2012 Annual Report
1a.Objectives (from AD-416):
The broad objectives proposed in this Project Plan are to develop and improve sustainable management strategies for weeds and insects. The Project Plan will have the following four objectives. First, identify management practices that lessen the impact of weeds in sugarcane including tillage, residue management, herbicides, etc. This will be accomplished by determining the impact of cultivation frequency and sugarcane variety on bermudagrass and johnsongrass infestations. Also to evaluate the impact of planting rotational crops during the fallow season on weed control and sugarcane production. Second, evaluate herbicides for potential utility in sugarcane. Included in this objective will be evaluation of herbicide timing of spring applications and compatibility of new herbicides with existing herbicides and their fit in current weed control practices. Objective three will be to identify and exploit non-chemical tactics for controlling stemborers. Specifically this will involve identifying new sources of resistance and the potential of role of silica. The fourth objective will be to assess the quantitative relationship between sugarcane aphid densities and yield loss.
1b.Approach (from AD-416):
The approach to meeting the objectives of this project plan will be in the form of field evaluations and a green house evaluation. Cultivation requirements for weed control as a function of the rate of sugarcane emergence and the crops ability to shade the row will be compared. The hypothesis that planting short-season seeded crops during the fallow season will aid in reducing johnsongrass and bermudagrass infestations and will be economically advantageous over a non-crop fallow system, will be tested. New herbicides will be evaluated for their ability to reduce bermudagrass emergence following winter dormancy. New herbicide chemistries will likely offer increased options for weed control in sugarcane and when available will be evaluated for efficacy. Current forms of resistance to the sugarcane borer are associated with low sugar yields. Related species of sugarcane will be evaluated for forms of resistance that may not be associated with low sugar yields. Silica will be evaluated in the greenhouse and in field plots for its potential of increasing insect resistance. Finally, a series of evaluations will be conducted in commercial sugarcane fields determining if feeding by the sugarcane aphid is sufficient to cause economic yield losses.
This project centers on improving weed and insect management practices in sugarcane. Studies were initiated to determine effects of tillage frequency and varietal architecture on bermudagrass and johnsongrass competition with sugarcane. This study is in its first year and there are no results to report. Studies were also conducted to evaluate timing of herbicide applications for management of bermudagrass in sugarcane. Results have shown that suppressing the growth of bermudagrass with herbicides early in the spring resulted in higher yields than with later applications. This was attributed to reduced bermudagrass control and increased sugarcane injury with the later applications. Trials are continuing and results have been reported at meetings attended by sugarcane farmers and consultants, and university extension personnel. Evaluations of the herbicides topramezone, indazaflam, tembotrione, and isoxaflutole were conducted to determine sugarcane tolerance and levels of weed control. Both topramezone and tembotrione were shown to have activity on bermudagrass with little or no injury to sugarcane. These trials are ongoing and will be expanded if it is determined that sugarcane tolerance is acceptable and weed control is similar or better than current standards used for weed control in the sugarcane.
Additional fields infested with sugarcane aphids were monitored for aphid infestation densities and yields were determined. Fields will be grid sampled employing a field computer interfaced with a global positioning system (GPS) receiver to locate and record sampling points. Soil samples were also collected from each location for later analysis and characterization. Data analysis followed a two-step approach. Initially univariate methods was employed to analyze sample variability and distribution. This included tests to determine if the data is normally distributed. In the second stage of the analysis, geostatistical methods were employed to determine if the data were spatially correlated. Further, a greenhouse study was conducted as a preliminary investigation into the role that silica may play in conferring resistance to the sugarcane borer. In this study two sugarcane varieties were evaluated in pots and silica was added at rates of 0, 1, 2, and 4 metric tones per acre. Individual plants were artificially infested with newly hatched sugarcane borer by camel-hair brush and data collected included determining if individual larva successfully established on a plant, number of internodes bored by larvae, and total length of resulting tunnels made by sugarcane borer larvae.
Barriers to establishing an exotic beneficial insect to control sugarcane borer in Louisiana. An ARS researcher at Houma, LA, completed research and published results investigating the feasibility of using alternative larval hosts and host plants to establish a new biological control agent in the temperate Louisiana sugarcane ecosystem. Findings from this research suggest that biological control agent, Cotesia flavipes, is not likely to become established in Louisiana sugarcane fields due to a lack of synchrony between the beneficial insect, host, and host plant and absence of a suitable alternative host. Therefore, little is to be gained by continuing research on this beneficial insect and before attempting to establish an alternative beneficial insect one should be sought that is better adapted to the Louisiana ecosystem.
Bionomics and larval descriptions of a candidate biological control agent of the sugarcane borer. An ARS researcher at Houma, LA, working with a cooperator at the National Museum of Natural History, Smithsonian Institute at Washington, DC, completed research on the bionomics and larval descriptions of a ground beetle with potential to become an important biological control agent of the sugarcane borer in Louisiana. Immature stages of this beetle have only recently become abundant in Louisiana sugarcane fields as a result of the use of greener insecticides by sugarcane farmers. Research has shown that the immature beetles, if found in sufficient enough numbers, are able to control sugarcane borer to a level that economic damage does not occur. Developing techniques to rear the beetles in the laboratory has allowed researchers to obtain descriptions of all immature stages and therefore provide details to be able to distinguish this ground beetle from closely related species.
Gimmel, M.L., Carlton, C.E., White, W.H. 2012. Polymorphism in Languria taedata LeConte, its occurrence in coastal Louisiana Spartina marshes, and clarification of some Motschulsky languriine types (Coleoptera: Erotylidae: Languriinae). Zootaxa. 3237:24-34.
Erwin, T.L., White, W.H. 2012. The Nearctic-Caribbean species Leptotrachelus dorsalis (Fabricius, 1801): Larval descriptions with a diagnosis of immature Ctenodactylini and natural history notes on the genus and tribe (Coleoptera: Carabidae). ZooKeys. 194:17-32.
White, W.H., Wilson, L.T. 2012. Feasibility of using an alternative larval host and host plants to establish Cotesia flavipes (Hymenoptera: Braconidae) in the temperate Louisiana sugarcane ecosystem. Environmental Entomology. 41(2):275-281.
White, W.H., Erwin, T.L., Viator, B.J. 2012. Leptotrachelus dorsalis (F.) (Coleoptera: Carabidae): A candidate biological control agent of the sugarcane borer in Louisiana. Florida Entomologist. 95(2):261-267.