04 July, 2024

Alpha Test: Field Guide to the Powdery Mildews of the Americas

This is your chance to test out the first field identification guide to powdery mildews!

What is this about?

In short: This is the first test run of a guide to powdery mildews of the Americas that I've developed. I'm asking you for your help in trialing it and refining it. The benefit to you is that you will get a free electronic draft copy of the guide to use for identifying both others' and your own observations of powdery mildews. This Field Guide to the Powdery Mildews of the Americas (henceforth: "Guide") is the first of its kind. No equivalent to it exists, since previous literature has always focused either on microscopic distinctions between species or on their pest-control treatment irrespective of species identity. Online resources such as agricultural factsheets (e.g. university extension web pages), plant interaction aggregator sources (e.g. Bladmineerders, DiscoverLife), or others are not recommended for species identification because they are heavily outdated with regards to powdery mildew taxonomy. This Guide is geared toward filling the gap in knowledge by making current species-level ID possible.

I've notified you about potentially participating in this alpha test because I've communicated with you through (or outside) iNaturalist about identifying powdery mildews, or have seen lots of your powdery mildew observations, and appreciate the effort put into your observing and/or identifying! The only catch is that I would like you to give active feedback on the Guide and to first validate and evaluate it through a small test run that is similar to iNaturalist's "Observation Accuracy Experiments". See below for details.

I'm also looking for additional testers from low-coverage regions! This refers to just about everywhere except for the United States (and adjacent southernmost Canada and northernmost Mexico). Special targets include Brazil, Argentina, Chile, and Canada. If you know someone who will be observing in these areas and would be interested in powdery mildews, let me know.

What is the "alpha test"?

The alpha test will consist of two "phases", described below. You may certainly opt in to both phases or even only Phase 2, though I would prefer that you not opt in to only Phase 1 as getting firsthand experience with powdery mildew is the most important part. Note that the Guide will be finished in its draft form and distributed on July 25th (Atlantic Time). You will have at least until then to opt in, ask questions, and so on. Over the next three weeks, I will be making some final revisions before it can be sent to you in its draft form.

Phase 1:

This will consist of a sitewide validation study, similar to the official iNaturalist "Observation Accuracy Experiments" in structure. You will be given a set of 9 existing iNaturalist observations from the Americas and asked to identify the observations to the best of your abilities. The main difference from the Observation Accuracy Experiments is that you will be asked to identify your assigned group of observations using the keys in the Guide! Also, I will offer my own identification on all test observations at the end of the identification period. Most observations used for this validation will be given to multiple users.

A number-one point: DON'T BE AFRAID TO DISAGREE WITH PRIOR IDENTIFICATIONS! Many existing observations are incorrectly identified simply because good information is hard to come by, and the best taxonomic treatment for many species is incredibly new -- phylogenetically supported updates are coming almost every year, multiple times a year for previously overlooked species — and these new definitions will be here to stay. I have personally and (to the best of my ability) exhaustively combed through the literature to make final updates to the Guide, some of which were new to me as well. Do not assume previous IDs were correct on iNaturalist observations you encounter -- even some older ones of mine from before I wrote this guide!

If you agree to participate in Phase 1, I will then send you a list of observations to validate. These will be tailored to the region(s) where you have observed or identified before, but will not include any of your own observations. Some may have existing IDs from months or years ago; please arrive at an independent ID decision based on your own judgment given the information in the Guide, and do not base your identifications in any evaluation of the previous identifiers' ability or expertise. Since many of you tagged to ask for your participation are top observers of powdery mildews for your region, you may see some of your own observations included as other participants' validation targets!

You can use any evidence at your disposal to help get through the key and reach an ID. Note (as you may already know) that host plant identity is absolutely critical to powdery mildew identification. Many if not most observations used as validation records here do have some information about the host plant -- be sure to check the observation description/notes, previous comments from identifiers, or host-ID-related observation fields. However, not all of the validation observations already specify the host plant. In that remainder, you'll either have to identify the host plant yourself (if you can), or you can ask for assistance (as always on iNaturalist). You're not expected to be "on your own" for host plant identification, since that's not the goal here. Always feel free to ask the observer to confirm what the host plant was, or to tag other users such as iNaturalist top identifiers, users with botanical expertise who are known to you, or even me for plant identification help. Be careful of previously existing ID suggestions which may or may not be correct.

Phase 2:

This will consist of an open period between now and October 1 to use the Guide to identify powdery mildews that you yourself observe in the wild. As you would with any field guide, please consult this Guide freely to assist with identification. Also as you would with any iNaturalist observation, please feel free to tag or message me about any of your finds -- whether to confirm an ID, ask for a general second opinion, or discuss some interesting feature.

In both phases:

Please think about the usability of the Guide as you reference it while making identifications and observations. Is the information clear? Are the dichotomous keys easy or difficult to follow? Is the information presented appropriately? Are you confident in your species IDs made using the Guide? It's your feedback that will be most important in shaping future versions of the Guide, whether you have only general reactions or a detailed critique. I won't circulate surveys or questionnaires about the Guide unless that would be a preferred way to send your feedback; responses can be informal. Just do send any thoughts and comments you may have!

What is the guide like?

The guide will be distributed as a PDF copy with simple formatting and a few embedded hyperlinks. In this form, it is searchable and (in some PDF viewers) allows jumping straight to sections, such as the key for a particular host plant family. Its front matter consists of several sections containing background information on powdery mildews, plus notes on other opportunities and current issues with powdery mildews. This is followed by a crash course in how to confirm that you're seeing a powdery mildew, how to observe and photograph them, and how to collect voucher specimens. The main part of it is the identification section -- this consists of a series of dichotomous keys separated by host plant family. If you are not very familiar with how to use a dichotomous key, there are a number of great free tutorials on the internet; I like the very brief one linked here.

I will issue updates to the Guide as necessary during the testing period, and will notify everyone who has agreed to participate in this alpha test, if new published studies or discoveries necessitate major revisions to the keys or other information. International researchers working on the taxonomy of the Erysiphaceae are likely to release further results in the coming year; I will strive to keep the Guide fully up to date with the current state of knowledge.

What are the terms of participation?

Even more so than an official iNaturalist experiment, you should feel no pressure to participate. If you are not currently able, willing, or available to pilot either phase of this identification guide, you may either decline to respond (that is, provide no response), or explicitly decline to participate by stating as such in a comment on this journal post or by contacting me via direct message or private communication. If you are interested in participating but have any concerns about accessibility or availability, certainly do get in touch to ask. You can also agree to participate in only one out of the two phases of this trial, if necessary -- see above ("What is the alpha test?") for the details.

You must consent to participate in this alpha test in order to receive a draft copy of this Quick Guide to the Powdery Mildews of the Americas. To do so, you may comment your assent on this post, or send me a direct message or email to agree. If you consent to participate, you agree and are bound: to provide feedback on the Guide in its current form such as you are able, in order to help improve its usability in future drafts or editions; to not distribute copies of the Guide, including any portions or excerpts, to unrelated third parties not involved in this alpha test; and to personally assume any ensuing responsibility for identifying powdery mildews to genus or species level, to the degree that new records for your state, country, or other jurisdiction may require official reporting to the appropriate agricultural authority.


I will be happy to answer any questions you have about this alpha test beforehand (up to and including the start date on July 25) or during the progress of the Guide alpha test! (This of course does not include any explicit confirmation of taxon identifications during Phase 1, except of host plants.) Please also reach out if you find a new record for your region, or if you wish to send collected material for inspection or accessioning to me, an institution I am officially affiliated with (University of Chicago; Field Museum of Natural History; The Morton Arboretum) or another fungarium in my current region (Midwest, primarily Greater Chicago)! As always, questions can be directed to me via public tagging (on iNaturalist posts), private message, or email. I am out of regular contact for up to two weeks while traveling for fieldwork or family reasons, including from July 4 through July 22; if any urgent question arises or if you are imminently planning to send voucher specimens, you can reach me most quickly via iNaturalist direct message, or email. My email address is currently sbrobeson AT uchicago DOT edu.

[Preliminary] FAQ:

Do you plan to publish this guide?

Yes! In the future, I would like to turn this into a full-fledged field guide. While I don't have a timeline on when this might happen, I am currently discussing options with colleagues. If the current alpha-test draft of the Guide is later directly edited into a full field guide, I will be happy to acknowledge participating testers in these phases for their contributions to its success.

Will you add pictures / full species descriptions / something else to the Guide?

I hope to add photos depicting the important features of species to the Guide in the future. If it is widely or universally requested by testers, I will also add photo media to the Guide, though please anticipate that this will be incomplete in terms of species coverage as well as significantly delayed due to the extra searching involved. Note that a very large number of species included in the keys lack any photo documentation anywhere, in iNaturalist or any other source. The best way you can help make photo illustrations a reality is by going out and finding under-documented species!

I think there's a species missing from the Guide; can you please include it?

I'd be very happy to incorporate any species I inadvertently missed into the keys -- message me or leave a comment about any oversights. For the mycologists or those most familiar with the literature on fungi, please notify me if you have news about any new scientific study on the Erysiphaceae.

[Actual asked and answered questions will go here!]

Final word and acknowledgements

Thanks very much for reading and considering participating. I will send the PDF form of the Guide and assign Phase 1 verification observations to all who have opted in when July 25 comes. If you have any concerns not covered above, please do reach out.

I would also like to extend my enormous gratitude to several people who made this work possible.
I'm specially grateful to Andy Donegan ( @andydonegan ) and Nicolas Schwab ( @nschwab ) for engaging with my early questions about phytoparasitic fungi, and for responding to my subsequent countless tags with patience and a deep knowledge of mycobiota.
I would also like to thank my botanical colleagues and iNaturalist co-sufferers Ryan ( @ryanfuller ), Jing-Yi ( @jingyilu ), Kasey ( @kaseykp ), and Gabe ( @gribicoff ) for their tolerance, camaraderie, and humor as I assembled this Guide with some difficulty, and for their determination in the face of what iNaturalist means to us as biodiversity scientists.

Identifiers/Observer Candidates

Thanks for your contributions already, and hope to see you in the alpha test.

@astrobirder @baxter-birdnird @brandoncorder @brnhn @cgmayers @cofa @crothfels @david99 @djringer @dylantomtaylor @dysm @eric-schmitty @epic2112 @hayden127 @human_landfill @imasongster @jemredwood @jocean @johnplischke @leytonjfreid @liamragan @matt227 @matthewbeziat @megan_blackmore @neontetraploid @okbirdman @picklejar @pipsissewa @radbackedsalamander @reptipods @silversea_starsong @sunguramy @sus_scrofa @susanhewitt @thehyphaemovement @tom1548 @tylbrooks1998 @yerbasanta @zee_z @zihaowang @zitserm

Posted on 04 July, 2024 04:21 by sbrobeson sbrobeson | 29 comments | Leave a comment