Russell W. Gesch

Herbicides Tolerated by Cuphea (Cuphea viscosissima × lanceolata)1

Partial seed retention line #23(‘PSR23’) cuphea is a hybrid of Cuphea viscosissima × C. lanceolata. It is a new, spring-planted, annual, potential oilseed crop that is highly susceptible to interference by weeds because of its slow growth during spring and early summer. Grass weeds are controlled easily in this broadleaf crop, but broadleaf weeds are an appreciable problem. Consequently, several broadleaf herbicides were screened for tolerance by ‘PSR23’ cuphea. Broadleaf herbicides to which cuphea showed tolerance in a spray cabinet and a greenhouse were tested in a field setting for 2 yr. Field tolerance was considered as absence of negative impact (P > 0.05) both years to any of four measured traits: overall vigor, dry weight, stand density, and time to anthesis. Cuphea showed tolerance in the field to three soil-applied herbicides (ethalfluralin, isoxaflutole, and trifluralin) and one postemergence herbicide (mesotrione). A few combinations of soil-applied and postemergence herbicides did not damage cuphea. These combinations were ethalfluralin followed by (fb) mesotrione, isoxaflutole fb imazethapyr, and isoxaflutole fb mesotrione. Availability of these herbicides for use in cuphea production may facilitate the domestication and acceptance of this new crop. Nomenclature: ‘PSR23’ cuphea, Cuphea viscosissima Jacq. × C. lanceolata f. silenoides W. T. Aiton. Additional index words: Capric acid, ethalfluralin, isoxaflutole, imazethapyr, lauric acid, mesotrione, oilseed, PSR23, trifluralin. Abbreviations: fb, followed by; MCFA, medium chain fatty acid; PA, plant-applied; PPI, preplant incorporated; ‘PSR23’, partial seed retention line #23; SA, soil-applied.

Winter oilseed production for biofuel in the US Corn Belt: opportunities and limitations

Interest from the US commercial aviation industry and commitments established by the US Navy and Air Force to use renewable fuels has spurred interest in identifying and developing crops for renewable aviation fuel. Concern regarding greenhouse gas emissions associated with land‐use change and shifting land grown for food to feedstock production for fuel has encouraged the concept of intensifying current prominent cropping systems through various double cropping strategies. Camelina (Camelina sativa L.) and field pennycress (Thlaspi arvense L.) are two winter oilseed crops that could potentially be integrated into the corn (Zea mays L.)–soybean [(Glycine max (L.) Merr.] cropping system, which is the prominent cropping system in the US Corn Belt. In addition to providing a feedstock for renewable aviation fuel production, integrating these crops into corn–soybean cropping systems could also potentially provide a range of ecosystem services. Some of these include soil protection from wind and water erosion, soil organic C (SOC) sequestration, water quality improvement through nitrate reduction, and a food source for pollinators. However, integration of these crops into corn–soybean cropping systems also carries possible limitations, such as potential yield reductions of the subsequent soybean crop. This review identifies and discusses some of the key benefits and constraints of integrating camelina or field pennycress into corn–soybean cropping systems and identifies generalized areas for potential adoption in the US Corn Belt.

Cuphea Tolerates Clopyralid

Abstract Cuphea is a new crop of temperate regions that produces seed oil that can substitute for imported coconut and palm kernel oils. Only four herbicides are known to be tolerated by cuphea to date. More herbicides, especially POST products, are needed for continued commercialization. In Minnesota and North Dakota, where cuphea currently is grown, greater control of Canada thistle and biennial wormwood is needed in cuphea. Because clopyralid is effective on both of these species, it was tested at rates ranging from about 25 to 850 g ae ha−1 in greenhouse and field trials. Visual assessment of injury, height, growth, and seed yield of cuphea were not reduced significantly in field-grown plants when clopyralid was applied at rates up to 400 g ae ha−1. Thus, at the rate commonly used in other crops, 200 g ae ha−1, clopyralid can be applied safely to cuphea. Nomenclature: Clopyralid; biennial wormwood, Artemisia biennis Willd.; Canada thistle, Cirsium arvense (L.) Scop.; cuphea, Cuphea viscosissima Jacq. × C. lanceolata W.T. Aiton.

The Role of Light in the Emergence of Weeds: Using Camelina microcarpa as an Example

When modelling the emergence of weeds, two main factors are considered that condition this process: temperature and soil moisture. Optimum temperature is necessary for metabolic processes that generate energy for growth, while turgor pressure is necessary for root and shoot elongation which eventually leads to seedling emergence from the soil. Most emergence models do not usually consider light as a residual factor, but it could have an important role as it can alter directly or indirectly the dormancy and germination of seeds. In this paper, inclusion of light as an additional factor to photoperiod and radiation in emergence models is explored and compared with the classical hydrothermal time (HTT) model using Camelina microcarpa as an example. HTT based on hourly estimates is also compared with that based on daily estimates. Results suggest that, although HTT based models are accurate enough for local applications, the precision of these models is improved when HTT is estimated hourly and solar radiation is included as a factor.