In-field surveys, which directly estimate weed population densities, typically utilize either random or nonrandom field selection methods. We used both methods to characterize the distribution and frequency of glyphosate-resistant (GR) horseweed populations and other late-season soybean weed escapes and to develop a database for tracking weed shifts, control failures, and the presence of other herbicide-resistant biotypes over time in Indiana. In-field surveys were conducted in a total of 978 Indiana soybean fields during September and October of 2003, 2004, and 2005. Information from fields with horseweed was obtained from 158 sites (19%) sampled through a systematic random site selection method and 128 fields through a nonrandom site selection method. When present, horseweed seed was collected and germinated in the greenhouse; rosettes 5 to 10 cm wide were sprayed with 1.72 kg ae/ha of glyphosate. Populations with less than 60% control at 28 d after treatment were determined to be glyphosate resistant. A selected subset of glyphosate-resistant populations was confirmed resistant by subsequent glyphosate dose response experiments. All populations in the subset with less than 60% control at the 1.72 kg ae/ha rate of glyphosate demonstrated 4- to 110-fold levels of resistance (R : S ratios). Glyphosate-resistant populations were found in all regions of Indiana; however, the highest frequencies were in the southeastern (SE) region with 38% of fields sampled and only 1, 2, and 2% of fields sampled in the northwestern (NW), northeastern (NE), and southwestern (SW) regions, respectively. Information gathered in this survey can assist in the development of applied research, as well as reactive glyphosate-resistant horseweed management education in the SE region of the state. Moreover, detecting resistance at low frequencies can direct proactive resistance education to farmers and practitioners in the other regions of the state as a means of providing an early warning system to address glyphosate resistance in weeds.

Experts have long sought to understand the factors that underlie farmer decision making for weed management. The majority of this interest has been in relation to the weak adoption of integrated management approaches and more recently, herbicide resistance strategies. In order to increase adoption in these contexts there is a need to understand better the underlying drivers for weed management decisions. The objective of the research reported here was to probe farmers' understanding of weed management to establish a baseline understanding of these key drivers. Thirty Ohio farmers participated in an in-depth interview where they were asked to reflect on how weeds are introduced and spread, what risks and benefits weeds pose, and what management strategies farmers are familiar with and which they prefer. Their responses were mapped, coded, and analyzed for dominant beliefs and major decision-making influences. The results indicate that farmers largely attribute the introduction and movement of weeds to factors outside their control (e.g., the environment, plant characteristics). They frequently cite diverse and integrated management, but their focus is on control as opposed to prevention. In general, they tend to receive messages about integrated and preventive approaches, but do not always put them into practice because of underlying beliefs about the inevitability of new weed introductions and spread.

Virginia buttonweed is a difficult-to-control weed in southern turfgrass. Typically, auxin-type herbicides are considered to be the standard treatment for this species. Field experiments were conducted to compare the efficacy of flazasulfuron, a sulfonylurea herbicide, to pyridine herbicides on Virginia buttonweed. Treatments included single and sequential applications of flazasulfuron (0.05 or 0.08 kg ai/ha). The sequential applications were applied 3 and 6 wk after initial treatment (WAIT). Three applications of 0.05 and 0.08 kg/ha flazasulfuron controlled Virginia buttonweed greater than 93% at 10 WAIT. Both treatments were comparable to 0.6 kg ai/ha triclopyr + 0.2 kg ai/ha clopyralid (80% control). These studies indicated that increased application of flazasulfuron increased Virginia buttonweed control regardless of application rates evaluated.

Southern crabgrass is a major weed in turfgrass and it primarily is controlled through preemergence herbicide application. Separate studies were conducted to evaluate the efficacy of trifloxysulfuron and flazasulfuron alone and in tank mixtures for southern crabgrass control in bermudagrass as MSMA alternatives. In 2001, two applications of trifloxysulfuron at 0.03 kg ai/ha 6 wk apart controlled southern crabgrass equal to MSMA applied twice at 2.2 kg ai/ha 7 d apart (91% compared to 90%, respectively) 90 d after initial treatment (DAIT), but provided greater control than MSMA in 2002 (80 versus 74%, respectively) 90 DAIT. Two applications of trifloxysulfuron at 0.02 kg/ha tank mixed with MSMA at 1.1 kg/ha controlled southern crabgrass 90%, greater than either two applications of trifloxysulfuron or MSMA applied alone (80% and 74%, respectively). In the second study, flazasulfuron applied at 0.05 kg ai/ha tank mixed with prodiamine at 1.1 kg ai/ha, pendimethalin at 1.6 kg ai/ha, or quinclorac at 0.84 kg ai/ha controlled southern crabgrass greater than a single application of MSMA at 2.2 kg/ha 60 DAT. In both 2005 and 2006 flazasulfuron applied alone provided similar or greater southern crabgrass control compared to a single application of MSMA at 2.2 kg/ha 60 DAT. At the conclusion of these studies, trifloxysulfuron and flazasulfuron alone or in tank mixtures controlled southern crabgrass similar to or better than MSMA; therefore these would be effective alternatives to MSMA in bermudagrass.

Two field studies were conducted in 2004 and 2005 to evaluate the response of glyphosate-resistant ‘TV52R42’ and ‘TV52R14’ soybean to glyphosate at 0, 458, 916, 1,375, 1,833, or 2,749 g ae/ha applied at the R4 reproductive growth stage and at R4 followed by the same rates at R6. A single glyphosate application at the R4 stage did not injure soybean or cause reductions in soybean height, nodes per plant, branch pods, main stem pods, or yield, regardless of application rate. Likewise, sequential applications of glyphosate at the R4 followed by R6 growth stages resulted in no adverse effects on growth parameters or yield. Preliminary findings indicate excellent tolerance to glyphosate application at reproductive growth stages beyond the currently labeled R2 growth stage restriction in varieties evaluated. Research findings warrant evaluation of an expanded range of germplasm under a variety of environmental conditions and potential effects on seed quality for establishment of tolerance levels and potential herbicide label amendments.

The process of labeling new herbicides for specialty crops has always been difficult. Progress in solving specialty crop weed control problems will likely be more challenging in the future. Major crops like corn, cotton, rice, soybean, and wheat are planted on millions of hectares, and most of these crops are treated with herbicides. In contrast, specialty crops (i.e., minor crops, e.g., container ornamentals or lettuce) are planted on 122,000 ha or less; thus, the potential value of herbicide sales is limited in these crops by the low number of hectares planted per crop. High crop value, small hectarage per crop, and generally marginal herbicide selectivity results in a high potential of liability for herbicide registrants and little incentive to label herbicides in these crops. The Interregional Project Number 4 (IR-4) program facilitates the registrations of pesticides on minor crops. Work needed to support pesticide tolerance in a given crop is conducted by IR-4 and cooperators. However, to develop new crop tolerances, the IR-4 process requires new herbicides. The success of glyphosate-resistant soybean has resulted in a less profitable herbicide market for all crops. In response, most primary pesticide manufacturers have reduced the size, or even eliminated herbicide discovery programs. As private industry slows or stops herbicide development, there will be fewer new minor-crop herbicides. Many questions face minor-crop weed scientists. For example, what are other practical solutions to control weeds in minor crops besides herbicides? Should research focus on development of competition models and decision thresholds or on weed removal tools such as robotics? What funding sources are available for minor-crop weed scientists? Are grant programs at the Federal level prepared to increase support for minor-crop weed research? Will university administrators replace retiring specialty crop weed scientists, knowing that their funding sources will produce little overhead? These questions require a response from all parties interested in specialty crop weed control.

The Interregional Research Project Number 4 (IR-4) Specialty Food Crops Program is a publicly-funded program initiated in 1963 to develop and submit regulatory data to support registration of pest control products for specialty crops. In the early to mid 1990s, nearly 45% of the IR-4 residue projects supported new herbicide registrations for fruits and vegetables with the other 55% devoted to fungicides, insecticides, and nematacides. In 2005, the number of residue projects conducted by IR-4 to support herbicide fruit and vegetable registrations was less than 30%. The three main factors that have contributed to this decline are: fewer herbicides available for registration; product liability concerns; and an increased focus on new, safer, and Reduced Risk Pesticides for insect and disease control. It has been a number of years since a new herbicide has been developed for a major crop that could be extended to specialty food crops. Many of the current IR-4 herbicide projects are with products that have been on the market for 20 or more years. Product liability is a concern because of the high value of many specialty crops relative to the potential market opportunity. In many cases, the registrant requires product performance data before IR-4 can proceed with a residue project. With limited funds for developing these data, many new projects never proceed to the regulatory stage. Although registrants can seek indemnification for some of these uses, it is a complicated often state-specific process. IR-4 has been successful in a number of areas, including the registration of a large numbers of uses through reduced data extrapolations for products such as glyphosate and carfentrazone-ethyl. Additionally, IR-4 submitted the first successful petition establishing an exemption of tolerance for a conventional herbicide (imazamox). Future IR-4 initiatives include collaboration with industry, growers, and academia to develop new herbicide technologies such as plant breeding or transgenic crops and generation of appropriate data to extend those products to specialty food crops. IR-4 will also assist in registering products that can be used on crops that have been selected (or developed through biotechnological approaches) to be tolerant to existing herbicides. Registrants should strongly consider developing herbicides for specialty food crops, with IR-4's assistance, as a means to expand markets and also as a means to extend data protection of their products, as allowed under the Food Quality Protection Act.

Multispectral images of leaf reflectance in the visible and near infrared region from 384 to 810 nm were used to establish the feasibility of developing a site-specific classifier to distinguish lettuce plants from weeds in California direct-seeded lettuce fields. An average crop vs. weed classification accuracy of 90.3% was obtained in a study of over 7,000 individual spectra representing 150 plants. The classifier utilized reflectance values from a small spatial area (3 mm diameter) of the leaf in order to allow the method to be robust to occlusion and to eliminate the need to identify leaf boundaries for shape-based machine vision recognition. Reflectance spectra were collected in the field using equipment suitable for real-time operation as a weed sensor in an autonomous system for automated weed control.

The level of past industry participation in registering herbicide minor crop uses has been a function of active ingredient discovery output and the combination of incentives and barriers that drive minor use registration decisions. Over the past 10 yr there have been several external factors negatively impacting the rate of new herbicide introductions by industry. These include industry consolidation, a decrease in the global value of the conventional herbicide market, adoption of Herbicide-Resistant Crop (HRC) technology, a substantial increase in required regulatory activity primarily through reregistration programs, and increased costs of discovery research and product development. The increased cost of conducting business in an increasingly competitive market has undoubtedly influenced herbicide registrants to adopt different discovery strategies. Economics dictate registration efforts only towards crops that will create a significant, positive return on investment. In most cases, development of new herbicides for minor crops is not economically viable due to low or negative return on investment and disproportionate liability risk. Therefore, to motivate increased participation, companies need incentives and mechanisms to mitigate risk and registration barriers. Increased data protection and the Interregional Project 4 (IR-4) program, a cooperative government program with the goal of developing data to support regulatory clearances of pest control products for specialty crops, are current government programs in place that provide incentives and defray cost. Other incentives should be explored to make minor crops more attractive targets. However, product registration, liability risk, and dedicating the necessary resources to adequately research crop selectivity are still major economic barriers. Creative solutions that ensure companies are not unreasonably exposed to yield loss claims would remove a primary reason why companies are reluctant to register herbicides for minor crops.