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

Entomology Update with Monique Rivera 

 So we are cruising right along towards bloom in western New York and in the Hudson Valley. There are places where they’re at king bloom and starting to head towards petal fall. So I thought it would be a good time to discuss some interesting potential management issues for your orchards.  

So let’s start out with plum curculio. This is an interesting and pervasive insect that we can never seem to quite get a handle on. And I think part of this is that they do overwinter outside of the apple orchards as adults, and then they migrate into the edges of orchards, usually when we hit about 55 to 60 degrees Fahrenheit during bloom.   

So this makes management especially complex. At bloom, we have the plum curculio adults in the trees, and petal fall is when oviposition is occurring. The length of time of oviposition depends on seasonal temperatures, but I think that the most effective things that you can do for control are preventative insecticide sprays that are applied from petal fall to the end of oviposition, which can be calculated in NEWA.   

Also, many of these potential options, which I’m going to mention in a second, also work to control European apple sawfly, if you have that issue.  

So the products that specifically I’m thinking about for controlling plum curculio would be Imidan, Actara, and Avaunt. They should also have some activity on tarnished plant bug.  

So moving on to tarnished plant bug, this is another one that’s similar to plum curculio, where it’s consistently causing damage and is very difficult to control. They feed on the buds and flower parts in the spring and can cause aborted fruit. They have two to three generations per year, so they’re active early in the season on warmer days, and some people choose to monitor for them. I used to monitor for them in peaches, and we would sweep net the row middles. We would do ten sweeps over probably five to ten different locations across the orchard, and have a look at what was going on in the row middle. So as an extension of that, I do think that a very good recommendation for controlling them, if you know you have a problem, would be to treat those row middles to get rid of the broadleaf weeds. You can monitor for these and I would monitor if you have a particularly bad problem. So I’ll go into a little bit about that. You should start monitoring along the border. The time to do that has passed, as normally those are set out at silver tip and there’s one trap every three to five acres. And then you’re looking at cumulative trap averages and action thresholds. So if you’re getting five to eight tarnished plant bug per five traps, that’s a really high population. And if you see this post bloom, it’s definitely an action threshold.  

So what’s problematic is that pyrethroids are the main group that works for this pest. But those obviously can have a lot of secondary issues. So I would be careful and diligent in using them to target multiple pest issues. Saving those pyrethroids, particularly in the Hudson Valley, for dealing with high infestations of brown marmorated stink bug would be good. That’s why I would focus on weed management in particular.  

Last today I wanted to talk about some of the options for control of woolly apple aphid. I found that across the state this is a pest that has appeared and resurged with a vengeance and seems very difficult to get under control. So the first and sort of nuclear option is diazinon. I think that for really heavy infestations where you have not been able to get in there at the very precise timing that you’ll need for a lot of the other products, diazinon is a strong option. There are a couple of neonics recommended such as Admire Pro and Assail. These products in a foliar spray will go systemic, but the systemic activity is not as great as if they were chemigated into the tree. There’s also the 4D Sivanto Prime. I don’t know how much people have played around with this in the state. It is a good rotational product, but it’s not going to have a strong amount of efficacy. I’m hoping to play with this in the future. There’s also Versys. I will be playing with this this year for Woolies and hopefully be able to report something back. And of course there’s always the very expensive, but also very effective product Movento, but it’s really key to get the timing right.   

So once you head into petal fall, it is time to start scouting for Woolies. For my trial I’m starting to scout even now just to get a sense of when precisely they show up. And so Movento is a great product, but if you want to take it one step farther, Senstar also has the addition of an insect growth regulator, the same AI as Esteem along with it. And then finally there’s also Beleaf. I’ve not played around with that, but all of these should be good rotationals.  

If you really have a strong infestation, I would focus on getting the Movento timing really dialed in, if possible. And if not, there is always a Diazinon.  

Pathology Update with Kerik Cox and Liga Astra Kalnina 

 Okay. This is Kerik from Cornell AgriTech, your tree fruit pathologist coming at you with another weekly update of apple scab. Maybe a little bit of fire blight… but not really. Yeah, Liga’s out this week. She’s busy teaching, spraying, developing disease forecasts, and doing research all at the same time. And we needed to squeeze in a slight update to our previous message, so we’re going to go tell you what’s going on.  

The forecast is constantly changing for the week, but what we can say is it’s going to be a big apple scab period throughout the state. In the Hudson Valley we’re in an infection event now all the way through the May 1. They’re looking at this really elongated cold. Apple scab release is reaching up to 21%, and the spore maturity is hitting at 93. Now remember, 21% is still a large chunk. The season is almost over, but we need to make sure we’re finishing strong. It’s going to be a cumulative 21%. Twelve will be coming out Thursday night. Make sure you’ve got coverage.  

Good options include: if you have rust, shoot for a group three fungicide. This would be your Inspire Super, your Cevya, those types of products. If you’re mainly focusing on apple scab, you could shoot for a nice group seven, the Luna products, Aprovia, Miravis. Another option would be Fontelis.  

With this cold weather, we don’t have a lot of fire blight for the most part. In the Hudson Valley and throughout much of the state, the blooms are open, but the highest EIP is about 0 and the highest TRV from Cougar Blight is about 2, which doesn’t even trigger the slightest bit of warning. It’s all green across the board.  

Capital District, we have the same thing happening. According to these forecasts, it looks like the rain is coming in a little bit later this weekend, probably Saturday. This is similar to what we’ll be experiencing in Geneva. It’s going to be a long period, but that period could extend all the way to May 2. This comes with a 28% spore release. Ascospore maturity will be at 47%. Fire blight is complete nothing. So it’s really time to focus our efforts on apple scab. It’s going to be almost 20% over the weekend with the rest of a cumulative coming out by the end of it. The biggest release looks like it’s going to happen on 4/30, on Sunday.  

If you get a break in the rain Friday morning, this is when you come back with some of those materials I mentioned earlier. Group 3 is if you got rust issues and maybe your strong group 7 fungicides if you don’t and it’s very cold.  

What does it look like in Niagara across the other side of the state? It’s not as going to be as bad. It is still a very long infection period and you should be well protected and make sure to get something on when you can get a break in the rain and make sure your coverage is good. If you’re going to get more than two inches of rain it might be time to think about recovering. It’s only going to be a cumulative 11% with a 20% maturity, but it is still a big problem.   

Finger lakes look a lot like the rest of the area, closer to the Capital District if you will. Looks like it’s going to start sometime Friday and end sometime on Monday. Same type of options as well for fungicides. The biggest ejection could be on Saturday with about 11%. Looking at some of the other types of model data and they show germinating ascospores pretty much all day Saturday into Sunday. So it’s a good time to make sure you’ve got stuff on the trees.  

Wayne county if you’re up closer to the lake it’s not so bad. It’s still an infection period but it’s not as bad as a little bit east so it seems like the worst of the weather is going to hit a little bit east and a little bit south. You’re still looking at about a 10% ascospore release, 17% maturity, and it’s going to be a long wetting period so you got to make sure you have these materials on there. Fire blight is still low throughout the state.  

Champlain Valley is still not as bad. 12% release, you’re at 20% maturity, you have a whole scab season to go and this is going to be a really long one. Starting looks like Saturday and moving all the way through almost Tuesday as well. It’s going to be a long cumulative slow release and remember, even if the spore release is 12%, out of trillions of mature spores, this is a lot to have to deal with, particularly if you’ve got green tissue out there. So some of these events may be lower than others, but take care to make sure those trees are well protected in this really long raining period.  

Now all that being said, let’s talk a little bit about post infection and curative activity. We’ve already experienced, or many of you experienced probably and are going to experience another multi day infection period. During these periods, depending on your region, you may have exceeded over two inches of rain. You may feel like coverage is lost or coverage will be lost this weekend and you’re like “what do I do”? And you might even be thinking about curative or kickback applications in the next week.  

Now, one of these things that you’ve got to be careful with curative applications because it’s one of the two practices that’s been known to contribute to the selection of fungicide resistance. This happens because when you’re getting the rain on there, scab might get inside the tissue, if it’s already infected and you’re going to go back and try to erase it, that scab gets into the tissues, it gets underneath the leaves and it starts its infection process and it’s protected from the fungicide arriving on the surface later.  

Now, if that fungicide can get inside the plant and do stuff, then you have a better shot. Now, that’s not how fungicides are made anymore. We don’t want them in the plant, particularly when you’re selling the fruit. So there are very few systemic, there’s some locally systemic products and there’s a few out there that have this potential.  So when you get the material on there, if it is inside the tissue, it’s like treating the fungus with less. If a little bit gets in there, it’s like using a really, really low dose of fungicide. And if anything lives or if there’s a naturally partially resistant member, it will go on to survive that application. This is why we’re often pushing the full and high doses to make sure that nothing is around. And when fungi go ahead and get established and they partially infect, they might last for a little bit and they might not be weathered by the application that you put on after they’ve started their infection processes.  

Now, if you decide to go for it, some of the best materials that we found over the past is Dodine marketed as Syllit. Now, sadly, this product does not have a post infection labeling, so you probably shouldn’t be using it. And once you’ve hit petal fall, it looks like, according to most of the labels I see on this, it can’t be used at all. So that’s probably not a good use, even though I’ve seen it work very well as the label was being developed in sort of research mode.  

So what do we do then? If you have rust in the area and you need to make a curative application, I’m going to recommend a group three fungicide. I’ve noticed though, I’ve searched a lot of labels, Liga spent 45 minutes looking at labels, and we could barely find anything. With curative applications, Inspire Super has a 48 hour curative application option on the label. If you do this, make sure to put in about 3 pounds of any formulation of 75% mancozeb. That’s going to help with any resistance escapes and the mancozeb is not going to get in the plant. But if something were to sporulate later and splash around on the tree, at least you would have some protection. Now, the other thing that’s nice about that mancozeb is it gives you a little bit of cedar apple rust control as well. If you don’t have any rust concerns, I’ve also noticed that Aprovia has a 48 hour curative option on the label, and you’re probably still going to want to put the mancozeb in there even if you don’t have rust, just to make sure we don’t get any resistant member escapes later on in the week as it continues to rain. Now, if you want, you can even try to try something like an adjuvant like Regulaid in there like we do for strep to get better uptake of the plant. If the fungus is in the plant itself already during the infection period, you probably want to try to get rid of it. So those are my thoughts on curative applications.  

As we go into next week. We’ll be deep into full bloom and it might not be so cold. There’s no risk anywhere of fire blight in the region. Doesn’t mean it won’t make you feel a little bit nervous if you see open flowers and the temperature starts to hit 60, but you don’t need to be in full panic mode. Next week we’re going to talk a little bit about how to assess the various risk periods that are mentioned in the various model outputs. And with that, I’ll go ahead and end it for the week and let you get on about your business and worrying about apple scab. 

State of the State with Anna Wallis 

So after the seasonably warm temperatures a couple of weeks ago and everyone got excited, things have cooled off pretty quickly and they stayed that way. Essentially, it’s like the trees and insects have been in a refrigerator for the past week and continue to be this week. So remember that degree days are a measure of heat accumulation and we use them to predict pest activity and tree phenology early in the season. Insects are cold blooded, so their activity is directly linked to the amount of heat they experience. And tree phenology is similarly well correlated with temperature and heat accumulation, although there are lots of other factors that contribute to the activity of both.  

For phenology early in the season, we’re keeping track of degree days base 43 Fahrenheit since January 1, which means we’ve only accumulated temperatures when temperatures are above 43. High temperatures in most of the state this week have been in the 40’s and 50’s, perhaps a touch warmer in the Hudson Valley. So we haven’t accumulated very many heat units or degree days.  

If you listened last week, you might remember that I said in the warm weeks we accumulated 150 or so degree days in many places over the course of the week. This week, in comparison, we’ve only accumulated about 30 or 50 in most locations, so things are moving slowly. We kind of suspended whatever phonology was taking place last week into this week.  

In the Hudson Valley, trees are at late bloom to early petal fall. In the lower part of the valley, bloom ranges from king bloom petal fall in McIntosh to no bloom open at all in Golden Delicious. It’s continuing to advance this week despite cool temperatures. Pollination has been a big question on everyone’s mind. We know honeybees prefer warmer, sunny conditions to fly, but really only a few hours are needed for sufficient pollination, which we had some windows over last weekend and likely will again this week at the end of the week and over the weekend. And there are many native pollinators out working which will continue to fly in cooler overcast weather.  

In the Lake Ontario region, most varieties are at the early pink stage including McIntosh, Gala, and Fuji. Across western New York, very early bloom is likely early next week.  

 In Geneva this week, McIntosh and other varieties are at pink. Even early varieties are at very open pink with some balloony looking kings, but nothing open yet. It will likely stay that way for a few more days. Peaches are at petal fall. Cherries, apricots, and plums are at late bloom. In the Capital Region, Saratoga growers are now into pink. With the cooler weather, things should progress at a more average pace over the next two weeks. We’re likely to see some early varieties moving into bloom early next week.  

In the Champlain Valley, phenology has progressed slowly since last Monday. McIntosh, Cortland, and Gala blocks in Peru are now at tight cluster. Honeycrisp and NY-1 are at early tight cluster as well, with a few spur leaves still needing to unfurl. We may be beginning to see some early pink next week.   

Now I’ll give you a rundown of the Degree Day accumulations at weather stations throughout the state. 

There’s a lot of moving pieces this time of year. On average, in McIntosh, bloom usually takes place at about 340 to 415 degree days base 43. As of the end of the day Monday, 4/24, degree day accumulations were: Geneva 307, Highland 466, Clifton Park 325, Peru 220, Medina 253, Appleton North at the Lake 215, Fairville at the Apple Shed 291, and Williamson DeMarree 255. You can also find the Degree Day average ranges correlated with phenology and pest management in the Cornell guidelines.