'Fun' with Outfield 2024

 My second year working with Oli Hilbourne and Jim McDougall from Outfield using my DJI Air 2S UAV (drone) to do blossom density, fruit variability, and – although not officially sanctioned – yield estimate ‘heat’ maps. (See my 2023 Outfield post.) My intent here is to just highlight some of my observations using this particular PACMAN (Precision Apple Cropload MANagement) tool in 2024. Although, I did have a specific applied research objective too, that is/was to compare the Outfield product to Vivid-Machines results, who I also worked with in 2024, but that will be a separate post.

So, regarding Outfield:

• I/we actually mapped a total of thirteen different apple blocks across five orchards in three different states (MA, NJ, and NY). Wow. Not all orchard blocks were mapped for all three Outfield products – blossom density, fruit variability, and yield estimates – but still, wow. Going forward, however, I am not going to bring up yield estimates because Outfield is not ready to roll this feature out yet. It’s kind of in Beta testing still, TBD?
• Two orchards in Massachusetts, the UMass Orchard in Belchertown and Tougas Family Farm in Northboro were included in flyovers and mapping. I also had the opportunity to demonstrate Outfield at a meeting of the New Jersey State Horticultural Society at Wightman’s Orchard in Morristown, NJ in June. See this Fruit Notes article. Plus in August did a demo at Crist Brothers Orchards in Walden, NY and Once Munsee Orchard in Wallkill, NY.
• When I say we, I mean I had help, Liam Ouelette who was a UMass CAFE summer scholar I was lucky to have help me out. Brain works much faster in young folks (Liam) than old folks (me), and he was a natural at flying the drone (Figure 1). As part of his summer scholar work, Liam produced a nice poster (Figure 2).
• In general, using the drone along with the Outfield Dashboard and Litchi app was pretty easy. File management got a bit tricky, however,  as the number of blocks we flew over increased. Flights typically averaged five minutes or so to complete, but it depended a bit on block size, which ranged from one-half an acre (< 3 minutes) to approximately nine acres (10+ minutes). One notable ‘incident’ occurred when Jon did not check a particular block perimeter closely, so the drone and an oak tree had a ‘meeting’ which resulted in the drone getting stuck about 30 feet up in the tree canopy. Fortunately, someone with an adept throwing arm was able to knock it out of the tree using – what else? – apples as the dislodging projectile. The drone was undamaged, amazing.
• Uploading picture files taken by the drone during the largely hands-off, programmed block flyovers resulted – within 24 hours usually – the Outfield ‘heat’ maps in their Dashboard. Examples of bloom density and fruit variability maps, as well as sample region/image locations are pictured in Figures 3 - 6. They are pretty self-explanatory.

OK, the “so what?”

• As I alluded, I was hoping to eventually compare the Outfield ‘heat’ maps to those produced by Vivid-Machines. I will have to dig into that more extensively, but it’s kind of like comparing apples to oranges so I will have to re-think that.
• Anyone can do this, i.e., buy a $1,000 drone, get your FAA Part 107 license (preferably), pay Outfield for their Dashboard and flight plans (rack rate circa $100 an acre in 2024), outline your orchard blocks of interest, and fly and make maps until your heart's content. Typically during full bloom (blossom density map), then once the fruits reach one inch diameter in mid-late June (fruit variability map), again in July, again in August (fruit variability maps).
• What’s actionable? Ideally variable rate sprayer to apply bloom and fruitlet thinners, or maybe you can just have the map in your tractor and speed up/slow down? The whole variable rate sprayer thing is coming, trust me. Hand thinning, give a map to the crew supervisor to make sure time is well spent, hand thinning where most needed? Pre-plan harvest operations, but really need a yield estimate from Outfield for that, hint 🙂. What about variable rate ReTain spraying? What am I missing? Please leave a comment!

Figure 1 - Liam piloting drone over Royal Red Honeycrisp block at Tougas Family Farm, July 3, 2024

Figure 2 - Liam presenting poster at UMass CAFE Summer Scholar Symposium, September 9, 2024

Figure 3 - Blossom variability map from Royal Red Honeycrisp block at Tougas Family Farm, May 9, 2024

Figure 4 - Example image regions/location during bloom in 'Royal Red' Honeycrisp block at Tougas Family Farm, May 9, 2024 

Figure 5 - Fruit variability map of 'Royal Red' Honeycrisp block at Tougas Family Farm, September 7, 2024

Figure 6 - Example image regions/location pre-harvest in 'Royal Red' Honeycrisp block at Tougas Family Farm, September 7, 2024

The Fruitlet Size Distribution (FSD) Model, my 2024 experience…

As an introduction – why reinvent the wheel? – per LAURA HILLMANN AND TODD EINHORN, Michigan State University:

“Fruit set prediction models aim to produce timely estimates of fruitlet abscission after thinner applications to guide precision crop load management. The time to generate a prediction after an application is important to facilitate grower decisions to re-apply thinners while they are still efficacious, avoiding expensive hand thinning operations. The fruitlet growth rate (FGR) model, developed by Dr. Duane Greene, is a powerful tool that can accurately predict the percentage of fruitlets that will set in an orchard. Although an Excel data template and App are available to run the FGR model via computer and smartphone, respectively, adoption has been limited by the measurement-intensive procedure. A new approach, termed the ‘Fruitlet Size Distribution (FSD) Model’, described herein, was developed to produce predictions of apple fruit set comparable to the FGR model but achievable with less time investment. The principle underlying both models is the same: the relative growth rate or size of a fruitlet is compared to the most rapidly growing or largest fruitlet within the sample date to determine if it will abscise. Most predictions can be made within 8 days from thinner applications, though the duration of time depends on climatic, biological and horticultural factors. To optimize the FSD model we suggest beginning the model three days after the average fruitlet diameter of the orchard is 6 mm. Thus, the model partners well with thinning applications between bloom and 6 mm. For example, if a prediction can be achieved by 8 days, assuming an average growth of ~0.8 mm per day, then fruitlets will be ~ 12 mm if another application is needed; 12 mm fruitlets are very sensitive to many thinning chemistries.”

https://pacman.extension.org/2024/03/28/the-fruitlet-size-distribution-fsd-model-a-how-to-guide-2024-update/ Including a complete HOW-TO guide.

Let’s see if I followed the instructions?

✔ At the UMass Orchard in Belchertown, MA, in 2024 I tried the FSD model in two tall-spindle apple blocks, one Ambrosia, the other Cripps Pink ‘Maslin’ cv. Both were on G.41 rootstock. I flagged 8 representative trees in each block at bloom. 

✔ Marked five representative flowering spurs (clusters) per tree for a total of 40 clusters per block.

✔ Oh yea, I counted the total number of flower clusters on five of the marked trees, which ranged from 50 to 80 in Ambrosia, 90 to 170 (a lot) in Cripps Pink. 

✔ Over the course of three “sample” dates – May 22, 26, and 30 – in each block I collected – by either snipping, or pulling off, fruitlet stem included, see Figure ? – the fruitlets from each cluster, brought them inside, and weighed them, sitting down, nice. More on that in a minute.

✔ Data went right into the FSD Excel spreadsheet – can download from above link, have to enable Macros, it’s easier to do on a Mac than a PC, but that is another story  – and Voila! %FRUIT SET predicted in a nice chart! Figure 1 and 2.

Figure 1 - FSD prediction results for Cripps Pink

Figure 2 - FSD prediction results for Ambrosia

Humph. In terms of so “what good is it?,” if assuming a good bloom, I want the fruit set to be in the 10% range, equivalent to one apple for every two clusters? Right? That is up to you to set that target fruit set. From what I could see, we were on the right track, but I could also see for Ambrosia at least (Figure 2) it might be wise to put another chemical thinner spray on? Not sure if that happened, both blocks had a good (too many?) apples at the end. Yea, my follow through could use help. 🙂

Now for the minute I mentioned above, I was kind of impressed, particularly no measuring fruitlets in the orchard in the hot sun and bugs, just collect, and bring them into the comfort of air conditioning (no bugs if you keep the doors closed) where you individually (sitting down) throw them on an accurate scale (down to 0.01 grams accuracy), record, and hit ‘Start Calculations’ in the XLS FSD spreadsheet. Now, you can do this manually, but I had some money so I bought an Ohaus 'Scout' (STX222 AM) scale, and the USB interface, about $550. After some serious digging around in the PC (no Mac here, sorry) system and application settings, I got it to work! I had a little help from Laura in Einhorn’s MSU lab too. Put the fruitlet on scale, hit the scale enter button, and automatically record it in the spreadsheet. Figures 3 & 4. How cool! I was pretty psyched!

Figure 3 - Collected fruitlets (note with stems), scale, USB interface, and computer for fast weighing and recording of fruitlets

Figure 4 - Close up of OHAUS scale and Excel spreadsheet data entry

“Less time investment?” Yea, maybe, between collecting the fruitlets and weighing them, probably took 30 minutes. But I could do it by myself, two people not needed as with measuring and recording, so in terms of people hours, yes, definitely less. Did I mention the personal discomfort index was less too! That’s important to me… 🙂

So, I proposed MARKUSIM previously and now FSD to achieve one level – precision pruning, precision chemical thinning actually USING the FSD model, and hand thinning being other levels – of precision apple crop load management (PACMAN) for mere mortals! Me, not being one to leave it alone of course, and have to try it myself, also worked with OUTFIELD and VIVID-MACHINES in 2024, that’s upcoming. If you are thinking I will tie it all together at the end, dream on…I will leave it up to you to decide what you can do in terms of precision apple cropload management, one size does not fit all.

MARKUSIM - Precision chemical apple fruit thinning for the rest of us?

Chemical thinning of apples is one of the most important sprays growers make all season. Final fruit set affects profitability greatly. Thus, being able to predict fruit set while making chemical thinning sprays is an important decision-making step. Although there are precision tools, including the apple fruitlet growth rate model, to help here, they are admittedly time consuming and onerous, particularly in orchards with many different blocks and varieties which may respond differently to chemical thinning sprays. Here, I will propose using a relatively simple method, “MARKUSIM,” for helping growers predict apple fruit set and determine need for chemical thinning sprays across their orchard blocks.

First, I have to give credit 100% to Mark Rusell and Jill Mackenzie, Two of Clubs Orchard, LLC, Appleton NY for “MARKUSIM” – get it, a play on “Malusim” – to come up with this method for predicting apple fruit set. I have, however, as described here, abbreviated their procedure somewhat. I have only done this one year and really need to do it for another year or two to get a better feel for its “accuracy.” My initial impression, however, is that it forces you at the very least to look at a defined sample of fruitlet clusters and give you great intuition quickly as to what is going on and how the chemical thinning sprays are working (or not).

The PROCEDURE, in as simple terms as I can describe it:

1. FLAG (with flagging tape, don't use white, D’oh!) ten representative trees per block/variety at the pink to bloom bud stage.
2. Attach numbered CLOTHESPINS to five flowering/fruiting clusters per tree at the pink to bloom bud stage. Colored (fluorescent orange spray painted) and numbered (Sharpie permanent marker) clothespins are easier to find. Or you can use fluorescent orange flagging tape alone or in conjunction with the clothespins. Bottom line is the clusters need to be easy to find over the next few weeks. And they should be in the TOPS of trees too! Figure 1 for example.
3. Beginning when FRUITLETS exceed 5 to 6 mm in size, go out and RECORD the NUMBER of apple fruitlets you THINK are growing and persisting. At first it will appear most are doing this. No need to measure! Just count the number of fruitlets that appear to be staying! RECORD! I used a simple Gsheet as in Figure 2.
4. After the first CHEMICAL thinning spray, 3 or 4 days later, again RECORD the NUMBER of fruitlets that appear to be GROWING. It will start to become quite obvious which are which, GROWING or NOT GROWING and likely to abscise. RECORD!
5. REPEAT two or three or four times to PREDICT fruit set and determine need (or not) for more thinning sprays. TYPICALLY, you want one apple remaining per two fruit clusters = 10% fruit set assuming bloom is good (no frost, etc.) and you have pruned trees to roughly a desired number of flowering/fruit spurs (precision pruning). 

OK, I did this (roughly) at the UMass Orchard in Belchertown in 2024. In a Honeycrisp and Macoun block, both grown to tall-spindle. I had some interesting results, mostly on account of the fact MARKUSIM was predicting a very low fruit set, far below 10% by the final date I counted. In fact, more like 2% for both Honeycrisp and McIntosh, as can be seen in Figure 2 for Honeycrisp. Also note Figure 3, depicting a final fruit set predicted to be less than 0.5 apples per cluster which would be 10% set. Needless to say, I was concerned. There was a frost/freeze event here in late April when trees were late tight cluster to pink bud stage, so I kind of figured that might be an issue. I don’t have chemical thinning details, but the presumption was petal fall and approximately 10 millimeter chemical thinning sprays went on. I did count the final fruit set (number of apples on tree) just pre-harvest, and in reality, fruit set was approximately 28 apples per tree in the Honeycrisp, assuming my target was about 60 apples per tree, that is 5% fruit set (assuming about 120 flower clustes per tree at bloom). Whoaa, what went slightly wrong with MARKUSIM? Not sure? Maybe I did not clothespin enough spurs in the tops of trees? (Note to self, ladder needed next year.) Maybe I picked errant behaving spurs? Maybe I was not a good judge of what appeared to be growing (or not) fruitlets? See Figures 4-6 for examples. I will say, however, and this may be fodder for another Fruit Notes article, but the other predicting fruit set tool I used (Malusim) were more on-target compared to what I ended up with MARKUSIM? Although Malusim predicted pretty low fruit set on Macoun. Anecdotally, here at the Orchard, we all kind of felt/agreed that the final fruit set at harvest was much better than expected in late May where we kind of thought excess thinning might have occurred. Crops in bottom of trees were definitely affected by the frost, whereas tops were still over-cropped. Damn weather!

So, I did tell you MARKUSIM needs a couple more seasons of evaluation before I can wholeheartedly recommend, but it was kind of fun and a heck of a lot easier than measuring fruitlets. Maybe it’s just “semi-precision?” Which is better than “no precision,” aka seat-of -the-pants? You decide.

Figure 1 - Example spur marked with numbered clothespin. Darn, thought I had a better pic but you get the idea!

Figure 2 - Gsheet used to record MARKUSIM data. Rows 2-51 are number of apples on each cluster determined to be growing (vs. starting potential of 5 apples). Sum is a calculation; % set is a calculation based on sum and potential (250 = 50 clusters times 5 apples per cluster); avg. no. apples is a calculation.

Figure 3 - Honeycrisp average number of apples per cluster. By 6/2 it should be about 0.5 apples per cluster, not still the nose bleed dive seen here.

Figure 4 - How many fruitlets growing/staying here? I'd say 4?

Figure 5 - How many fruitlets growing/staying here? 6? 5? 3? It's not always clear cut is it?

Figure 6 - How many fruitlets growing/staying here? Easy-peasy, ONE!

IFTA California here we come...

 

Yup, July 16-18, 2024 IFTA Summer Tour California's Central Valley. Sacramento to Fresno. I got to admit, I went mostly for a change of scenery, as I felt I really needed it. Specially to escape the humidity here in Massachusetts. Fortunately, the week I -- and about 60 +/- other Tour participants, including a pair from as far away as Kenya (Africa) where they grow Mangoes -- was substantially cooler (less hot?) than it had been out there. We "enjoyed" full sun and temperatures mostly in the mid-upper 90's. It did get hotter (100?) though as we went south from Sacramento to Fresno.

OK, lacking notes, here is what I remember and a few take-home messages. All the pictures are mine, but I am going to draw too from IFTA's handout and our good industry publications -- Good Fruit, American Fruit Grower, and Fruit Growers News -- in attendance.

DAY 1 - SACRAMENTO RIVER DELTA

A morning stop at UC-Davis for an autonomous robot demonstration. Frankly, I was not terribly impressed, but it was interesting to find out these 'bots' are being used by California strawberry growers during harvest to save trips previously made by the pickers to unload their harvest. So they could concentrate on just picking. Sounds like a win for labor efficiency?

Autonomous 'bot' at UC-Davis. Meh...

Afterwards, Rivermaid Trading Company on the Sacramento River Delta. California's number one pear producer. Pears looked pretty good but what do I know about pears? Pleasant guest surprise was UC's retired advisor Dr. Rachel Elkins who came down from Lake County. Rachel and I are friends from the NC-140 Regional Rootstock Research Project. It was good to see her and I had no idea how great she spoke to growers on almost any pear subject, including here some of her early work on IPM in pears. Nice.

Nice looking pear orchard at Rivermaid, Red Anjou? Nope, but a look-alike?

Great Extension talk on pear IPM, after lunch I grabbed this selfie with friend Rachel!

Lodi Farming, Inc. where I saw some apples, a new early variety being introduced by Zaiger that was going to be harvested within the week. It was OK. But, Jeff Colombini (2013 Good Fruit Grower of the Year), President was kind of high on olives being grown in a somewhat hi-density fashion, to be harvested and quickly pressed into EVOO. Low labor needs (mechanical harvest) and well adapted to dry conditions. Nothing for me to take-home here, although he did note much of the EVOO sold in this country is not 'extra-virgin' being adulterated with inferior olive oil? But I am not a big olive oil aficiando either, we buy Costco (Kirkland Signature) EVOO. Good enough for me.

In an apple orchard at Lodi Farming! Yea!

But President Jeff really likes the future of olives for EVOO which we got an education on!

DAY 2 - LODI

After an overnight in Lodi, and this got a little confusing but two businesses that may have been related or not? I found a rather stark difference between the two though in terms of growing philosophy. Chinchiolo Stemilt California vs. Prima Frutta. I guess they are not the same, maybe they are just close to each other? Both the focus was on cherries. One, Chinchiolo, more a traditional grower of steep-leader cherries, albeit younger plantings and somewhat hi-density. Rootstock details escape me, Krymsk? Not fans of Gisela. Very nice looking blocks of cherries IMHO. A bit of heated discussion on early training, it was kind of amusing. The other (Prima Frutta?) was doing a lot more with planar training and pruning on 'trellis' but I found it under-whelming, seems to me they were trying to copy what we saw cherry growers doing in Washington on previous IFTA tours. Labor and expense better yield better quality and returns? I dunno. Did I mention this Coral Champagne cherry is their hot new early cherry? I think? All cherries were harvested already BTW. I hope I did not get these two operations mixed up?

Nice looking cherrry orchard (sans cherries) at Chinchiolo-Stemilt

Somewhat heated -- but tame by old IDFTA standards! -- discussion on young cherry tree training and pruning

Prima Frutta cherry orchard. Read the text to see what I think? But who am I to tell anyone how to grow cherries in California?

After what was arguably one of the best lunches ever on an IFTA tour, Zaiger Genetics. Yup, that Zaiger, birthplace of bac-spot susceptible peaches and nectarines which I say "just don't do it" here in the humid east. Although I wish we could, they of course are pretty famous for peach/netarine/plum/apricot/interspecific hybrid varieties with exceptional sweetness. We just can't grow them here in MA! Bac spot! OK, we had a walking tour of their breeding/testing orchard and were treated to a tasting. To me, Zaiger looked a bit "tired" but I also think they have been doing this for a long time and know what they are doing. Just not spending a lot of money to do it, which is OK. More hype here about those 'cherry' plums! Gotta admit, pretty good off the tree.

A two Manhattan lunch?

Leith(?) Zaiger, Floyd's daugher introduced us to Ziager Genetics

Field variety selections grown in pots at Zaiger (many) and one of those cherry plums

Some pretty tasty stone fruits (and one apple) at Zaiger

Off to Fresno for Day 3 (tomorrow), but I have to mention the excellent hospitality we were treated with at Sun Valley Packing House upon arrival to the Fresno area, BBQ steaks, beer, wine, etc. all in a nicely decorated on-site venue. A converted packing house? Good times, good people. No pictures though :-(

DAY 3 - FRESNO

UC Kearney Ag Research & Extension Center, famous for their work -- specifically Kevin Day and Ted Dejong of UC -- on higher density peach training systems, such as the perpendicular-V (which has now lost favor) and the Controller series of peach/nectarine rootstocks. I remember when I was at Michigan State University Extension Bill Shane invited Kevin to the Southwest Michigan Research & Extension Center for a perpendicular-V peach pruning demo way back in 1999, Kevin made quite an impression on me. It was good to see him, and he showed us the 'Peach and Nectarine Orchard of the Future' on various rootsrtocks, particularly the Controller series out of UC Davis. Kevin has a no BS way of explaining things, my take-away was quad-V on one of the Controller rootstocks -- 6?, 7?, 9?, some confusion there -- provides advantages (shorter and somewhat more compact) peach trees for California (and beyond?) growers compared to the Nemagard standard peach rootstock they use out there.

Retired UC Extension advisor Kevin Day in the 'peach and nectarine orchard of the future'

HMC Farms -- a bit of a blur, it was getting hot. Long time standing and listening in a nicely trellised (and tall!) plum orchard, and then seeing some netting over nectarines, largely there to keep the skin of nectarines from blemishing with water. I much prefer to grow peaches here as they don't have that problem that nectarines have! Good luck growing a clean nectarine around here! Note I am providing website links here to all our orchard hosts if you want more information, you are not going to get if from me!

The 2-D 'trellised' plum orchard at HMC Farms, set up for platform pruning and harvest. Thank you random IFTA participant for 'letting' me take your picture!

I had to sneak out of the plums to see what I thought was a nice peach orchard at HMC Farms

Netting over this nectarine block to keep the fruit finish clean? Was kind of a test?

Kingsburg Orchards -- This guy was pretty entertaining in their nectarine orchard (second pic) which was pretty impressive a week away from harvest. I need to note here the family nature of many of these farms/orchard, not so much corporate but pretty big, multi-generation families. A bit different(?) than Washington apple orchards which are increasingly corporate (non-family) owned?

"This guy"at Kingsburg Orchards in a nice nectarine block (with no blemishes)

Warmerdam Orchards -- OK, now it was getting hot, particularly when standing in an older cherry orchard that was a bit wet (and humid) from irrigation and no breeze. There was some interesting things going on here -- like netting pulled over the cherry trees in the fall to help with chill hours and acclimation so as to get good bloom in the spring -- but I was increasingly disengaged. For obvious reasons?, chill hours, big old cherry trees, not a particular interest of mine.

How did I miss getting a pic of the "netting" they were using over these cherry trees at Warmerdam Orchards, but you can see some of the wires. I thought it got kind of rambling here but I was kind of hot and tired of looking at cherries (with no cherries on them) :-)

Family Tree Farms Research Center -- "The Most Flavorful Fruit in the World." OK, maybe. An interesting visit for sure to end the tour. Had to take in a bit of religion from David Jackson (not pictured below) who was quite entertaining and I could use a little religion from time to time. "Nothing grows well if your shadow is not on the soil" he said, how true. Um, if I had not known previously, I would have said this was Zaiger Genetics. Another tasting here of "the most flavorful fruit in the world," I would not argue, although some of the peaches and nectarines were cloyingly sweet. This showroom is where they bring potential customers in from across the world to sample "the most flavorful fruit in the world." A small group of potential buyers was there from Korea (South presumably) sampling "the most flavorful fruit in the world." Getting the message? They are good at it...

A well orchestrated tasting of the "most flavorful fruit in the world?"

I want to close by saying it was hard getting home for a lot of people on Thursday night/Friday because of the airline data system meltdown. I was on Southwest so was largely unaffected (just a little delayed) but I met up with my friends from Summit Tree Sales in the Fresno airport who had been trying to get a flight out for over 12 hours. I felt pretty bad for them, but it was some good company.

Thanks Dawn and Matt for keeping me company during my rather (comparatively) short stay at the Fresno airport while they were enduring a lengthy ordeal (during the Delta Airlines meltdown) trying to get home!

One more thing, I thought the folks at Ag Association Management -- Shane, Sheri, and Bethany -- our IFTA management company did a great job of accomadating various people's needs and running things smoothly (including hotel check-ins) over the three Tour days. Bethany ran the IFTA Facebook show, great job there. And of course thanks to Greg Lang (IFTA Education Director) for lining up and introducing us to our hosts at the eleven orchards we visited. 

©Jon Clements 2024

The NEWA Fire Blight Tool: too much information, too little explanation?

This time of year -- apple and pear bloom -- I/we get lots of grower questions (and I get precious little sleep) about how to interpret the fire blight risk values displayed in the NEWA Fire Blight Tool. I contend it is a case of too much information, too little explanation. Can I boil it down to a simpler take on the risk values? Sure, let's try.

First, you need to understand that on the left, you have Cougar Blight, and on the right you have "NEWA Blight" aka Maryblyt. (Figure 1.) Two different tools. Cougar Blight was developed in arid Washington, while Maryblyt was developed in the more humid east/northeast. Which do you think might be a better tool here? Yea, the one on the right.

Figure 1. Cougar Blight TRV left column, 'NEWAblyt' (aka Maryblyt) EIP right column.

Cougar Blight is much simpler, only accumulating heat units based on -- you got it -- temperature. YOU have to decide whether you had a sufficient wetting event -- be it rain, heavy dew, or even a dilute spray application (fungicide or PGR's only, no insecticides durin bloom) -- to get a fire blight infection. Here's all you need to know about Cougar Blight:

The Cougar Blight V8 (Version 8, not the motor in your 60's Camaro) Daily TRV column header for Cougar Blight means Total Risk Value. No, not Tree Row Volume here either. Arghhh.

1. Use  fire blight "occured in the area last year"
2. MARGINAL = 0-149 TRV (keep checking back); HIGH (pay close attention, have the strep and sprayer handy) = 150-349 TRV; and EXTREME (you will get a fire blight infection if it gets wet and you don't spray streptomycin) = above 350 TRV.
3. Oh yea, you have to have open blossoms too. D'oh!

Simple, you have to go from there, but EXTREME should make you too getting any sleep iffy.

NEWA Blight (aka Maryblyt) is a bit more complex. Study the table below (Figure 2.), and know this: when all FOUR of these requirements are met you WILL have fire blight infection unless you get out there and spray strep (unless you already did just prior the infection event).

BLOOM: flowers must be open (D'oh!) = BLOOM;

DH: (Degree Hours) must accumulate sufficiently >65 degrees F. 

TEMPERATURE: average daily >60 degrees F.;

WETTING: there must be a wetting event, rain or dew, but don't discount a dilute spray application is equivalent to dew (but NEWA does not know you did that, did it?)  Got it?

Figure 2. Simple graphic of how Maryblyt assesses risk of infection.

Now, there are some nuances and significant calculations to NEWAblight/Maryblyt, you don't need to worry about that, NEWA takes care of it. The important thing, any time Infection Potential EIP value (right column) goes above 100, you really need to stay on top of when the color goes ORANGE because then three conditions above have been met, and all it's going to take is some wetting to have an infection which cold turn into a fire blight epidemic. (Yikes!) As NEWA says "risk is 'HIGH' and forecasted wetting events should be carefully considered and a bactericide applied just before or after a rain"when it is ORANGE. If it turns RED and says "Extreme or Infection and antibiotic should (must?) be applied just before or after a rain." Must. Must. Must.

I am going to stop for fear of making it more complicated. It's not really. You just needed that explanation. Excellent references on Cougar Blight and Maryblyt from which I deduced all this for you are below. Read them. Please don't call me anymore... :-)

Cougar Blight Model

Maryblyt 7 Manual -- A Predictive Program for Forecasting Fire Blight Disease in Apples and Pears

RIMpro – to spray or not to spray using ‘virtual’ vs. weather station weather data

 RIMpro from their website (rimpro.cloud) “is a decision support system (DSS) for the sustainable management of pests and diseases in fruit and grape production. Every day, the cloud service together with the weather data system help thousands of growers and consultants worldwide to make the best decisions to protect their crops.” 

In 2023 I subscribed to RIMpro using both a hardware based weather station connected to NEWA (newa.cornell.edu, as Belchertown-2) and their virtual weather data service Meteoblue (meteoblue.com). My intent for using both was to be able to make a comparison of the weather station vs. virtual weather data ‘after the fact’ in terms of making spray decisions to manage apple scab, fire blight, and codling moth. It’s obvious the two sources of weather data  are going to differ, but that was not the point in making these comparisons. So I won’t belabor that, but I will discuss how using the two different sources of weather data may have made an impact on the decision-making process to “spray or not to spray” to manage the above-mentioned pests. The answer, of course, and as always, is “it depends.” Realize also this comparison was made at the end of the growing season when all the weather data was “in.” No attempt made to compare the forecasts in the midst of the growing season. (That’s a whole nother story.)

Apple scab

I just looked at primary scab using 1-April as a green tip date. Weather data that factor into the scab model include temperature (I presume but it does not show up in the RIMpro data file?), rainfall (to trigger spore release), and leaf wetness (duration). Looking at timing of spore maturity and last available spores to cause infection, there is not much difference there in the RIMpro chard (Figures 1 and 2) with an end date of approximately 10-June. I don’t care so much about that as long as they are close, but what I do care about is the RIM value(s) which are a measure of infection risk, being low, medium, or high. In Figures 1 and 2 I placed the arrows where I figured, based on what I know about RIMpro and primary scab management with fungicide sprays of some sort -- be it protectant, or protectant plus kickback fungicide – would have been required to manage a primary apple scab infection. Count how many fungicide spray black arrows there are in either plain old UMass Orchard or UMass Orchard-MB (MB = Meteoblue, virtual weather data). I count seven for each weather data source. No difference in number of sprays, right? (I'm sure my assumptions about spray timing will be argued.) But, what bothers me a bit, is it appears the RIM value is much higher for MB in several infection “events.” Looking at the raw weather data RIMpro uses, it’s clear that MB  “overestimated” by a factor of approximately two times both rainfall and leaf wetness compared to the weather station. “Overestimated” is assuming the weather station is correct? In particular, it’s likely the leaf wetness hours were the primary contributor to the difference in magnitude (as measured by the RIM value) of the infection events. Begs the question, which is correct, the leaf wetness sensor on the weather station – and we know there are issues there – or the modeled leaf wetness by MB? Good question. (Here's more on how RIMpro models leaf wetness duration for virtual weather station.) Just look at the duration of light blue which signifies leaf wetness in the weather data charts (Figures 3 and 4). What’s my inclination here? Well, looks like the MB output is a bit more conservative in the approach to manage apple scab = better safe than sorry? Know what I mean? Although not affecting the timing of fungicide sprays, the rate of fungicide might be adjusted upwards? I can see the plant pathologists out there shuffling in their seats.

Figure 1 - apple scab model output using weather station data

Figure 2 - apple scab model output using MB virtual weather data

Figure 3 - weather data chart using weather station

Figure 4 - weather data chart using MB virtual weather data. Note the extended periods of wetness (light blue) compared to Figure 3

Fire blight

I am no fire blight expert. We did have a significant fire blight outbreak in 2023 at the UMass Orchard. I don’t quite understand why MB showed that two more infection thresholds were reached compared to the weather station? Using the MB approach, three streptomycin sprays should have been applied vs. one for the weather station  (Figures 5 and 6). Which do you think would have been the better defense? Well, after the fact, and given our observed fire blight outbreak by early summer, following MB might have been the better strategy? I note that the prediction of visible symptoms was pretty much right on in RIMpro, as fire blight was indeed seen on June 5 (Figure 7).

Figure 5 - fire blight model output using weather station weather data. Date of strep spray is estimated

 

Figure 6 - fire blight model output using MB virtual weather data. Dates of strep spray are estimated

Figure 7 - fire blight symptoms observed 5-June, 2024 at UMass Orchard

Codling moth

I am no entomologist. But I do know something about codling moth management based on adult flight, mating, and larvae hatch, the latter being the ideal time to control codling moth with a targeted insecticide. So, looking at both outputs I see little difference in suggested insecticide timing between the two sources of weather data (Figures 8 and 9). Likely because the model is largely based on temperature, and we know that virtual weather data is pretty good at predicting/adjusting temperature such that over time the two sources of weather data end up being pretty closely aligned. That is about all I have to say about codling moth, I’d feel comfortable using MB there. And you have to love RIMpro’s approach of tagging ‘virgin’ females and ‘mated’ females. Maybe I am the only one that finds that amusing?

Figure 8 - codling moth model output using weather station weather data

Figure 9 - codling moth model output using MB virtual weather station data

A final note about Meteoblue, you can subsctibe to a free daily email from them that gives you a succinct graphical image of the weather forecast specific to your location. I get it daily, and have found the forecast to be about as good as anything else, although far from the perfect forecast. I particularly like their graphic which gives you a one-shot-in-one-place-in-your-face picture of the forecast as seen in Figure 10.

Figure 10 - Meteoblue Meteogram forecast for Belchertown, MA on 19-May, 2023 

So, although RIMpro is not for everyone as it's a bit dense unless you are really into it, I do highly recommend it as a 'precision' pest management tool. RIMpro has other models too numerous to mention here, but the stone fruit brown rot model might be worth mentioning. And, it can be site-specific (anywhere in the world) using the MB virtual weather data. Colleague Srdjan Acimovic at Virginia Tech University is a big proponent of RIMpro, and he is hosting a webinar about RIMpro on 20-February, 2024. I will be there. Rimpro also just launched on the App Store for iPhone and iPad...