Biology subjects

McRoberts, N.

Publications and source records attributed to McRoberts, N..

4 recordsLinked to original sources

bioRxiv2022

The value of volunteer surveillance for the early detection of biological invaders.

Early detection of invaders requires finding small numbers of individuals across large landscapes. It has been argued that the only feasible way to achieve the sampling effort needed for early detection of an invader is to involve volunteer groups (citizen scientists, passive surveyors, etc.). A key concern is that volunteers may have a considerable false-positive and false-negative rate. The question then becomes whether verification of a report from a volunteer is worth the effort. This question is the topic of this paper. We show that the maximum plausible incidence when the expert samples on its own, [Formula], and the maximum plausible incidence when the expert only verifies cases reported by the volunteer surveyor to be infected, [Formula], are related as O_FD O_INLINEFIG[Formula 1]C_INLINEFIGM_FD(1)C_FD Where {theta}fp and {theta}fn are the false positive and false negative rate of the volunteer surveyor, respectively. We also show that the optimal monitoring programme consists of verifying only the cases reported by the volunteer surveyor if O_FD O_INLINEFIG[Formula 2]C_INLINEFIGM_FD(2)C_FD Where TN is the cost of a sample taken by the expert and TX is the cost of an expert verifying a case reported by a volunteer surveyor.

ecology↗

bioRxiv2020

Spinach growers value host resistance and synthetic fungicides in the fight against downy mildew

California spinach growers struggle to manage spinach downy mildew disease. The disease is especially difficult in the organic crop, which currently relies on resistant varieties to maintain disease-free crop. Alternative control measures are available, but it is not clear how growers perceive the efficacy of these methods. It is also not clear who growers contact to find out information on spinach downy mildew disease management. In this study, we conducted an online survey of people involved in spinach production, asking about their beliefs in the efficacy of different control methods and who they contact frequently to discuss spinach downy mildew control. We found that respondents were most positive about the efficacy of resistant varieties and synthetic pesticides, with much lower perceived efficacy for the practices of disking diseased fields, roguing diseased plants, and organic pesticides. Growers most frequently contacted pest control advisors (PCAs) about management strategies for spinach downy mildew. These results suggest that respondents are most confident about the efficacy of resistant varieties and synthetic pesticides and may be hesitant to adopt new control strategies like organic pesticides. The results also suggest that future extension efforts can be focused on PCAs to reach the most stakeholders with up to date research on downy mildew control.

scientific communication and education↗

bioRxiv2018

Modeling Uncertainty in Grapevine Powdery Mildew Epidemiology Using Fuzzy Logic

Powdery mildew is the most important disease of grapevines worldwide. Despite the potential for rapid spread by the causal pathogen, grape powdery mildew has been effectively managed using fungicide applications applied based on a calendar schedule or modeled disease risk index. Various epidemiological models for predicting disease development or risk have helped to improve disease management. The Gubler-Thomas (GT) risk index is a popular disease risk model used by many growers in the western U.S. We modified the GT risk index using fuzzy logic to address both biological and mechanical uncertainty in the pathosystem. The spraying schedule suggested by the fuzzy-modified GT risk index was tested in eight site-years. Overall, the fuzzy-modified risk index maintained comparable levels of disease control as both the original model and a calendar based treatment, and had significantly less disease than the untreated control. The fungicide use efficiency of the fuzzy-modified GT risk index suggests that the updated risk index was significantly more efficient with fungicide applications than both the calendar and original GT risk index.

epidemiology↗

bioRxiv2017

Temperature and Light Effects on Germination of Peronospora effusa Sporangia

Spinach downy mildew, caused by the biotrophic oomycete Peronospora effusa, is an economically important disease that is found in all spinach growing regions of the US. To effectively predict disease risk we need to understand the response of P. effusa to different environmental conditions. We conducted several germination assays, exposing P. effusa sporangia to different temperature and lighting conditions. Between 5 and 25{degrees}C under constant darkness, germination of P. effusa sporangia on water agar declined. These results were qualitatively different from a previous study of P. effusa germination that found a bimodal response curve, with increased germination at lower and higher temperatures. Time course studies revealed that sporangia consistently germinated within the first twelve hours of plating, regardless of incubation temperature. Sporangia exposed to blue light had significantly reduced germination when compared with those exposed to red, yellow, or no light. Light intensity and color significantly impacted germination, although the effect of color varied by light intensity.

plant biology↗