2013 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.
Sugarcane varieties are being compared for their ability to compete with the problematic weeds (johnsongrass and bermudagrass) with data showing reductions in these weeds when varieties with high leaf area indices are planted.
The utility of soybean and sweet sorghum as rotational crops in between plantings of sugarcane continues to be evaluated. Two years of yield data have been collected for these alternative crops and their effects on subsequent sugarcane crops is being evaluated.
Timing of herbicide application for control of bermudagrass in sugarcane continues to be explored. Earlier application timings for the herbicide clomazone have been shown to be less injurious to sugarcane, whereas application of metribuzin can be delayed somewhat to provide suppression of bermudagrass later into the spring without risk of crop injury.
Several herbicides are being evaluated for their potential utility in sugarcane. These include metolachlor for grass and nutsedge control, indazaflam, topramezone, and tembotrione for bermudagrass and seedling weed control.
Progress continues toward identifying a new source of resistance to the sugarcane borer. A replicated experiment was planted in 2012 for evaluation in the 2013 growing season. This evaluation is comprised of offspring from a bi-parental cross that were identified as having high antioxidant concentrations and those that expressed low concentrations of antioxidants. Native sugarcane borer infestations will be supplemented with laboratory-reared borer larvae and data will be collected at harvest to determine levels of borer damage (percent bored internodes and as visable damage ratings).
Laboratory diet incorporation feeding evaluations will also be conducted to establish the presence of plant-derived compounds that affect insect growth which will be correlated with previously determined antioxidant levels. If this relationship is sufficiently strong, screening for antioxidant levels could be used as a selection technique to identify borer resistance in sugarcane seedlings without incurring the time and expense of progeny testing.
A greenhouse study was completed and a manuscript written reporting the correlation of sugarcane borer resistance with increased levels of silica. Land has become available in 2013 for a small-plot field evaluation for further verification of the relationship of insect resistance and soil silicon amendments.
Finally, it is hoped that native infestations of sugarcane aphid will be present and in sufficient numbers to allow the collection of additional yield data to ultimately establish if this insect is an economic pest of sugarcane.
Insecticide for reducing West Indian canefly damage to sugarcane. Sugarcane in Louisiana is attacked by a number of insects representing several important groups (e.g., beetles, moth stem borers, and sap-feeders). The sap-feeders are the most diverse group representing six species:.
1)aphids (yellow sugarcane aphid and sugarcane aphid),.
2)planthoppers (sugarcane delphacid and West Indian canefly), and.
3)Pulvinaria spp. (pink mealybug and soft scale). In 2012, unusually high numbers of West Indian canefly infested much of the sugarcane grown in Louisiana. In response to grower concerns, two experiments were established by Sugarcane Research Unit scientists at Houma, Louisiana, to identify effective and safe insecticides to control this insect as well as to determine yield losses ascribed to canefly infestations. Utilizing control data generated from these two studies and other studies, the Louisiana Department of Agriculture and Forestry (LDAF) successfully obtained a Section 18 Crisis Exemption for the insecticide imidacloprid. Approximately 16,000 acres of sugarcane were treated over the 15 days that the Crisis Exemption was valid. Results from trials showed that canefly feeding resulted in an approximate 23% reduction in sugar yield. An economic analysis conducted by the LSU AgCenter showed a gain of $397/acre resulting from insecticide treatment with a total economic gain for the 16,000 acres that were treated of $6.5 million. These data, plus additional data generated by cooperators, was used as the basis for submission of a Section 18 Specific Exemption by the LDAF for imidacloprid for canefly control during the 2013 growing season which was granted by the Environmental Protection Agency.
Dalley, C.D., Viator, R.P., Richard, E.P. 2013. Integrated management of bermudagrass (Cynodon dactylon) in sugarcane. Weed Science. 61(3):482-490. Available DOI: http://dx.doi.org/10.1614/WS-D-12-00124.1