insect to fully invade the state’s sugarcane and rice producing area by natural migration rather than by accidental introduction. The rapid deployment of appropriate management tactics will have a key role in reducing the anticipated economic impact of E. loftini once it becomes a pest in Louisiana sugarcane and rice.

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

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.

Sampling for the Sugarcane Borer (Lepidoptera: Crambidae) on Sugarcane in Louisiana

Abstract After 15 failures to establish Cotesia flavipes (Cameron) as a parasitoid of the sugarcane borer, Diatraea saccharalis (F.), in Louisiana sugarcane fields (Saccharum spp.), four release refuges were established as sites for an intensive study of the crop, host, and parasitoid interaction for a full crop cycle. These refuges were maintained with minimal disturbance from June 2001 to June 2002 to encourage the establishment of C. flavipes. Refuges were managed in a manner such that (1) sugarcane borer larvae were abundant, (2) predation of parasitoids by the red imported fire ant, Solenopsis invicta (Buren), was minimized, (3) host and parasitoid were not exposed to insecticide applications used to control economically damaging sugarcane borer infestations, (4) presence of parasitoids was insured through repeated releases during the growing season, and (5) the sugarcane was not harvested to enhance overwintering opportunities for C. flavipes. C. flavipes was successfully recovered in all established refuges and overwintered in three of the four refuges. However, parasitoids were not collected during May of the following spring. The inability of the parasitoid to use first-generation sugarcane borer larvae seems to be a major limiting factor preventing establishment of C. flavipes in Louisiana sugarcane. In May, the sugarcane stalks have not formed internodes, which may preclude important host finding and host acceptance cues such as frass and silk in the tunnel entrance. Although efforts were made to suppress the red imported fire ant at the study sites, ant predation on C. flavipes was also a major factor limiting establishment.

Selection and Life History Traits of Tebufenozide-Resistant Sugarcane Borer (Lepidoptera: Crambidae)

Abstract Two separate attempts to select the sugarcane borer, Diatraea saccharalis (F.), for resistance to tebufenozide were unsuccessful. Both selected colonies were lost after the fourth generation due to a lack of oviposition. Differences were not detected in fecundity or percent egg viability for 5-d-old third instars exposed to concentrations (EC5, EC15, and EC30) of tebufenozide for 7 d. Decreases (P ≤ 0.01) in mean female pupal weights were detected in larvae exposed to EC15 and EC30 concentrations. An ovicidal impact using serial dilutions of tebufenozide (10, 100, and 200 ppm) also was detected. Percent viability was reduced from 98% for untreated eggs to 61% for eggs dipped in 10 ppm and below 6% for eggs dipped in ≥100 ppm. Eggs treated with 200 ppm did not hatch. Though some embryonic development was observed on eggs treated with the high concentrations (100 and 200 ppm), sclerotization of head capsule was not apparent. The ovicidal property of tebufenozide may enhance its effectiveness in controlling populations of the D. saccharalis on an area-wide basis. Fecundity and egg viability were affected in later generations of selection; however, separate studies assessing individuals that were exposed to sublethal concentration (EC5, EC15, and EC30) of tebufenozide as third instars for 7 d in one generation did not detect differences.

Life Cycle and Larval Morphology of Diomus Terminatus (Coleoptera: Coccinellidae) and its Potential as a Biological Control Agent of Melanaphis Sacchari (Hemiptera: Aphididae)

Abstract Actual or simulated sugar-cane borer (SCB), Diatraea saccharalis (F.), damage together with stalk rot (red rot, Colletotrichum falcatum Went, inclusive) infection resulted in reductions (16.6–32.9%) in sugar-cane plant-population density. Estimated yield losses caused by stalk rots in combination with SCB damage to standing cane were as much as 33.0% or 2.5 metric tonnes of sugar per hectare. The incidence of C. falcatum recovery from the external surfaces of bored and unbored stalks was similar, 59.5 versus 67.1 %, respectively. In the internal cane tissues, however, this organism was detected in only 9.5% of the bored stalks and in none of the unbored stalks. These data indicated that SCB damage, to a small extent, assists the invasion of sugar-cane by C. falcatum and other stalk rot fungi.