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Entomology Update with Monique Rivera

Monique Rivera: Welcome to Scaffolds Podcast, a weekly roundup of the timely updates on insect and disease management, as well as phenological developments across New York State for apple growers. This is Monique Rivera, your host and assistant professor of entomology at Cornell Agritech. Co-hosting with me will be Kerik Cox, associate professor of Plant Pathology, along with Anna Wallis, IPM fruit Coordinator. In this episode, I talk about how to optimize your sprays to ensure proper efficacy. Kerik Cox discusses fruit finish issues, and Anna Wallis gives us the State of the State update on our continued Degree Day accumulation.

Today, on our second to last episode of Scaffolds, I want to discuss or rather review some key elements to keep the efficacy of pesticides at their intended rate and to optimize spray coverage with air blast applications. So first, let’s talk about water pH and quality. So, pH, you probably studied this at some point in your education. But to recap, a pH is a value that describes the relative acidity or alkalinity of a solution, and the pH scale runs from 0 to 14, where a PH less than 7 is considered acidic and a pH of 7 is neutral, and a PH greater than 7 is considered alkaline. Most pesticides perform best in water with a pH between 4 and 6.5. When the spray solution is outside of this ideal range, the pesticide will be hydrolyzed and degraded and will not work as well.

So, moving on to water quality. So, water quality can be measured by two different attributes. First, water hardness and second, water turbidity. So, starting with water hardness, this is a measure of the total concentration of positively charged calcium, magnesium, iron, sodium, and aluminum ions in the water. Water hardness is measured in milligrams per liter (mg/L), parts per million (PPM), or grains per gallon. And hard water is really common. It can be found in over 85% of US. water resources. And when hard water is used to mix pesticides, negatively charged pesticide molecules can combine with positively charged ions in the hard water to create molecules that can precipitate out of the solution. So, you’ll see granules at the bottom of the solution, or it will enter the target pests at a much slower rate. And lastly, it can possibly interfere in a way which prevents the molecule from entering the target pests at all.

So lastly, water turbidity. This is a measure of the total suspended solids in the water. A high turbidity can give the liquid a hazy look because of the suspended solids. So, turbidity is usually caused by soil and organic matter, which can reduce the effectiveness of active ingredients. And positively charged pesticide molecules can be attracted to the negatively charged particles found in the water, making them again available for plant uptake. In addition, soil particles and organic matter can plug nozzles and screens, which can further contribute to uneven spray patterns. And when you have to repair equipment because of this, that also creates a loss of time.

Next I want to move into mixing order. I myself didn’t really know about this until working in California and was working with a group of organic growers where mixing and formulation is even more important than in conventional pesticides. So, I learned all about this mixing order, and the way I learned it is by remembering an acronym that is WAM LEGS. And this just relates to or translates to the W stands for first adding your water-soluble packets, wettable powders, or dry flowables. And then the A is agitation and buffers. M is microcapsule suspensions, L is liquids and solubles, E is emulsifiable concentrates, G is high load glyphosate products, and S is last, which is surfactants. And so, when you’re mixing, I think that it’s important to remember that insecticides may have different chemical properties and some formulations may not be compatible with others. So, mixing incompatible insecticides can really lead to this formation of chemical reactions within your tank mix, which might reduce the effectiveness of the individual products or even create harmful byproducts. It is essential to follow the manufacturer’s guidelines regarding which can be safely mixed together. Sometimes labels don’t mention this at all, and it’s important to recognize that when you do mix a big concoction in your tank, you really don’t know what’s going on in there unless it’s been previously studied. Also, when it comes to stability, some insecticides can break down or degrade when mixed together, leading to reduced potency, or also altered efficacy. And this order of mixing can influence the stability of the mixture overall.

And then we have physical compatibility of insecticides. So, in addition to chemical compatibility, there can also be physical compatibility issues as well. For instance, some formulations may not mix well resulting in the separation of components, again, clogging of spray nozzles and that overall contributing to inconsistent application. And if you mix the wrong things, sometimes they can emulsify each other. And so, some insecticides require specific mixing techniques or adjuvants to ensure they form stable emulsions. And this is usually what you find in an emulsifiable concentrate. They need to be emulsified in order to act with water. And again, for this, the order of mixing and the use of adjuvants can have an impact on the emulsification process. So, if something’s going to emulsify and it’s an active ingredient that you’re seeking to have efficacy with, make sure that goes in before you’re adding adjuvants or surfactants. And then when it comes to target pests and crop, this can also create a variation in the importance of mixing order. Sometimes if you mess up the mixing order for a specific pest or a certain cropping system, maybe in vegetables, they typically use a much different spray apparatus to get that application on with booms rather than our air blast sprayers. So, the order of mixing can possibly not have a significant impact for some target pests and crops, and it can be more critical for others. So again, just doing due diligence and making sure that those large tank mixes everything is compatible.

So, the last topic I’m going to talk about is gallons per acre and drive speed. This is a topic I’ve literally been trying to push or just keep reminding people of across the literal continental United States. You know, I had this conversation a lot in California, and I find it funny that I’m also having it here. And so, the main point I want to make is that it’s super important to recognize the relationship between spray coverage and gallons per acre and drive speed. In apples, we have this amazing advantage of high-density systems, and you can get great coverage with a lower water volume than is typically recommended for full size trees. So overall, typically the slower you drive and the higher water volume you apply, the better. And I understand why this is not ideal. Slower means the application takes longer and labor is expensive. More water is annoying because you need to refill more. But there is a happy middle here. In high density orchards I recommend keeping your speed at 2.5 mph or below and keep your gallons per acre at 100 or more. I know people love to apply at 50, but I feel that for specific pests, in particular woolly apple aphid, it is critical to get that up to 100. Also in old-style plantings, you’re going to need more water because the water is what’s driving the coverage, the water is what’s carrying the molecule. And so, I keep the same recommendation for speed, but ideally let’s go as low as 2 mph with 200 gallons per acre or more. I know that’s frustrating, but those old-style plantings and older trees, you have an entire canopy to really saturate and that extra water is going to help that, especially with something like woolly apple aphid, where it’s more likely feeding on that woody material on the interior of the canopy. You really want to dial in that spray coverage. So that’s all I have to say for this week. And next week I’m looking forward to our final episode recap the season’s pest and disease issues.

 

Pathology Update with Kerik Cox

This is Kerik coming at you from Cornell Agritech with another pathology update. It’s probably the next to last one. I think this is the next to last episode of Scaffolds that I’ll be doing and for the season and figure I’ll talk a little bit about some fruit disorders that you could be seeing now, or you could see in the future.

Last week I had a talk about potential Captan injury in the summer. And in a follow up conversation after the presentation, when we were approaching the lakeside picnic part of the Lake Ontario Fruit Team summer tour, the apple scarf came up as a potential outcome from injury and other things, and so I thought it might be pertinent to talk a little bit about it. It’s a fruit finish disorder and it’s going to manifest as a whitish or cloud-ish cast over the fruit peel and it can range in size from just a frequency to trace maybe about 15% to 20% to coverage over the entire surface. Once it gets to be about 25% of the fruit, it can look fairly unsightly. And what it looks like is if you’d gone out to your orchard or an apple and you decided to clear coat it on a really humid day. If you ever put clear coat on a humid day or cold humid day, it’s always a no-no because the first thing it does is sort of clouds up. So, if you want to see what it looks like, go grab yourself a cheap can of clear coat and you’ll put on it makes sort of a haze.

It’s first been recorded in the US in around the 1900’s in western New York of all places. It can happen on any cultivar and often appears to be a characteristic of Gala, but it’s not normal and doesn’t have to be there. It often shows up in NY-1 as well, where it’s become really detrimental to fruit finish and marketing of fresh market apples, and it has no known influence on the nutritional value, tastes the same, but it can be easily mistaken or perceived as a pesticide residue or some other unsightly disorder and can just lead to consumer rejection. It’s not uncommon for incidences in the packing houses for rejecting loads of fruit when the area gets a little higher than about 25%. It comes in about the first 40 days after bloom. Oh no, that means it’s too late for you to really do anything about it now, but if you see it, I wanted you to know about it and so that you can be prepared for next year as well. And the severity is going to be dependent entirely on orchard climate, fruit size and the influences of various pesticides and oils. And it could be that even Captan plays a role if applications were made during that 40-day period. What ends up happening is during the first 40 days after bloom, the fruit surfaces experience considerable strain on the elements that make up the fruit cuticle. As the fruit begins to go its highest rate of surface air expansion during the development and this could lead to the micro cracking and it’s that micro cracking that gives that hazy appearance. The whole process can be just made worse if we have a lot of other environmental or external factors such as a lot of rain or constant humidity.

How do you manage? It usually involves regular applications of gibberellins, a G4 and a G7, G4+G7  during the first 40 days after bloom. Like I said, there’s not much you can do about it now, but what these gibberellins will do is they’ll promote smaller, more uniformly sized epidermal cells and these will be sort of characteristics that help manage that physical strain on the fruit as it develops. And so, at this point right now, there’s a lot of uncertainties that are really surrounding like “How does it develop one year and not others?”.

We do know that it’s often worse in really wet years. And we have a study coming out in the New York Fruit Quarterly in this falls issue, I’m told, on the fruit disorder itself. My student David, Mark Russell, and Jason Londo and his team have put together a paper in the Fruit Quarterly on this topic. So, if you want to learn a little bit more and prepare yourself for next year and see some of the things that they found or some of the uncertainties that we’ve uncovered, check that out in the coming months.

Now what else can we talk about? There’s two other problems that you might see going into the fall that we’ve not covered in scaffolds or anything else. One of them is moldy core. And much like the apple scarf skin, it can happen right around petal fall and usually heavy rains. What ends up happening is the fruit gets colonized by a bunch of really fairly weak pathogen type species that aren’t really big pathogens of apples. But they can colonize that fruit right around near the sepal area. And as the fruit develops, the entire area where the seeds are held will be filled with sort of a fluffy grayish white mycelium and can look very unsightly and lead to load rejections. It won’t really show up in harvest and it won’t show up till someone cuts the fruit. But it can also be a big concern.

Alongside of this in some years, particularly wet years, in other years where the fruit is undergoing stress as it develops for a variety of different reasons, could be drought, could be drought followed by rain, other different things, is there can be this other problem called callus core. It’s just a physiological response of the fruit as it’s developing. What it will do is it’ll put these undifferentiated callus tissue, that’s just apple tissue around the seeds. They’re crystalline and they’re not soft like fungal mycelium. And there’s no off color or off flavor like you might find with a molding core. It’s just pretty white and crystalline. However, a lot of times this can be mistaken for moldy core and lead to rejections as well. I don’t think anyone understands the reasons and causes for how to prevent it and when it occurs and on what varieties, the one the variety we’ve got some pictures of are on Fuji, but it’s something to be aware of. It’s not mold, it’s not dangerous, it’s just apple tissue and it’s a physiological response. That argument may not win you over with the marketer who wants to reject your fruit. And I think that’s all I’m going to cover for this last little section in terms of sort of post-harvest concerns. You’ve got all the other characters as well. And who knows, maybe we’ll talk a little bit about those in the final episode roundup if we talk about other different things that happen during the season. All right, that’s all for me this week, and good luck and have a fantastic week.

 

State of the State with Anna Wallis

 And now for the State of the State, your weekly roundup of Degree Day accumulations and phenology from the major fruit production regions of the state. As always, this information has been aggregated from the regional specialists, NEWA, and my own observations. We’re down to the last week or so before apple harvest. Some of the stone fruits are harvesting now. Earlier varieties of peaches and plums and cherries are nearly finished. For the month of July, weather was record wet and record warm. According to the Northeast Regional Climate Center, there were rounds of flash flooding, extreme precipitation, and extreme heat. Many parts of the state experienced 150% to 200% of normal precipitation from 5 inches to over 10 inches were recorded at NEWA weather stations across the state. Just this past week, we had 2 to 3 inches in many places. July temperatures were about 2 to 4 degrees warmer across the state, according to historical averages. More information on weather and extreme weather events can be found on the NRCC Northeast Regional Climate Center and NOAA weather websites, including forecasts and archives of storm reports. Over the next few days, we’re getting some relief with some cooler weather across the state at the beginning of the week, then warming again at the end of the week. Forecasted precipitation is about average or slightly above average compared to historical averages for this week. In August, we expect the month to be wetter with higher amounts of precipitation than average according to the NOAA forecast, and temperatures are predicted to be slightly below or near average temperatures.

We’re continuing to track Degree Day based 43 as an indicator of insect activity and phenology. Both 43 and 50 have been used historically to keep track of these things and are summarized in the tables in the show Notes. And you can find an average range of Degree Day accumulations for phenology and arthropod pest activity in the Cornell Tree Fruit Guidelines table 7.1.4. As we say every week, you know that degree days since January 1 isn’t the best predictor of all pests, so we encourage you to use the models in NEWA that correspond to each pest and be trapping appropriately. In general, this season, degree days have been slightly behind seasonal averages, and insects have emerged slightly later. In addition, the Champlain Valley has been nearly the same or even slightly ahead of western New York, particularly lake sites, which isn’t always the case.

A few pests that are active now include apple maggot, which is active in most places across the state. We had our first trap captures in the Hudson Valley and had reached thresholds last week in the Champlain Valley, and this week we had our first trap captures in Geneva, although it hasn’t been captured in places where we’re looking in the western part of the state yet. Overall, it appears to be fairly low pressure this year. Stings from this insect look a lot like stink bug, except that you would see tunneling in the fruit and sap would come out of those stings as opposed to stink bug stings which tend to be more calloused and corkier on the inside and can be more suppressed and don’t have that tunneling on the inside. To trap for this insect hopefully you have your red sticky sphere traps hung along borders where you know that there’s pressure from the past. The threshold for management for this insect is five flies per baited trap or one per un-baited trap.

 Stink bugs are also active now throughout most of the state. In western New York and in the Hudson Valley we’ve captured them in low numbers. You can be trapping for these using clear sticky panels, which we generally recommend. One or two insects per trap indicates activity. Or you can also be using black pyramid traps.

Woolly apple aphid continues to be problematic across the state. They begin inside the canopy on pruning cuts, and then they start to move to new shoots when populations become higher, so make sure that you’re scouting really well for those insects. Other aphids are also present in low numbers in some locations across the state, so be looking for those.

Codling moth second generation pressure remains low across the state. We’ll be moving into the third generation, it’s on the horizon soon in most of the state, so make sure you’re staying covered if you’re at the appropriate timing.

Obliquebanded leafrollers continue to be in low numbers in some locations throughout the state. And we would be expecting to soon be seeing the second generation where there’s been pressure in the past. So now would be a good time to be breaking apart clusters, looking for fruit-feeding on the surface of the fruit, or for the insects.

Apple leaf curling midge second generation is active where it’s been a problem in the past.

Mites continue to be present in orchards. Both European red mite and two spotted spider mite have been reported across the state.

San Jose scale has showed up in a couple of places, and spotted winged drosophila continues to be present in populations building throughout the state where they are not being managed. You can use either a sticky trap or a jar or drowning trap to detect if flies are present, and you can use a salt float to detect if the maggots are present in your fruit.

As far as diseases, secondary scab infections and summer rots, sooty blotch and fly speck, these diseases thrive in wet human conditions, so the conditions that we’ve been having are perfect. Make sure you’re staying covered with a 10-to-14-day interval. Fire blight continues to be present but is mostly under control at this point now that we’ve reached our terminal bud set in most locations, but keep your eye out and make sure that you’re pruning out any strikes. We’re also continuing to get reports of other disorders, including lenticel breakdown, scarf skin and sunburn, which can lead to rot. So, make sure you’re looking out for those things.

And finally, here’s the rundown of Degree Day base 43 accumulations at newer weather stations throughout the state. As usual, they’re always in the show notes for you to reference later.