Location: Sugarcane Research
2020 Annual Report
Objectives
The main objectives proposed in this Project Plan are to develop and improve sustainable management strategies for weeds and insects. Effective integrated pest management (IPM) programs are vital to a sustainable cropping system. Over the next 5 years, the project will focus on the following objectives:
Objective 1: Evaluate newer herbicide chemistries (i.e., 4-hydroxyphenylpyruvate (HPPD) inhibitors, cell wall biosynthesis inhibitors, etc.) for efficacy of weed control in sugarcane and crop safety, as well as older, currently registered herbicides to improve weed management (tank-mix combinations, timing of application, use of spray adjuvants, etc.).
Objective 2: Evaluate cultural control methods for reducing weed interference in sugarcane including, but not limited to: varietal differences in competitiveness of sugarcane, inter-row tillage timing, type, frequency, and rotational crops (including green manure cover crops) that could be used during fallow season compared with chemical fallow, and site-specific management.
Objective 3: Enhance the role of plant resistance in managing damaging infestations of stem borers (i.e., sugarcane borer and Mexican rice borer) in sugarcane.
Sub-objective 3.A: Characterize fiber among commercial sugarcane cultivars resistant to the sugarcane borer and Mexican rice borer.
Sub-objective 3.B: Identify borer resistant progeny in high sucrose bi-parental crosses.
Objective 4: Identify control tactics for managing damaging infestations of a hemipteran complex (e.g., sugarcane aphid, yellow sugarcane aphid, West Indian canefly, and sugarcane delphacid) to include the role of soil health on these infestations and new insecticides for controlling the complex.
Approach
The approach to meeting the objectives of this project plan will be primarily in the form of replicated field experiments. Some of these field experiments will also be supported by laboratory analyses. New herbicide chemistries, when they become available, will provide the potential for greater efficacy in weed control; however, determining appropriate application rates, application timing, and application methodology will require replicated field experimentation that are repeated in multiple years. Results from these experiments will be used for obtaining labeling by EPA and ultimately in formulating extension recommendations to sugarcane growers. Cultural controls provide opportunities for reducing weed pressure by planting sugarcane varieties with greater competitiveness resulting in more efficient tillage practices (i.e. fewer cultivations). Planting rotational crops (e.g. soybean and sweet sorghum) will provide an additional income stream to growers while also aiding in suppressing weed infestations. To develop these improved cultural practices will also require a series of field experiments. The results from these studies will also be used to develop extension recommendations for sugarcane growers. Enhancing the role of plant resistance in controlling the sugarcane borer and Mexican rice borer will require a more in-depth knowledge of fiber composition in commercial sugarcane varieties. A replicated field experiment consisting of sugarcane varieties with known reaction to sugarcane borer and Mexican rice borer will provide plant tissue for detailed fiber analyses. Ultimately a fiber profile will be qualified and quantified that will allow selection for stem borer resistance in the absence of the insect pest. Finally, field experiments will be conducted to identify control tactics for managing damaging infestations of a four-species hemipteran complex infesting sugarcane. These experiments will seek to better refine damage thresholds and ultimately establish action thresholds for initiating insecticide applications. The most effective insecticide formulations will need be to be identified as well as determining their most economical application rates. Ultimately, the findings from this Project Plan will be used to develop improved and sustainable management strategies for weeds and insects pest of sugarcane primarily in Louisiana, but the findings are generally applicable for sugarcane grown in Florida and Texas.
Progress Report
To consolidate and strengthen complementary efforts in sugarcane research, National Program (NP) directed this unit to merge this project with NP 305 titled “New Crop Production and Protection Practices to Increase Sugarcane Ratoon Longevity and Maximize Economic Sustainability”. Therefore, this will be the final report and will summarize results for the duration of the project. Continued progress can be found in annual report for the new consolidated project - 6052-21000-017-00D.
An experiment was initiated by ARS researchers at Houma, Louisiana, in 2016 and repeated in 2017 to evaluate the effect of growing green cover crops (soybean and sweet sorghum) in comparison to traditional fallow practices (cultivation and chemical weed control) on sugarcane yield parameters and weed control. Sweet sorghum can be planted as a rotational crop, or as a bioenergy feedstock, during the fallow period after sugarcane roots have been destroyed and before sugarcane replanting in August. Sorgoleone, a natural compound excreted by sorghum roots, exhibits herbicidal activity and slows the growth of certain broadleaf and grass species. This potential may assist sugarcane growers in controlling weeds that are normally harmful to sugarcane production. However, if sugarcane is planted too soon following sorghum harvest, any residual sorgoleone remaining in the soil may be detrimental to the early germination and growth of sugarcane seed pieces. Therefore, ARS scientists at Houma, Louisiana, and researchers at Nicholls State University in Thibodaux, Louisiana, developed a method for extracting and detecting sorgoleone in soil samples. Using this method, scientists observed only very low levels of sorgoleone, less than 1 part per million, in soil samples taken immediately after sorghum was harvested in 2016 and 2017. Although very low levels of sorgoleone were detected, plant-cane sucrose yields following sweet sorghum were lower when compared to sugarcane that followed soybean, chemical fallow, or traditional tillage fallow. Consequently, growers might consider other options besides sorghum as a rotational crop. In past research, ARS researchers at Houma, Louisiana, demonstrated that legumes such as soybean, cowpea, or Sunn hemp, did not reduce sugarcane yields of the subsequent crop. Each year prior to sugarcane harvest, weeds were identified by species and counted to determine infestation levels within each treatment-cultivar combination. Plant-cane, first-, and second-ratoon yields were collected for the 2016 trial and plant-cane and first-ratoon for 2017. To complete the study, sugarcane yield data will be collected until second ratoon (October 2020).
Current preemergence and postemergence industry standard herbicides have shown to poorly control divine nightshade, a problematic broadleaf weed that infests both plant and ratoon sugarcane in Louisiana. Plants can produce high quantities of seed if not controlled before sugarcane harvest. Sugarcane is mechanically harvested green (green-cane harvest) using a chopper harvester that cuts sugarcane at the soil surface. Blades segment the stalk into several 12 to 18" billets and an extractor fan removes lightweight leafy material and tops from billet segments before billets are dumped into a high clearance tipper wagon. Approximately 3 to 10 tons of postharvest residue remains on the soil surface following green-cane harvesting. Previous experiments showed divine nightshade and itchgrass seed deposited on the soil surface were susceptible to high temperatures experienced during a prescribed burn. Therefore, an experiment was conducted by ARS researchers at Houma, Louisiana, in the fall of 2019 (run 1) and will be repeated in the fall of 2020 (run 2) to determine the effect of simulated weed seed drop following sugarcane harvest at three timings (October, November, and December) and burning intervals following harvest (October, November, December, January, February, no burn, and mechanical residue removal). Initial findings by ARS researchers at Houma, Louisiana, showed little effect of burn timing on itchgrass seed mortality when sugarcane was harvested in October, and was due to warm October and early November air temperatures that promoted itchgrass emergence before burn treatments were implemented. Divine nightshade emergence appeared to be greatest when sugarcane was harvested in December and postharvest residue burning was delayed until February, not removed, or mechanically removed.
Several replicated field studies evaluating herbicide tank mixtures and tillage timing previously established in 2017 (run 1) were completed by ARS researchers at Houma, Louisiana, in 2019 following harvest of the plant-cane, first-, and second-ratoon crops. Studies established in 2018 (run 2) will be completed in 2020 after harvesting the second-ratoon crop in late October. Early-spring treatments were applied in March before sugarcane fertilization. Sequential herbicide treatments or studies with multiple herbicide and or tillage applications were applied after fertilization in May. Sugarcane stalk counts and stalk height measurements will be recorded in August 2020. Initial findings averaged over the five harvests showed season-long bermudagrass competition with sugarcane reduced sucrose yield 7 to 17% depending on herbicide treatment timing and number of herbicide applications.
A survey that was originated in 2003, was continued by ARS researchers at Houma, Louisiana, from 2016 to 2020 across the Louisiana sugarcane industry (231 sites) to determine the quantity and distribution of sugarcane plants with dead hearts. Dead hearts result from stem boring insects, like the sugarcane borer, attacking the inner whorl of leaves. Populations of overwintering sugarcane borers in Louisiana have decreased over the past five years and this has been accompanied by a decrease in the number of sugarcane fields that require a pesticide application. Results from this study have demonstrated that field estimates of dead heart density can aid in predicting pest pressure later in the growing season.
Several yield reduction trials on experimental and commercial Louisiana sugarcane cultivars were established to determine the level of plant resistance to the sugarcane borer. In these trials, the experimental plots are artificially inoculated with sugarcane borers to insure that sufficient pest pressure exists to evaluate the cultivar's resistance level. Bored internode data was collected from the cultivars and was used to help researchers determine candidate sugarcane cultivars for commercial release. The Louisiana trials were collaborative studies with ARS researchers from Houma, Louisiana, and Louisiana State University. Similar trials were established in Texas in collaboration with the University of Florida, Texas A&M, and Rio Farms to evaluate Texas sugarcane cultivar's resistance to the Mexican rice borer. The Mexican rice borer has been identified in some areas in Louisiana, but is more abundant in Texas.
In the fall of 2016, ARS researchers at Houma, Louisiana, planted with HoCP 85-845, HoCP 04-838, Ho 07-613, and HoCP 00-950 to determine how the fiber components of the four varieties change during the growing season. This data will then be related to borer infestation data from separate yield reduction studies. The plots were sprayed with insecticide to maintain the plots free of sugarcane borers in the spring and summer of 2017. Stalks were collected on a monthly interval from June through September for fiber component analysis. All plots were harvested in November 2017 to determine cane and sugar yields of the plant-cane crop. In 2018, the first-ratoon crop was also sprayed with insecticide to maintain the plots free of sugarcane borers in the spring and summer of 2018. Stalks were collected on a monthly interval from June through September for fiber component analysis and stalk counts were determined in August of 2018. All plots were harvested in November 2018 to determine cane and sugar yields of the first-ratoon crop. Finally, in 2019, the second-ratoon crop was also sprayed with insecticide to maintain the plots free of sugarcane borers in the spring and summer of 2018. Stalks were collected on a monthly interval from June through September for fiber component analysis and stalk counts were determined in August of 2018. All plots were harvested in October 2019 to determine cane and sugar yields of the second-ratoon crop. Fiber component analysis of the 2017 and 2018 crop samples are complete. Fiber component analysis of the 2019 crop will be completed in the fall of 2020.
Two insecticide trials were initiated by ARS researchers at Houma, Louisiana, in June 2019, one in a plant-cane field of HoCP 09-804 and the second in a first-ratoon field of HoCP 00-950. The test was repeated in the first-stubble field of HoCP 09-804 in 2020. The trials evaluated the efficacy of two commercial insecticides (Confirm and Prevathon) on the control of sugarcane borers. In addition, an early (pre-threshold) application of both materials was compared to the standard threshold timing. Cane and sugar yields were determined to evaluate the effects of each insecticide on sugarcane borer control. In addition, stalk samples were collected (before combine harvest) to determine bored internodes for a direct evaluation of the insecticide’s efficacy.
Accomplishments
Review Publications
Spaunhorst, D.J., Orgeron, A.J., White Jr, P.M. 2019. Burning post-harvest sugarcane residue for control of surface-deposited divine nightshade (Solanum nigrescens) and itchgrass (Rottboellia cochinchinensis) seed. Weed Technology. 33(5):693-700. https://doi.org/10.1017/wet.2019.65.
Spaunhorst, D.J. 2020. Influence of establishment timing on growth and fecundity of two itchgrass (Rottboellia cochinchinensis) biotypes grown in Louisiana. Weed Science. 68:418-425. https://doi.org/10.1017/wsc.2020.30.
Spaunhorst, D.J., Orgeron, A.J. 2019. Dry heat and exposure time influence divine nightshade and itchgrass seed emergence. Agronomy Journal. 3(5):2226-2231. https://doi.org/10.2134/agronj2019.02.0072.
