Adding Epidemiologically Important Meteorological Data to Peanut Rx, the Risk Assessment Framework for Spotted Wilt of Peanut

Management of disease affecting peanut in the southeastern United States has benefited from extensive field research identifying disease-associated risk factors since the 1990s. An assessment of risk factors associated with tomato spotted wilt (TSW), caused by tomato spotted wilt virus and spread exclusively by thrips, is available to growers through Peanut Rx, a tool developed to inform peanut management decisions. Peanut Rx provides an assessment of relative TSW risk as an index. The assessment provides information about the relative degree to which a field characterized by a specified suite of practices is at risk of crop loss caused by TSW. Loss results when infection occurs, and infection rates are determined, in part, by factors outside a grower’s control, primarily the abundance of dispersing, viruliferous thrips. In this study, we incorporated meteorological variables useful for predicting thrips dispersal, increasing the robustness of the Peanut Rx framework in relation to variation in the weather. We used data from field experiments and a large grower survey to estimate the relationships between weather and TSW risk mediated by thrips vectors, and developed an addition to Peanut Rx that proved informative and easy to implement. The expected temporal occurrence of major thrips flights, as a function of heat and precipitation, was translated into the existing risk-point system of Peanut Rx. Results from the grower survey further demonstrated the validity of Peanut Rx for guiding growers’ decisions to minimize risk of TSW.

Virginia Nursery and Greenhouse Grower Survey of Best Management Practices

A survey, focusing on the use of irrigation and fertilization best management practices (BMPs), was designed and released to Virginia nursery and greenhouse growers. The objectives of the survey were to determine the most widely used BMPs, assess the reasons for their use, and identify barriers to BMP adoption. The survey was distributed in person, via e-mail attachment, or link to 357 Virginia growers in 2016 with 60 respondents. Survey results demonstrate that the most widely used BMPs in Virginia included irrigation scheduling, integrated pest management (IPM) implementation, altering irrigation practices to optimize irrigation efficiency, controlled-release fertilizer (CRF) use, and plant need–based watering. Respondents selected environmental/resource savings as one of the most cited reasons behind BMP use for water, fertilizer, and runoff management. Cost was the most cited barrier to BMP adoption for all BMPs. Fertilizer management BMP implementation was primarily an economic decision. The value of determining the most widely used BMPs and impediments to BMP adoption is that we can 1) communicate this information to growers who currently do not employ BMPs to encourage BMP adoption and 2) subsequently inform the regulatory community of BMP use. Increased BMP use can boost the potential for mitigation of agricultural nutrient and sediment runoff into impaired waterways, including the Chesapeake Bay, and help growers increase efficiency of operation inputs, such as water and fertilizer resources, while potentially saving money.

Delayed Senescence in Soybean: Terminology, Research Update, and Survey Results from Growers

The terms used to describe symptoms of delayed senescence in soybean often are used inconsistently or interchangeably and do not adequately distinguish the observed symptoms in the field. Various causes have been proposed to explain the development of delayed senescence symptoms. In this article, we review published reports on delayed senescence symptoms in soybean, summarize current research findings, provide examples of terms related to specific symptoms, and present an overview of the results of a multi-state survey directed to soybean growers to understand their concerns about delayed soybean senescence. Some of these terms, such as green bean syndrome and green stem syndrome, describe symptoms induced by biotic factors, while other terms describe symptoms associated with abiotic factors. Some delayed senescence terms involve the whole plant remaining green while other terms include just the stem and other plant parts such as pods. In the grower survey, 77% reported observing soybean plants or plant parts that remained green after most plants in the field were fully mature with ripe seed. Most respondents attributed these symptoms to changes in breeding and choice of cultivars. At the end of this article, we standardized the terms used to describe delayed senescence in soybean. Accepted for publication 23 March 2016. Published 15 April 2016.

Benchmark Study: IV. Survey of Grower Practices for Managing Glyphosate-Resistant Weed Populations

In 2010, a grower survey was administered to 1,299 growers in 22 states to determine changes in weed management in the United States from 2006 to 2009. The majority of growers had not changed weed management practices in the previous 3 yr; however, 75% reported using weed management practices targeted at glyphosate-resistant (GR) weeds. Growers were asked to rate their efforts at controlling GR weeds and rate the effectiveness of various practices for controlling/preventing GR weeds regardless of whether they were personally using them. Using the herbicide labeled rate, scouting fields, and rotating crops were among the practices considered by growers as most effective in managing GR weeds. Sixty-seven percent of growers reported effective management of GR weeds. Between the 2005 and 2010 Benchmark surveys, the frequency of growers using specific actions to manage GR weeds increased markedly. Although the relative effectiveness of practices, as perceived by growers, remained the same, the effectiveness rating of tillage and the use of residual and POST herbicides increased.

Barriers to Adopting Sustainable Floriculture Certification

In recent years, the commercial greenhouse industry has begun to implement sustainable production practices. However, floriculture certification programs for sustainable production practices are a relatively new phenomenon in the United States. Between July and Oct. 2008, a commercial floriculture grower survey was conducted to determine potential barriers to sustainable floriculture certification. Using a logistic regression model, seven potential areas were evaluated: risk, profitability, economic viability, prior experience, education, operation size, and customer types. Although respondents had positive attitudes toward sustainability and had adopted sustainable practices, respondents had little knowledge and interest in U.S. certification.

A Grower Survey of Herbicide Use Patterns in Glyphosate-Resistant Cropping Systems

A telephone survey was conducted with growers in Iowa, Illinois, Indiana, Nebraska, Mississippi, and North Carolina to discern the utilization of the glyphosate-resistant (GR) trait in crop rotations, weed pressure, tillage practices, herbicide use, and perception of GR weeds. This paper focuses on survey results regarding herbicide decisions made during the 2005 cropping season. Less than 20% of the respondents made fall herbicide applications. The most frequently used herbicides for fall applications were 2,4-D and glyphosate, and these herbicides were also the most frequently used for preplant burndown weed control in the spring. Atrazine and acetochlor were frequently used in rotations containing GR corn. As expected, crop rotations using a GR crop had a high percentage of respondents that made one to three POST applications of glyphosate per year. GR corn, GR cotton, and non-GR crops had the highest percentage of growers applying non-glyphosate herbicides during the 2005 growing season. A crop rotation containing GR soybean had the greatest negative impact on non-glyphosate use. Overall, glyphosate use has continued to increase, with concomitant decreases in utilization of other herbicides.

Delaware Soybean Grower Survey on Glyphosate-resistant Horseweed (Conyza canadensis)

In November 2004, a 29-question survey was mailed to Delaware soybean growers to determine grower perceptions of glyphosate-resistant (GR) horseweed and if glyphosate applications, GR soybean usage, and management practices had been altered in lieu of the presence of resistance. A total of 213 valid responses were received. Ninety-eight percent of respondents reported planting GR soybean at some point in the last 5 yr, with 90% reporting having planted GR soybean 3 or more years. The presence of GR horseweed on-farm was reported by 38% of the respondents and 95% of those growers with GR horseweed on-farm reported implementing one or more changes in GR soybean management. The most frequent change (66% of growers) due to resistant horseweed was the application of another herbicide with a different mode of action before planting. Forty-eight percent of growers with resistance on-farm reported a $5 to $17/ha increase to manage for GR horseweed, with 28% reporting a greater than $17/ha increase. Regardless of experience with GR horseweed, approximately 80% responded that it was worthwhile to incur additional costs now to preserve glyphosate for future use. Soybean grower reliance on glyphosate has not decreased in light of GR horseweed in Delaware. Misconceptions of timing for the selection of GR horseweed biotypes and the future availability of new herbicides with different modes of action exist within the farming community.

Impact of Low Iron and Phosphorus Stresses on Acidification of Nutrient Solution by Geranium

The cause of sudden substrate pH decline by geranium is unknown. Low Fe and low P have been shown to cause many plant species to acidify the substrate. Research was done to determine if low Fe or P stresses caused four geranium (Pelargonium ×hortorum Bailey) cultivars to acidify nutrient solution. Two cultivars were susceptible and two resistant to substrate acidification based on a grower survey. Rooted geranium cuttings were transferred to 4-L containers containing modified Hoagland's solution with N supplied as 15% NH4 and 85% NO3. The plants were grown in a greenhouse for 44 days. Treatments consisted of a complete nutrient solution and two similar solutions devoid of either Fe or P. Solutions pH was set at 5.8, changed weekly, and tested 3 and 6 days after each change. Because all cultivars showed similar responses, results were combined. Twenty days after transplanting (DAT), plants in all treatments, including control, caused solution pH to fall below 5. At 37 DAT, the solution pH levels for control, minus Fe, and minus P treatments were 4.1, 3.7, and 3.6, respectively. Results indicated that geranium is an acidifying plant when N is supplied as 15% NH4 and 85% NO3. Additionally, low Fe and low P stresses increase the acidification rate. Total dry weights of minus-P plants were about half that of minus-Fe plants. This indicated that plants under P stress had a higher specific rate of acidification than plants under Fe stress.

Grass grub damage and mycorrhizal colonisation of grapevine rootstocks

Field observations and a grower survey during 2002/2003 indicated that grass grub larvae might be responsible for the death of young grape vines In November 2003 a pot trial was established to determine whether grass grab larvae feeding caused sufficient root damage to account for observed vine deaths The experiments also evaluated whether arbuscular mycorrhizal fungi (AMF) colonisation of grape vine roots was affected by grass grub feeding Grass grub damage was found on the belowground portion of the trunk and was proportional to the numbers of grubs present However root and shoot weight and shoot length were not affected by grub density when measured two months after grubs were introduced AMF colonization varied between the four rootstocks in the trial and was higher where grass grubs had been introduced Further research is required to elucidate the causes of young vine decline in Marlborough