2010 Annual Report
1a.Objectives (from AD-416)
Develop new and modify existing production-year strategies for integrated and sustainable weed and insect management in sugarcane to:.
1)determine the degree of weed control that current and alternative cultural and mechanical controls afford, weed species that are most susceptible, and conditions that affect efficacy; 2)evaluate and provide efficacy data on new chemistries for selective control of weeds and determine compatibility of new herbicides with currently used herbicidal practices;.
3)identify and evaluate a biological control agent for controlling season-long infestations of the SCB; and.
4)identify new sources of SCB resistance within a population of Saccharum spontaneum. Measure the long-term impact of changing agronomic and harvesting practices on weed and insect pest development during a 4-year sugarcane cropping cycle to:.
1)measure the impact of changing agronomic practices on bermudagrass and johnsongrass development and their competitiveness with sugarcane during a 4-year crop cycle and identify synergistic practices that result in optimum weed control and crop yield; and.
2)measure the effects of soil health, fertilizer, moisture, ground cover, and other sugarcane production practices on insect pests and their natural enemies.
1b.Approach (from AD-416)
Field evaluations will be conducted to evaluate new and/or modify existing production-year strategies to include cultivation frequencies, herbicide application timings and placement, and the utilization of post-harvest crop residue blankets for the management of itchgrass, johnsongrass, and morningglory within a sugarcane crop. Synergistic practices will be identified and subjected to further testing. In addition, the efficacy of high-unit activity herbicides in controlling these weeds will be evaluated as new herbicides become available in an attempt to add additional tools to effectively manage weeds. Separate studies will be conducted to evaluate the long-term (4 to 5-year crop cycle) effects of adopting these practices on crop yield and weed development. In an attempt to lessen the industry’s dependence on insecticides for the control of the sugarcane borer, studies will be conducted to evaluate Cotesia flavipes as a biological control agent for controlling season-long infestations of the sugarcane borer; to identify and develop germplasm with increased resistance to the sugarcane borer, and to assess the effects of sugarcane planting date, soil fertility levels, and post-harvest residue blankets on the population of the sugarcane borer and foraging predators to include the red imported fire ant.
This project receives support from the American Sugar Cane League through a Trust Funded Cooperative Agreement (6410-21000-014-04T). Additional details of research can be found in that report.
In 2009, evaluations continued on the impact of cultivation, post-harvest residue management, and herbicide application on bermudagrass and johnsongrass interference in sugarcane. Reducing cultivations (from four to two) did not affect sugarcane yield or increase weed infestation, whereas using a no-till approach reduced crop yields and increased weed infestations. Burning residue following harvest slightly increased yield compared to no residue removal and did not effect bermudagrass infestation of sugarcane. However, removing residue increased johnsongrass infestations.
The sugarcane borer is the most important insect of Louisiana sugarcane costing the industry roughly $200 million in yield loss and $5 million in insecticides per year. A habitat manipulation study was conducted as a means to establish the exotic beneficial insect Colesia (C.) flavipes. Small refuge sites were established with johnsongrass, vaseygrass, and an energy cane. After three years of evaluation we were not able to recover C. flavipes from sugarcane borer collected in a sugarcane field contiguous to the refuge sites, nor were we able to collect C. flavipes from the insect Diatraea evanescens infesting vaseygrass. Habitat manipulation is unlikely to provide a bridge for C. flavipes to survive from winter dormancy until sugar cane develops an above-ground stem. We suggest two reasons for failure of habitat manipulation. First, inherently low populations of sugarcane borer are found in grass weed species as they provide an inadequate site for winter survival of larvae. Second, while Diatraea evanescens is an acceptable host for C. flavipes in the lab, in nature the larvae of this borer are found well within the crown of the plant making it nearly impossible for female C. flavipes to attack, as there is no clearly defined entrance hole for the female parasite to ingress.
Botanical descriptors were provided for two germplasm clones with low resistance levels to the sugarcane borer; the last stage before official registration. We are confident that this resistance can be transferred to commercial sugarcane varieties and are hopeful that this resistance will be less correlated with sugar yields. The unique combination of sugarcane borer resistance and high early-generation sugar yields makes these two clones attractive to sugarcane breeders to develop insect-resistant sugarcane cultivars as well as for testing as possible biofuels feedstock.
Pit-fall trapping was used to monitor the impact of post-harvest residue on soil inhabiting insect predators. It is not known if this residue impacts predators of the sugarcane borer. Three years of pit-fall trapping in a second sugarcane field was completed. In the first experiment, fewer fire ants, the most important predator of the borer, were trapped when the residue remained, but not in the second experiment. A third trapping cycle may be required to make a final determination on the impact of residue on soil inhabiting beneficial insects.
Identify New Sources of Sugarcane Borer Resistance within a Population of Saccharum spontaneum. Releasing sugarcane varieties with resistance to the sugarcane borer offers an attractive alternative to ecologically disruptive insecticides. Avoiding the use of insecticides can save the Louisiana sugarcane growers up to $5 million per year in direct costs for insecticides and $200 million per year in yield loss due to tunneling by borer caterpillars. Unfortunately, current resistant varieties are high in fiber; a trait that inhibits extraction of sugar. A new source of resistance was sought and found in a species of cane closely related to sugarcane. Two offspring (Ho 08-9001 and Ho 08-9003) resulting from a cross of this new source with a traditional borer–resistant sugarcane variety, were identified as superior to the others in resistance and sugar yield potential and will be released to the public as new breeding lines. The unique combination of sugarcane borer resistance and high early-generation sugar makes these two clones attractive to sugarcane breeders for both further backcrossing to develop insect-resistant sugarcane varieties as well as testing in various environments as possible biofuels feedstock.
Evaluation of Glyphosate as a Sugarcane Ripener Throughout the Harvest Season in Louisiana. Glyphosate applied as a ripener has been shown to increase sugar in cane harvested early in the harvest season; however, the response in cane harvested later in the season has not been fully determined. During three harvest seasons, glyphosate was applied at 0.21 kg/ha at four, four-week intervals beginning in mid-August to determine sugarcane's response to glyphosate throughout the harvest season. Sugarcane was hand-harvested at 4, 5, 6, and 7 weeks after glyphosate application and stalk weights and sugar content were determined. The response of sugarcane to glyphosate was greatest (21%) when applied early in the harvest season and this response decreased with each four-week interval between applications. No response to glyphosate was observed when glyphosate was applied in late October or early November. Results of this research were used to adjust recommendations for ripener applications published through the Louisiana State University Extension.
Identify and Evaluate a Biological Control Agent for Controlling Season-long Infestations of the Sugarcane Borer (SCB). The SCB is the most important insect pest of sugarcane in Louisiana. The Louisiana sugarcane industry spends roughly $5 million per year in direct costs for insecticides to control this pest. Attempts to establish exotic beneficial insects into the Louisiana sugarcane ecosystem to reduce the dependency on insecticides have been generally unsuccessful. The biological control agent Colesia (C.) flavipes can now be added to the list of introduction failures in Louisiana. Lack of synchrony with the sugarcane crop appears to be the basis of this failure. In Louisiana, the entire sugarcane crop is removed in the fall thereby removing any potential host larvae for the parasite following overwintering and thereby preventing its re-establishment the following year. Creating refuges of alternate weed hosts for the sugarcane borer and for a closely related borer species of the sugarcane borer have proven to be ineffective. Again, the limiting factor seems to be inaccessible host larvae for the parasite. Host larvae, although present, are below ground and therefore protected. There is no accessible borer tunnel for the female parasite to access larvae. C. flavipes would be effective as a biological control only if it was released in large numbers every year, but the cost associated with this approach would be prohibitive.
Hummel, N.A., Hardy, T., Reagan, T.E., Pollet, D., Carlton, C., Stout, M.J., Beuzelin, J.M., Akbar, W., White, W.H. 2010. Monitoring and First Discovery of the Mexican Rice Borer Eoreuma loftini (Lepidoptera: Crambidae) in Louisiana. Florida Entomologist. 93(1):123-124.
Zhou, M.M., Kimbeng, C.A., Da Silva, J.A., White, W.H. 2010. Cross-resistance between the Mexican Rice Borer and the Sugarcane Borer (Lepidoptera: Crambidae): A Case Study Using Sugarcane Breeding Populations. Crop Science. 50:861-869.
Dalley, C.D., Richard Jr, E.P. 2010. Herbicides as ripeners for sugarcane. Weed Science. 58:329-333.