It's a Trap! Part II: An Approachable Guide to Constructing and Using Rotating-Arm Air Samplers.

An increasing number of researchers are looking to understand the factors affecting microbial dispersion but are often limited by the costs of commercially available air samplers. Some have reduced these costs by designing self-made versions; however, there are no published sampler designs, and there is limited information provided on the actual construction process. Lack of appropriate reference material limits the use of these self-made samplers by many researchers. This manuscript provides a guide to designing and constructing rotating-arm impaction air samplers by covering (i) environmental considerations, (ii) construction materials and equipment, (iii) the construction process, and (iv) air sampler deployment. Information regarding how to calculate rotational velocity, motor speed, and power supply requirements and to troubleshoot common issues is presented in an approachable format for individuals without experience in electronics or machining. Although many of the components discussed in this guide may change in their availability or be updated over time, this document is intended to serve as a "builder's guide" for future research into air sampling technology for phytopathology research.

It's a Trap! Part I: Exploring the Applications of Rotating-Arm Impaction Samplers in Plant Pathology.

Although improved knowledge on the movement of airborne plant pathogens is likely to benefit plant health management, generating this knowledge is often far more complicated than anticipated. This complexity is driven by the dynamic nature of environmental variables, diversity among pathosystems that are targeted, and the unique needs of each research group. When using a rotating-arm impaction sampler, particle collection is dependent on the pathogen, environment, research objectives, and limitations (monetary, environmental, or labor). Consequently, no design will result in 100% collection efficiency. Fortunately, it is likely that multiple approaches can succeed despite these constraints. Choices made during design and implementation of samplers can influence the results, and recognizing this influence is crucial for researchers. This article is for beginners in the art and science of using rotating-arm impaction samplers; it provides a foundation for designing a project, from planning the experiment to processing samples. We present a relatively nontechnical discussion of the factors influencing pathogen dispersal and how placement of the rotating-arm air samplers alters propagule capture. We include a discussion of applications of rotating-arm air samplers to demonstrate their versatility and potential in plant pathology research as well as their limitations.

First report of Neofusicoccum ribis causing stem blight and dieback of blueberry (Vaccinium corymbosum) in Michigan.

In July 2020, a 3-year-old 'Envoy' northern highbush blueberry bush (Vaccinium corymbosum L.) from a commercial farm in Van Buren County, Michigan was submitted to the Plant & Pest Diagnostics laboratory at Michigan State University. Field disease assessments across the 2-acre planting were an incidence of 2-5% and a severity of 50-100%. Symptoms included red shoot flagging and dead shoots retaining dry leaves, shoots with light green leaves and necrotic margins, and brown-black cankers at the base of the symptomatic shoots. Shoot sections displaying wood discoloration were surface disinfested by dipping in 95% ethanol and flame sterilized. The internal discolored tissues (0.5 cm2) were plated onto 1% ampicillin and streptomycin, quarter-strength potato dextrose agar (PDA) and incubated at room temperature until fungal colonies were observed. A fungus with rapid growth, developing white and then dark gray mycelium, resembling species in the family Botryosphaeriaceae was isolated and subcultured. After DNA extraction and amplification, sequences of three loci were obtained: the internal transcribed spacer (ITS) region, ß-tubulin (Bt), and elongation factor 1-α (EF1) using primer pairs ITS1/ITS4, Bt2a/Bt2b, and EF1-728/EF1-986R, respectively (Slippers et al. 2004). The sequences showed 100% identity with Genbank numbers KF766205 (ITS region, 562 bp - OP588109), MT592721 (Bt, 436 bp - OP585548), and MT592229 (EF1, 306 bp - OP585547) of N. ribis (Slippers et al. 2013, Zhang et al. 2021). Sequences were identified using PopSet 1995604550 (Zhang et al. 2021). Pathogenicity was tested on 2-year-old 'Blueray' blueberries. Five plants, 3 shoots per plant (n = 15) were surface-sterilized with a 3% bleach solution by rinsing, wounded with razor blades using a scratching method in 'X' patterns across the length of the wound, and then inoculated using mycelium plugs (5 mm) from 7-day old cultures grown on full-strength PDA. Plugs were crushed and spread onto the wound and the wound was wrapped with parafilm. Control plant shoots (n = 9) were mock inoculated using sterile PDA plugs. Plants were maintained in the greenhouse at 23°C under a 14-hour photoperiod and imaged at 0-, 7-, and 12-days post inoculation (dpi). Symptoms began developing within 7 dpi. At 12 dpi, 9 of 15 inoculated shoots began displaying leaf necrosis and deep red or brown stem discoloration 6 cm above and below the wound, while controls remained healthy. Fungi morphologically identical to the original isolate were reisolated from sections taken from 2.5, 6.3, and 7 cm above and below the inoculation site. Species identity was confirmed by sequencing as described above. Neofusicoccum species are widespread and commonly associated with canker and dieback symptoms of blueberries (Flor et al. 2022). To our knowledge, this is the first report of stem blight and dieback caused by N. ribis in Michigan blueberry production. The species N. parvum and N. ribis have been reported on southern highbush blueberries in California (Koike et al. 2014) and Florida (Wright and Harmon 2010), but neither has been reported on blueberry in Michigan. Accurate diagnoses of Botryosphaeria fungal species in blueberries is critical for effective disease control and yield loss reduction.