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Monique Rivera interviews Dr. Anne Nielson

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 today will be Dr. Kerik Cox, associate professor of Plant Pathology, and Dr. Anna Wallace, fruit IPM coordinator. I am interviewing Dr. Anne Nielsen from Rutgers University, who is my former boss and the person who’s taught me the most about tree fruit entomology and deciduous systems. So, Anne, you are our resident Brown marmorated stink bug expert. What do you think? What do you think is the most important management technique we’ve developed over the time you’ve been researching this?

Anne Nielsen: Thanks for having me. But I also do think that we have a couple different components of management for BMSB. So, we have our insecticide-based management, which is going to mitigate populations in the season, try and prevent damage happening right now that is currently insecticide based. But we have different strategies on how to apply less insecticide or to apply it on a more spatially refined area. So, my lab’s done a lot of work with border sprays, where we’re just spraying the trees that are on the periphery of the orchard. We’ve done that in peaches, and we’ve done it in apples across multiple states for multiple years. And what we see is about a 25% reduction in total insecticide application because we’re only spraying the borders. We’ve done this from five to 20 acres, and we get approximately, it varies a little bit by year to year in harvest state, but we get about the same level of injury as we do with our alternate row middles or full block sprays. So, by focusing our insecticide application to the edges, what we’re doing is we’re maintaining a fresh residual of insecticide where BMSB is stopping in the orchard as they move in. So, it’s a behaviorally based management tactic. It works really well with mating disruption for codling moth or for oriental fruit moth, or for both if you’re in apples. And we’ve even shown an increase in natural enemies in terms of natural enemy diversity and increased parasitism against BMSB in systems that are using this, what we call IPM-CPR or border spray approach. The other aspect of this would be attract and kill systems where you’re baiting select trees with high doses of pheromone and then concentrating your killing agent on those trees, either with an insecticide treated mesh on the outside of the orchard because that’s not labeled for use in the orchard, or just focusing your insecticide sprays on those select areas of the orchard.

Monique Rivera: Are pyrethroids still the ideal for that, or are there other new compounds?

Anne Nielsen: There’s not new compounds, unfortunately, but it’s not just pyrethroids. Pyrethroids are a cheap option. What we’re seeing, however, in a lot of our systems is overuse of pyrethroids has led to a lot of San Jose scale problems. So, we now are battling with San Jose scale in a lot of our orchards, we see mite problems as well. But I think if you’re using pyrethroids as a management tool, you need to be very cognizant of the fact that you could be exasperating problems of a secondary pest, which is actually more difficult to control and more expensive long term. Once you get San Jose scale or woolly apple aphid in your orchard, that’s a tough pest to battle with. So we also have neonicotinoids that are effective against brown marmorated stink bug. I prefer using neonics against stinkbug. They have slightly longer residuals and they have very high efficacy or killing power against BMSB.

Monique Rivera: So one of the things that I’ve noticed about BMSB, or we were noticing, especially last year when we were surveying, is that they do, in the fall enter the orchard, but they tend to enter in a sort of a clumped manner. What’s the biology behind that and why are they clumping and can we find them in the same place from year to year?

Anne Nielsen: Short answer is no, you can’t find them in the same place from year to year, but your farm history is going to probably lend certain aspects that will help guide your surveys. So we’re pretty sure we know through some large landscape level surveys that we’ve done and trials, that we see these hotspots in systems, specifically along the wood edge. So if there’s a wood edge, we see a hotspot. We don’t see that hotspot from like an orchard-orchard interface or even an orchard-field crop interface. But if we have this wooded area and tree fruit, specifically apples, we’ll see these hotspots especially later in the season, just like you mentioned. Those hotspots, though they do move from season to season. It may be in the same plot, but it may be at the other end of the plot or a different side, different trees. Some of it is probably varietal differences. Some of it is probably driven more by the landscape composition and maybe even other resources. So, they’re clumping most likely just due to the aggregation pheromone that is released by the males.

Monique Rivera: So, interesting idea about the idea that you can prioritize where you’re sampling, right? So, you know your farm history. So, would you suggest if you were going to sample year over year, the edge where you found them before, but maybe do the complete wooded edge rather than trying to go back to the same spot?

Anne Nielsen: Yes. So, what I would do if you’re sampling with a pheromone trap, we have a clear sticky panel pheromone trap that you just put on a four-foot-tall tomato stake now, and that costs about $3 a trap. The lures last almost the entire season now, which is phenomenal. So that’s a really effective way to monitor for stink bug without investing a lot of human time. If you’re going out and physically looking for them, yeah, you’re going to need to probably do shake or beat samples throughout your orchard but concentrate on the edges. If you’re using the pheromone trap, they have to be placed 50 meters apart. That’s covering a pretty large area, but again, placed on the edge.

Monique Rivera: So, what about the varietal differences? There is this idea of Honeycrisp being a target variety for apples. Are there any other varieties that you guys have found that are particularly attractive?

Anne Nielsen: So that hasn’t been a major focus of my research because we primarily study peaches. But yes, they love Honeycrisp. However, it’s really important, especially for Honeycrisps, to make sure you’re differentiating between stink bug damage and bitter pit. They can look very similar and calcium deficiencies will show up overnight. To the untrained eye, there’s a lot of overlap in the symptomology, and Honeycrisp is very susceptible to bitter pit. So, I think for Honeycrisp, it’s about timing. We also see a lot of damage on Pink Lady. Honeycrisp is ripening Labor Day (in New Jersey), and that’s when populations in apples are really, really high. I think Pink Lady gets hit pretty hard because it’s out there so long, because it’s such a late season apple. I think some of the Golden Delicious get hit pretty hard, but that’s also because damage is really easy to see on Goldens because of their color.

Monique Rivera: So, what do you think about the difference in varieties? Do you think this is also scent based that they might prefer? Or do you think it’s specifically timing?

Anne Nielsen: I don’t have a good answer for that. My gut tells me it’s timing more than specific volatile blend, but it’d be really great if it’s volatile-based. I think it’s also where that variety is planted. If you have a variety that is equally attractive and it’s planted on the wood edge, it’s going to get hit harder than something is planted in the middle of a thousand-acre field.

Monique Rivera: That definitely makes perfect sense. So basically, looking at your orchard and trying to figure out where to strategically plant sensitive varieties, if you are growing them.

Anne Nielsen: Put them away from the edge.

Monique Rivera: Do you think that we’ve resolved BMSB management? What do you think is the future here?

Anne Nielsen: We definitely have not resolved it. It’d be great if we had, but this bug keeps surprising us. The key to long term management is biological control, and we’re fortunate that we have two different tools. So, we have Trissolcus japonicus, which is the samurai wasp. It’s a co-evolved egg parasitoid. So, it’s a tiny stingless wasp. It got here on its own from Asia. Each state has their own populations. They are naturally reproducing on brown marmorated stink bug and possibly native stink bugs in the landscape. And so that’s a really key biological control agent long term. And then, of course, the second aspect of this is the microsporidia Nosema maddoxi. However, for both of these, we need to better optimize how these species are deployed as biological control agents and what their realized impact is. So, we have Trissolcus here, but it’s not parasitizing at the levels we would expect or that are reported from Asia. So how can we better optimize its impact? And then for Nosema, we just are still learning a lot about this microsporidia. We know its impacts in terms of insect fitness, but we don’t know if there’s any microsporidian tool for it, although I’m hoping there is. And we don’t really know what percent of mortality we’re seeing in the field or percent reduction in injury. So however, the two of these combined, I think, provide a really strong long-term top-down control approach. But we need to refine our management approaches to allow these biocontrol services to occur. So, if we’re using a lot of pyrethroids in our systems, we may be accidentally removing Trissolcus and not the stink bug.

Monique Rivera: So, is there a place to get Trissolcus commercially or is it just native populations?

Anne Nielsen: You may not purchase it locally. Each state, because it’s not federally approved for releases yet, it’s possible you could purchase them from your Department of Agriculture, I don’t know the current status in New York, but some states, state agricultural agencies are starting to look at release programs, but it’s not available for purchase.

Monique Rivera: Wow, that’s good to know. Well Anne, I don’t have too many other questions, but this was great. I think that was a lot of information in a short amount of time and thank you for coming on Scaffolds today.

Anne Nielsen: Thanks for having me.

 

Disease and Pathology Updates with Kerik Cox

Kerik Cox: Okay, it’s Kerik coming at you from Cornell Agritech your tree fruit pathologist and another episode of Scaffolds. What are we going to talk about this week? We’re getting deep into the late part of the season. A lot of the main disease concerns are over, but with all the wet weather, there are things that can still start to show up and it might be time to talk a little bit about tree cankers.

So, what are tree cankers? You’re going to see things that might look like fire blight, might look like a dying scaffold or a dying leader in many instances. And what these are, are typically some cause and it can be some of the fungi mentioned, but it can be herbicide, salt, cold, really, really wet weather, and some weakly pathogenic fungi in combination with summer pruning wounds. I mean summer pruning could be happening right now. And some of these things you might start to see and show up. They’ll have some names like Botryosphaeria, you might see something called Schizophyllum or you might hear the word Nectria, these types of things. And a lot of these things are going to show up typically around crotch angles in trees, sort of those areas where shoots branch off. That’s where some of the more excitement has happened around the tissues and generally are considered sort of weaker areas. These are generally a little more easily injured. Now if you’ve also been pruning them, they’re terribly easily injured.

Now, Nectria and Botryosphaeria can look fairly similar. What you’re going to end up seeing in these cases, they’re sort of dark to pale brown wilted shoots and they can completely crook and look like fire blight. Now, where things will look different with fire blight is that fire blight will be blacked down the tip of the midrib and fire blight will generally turn a little darker as it begins to move. A very rapid, quick blackening necrosis. And these others are sort of more of a dying and drying out. Now, what other tricks can you use to determine what you have? Now, you might see the fruiting bodies, but the one other thing you can do to differentiate these sort of tree cankers from fire blight is to look at where they go. Follow that shoot back to the base. In many instances, if you have a Nectria canker or Botryosphaeria canker, you will see at the base, instead of a blackened shoot tip from fire blight, you will see a canker or a pruning cut right around the start of the affected shoot or affected shoot problems. And when you see that canker, that’s going to give you an indication that you have maybe a wood decay canker as opposed to sort of a fire blight canker, which may require more immediate action.

Now, the Nectria and the Botryosphaeria aren’t very aggressive pathogens compared to something like fire blight, and aren’t going to warrant immediate concern. You can kind of prune them out. We’ll talk about what to do with them. Sometimes when you do follow that dead shoot back to the base and the source of the problem, you’re going to find a canker. And as we move into August and into September, you might start to see fruiting bodies. These things will look like little, tiny hard pink or cracks in the bark filled with black, hard-ish pustules. And those are something called stromata, stromata that is just sort of filled with spores. In the case of nectria, they’re going to be pink and salmon colored. You might see them now and, in the indication, these are just in many instances conidia, they will form an ascospore like apple scab and the other stuff. But that could occur in sort of in the late winter stages as these things mature if the right fungal mating has actually occurred. Now, what these things can and will do is if they’re already sporulating and you see those salmon colored puffs, they can release more conidia and cause infections during summer pruning in wounds, or even leaf scars as the leaves begin to fall off the trees.

So there’s a couple that are well known, I’ve mentioned, Nectria cinnabarina is the one that actually makes those sort of salmon colored pustules. And Botryosphaeria will make more cracks in the very surface of the epidermis of the bark. And these will be filled with harder, black, smaller fruiting bodies. Typically, Botryosphaeria is considered a little more aggressive and now that we have all this wet weather, one might begin to see this as well. And they’re really going to be going after trees that are compromised by mild winter injury. Even if the winter injury occurred back in the late spring or winter shoot blight of fire blight. Sometimes it’s the fire blight canker that may not have knocked out the whole shoot, but is the part where allows these two fungi to get in and finish the tissue off, if you will. It can be hailstorms, it can be various boring insects, it can even be deer browsing and wet seasons.

Now, these things are going to survive sort of quintessentially in the cankers. Infections might have happened long ago or they may be present on pruning on orchard floors. Now, most of these things are wood decay fungi. They don’t necessarily need a live tissue like fire blight does. And you can see them very commonly on dead stuff. That lets you know right now, if you have dead wood in the orchard or on your trees, probably a good idea to get it out, because those are the ones that when the nutrients run out or to the fungus, they’ll start thinking, well, time to sporulate. And let’s see within this next awful three inches of rain that we have, if I can, infect a new, damaged piece of wood, they’re really kind of tricky to manage. They’re going to be deep and protected tissue, but for the most part, they aren’t as aggressive as many of the other fungal pathogens that we have. You really don’t need to worry about applying materials for them.

Now, a lot of the work that has come out on managing these things does actually come up a very devastating canker pathogen that we only have in Brazil and Europe that’s not really present here. But they do give us some advice on how to manage. Now, if you do start seeing dead shoots in the orchard or a dead leader, try to find one of these cool periods that isn’t going to have a pop-up rainstorm and hope that there are at least two days of dry weather around it. You can remove them. If the whole leader is shot, maybe it’s time to just remove the tree. Isn’t as important as for fire blight, but these things can spread around a little bit and lead to more problems in later years. Now, they’re not going to knock out your whole planting, but they may be annoying, and they may show up and perplex you as to how they occur if you do get them. These can still fruit on the floor, so get the prunings out of there. They can still infect from the ground. They just like dead wood, which leads to a lot of forest pathologists to really not consider them pathogens. But in our case, we often have very compromised, very stressed trees that are pushed to make a lot of fruit and they may behave more like a pathogen in this case. Now, if leaf drop becomes an issue, you can always apply at about 20 and 80% leaf drop, usually coppers right around the end. You got to watch out for your PHIs with these, but this will usually happen after you’ve harvested. If you’re losing a lot of leaves, you’re probably done at that point. And it looks like some of the ones I’ve seen, some of the Kocide, the Badges might be labeled, these labels change often, so check them out.

Another thing that has been mentioned in some of the literature to be very beneficial are the thiophanate-methyl type materials. Why? We’ve sort of given up on them for apple scab in the early season because of resistance concerns that developed tens of years ago. They can still do something for some of these summer pathogens to which resistance had not occurred. So they still have a place in your summer programs and can be effective in sort of getting rid of some of these problems.

And I think that’s all I have for this week. Next week, talk a little bit about some fruit disorders, or you may even mention phytophthora and what that is, and talk about getting into winter injury. All right, well, have a great week, and I’ll see you at the Lake Ontario summer tour or in Mike’s meeting the week after. Have a good one.

 

State of the State with Anna Wallis

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 our regional specialists, NEWA, and my own observations.

It’s been a bit of a slower week between the beginning busy spring season and getting ready for harvest, so hopefully everyone is getting a little bit of a rest, taking a vacation, and staying covered before harvest. Cherry harvest is continuing, with tarts wrapping up in many locations, and apples are continuing to size in color. We’ve continued to see quite a bit of frost damage in some places, while other places have a very nice crop.

Severe summer thunderstorms took place this week in many parts of the state, including more rain and high winds. Some places over the Monday and Tuesday this week received almost an inch of accumulation, with eight tenths of an inch recorded in Geneva, while other places recorded zero accumulation, according to NEWA weather stations in New York for the month of July. So far, over eight inches have been recorded in some parts of the state, notably in the Hudson Valley, while other parts of the state, such as the far western part of the state, are still in a D1 or moderate drought condition, according to the US. Drought Monitor. In the forecast for both short- and long-term outlooks, the projections are close to normal for the amounts of precipitation and for temperature. The 30-day forecast issued by NOAA on July 20 showed predictions going into the middle of August, looking near normal for precipitation and temperature for this time of year as well.

We are continuing to track degree day base 43 as an indicator of insect activity. As we’ve said in the past, both 43 and 50 base temperatures have been used to track this in the past, and that’s summarized in the table in the show notes. And you can also find a range of degree day accumulations for phenology and arthropod pest activity in the Cornell Tree Fruit Guidelines in Table 7.1.4. As you know, degree days since January 1 aren’t always the best predictor of all apple pests, so we also encourage you to use the models in NEWA that correspond to each pest.

Here are a few things that are active now and to be looking for.

Apple maggot is present in some places throughout the state. First trap captures were recorded in the Hudson Valley, but these have primarily been in abandoned orchards, and pressure appears low in most places where we’re looking. In the Champlain Valley, several sites are over threshold at this point, and in western New York, pressure also appears to be low where we’re trapping with very few flies reported yet. As we know, this can be extremely site dependent. Typically, flies move in from borders or hedgerows where there’s high riparian zones, so high moisture or trees that are harboring those pests. So, you can be placing traps, those red sticky sphere traps along the edges where known pressure exists, and then the threshold is five flies per baited trap.

Stink bugs are active in most of the state at this point, both brown marmorated stink bug as well as green stink bugs and other stink bugs. The first trap captures were recorded in western New York and the Hudson Valley last week. None have yet been detected. In the Champlain Valley, you can be using clear sticky panels for monitoring and gauge general activity.

Woolly apple aphid is peaking across the state, so hopefully you’ve stayed ahead of that, using some kind of systemic insecticide like Monique has talked about the past few weeks. We’re continuing to see them mostly on pruning cuts and inside the canopy where there is a problem, or then moving to new shoots when populations get higher.

Green aphids have also showed up again in several locations where we’re checking. They seem to be low in most locations, though.

Codling moth second generation flight is beginning in most of the state, so we hope you’re staying covered with about a 10-to-14-day spray interval.

Oblique banded leaf roller trap captures are low in most of the state but beginning to increase. Now would be a good time to be scouting for that insect, breaking apart clusters and looking for feeding damage on the surface of the fruit, especially in places where there’s a known pressure in the past.

Apple leaf curling midge second generation appears to be active where there is a problem.

Mites are present. Both European red mite and two spotted spider mite have been detected in many locations throughout the state. Also, there appears to be populations of predatory mites in many locations in the state, particularly where insecticide programs have not included harsh chemicals. Pyrethroids typically get included in those detrimental to predator mite populations.

Spotted winged drosophila is also present throughout the state. We’ve been using red sticky traps and jar or drowning traps to detect this pest. You can also be using a salt float to detect if the flies are present in the fruit that you’re harvesting so that you can make appropriate management decisions and marketing decisions.

In terms of diseases, fire blight appears to be more under control, but is present in locations where there’s been problem in the past, so continue to stay vigilant and prune out any strikes, especially through terminal bud set. Trees become much less susceptible once they start putting on new growth. Secondary scab infections continue to pop up in places that perhaps slipped through due to rain or residue washing off the trees. Summer rots are continuing to show up in some locations, so make sure you’re staying covered for those diseases, typically using a ten-to-14-day interval, or if there’s been excessive rainfall, you might want to tighten up that interval. Sooty blotch and fly speck are beginning to show up, especially with the warm, humid weather. Typically, those are also controlled with the materials that are used to manage rot, so hopefully you’re staying covered there.

We’ve continued to get more reports on declining trees from various places across the state, so we encourage you to be looking at the many possible contributing factors that can cause to decline and reaching out if you’re in need of more support for proper identification so that you can make informed management decisions. Other disorders that we’ve had more reports of include lenticel breakdown, fruit finish disorders such as scarf, skin, and sunburn. And finally, here’s the rundown of Degree Day base 43 accumulations at newest stations throughout the state. As usual, they’re in the show notes for you to reference later too.