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 

This week I want to change gears a little bit and talk about chemigation. So companies are starting to come to me and ask if I can test their products via chemigation. And one thing that was really surprising to me when I came to New York was that this was not really an option and that irrigation systems were not consistent throughout the industry. So chemigation is specifically limited to products that have chemigation on the label, so you can’t just use anything in this manner. It’s important to note that insecticides that are systemic have an active ingredient that is primarily absorbed by the plant roots. Then it’s transported through the plant to various locations, such as growing points, where it can impact pests that feed on the plant tissue.  

The movement of systemic insecticides occurs within those vascular tissues, which can either be the xylem, which is responsible for water transport, or the phloem, which is responsible for nutrient distribution up and down the plant. So it’s important to note that xylem only goes in an upwards direction as the water moves up the plant, and phloem is a material that is transporting the nutrients of the plant, for example, amino acids, up and down the plant to grow specific plant parts, or moving amino acids there in response to insect feeding.  

Most systemic insecticides are specifically moving upwards within the plant through the water conducted tissue, which is the xylem. Systemic insecticides are specifically highly effective against insects with piercing, sucking mouth parts. So these insects are feeding on that vascular tissue. They’re sipping on the water, and they’re sipping on the nutrients and the phloem. And this includes insects like whiteflies, aphids, soft scales, and mealybugs. Although spider mites do feed on the plant, they’re not actually feeding on the vascular tissue. They are removing plant chlorophyll from individual cells, so they are feeding in a much more surface level manner to the plant.  

 So I do feel like there is a use for chemigation in the IPM program here in New York. In particular, my thought process is that this could be really promising for annual and persistent woolly apple aphid populations. So an important thing to consider if you’re thinking about installing the ability to chemigate is to make sure there are proper controls in the system to limit backflow. The main concern with backflow is contamination into your primary water source, whether that be a well or city water. And this is regulated to be installed on all chemigation in the state of California. And if it’s not already regulated here, I’m sure it will be eventually. So I think it’s really important, if you’re thinking about the ability to chemigate, to make sure those controls are in place at installation so you don’t have to go back or there are no additional errors with regulators.  

 There are some limitations to chemigation. I want to talk about them in part because I do want to mention my friend that has inspired me a lot. I think one of the most interesting things about being in academia is you have these people in your life that can just become your friend. You meet them, happenstance at a job, but they completely change the nature of the way you think about your research. And for me, this person is a gentleman named Frank Byrne, an Irish immigrant to the United States who was an entomologist who studied pesticides for his whole career. Frank found that in heavy clay soils, the uptake of imidacloprid can be really limited because it binds to the clay. In particular, when water is not available to keep the imidacloprid solubilized, then you really limit the ability of the plant to uptake the water. So if there’s no water to release it from the binding sites on the soil particles, imidacloprid uptake can be severely compromised.  

 So this is something to seriously consider going forward. I haven’t started any of this research yet, but I do want to talk about chemigation and keep it on your radar because I do think this is the way things are going. Also, as an aside, I want to make sure to note the differences between a systemic and a translaminar activity on an insecticide. So while systemic and translaminar insecticides are two different types of insecticides with distinct modes of action, there are some systemic insecticides that can be used translaminarly depending on the specific chemical properties of the insecticide compound. So what is translaminer? These are a lot of kind of fancy terms being thrown around here, but translaminer movement refers to the ability of an insecticide to penetrate the leaf surface and move within the leaf tissue. This is why with products, for example, Movento, you really need that penetrant surfactant to get it into the leaf.  

 Some systemic insecticides have properties that allow them to penetrate the leaf surface and distribute within the leaf tissue, providing some translaminar activity in addition to their systemic activity. However, I do think it’s important to also note that not all systemic insecticides can be used translaminarly. So make sure to be careful and read the label there. And the effectiveness of an insecticide used translaminarly may vary depending on the insecticide and the specific pests.  

 So all of this depends on those interactions, which is why we need to continue doing this research so that we can make good recommendations.  

 So outside of this chemigation conversation, we were servicing our black stem borer traps last week and we were starting to see ambrosia beetles in them. So these traps are spread throughout western and northern New York. And I think that if you have had a problem with black stem borers in the past, now would be a great time to go out and have a look and start your scouting in those specific areas where you’ve had problems previously.  

 Pathology Update with Kerik Cox and Liga Astra Kalnina 

 First thing I want to talk about is prolonged wet weather and Captan. Last week, and even a little bit into this week, we talked about prolonged overcast wet weather in curative or post infection fungicide applications. Now the weather trends are continuing. It’s kind of still overcast and wet a lot of the week, but the end of the week was starting to look sunny. However, there could be more cool overcast wet weather as the trees move into petal fall.  

 If you’re in the Hudson Valley, you could be experiencing some sort of late bloom/almost petal fall wet weather. If that happens, I think it’s important to make sure you take caution with Captan. Dave Rosenberger warned about it in his blog and I’ve been thinking about it all weekend as well. Now, tank mixing Captan with foliar nutrients, various adjuvant sprays, some that may enhance penetration like Regulaid and maybe others, we don’t know what they’re doing, or we don’t know what they’re doing in reaction with Captan. These could severely damage fruit finish and/or cause leaf spotting in the foliage, particularly on different varieties.  

 Now, the potential for fruit finish and foliar phytotoxicity will increase when applications including captan and tank mixes are made under slow drying conditions. This means relatively high humidity, overcast skies, cloud cover, light rain, and what I would say is, given the potential for fruit finish and foliar damage and the prevalence of adjuvants, constantly using tank mixes, and the susceptibility of young developing apple tissues at this time, Dave and I agreed and have put this in the guidelines that Captan should be avoided in these type of weather conditions from petal fall to second cover.  

 Now, if you need to add a protectant during this type of weather for fungicide resistance management, use mancozeb, particularly if you’re still in the PHI window for your variety. You could use sulfur as another option for a protectant, and that would also be helpful for powdery mildew. Mancozeb will be better for rust, sulfur for powdery mildew.  

 Now, sulfur can also cause injury as well, but that’s more of a hot weather condition, but you don’t want slow drying conditions with sulfur either. But at least it would be cool outside. Now you might be asking yourself, do I need any of them? Will I get fungicide resistance if I make one or two applications of a single side fungicide alone? It’s highly unlikely. We make applications up to four of single site fungicides alone all the time and I couldn’t make fungicide resistance show up if I tried, but that doesn’t mean it can’t happen. It’s highly unlikely, but at the same time it would be much better to skirt a little bit on any other issues than running your entire crop with a potentially damaging tank mix during fruit thinning and early fruit development by unnecessary additions of Captan. So be careful with that material.  

Now, if it is going to get warm, we might as well talk a little bit about how to keep track of fire blight forecasting events. Much of the state will still be in bloom by next week and we’re starting to get into 60-70 degree weather. So this is sort of my advice for watching these dates. Now when it’s really cold and the TRV is like below 100, which usually gets really high into high as 800 and the EIP can get up to almost 200 but really hits thresholds around 100, then we need to start thinking about things.  

 But right now things are so low it’s almost silly to be thinking about applying for Fire blight. In that sense, what to do? Okay, the first thing you want to do is keep track of all the first blossom open dates for each of your varieties, particularly ones that are highly susceptible for fire blight. These are the ones you’re going to want to take most care of and look most critically at when you’re making applications for fire blight or considering a risk period. Write these dates on a piece of note paper. Take the first blossom dates and those applications and make sure to use these dates and your NEWA fire blight models to increase the precision of the various predictions. Now avoid any less accurate model default dates, over generalized stuff, or region-wide dates. Try to use the most precise bloom information for yours. It’s going to pick a date for you. Don’t go with that one.  

 Now, as you go in and start seeing some of these outputs, here are some things to consider. Always remember that the predictions and forecasts are theoretical. They’re just predicting looking at weather data that’s collected or forecasted from weather stations. These results should definitely not be substituted for actual observations of plant growth stages or disease scouting or anything else that you’re monitoring on the farm. If you’re starting to sweat, as Dave Rosenberger used to decide the amount of sweat he was out in the orchard, then it was time for fire blight. If it seems hotter than it normally is, you might be in a pocket or microclimate and you may need to make different considerations. However, if it’s colder, frost on the ground and is telling you to spray at the same time is probably not necessary.  

Second thing to consider is the history of fire blight in the planting. If you didn’t have fire blight the previous season, if you’ve never had fire blight, don’t let a bunch of excessive model predictions or extension alerts, including this podcast, intimidate you into applying unnecessary antibiotics each time you get a scaffolds update or each time you check out our blog, et cetera.  

 The other thing to consider is the age and susceptibility of your trees. Age, variety, and particularly the cider varieties can be highly susceptible, so think about the different age and variety as you’re looking at the models. None of the models consider these factors in a formal sense, so you’ll have to adjust the interpretations yourself based on what you know about your tree age, your variety, and maybe even rootstock, particularly scion, especially if you start to have these cider varieties, which can go very quickly with fire blight infections.  

 Now, if you do have a young planting of a highly susceptible variety, let’s say it’s a cider variety, it may be important to focus on protecting those blocks instead of worrying about on the fence model predictions in your 15 year old McIntosh planting on resistant rootstocks. In that scenario, the young planting might actually warrant an application, while the older plantings probably wouldn’t need one, particularly if an on the fence risk level shows up as you’re looking at the forecasts.  

 Now also, really, the models only identify risks based on weather conditions and includes temperature and moisture. Now we have the wetting events color coded in light blue, so you might see some heat, but there may not be any moisture present. At the same time, keeping mindful of all the different sources of moisture, including relative humidity, dew, and some of the other things which could be enough if the heat is high enough.  

 Also remember, despite the use of words such as extreme and infection and bright red, the models are only just looking at favorable conditions and spitting back a word. If the variety is not highly susceptible, if you don’t have any history of fire blight, and your trees aren’t moving into incredibly high vigor with nitrogen, maybe you’ve got an organic planting and it’s just moving along quite slowly, the actual risk in these scenarios could be almost nonexistent.  

 Now the other thing I have noticed is that the model predictions change frequently. We’re looking at going into Sunday with some warm weather almost approaching the 70s, so you’re going to have to check these a lot. The predictions are based on weather forecast. The forecasts have been changing erratically throughout the last couple of weeks, and bacteria populations double once every 20 minutes in general. And this would be the case for the fire blight bacterium Erwinia amylovora. Once temperatures start to get above 60, this thing will be on the move and can actually begin to grow fairly well. And these models use hourly weather data rather than daily summaries to help accommodate for the rapid growth of this particular type of pathogen. So check the fire blight predictions pretty frequently, particularly those in the forecast. And remember, make sure to always keep abreast that the one to two day forecasts are more reliable than the three to five day predictions. NEWA uses the National Weather Surface Forecasts in which you can compare to your various local favorite weather forecast provider and see what’s happening in your area.  

 I watch the models, I look at all the apps, I don’t look at just one, I look at several, and then that’s how I make choices. In my case, I’m trying to cause fire blight, and so I will do the same thing to identify these exact periods when you would want to protect it. I also want to protect it and then cause disease so I can see how the various products work. I would never go out and try to run my fire blight trial on a day like this Wednesday when it’s 40 degrees outside. It would be a disaster. But come this weekend, I’m going to be looking really hard at those predictors, and you should as well, in terms of protecting your crop.  

 So, with all of this big rain this past week, it seems like most ascospores have been released in the Hudson Valley and in Long Island. So even though there’s a current infection event until May 5, the spore release is very minimal, somewhere between two and 3% for both regions. If your last applications were single site fungicides for the past two or three weeks, this might be a good week to do a cover spray to manage resistance concerns. Some good options include Double Nickel or Serenade Opt if you like biologicals, or if you want to stick with the conventional, Manzate Max will be your best bet. With the cool weather, there’s no to low risk of fireblite this week, but I would suggest to monitor NEWA closer to the weekend as the weather may get warmer and the risk might increase. I would say maintain desired coverage, but take account orchard history and cultivar susceptibility before making applications.  

 When we’re thinking about Niagara County, Wayne County, and the Champlain Valley, even though we have had also a very long infection period that is still continuing probably until May 4 or May 5, and it’s been raining this whole time, and there’s been a lot of leaf wetness hours, since ascospore maturity is lower, the risk of infection is as well, the same thing applies. Once you get a break in the rain it would be a good time to apply a cover spray. Like I said, Double Nickel or Serenade Opti would be a good option, or captan tank mixed with Manzate Max. Monitor NEWA closer to the weekend as the weather is increasingly getting warmer to look for fire blight risk.  

 For the Capital District, it’s been a nonstop rain this whole time, and this infection period is predicted to last until May 4. Even though there was probably more than 25% of ascospores released over the weekend, there’s still another 12% getting released Tuesday through Thursday.  If you had made back to back single site applications for the past three weeks, consider applying a cover spray. If you have not made a single site application, then when you get a break in a rain would be a good time to make a single site application.  

So when it comes to Finger Lakes, the spore release is also very low. It’s only 6%, so also if you have time and energy, include a Double Nickel or Serenade Opti this week. 

State of the State with Anna Wallis 

Remember that degree days are a measure of heat accumulation. We’re using them to predict pest activity and tree phenology early in the season. And we’re using Degree Day base 43 Fahrenheit starting from January 1 through the present, which means we’re only accumulating heat and degree days when temperatures are above 43.  

 So there’s not very much to report on the Degree Day front. Again, this week it’s continued to be really cool. High temperatures in most of the state, again, were in the 40’s and 50’s, and it’s going to continue that way. If you listened last week, you probably remember I said that in the warm weeks, we accumulated over 100 to 150 degree days in the course of a week. Last week we accumulated about 40 or 50. Again this week we’ve had about that or maybe even less, about 30 to 40 degree days over the past week. So phenology is progressing slowly and steadily.  

The main difference this week has been the rain. Everyone’s talking about it. With over two inches of precipitation recorded in most places, it’s been really important to stay covered for scab for a couple of reasons. First, the rain is probably washing off your residual. It’s also probably encouraged growth, leading to a lot of unprotected tissue. On the insect front, however, in most regions of the state, most people are reporting pretty low levels of activity.  

 In the Hudson Valley, phenology is quite spread out depending on the region and variety. Ranging from fruit set with some RD not quite 5mm, Macs still at early PF, Crimson Crisp still has a lot of pink.  

In the Lake Ontario region, trees are at more advanced pink stages with cluster separation. Idared at inland sites (some of the most advanced in the region) had more than 40-45% bloom. Honeycrisp was still at early pink in Sodus. At lake sites, varieties including RubyFrost, Gala, and Fuji did not yet have open kings. Things are moving slowly, and full bloom isn’t expected until early to middle of next week. 

In Geneva this week, McIntosh and Gala had a few open kings on Monday. Earlier varieties had a few more blossoms open, some other later varieties are still at pink. Peaches, apricots, plums, and tart cherries are at petal fall. Sweet cherries are at late bloom. 

The Capital Region is progressing into bloom, with petals just starting to fall off some kings in early varieties in southern Saratoga county. Expecting a cool, rainy bloom.  

In the Champlain Valley, McIntosh and Cortland are now at about pink. Honeycrisp, NY-1, and Gala have a touch of pink starting to show on the kings, possibly a lateral here and there.  

Now I’ll give you a rundown of the DD accumulations at NEWA weather stations throughout the state. Every week, we’re including a Table in the show notes for you to reference later. On average, in McIntosh, bloom usually takes place in the upper 300s to low 400s. Petal Fall is usually in the mid 400s to lower 500s.  

 As of the end of the day Monday 5/1, DD accumulations were: 

There are quite a few pest events to be looking out for during this period. Based on observations of pest activity and the corresponding average DD range recorded over the past years, here are a few things that may be taking place around now (in the range of 200-400 DD 43). There is also a table in the show notes summarizing this.