Scaffolds 2024 Digest: Week 2

This post is a text digest of the Scaffolds Podcast. To listen to the original episode, visit the following link: Scaffolds Podcast on Spotify

Monique Rivera: Welcome to season two of Scaffolds. This is Monique Rivera, your host and assistant professor of entomology at Cornell AgriTech. Co-hosting with me is my pathology counterpart, Kerik Cox, who’s an associate professor of plant pathology. This year, we will also be joined by Kelsey Tobin, a postdoctoral researcher in my lab, and occasionally by Anna Wallis, our New York State Fruit IPM Coordinator. We are back with a rebranding and excitement for a new season. This podcast is a weekly roundup of timely updates on insect and disease management, as well as phenological developments across New York state for apple growers. This season, we will have some fun guests, so stay tuned. In this episode, we talk about unexpected woolly apple aphid populations springing up in western New York, forecasting apple scab events across the state, and our regular state of the state degree day accumulation and phenology updates.

 

Entomology Updates with Dr. Monique Rivera

Alright, let’s get into it. This is kind of a somewhat depressing episode for me to be recording. Last week, basically right after I submitted my podcast recording, I was called by a colleague, friend, collaborator to come look at what looked like woolly apple aphid infestations. Now, when we went out there, we kind of thought, well, maybe these are just leftover from last year and they’re dead, so Kelsey Tobin and I collected some wood and brought it back to the lab, and basically, you know, maybe they’re not moving yet because it’s still chilly outside. Anyway, long story short, left them in the lab overnight and came back and looked at them under our fancy camera microscope and found that they were indeed moving and producing honeydew.

So, this is against all messaging that we’ve ever provided on woolly apple aphids. And I am not sure if maybe this is common in places where there have been high infestations (This was in a research block). I’m not sure if it’s just about the mild winter, or maybe this has been occurring in places with high infestation, year over year. So, I think we can assume, at least to some extent, that it’s due to the mild winter, but it’s not a for sure thing. Just to touch on some previous research, I wanted to discuss an article that was published by Dave Crowder’s lab in 2017. Well, done in 2017, but published in 2019. It’s time to start, maybe as entomologists digging into or thinking about the aerial colonies, how they’re getting there, are they really coming up from the roots, and what’s going on in terms of dynamics with the below ground communities of woolies and the aerial woolies that we find on the aerial parts of the tree.

So, in this paper, they use sticky barriers to restrict upward woolly apple aphid movement into the tree canopy. And they also looked in the greenhouse at using mulches and sand amendments to restrict downward movement to the roots. So in the field, what they found is that blocking aphid movement up the tree trunks did not decrease the number of colonies in tree canopies. And so instead, they found that the sticky banded apple trees actually had higher numbers of aphid colony counts later in the study. So, what they think is, the reasoning there is that, in particular, earwigs, which are generalist predators, and in particular enjoy eating woolly apple aphids, they were excluded from the tree canopies with the sticky bands.

Now, I do want to make a caveat here that this is from Washington State, totally different orchard dynamics. We have a lot more green. We probably have a lot more biodiversity in our orchards, but we also probably spray a lot more because we have a lot of disease pressure. And then in the greenhouse, what they were finding was that they found fewer root galls, which are what they were using to indicate feeding of the woolly apple aphids occurring on trees potted in sandy soils and on those with mulch. So maybe these are some potential ways to think about alternative management techniques. But overall, what I think this is indicating is that reducing populations may hinge a lot on biological control. And I think the timeline at which Woolies show up makes this really difficult in a way, because this is, you know, a time when there is a lot of spraying, not just fungicides, but once we hit petal fall, tons of insecticides are going out for the various apple pest complex.

So, anyway, I think this is somewhat depressing, but also somewhat ironic or maybe predictable, because last week I was saying, I think insects are going to be a monster. And here we are.

So let’s talk a little bit about what we saw and how I think you should look for them. We actually collected woody material and brought it back to the lab. So we were cutting branches and taking them back. But one of the things that was the easiest indicator to see initially was it looked like white residue of former wool. So we were targeting those using hand lenses and pulling when we saw aphids, even if they look like they were carcasses. What I think makes this really difficult is that the younger nymphal populations are this purplish brown color that really tends to blend in with the wood. So, they are quite difficult to see. So hopefully, if you have those white indicators of old infestations, that could be a helpful way of making scouting cool quicker.

So, what else? The other thing that was interesting is we tended to find the younger colonies around what looked to be dead older adults like they were black and some of them had exit holes from parasitoids. So, I think this is really interesting. I was not expecting them to be alive, but there were all ages there, including adults. That’s how bad this is. However, if you don’t have a hand lens, don’t like using a hand lens, are willing to collect woody material – if you just go online like Amazon or whatever you’re using to buy things online, look up “USB microscope” and you can find really great options for $40 and under to be able to take a better look at what you’re seeing. Not sure that everyone has time for that, but I do feel like if you had a pretty heavy infestation of woolies last year, you really should get out there and take a look.

Well, overall, what do we think this means for woolly apple aphid management? So, I’m going to harp again on the dormant oil. There has not been a ton of work on insecticides at this timing for this pest. So, I think it’s difficult to make those recommendations and I think that that’s a more expensive adventure. It is worthwhile to get an oil on for a couple reasons, but in particular because right now we’re in some more mild temps. If you can dodge the freezing and maybe get it out after Thursday [April 4, 2024] when we have some warmer weather timing, it should be a little bit easier given that more mild forecast because I think there is valid concerns about freezing temperatures with oils. So the other advantage to getting something on right now is you’re never going to get better coverage. Truly, there are no leaves. If you want to apply at 50 gallons to the acre, you’re going to make great contact with the woody material. Just don’t go every other row for a pest like this because they tend to be in these tiny crevices. When we were finding them in particular, they were also in damaged areas of the bark.

Getting that dormant oil on is the best bet overall, it’s the thing that I think we can hedge our bets on. However, I have heard of people applying diazinon. I don’t think applying diazinon before bloom is ideal. And also, remember what I just told you about this West Coast experiment. You’re wiping out all of the biocontrol agents too, with such a noxious chemical.

So with that being said, I think that’s all I’m going to update on this week. If you have any questions, feel free to email me at monique.rivera@cornell.edu. Happy to discuss any treatment options. And sorry to bring this not encouraging information this week, but hopefully next week we’ll have something a little bit more uplifting. In that case, good luck. And again, feel free to contact me.

 

Pathology Updates with Dr. Kerik Cox

All right, welcome to another edition of Scaffolds coming to you on Easter Sunday, March 31. The one thing I’ve realized is that while, you know, a lot of places are closed and no one’s at work and students are resting, apple scab doesn’t rest and it doesn’t make accommodations for anything. It is live and active and we’re actually seeing some rain this week. So I want to go through and at least give you a brief update on what looks like is going to happen for the week throughout the state of New York for apple scab productions.

Let’s take a look at Riverhead, Long Island. We’re going to go with the LIHREC station. Pretty hefty maturity by this part of the season and about 25%. And we’re looking at almost 12 to 15% ascospore ejection in a combined forecasting event that’s coming up. We’ve already had a total of 20 or so percent of the ascospores ejected. It looks like they even had a little blip of an infection event over the weekend. And now we have just a few days before a larger rain event is coming, about 40 or so hours of leaf wetness. Fortunately, a lot of it happens at night, which is a very good thing because the ascospores don’t eject at night. It’s a combined event from [April 2 to 4]. Other interesting thing about it is that it’s really cold. 37, 41, 43 [°F]. This is a cold event. This isn’t going to be a massive infection. So as long as everything is protected, you should be fine going into the week, getting you all the way to the weekend. If you haven’t had a spray in a while, maybe you can squeeze one in tomorrow [April 1, 2024] before the rains.

All right, what’s our next area? Let’s move up the state. Take a look at the Hudson Valley and Walden. And what do we have? A very similar situation, except lower maturity, 10%, only about a 5% discharge and about a cumulative ten to 15% discharge as well. I’m looking at the infection event. There is one coming from the second to the third [April 2-3, 2024]. Once again, a lot of ejection at night, a very similar 45 hours of leaf wetness. Intense, but it’s 35, 39, 43 [°F]. Those are your temperatures. Apple scab doesn’t like to grow in that, and so it’s going to be a pretty weak source of infection, period. I don’t really think you need a heavy material. As long as you’ve got good coverage from the week before, or if you sprayed close to the weekend, you’re probably fine. Going on through the week with this really, really cold, but wet weather, but still very cold. Almost too cold for apple scab.

Looking up at Capital District, NEWA likes to tell me that it’s not quite green tip yet, but as I mentioned before, some varieties flower earlier than that 50% flower bud break on McIntosh. So let’s just pretend we had an early flowering thing and dial that back about ten days or so to about the 21^st [March 2024]. And in that case, even if we did already have maturity and it was developing, it’s still really low, 3%, less than 2% ejection in the event that’s coming up from the second to [April 4], a good bit of leaf wetness hours, but once again, very cold. 35, 38, 43[°F], and nighttime rains. This is going to really make it not a big deal. If you haven’t done the silvertip application of copper, put one on now, and if you’re going into the week with everything well protected, you’re pretty good off, I think. I wouldn’t really panic in this particular instance and try to cram something in. If you have protection from the end of the weekend, you should be fine as well.

And as we move up into the Lake Champlain area, into Peru, also says, oh, not at green tip, fine, but click it back a little bit. Hardly any ejection at all. It’s just too cold for that coming wetting event, and it’s even less wetting than some of the other areas, about 40 hours of leaf wetness predicted. Day temperatures all below 40[°F], too cold for apple scab. And a lot at night is happening as well. So not a lot of ejection. A really safe time to sort of relax and get that silvertip copper on if you haven’t done it already, or just go in with a light protectant, you know, so you can try out a biological, if you feel like it.

All right. Into the Finger Lakes area, into the Ithaca Geneva area around Interlaken is where we like to look. A longer wetting event is predicted about one from about April 1, even going all the way until the fourth. So, a pretty long bunch of really kind of really, really cold, really, really wet weather. Temperatures are still all near or below 40[°F], but about 60 to 70 hours of leaf wetness over the combined event. But the problem is a lot of it’s happening at night. It’s not going to be a lot of ejection and there’s not a lot of conidia. If everything is protected going into the week, you should have no problems whatsoever.

Now let’s move a little bit west of that and let’s finish up by checking out Sodus area around the lake and Williamson, it’s a little bit close to lake. And remember, if I’m checking the lake sites, maybe you want to take another peek yourself with some more interior sites as well. Same type of thing, 5% apple scab like 1% ejection. A lot of leaf wetness over the course of today creeping into about April 4 and our last really nice sunny day for this nice Easter Sunday, but really cold. A lot of leaf wetness, a lot at night. So you don’t really have to panic. If you have good coverage from the weekend or the week before, should be fine.

Let’s take a look at Niagara Appleton once again, it’s going to be a little scary if temps are in the forties or just below 40[°F ] for the average temperatures. A lot of wetness, a lot of nighttime rain is predicted and not a lot of ejection. A little bit like 3% out of 6% total. This is the time to, like, let your protectants do the work. Specifically, if you spray it over the weekend, you should be even better going in than today because it’s just going to get colder and nothing is really going to be moving. That being said, make sure you all have your protection. There’s a lot of panic all over the Thruway signs here, state of emergencies being called, all sorts of silliness as related to the eclipse. So, you don’t want to be out managing your orchards during the eclipse with a lot of heavy traffic around and what other silliness occurs around that time. And with that, that’s it for this week of scaffolds. Have a great Sunday and we’ll catch up with you next week with some more tips on managing apple scab from that half inch green or green tip, depending on where you are all the way into bloom as well as forecasts.

 

State of the State with Anna Wallis

And now for the state of the state, your weekly roundup of the phenology and degree day accumulations for major fruit production regions across the state. I’m Anna Wallis with the New York State IPM program at Cornell. The information we’re sharing here has been aggregated from the regional specialists across the state, including Mike Basedow, Janet van Zoeren, Mario Miranda Sazo, Craig Kahlke, and Dan Donahue. It also includes information and observations that we’ve made and collected from NEWA.

I think it’s a good idea to start the season with a quick reminder of what degree days mean for those of us that have been in the industry for a long time. We’re used to the term, but in the introductory classes I’ve realized that that term can be really misleading. It actually has little to do with “days” in the conventional sense that we use that word. It’s really just a measure of heat. It might be better called “heat units” or the accumulated heat over the course of the season. Because trees respond to warmth, we can track warmth accumulation, and then use it to predict phenology. Also, insects are cold blooded, so their activity is directly related to the amount of heat that they experience. We can use it also to forecast their activity. Certain insects aren’t active below certain threshold temperatures, so we simply don’t count any temperatures below that during the day. We call these base temperatures. 43 and 50[°F] are commonly used in the models that we use to predict activity.

For a quick reminder of how degree days are calculated, check out the video recorded by Art Agnello explaining the basic apple insect targets and IPM practices. We’ve linked it in the show notes. This video is part of a series of the Apple IPM intensive workshops offered by Cornell in the New York State IPM program.

(Apple IPM Intensive Workshop https://www.youtube.com/playlist?list=PLoNb8lODb49vifrm9Tla4GmAVhlIL0527 )

For phenology across the state in general, the temperatures have cooled off over the past week and we’ve seen a considerable amount of rain. While phenology has continued to progress just a little bit, it’s really slowed down. Rain and snow are predicted to continue for the rest of the week, and we’re likely to see little movement as well.

In the Hudson Valley right now, apples are between green tip and quarter inch green for most varieties. They’re a little bit more advanced for earlier varieties and warmer sites, like in the lower Hudson Valley. Half inch green is predicted for early next week. Pears are at swollen bud, approaching budburst on early varieties and sites. Peaches, plums and cherries are all at bud swell with a little bit of green tissue showing. In western New York, the Lake Ontario region, which is typically a week or more behind the Hudson Valley, phenology this year continues to be almost the same or slightly ahead, in some cases. We’re at about quarter inch green in most apple varieties at many sites near the lake. In the Capital Region, we’re just beginning to see some bud swell in development with a little bit of green tissue. Green tip is predicted for early next week. And in the Champlain Valley things are still pretty dormant, with silver tip predicted early for next week.

A few upcoming pest events to pay attention to include the first pear psylla eggs which were observed in the Hudson Valley and western New York this past week. The first flight of speckled green fruit worm and red banded leaf roller have also been observed. These are the first lepidopteran insects to be active during the season. They’re not usually as problematic as the other leps, including codling moth and OFM, which will begin a bit later. Thanks to Dr. Andres Antolinez for servicing traps at the Hudson Valley Research lab in Highland. For more upcoming degree day accumulations and corresponding fruit phenology and arthropod pest events, check out table 7.1.4 in the Cornell Pest Management guidelines.

We’ve also summarized the upcoming events in the show notes. A reminder that we will have a virtual scout training on Monday, April 15 from 2:00 to 04:00 p.m. and we’ll have DEC credits available for the training. If you’re a farmer, a farm employee, or another industry member with IPM or pest management responsibilities looking for a new or refresher training, this would be a great opportunity. Myself, Anna Wallis, Mike Basedow from the Eastern New York Commercial Horticulture program, and Janet van Zoeren from the Lake Ontario Fruit team will be broadcasting live from orchards in our regions to discuss best practices and then monitoring and scouting procedures for major economically significant pests. There will be a registration link in the show notes and you can find it in the regional extension newsletters.

 

Degree Days with Kelsey Tobin

Hey everyone, it’s Kelsey Tobin here to give you the current degree days in the major fruit producing regions of the state, as well as the projections through the end of this week. Throughout this season, we’ll be aligning this information with some previous work done by Art Agnello relating to McIntosh phenology and degree days. Things are starting to warm up around the state, but we’re still pretty early in the season in most of the regions and we’re at or around silver and green tip. For McIntosh, silver tip is at or around 58 to 106 degree days at that 43 degree Fahrenheit BE base temperature. Green tip is at or around 99 to 144 degree days.

Starting with degree days here in Geneva, we’ve reached 139 degree days and projected to reach 155 by the end of this week. At Highland, they’re at 162 degree days, projected to reach 183. Clifton park is at 98 and projected to reach 112 by the end of this week. Peru is at 57 degree days and projected to reach 64 and those trees are still dormant. Medina is at 151 degree days projected 168. Appleton north is at 118 degree days and is project to reach 129 by end of the week. Williamson Mason is at 123 and is projected to reach 133,  and Williamson-Demaree is at 139 and is projected to reach 146 be the end of this week. We’ve had some comfortable days over the weekend here in this region and we’ve accumulated just a couple degree days, but we haven’t had any major jumps in those temperatures yet. Things are holding pretty steady this week and most places will hang out around the same degree days that they’re at and maybe add one or two by the end of this week. Bud development has reached green tissue in multiple varieties throughout the Lake Ontario fruit region, so just keep an eye out on your trees and we will be back next week with some more updates.

 

McIntosh Phenology and DDs (43F) (avg +/- std)
Phenological Stage	DD Accumulation
Silver tip	58-106
Green tip	99-144
Half-Inch Green	150-201
Tight Cluster	206-257
Pink	267-316
Bloom	344-415
Petal Fall	439-523

 

Phenology and DDs (43F) for NY NEWA Stations from 1/1-4/1
Station	DD Progress	End of Week DD Projections	Phenological Stage
Geneva	139	155	Green Tip
Highland HVRL	162	183	1/4 ” Green
Clifton Park	98	112	Nearing Green Tip
Peru (Forrence)	57	64	Dormant
Medina – Inland	151	168	1/4 ” Green

Appleton North – Lake	118	129	Green tip
Williamson (Mason) – Inland	123	133	1/4 ” Green
Williamson (DeMarree) – Lake	139	146	1/4 ” Green

 

Monique Rivera: That concludes this week’s update. Thanks for listening!

 

 

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