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Monique Rivera interviews Gennaro Fazio
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. I am Monique Rivera, Assistant Professor of Entomology at Cornell Agritech, and today my co-host is Dr. Anna Wallis, Fruit IPM Coordinator with the New York State IPM program. In this episode, I interviewed Dr. Gennaro Fazio, a research geneticist at USDA based in Geneva, New York. We talk about apple rootstocks and how rootstock choices could help with the management of woolly apple aphid. And then Anna Wallis gives us our State of the State update on the continued degree day accumulation and a ramp up for the second round of pests.
Monique Rivera: Okay, so today we are talking to research geneticist Gennaro Fazio. Hi, Gennaro.
Gennaro Fazio: Hello, Monique. Good to see you.
Monique Rivera: I first want to hop into this and ask you, can you tell us about your program at USDA? As a plant geneticist, I know you work on breeding, but specifically as it relates to apple, what projects have you been working on?
Gennaro Fazio: We work on apple rootstocks and breeding and development of new apple rootstocks. It’s actually a joint breeding program with Cornell University that started about 55 years ago. My goodness. It is the only one to date that has delivered to the industry apple rootstocks that are specifically bred for resistance to fire blight and also specifically bred for resistance or tolerance or immunity to colonization with woolly apple aphid. In addition to that, we have discovered that these rootstocks are tolerant to other things like crown rot and root rot and replant disease. And so, it has a plethora of benefits when you place them into the orchard. That’s what we do in our breeding program. To describe our program, we use conventional breeding where we hybridize parents and then select the progeny for the best possible outcome with regards to each of the traits that we’re looking for. The most important traits, obviously, for apple rootstocks would be productivity and dwarfing.
Monique Rivera: You go through the different disease and insect resistances in terms of using rootstocks to manage woolly apple aphid, what do you think is the future of that? And what current rootstocks would you recommend that are already on the market?
Gennaro Fazio: So, the best rootstock with the best resistance out in the market is G.41. What we have seen in our both research and commercial experience is that when you have a method to control the woolly apple aphid in the tops of the trees, so either with oils or whatever, the resistant rootstocks negates the ability of the woolly apple aphid to feed on the root systems during the wintertime. And therefore, it negates half of the opportunities for the woolies to propagate or infest. And what we’ve seen in experiments, if you have an entire orchard or a couple of rows on G.41, the woolies don’t come back and colonize susceptible scion varieties after a couple of seasons. So, they’ll be present, but basically, they get eliminated from that. And the only way to recolonize the place is actually for the woolies to be brought in into the orchard by some other means.
Monique Rivera: So, what specifically is the mechanism there that is preventing them from recolonizing? Is it like, a thicker woodiness or a different texture to the roots?
Gennaro Fazio: That is a very good question. It’s one I had no idea about. We conducted experiments in, oh, I think it was 2008 in Washington State collaboration with Elizabeth Beers. What we saw was that G.41 was not being colonized and there was no reproduction happening with woolly apple aphids. They were not feeding on it. It’s not like they didn’t try. They tried, but they just didn’t like what they tasted. And so I don’t know if it’s a reaction to specific compounds that G.41 is developing, but we kind of know the genetic heritability of this resistance trait. And so we’ve been using it to select new rootstocks that possess the same resistance.
Monique Rivera: So what other root stocks other than G.41 at least show some resistance? Because trying to get trees, I’ve noticed that sometimes it’s hard to get the specific root stock that you want. So are there any other suggestions of what else might be good to pick or has good resistance to fire blight, for example?
Gennaro Fazio: Right, so G.214 comes to mind. G.969, G.890 and G.222. Of course, they have been shown to have various levels of tolerance. So last year we conducted an experiment in our greenhouse to make sure that everything was checking out based on our former experience. Anytime you create a new rootstock, it’s a combination of all kinds of genes and traits that perhaps not as active as what you see in G.41, but it is active. Just like with people. You have children from the same parents, and some people get dark hair and some people get lighter hair from the same parents. And so that’s sort of what we experience with the expression of this resistance. So we’ve noticed that, but we also noticed that for sure, G.41 was completely free of woolly apple aphids after a few months, being exposed while B.9 or Bud 9, B.10, G.935 were extremely sensitive to these. We also saw colonization of G.11. Now, G.11, we’ve heard from other countries in Italy, for example, that it was displaying some resistance to woolly apple aphids, but in our test it was intermediate, so it was not complete resistance, but it was somewhat tolerant. It didn’t have that many compared to other rootstocks. G.202 was another one that was very resistant and that showed resistance in our experiment. So, we’re repeating it, testing new rootstocks as well, and giving it our best to inoculate these other new root stocks and describe them based on where they’re feeding and what the behavior is. Of course, I’m not an entomologist. I’m a geneticist.
Monique Rivera: True. So that’s where my question bells start dinging. So, for example, if you’re seeing resistance on the roots, does that mean you also, in addition, see less colonization of the scion?
Gennaro Fazio: That is correct.
Monique Rivera: Okay, yeah, that’s what I would expect. But what if they’re coming in from the region? So do you think that most of these populations, when they’re thriving intensely, it’s because of this interaction with the rootstock? That’s my guess, too, after now having worked with it for a season. But do you think that’s what’s keeping them persisting? And do you think that encourages them to move to a new area?
Gennaro Fazio: I don’t know the answer to that question. So obviously they want to live and they want to feed on something, so they’ll feed on whatever they can. I’m not sure about wild plants around orchards that are secondary sources of feeding for woolly apple aphid, but I think the Northeast is their natural environment, so there might be some secondary sources where they stay around. But if we’re talking about an entire orchard, for example, that has the same rootstock and the same scion, and let’s say that you have picked G.41 or G.969 or G.214 or G.202, some of the most resistant ones. And let’s say that in this northern weather, the woolies do not overwinter well above ground. My expectation and my observations have been that they will not come back if there is a presence of them. So, another possibility, though, is that they may find refuge in pollinator trees that are using a rootstock that is not resistant.
Monique Rivera: We do know that their alternate host in the environment is American elm, but I don’t think that’s going to have as much of an effect on the intensity of the infield infestation as the rootstock. So when we were working with them this summer, so far, we were seeing intense infestations on M.9 that was just blown up crazy. So it definitely seems that even if the population was moving over from a wild tree host, they have a lot of interruptions to that potential travel to get deep into the orchard right after working with them. I’m much more of a believer in the rootstock resistance because you can just see the difference between the plantings. They’re right next to each other.
Gennaro Fazio: So M.9 basically likes to feed woolly apple aphids, and they propagate quite well, both M.9, B.9, B.10, and similar rootstocks that were not bred with this resistance. One of the ways I can see organic apple growers struggling with this, and one of the ways we have proposed to help in this situation is actually utilizing rootstocks that are resistant to woolies, or at least they deny them an opportunity to propagate what you use on top. I think some oils are considered organic so they can eliminate the threat or really downgrade it from standpoint of the scion, but also cold, cold is a killer. So up here in New York, so we have cold that kills the above ground woolly apple aphids in the wintertime. But as you move further south, where you don’t get as much winter kill and you still get woolly apple aphids that may survive on the scion parts even during the winter while the tree is somewhat dormant, that we have to look at and see what we can do. Obviously the woolly apple aphids becomes an important part because it’s denying the feeding during the wintertime, but then there might have to have different treatments in the wintertime because we don’t have that really harsh cold kill.
Monique Rivera: So is this why on the west coast it seems like they have a more consistent problem with woolies across the board, where here it’s popping up, I think is more of a secondary loss of Lorsban issue? And when I was out west they seem to have it pretty consistently across. So do you think that’s because of the survivorship on the scion?
Gennaro Fazio: I think out west they do get the kill temperatures, so I think the survivorship was probably due to the amount of M.9 and other susceptible rootstocks that were being planted. I should have a chat with some of the entomologists out west to see what they see in the large plantings of, for example, Cosmic Crisp on G.41 and similar plantings that they have up on G.41 to see what the prevalence is of woolly apple aphids.
Monique Rivera: So I guess I have one last question for you before I let you go here, and that is, is there any logic to the numbers? So G is for Geneva, right? So what do the numbers mean?
Gennaro Fazio: Basically it’s the seedling number. So there is no logic. We maintained the original seedling number, that name that you received maybe 40, 50 years ago, there is another code. So G.41 was known as 3041. And the initial number that three meant that it was a dwarfing level three in a scale of one to ten. Really it’s just a number that represents the breeding line that we were developing. I wish it was different, but we have done so many of them that right now people have to really know what number they’re using.
Monique Rivera: Well, I mean, you could always give it like a cheeky name, like no wool 41.
Gennaro Fazio: We thought about it, I don’t know how well it would be received in the nursery business. We just like to keep things nice and short. The Geneva name is trademarked and so it represents the whole process and quality of disease resistance and insect resistance that the breeding program has developed.
Monique Rivera: So is this the main breeding program in the US?
Gennaro Fazio: It’s the only one in the US. It’s the only one in North and South America, five active in the world. I’m not sure how active the other ones are. One thing that I want to say is that this woolly apple aphid resistance has been deployed in South Africa, and it works there. It’s been deployed in Brazil and it works. But then there may be surprises in other places in other countries because of the natural mutations that may happen in woolly apple aphids.
Monique Rivera: We probably have the most of them here. Also, because we’re the home country.
Gennaro Fazio: We’re In the process of studying that diversity. Along with a fellow scientist at UC Riverside last year, we collected a whole bunch of woolly apple aphids from all over New York State, Pennsylvania, Michigan, all the way down to West Virginia and so on and so forth. And we are running a diversity panel to find out how consistent the genetics are with the woolly apple aphids. The sexual reproduction happens only when they are feeding on elm, their main tree, but who knows?
Monique Rivera: Yeah, there actually have been some conflicting reports about that, that they have found breeding populations on apple. But I think it’s rare in nature.
Gennaro Fazio: I don’t think it has boundaries that you want to set. There’s always an exception to the rule.
Monique Rivera: Well, we’re definitely struggling with the insecticides for them. I think that timing is really critical. We’re still learning about it on the entomology side as well. This was my first year working with them, so we’ll see if we can figure this out. But it does seem like a combination of a solid rootstock and just having in your IPM program a well-timed spray. Hopefully a softer chemical would work better for the lighter populations. That would help a lot.
Gennaro Fazio: I agree.
Monique Rivera: Well, OK, Gennaro, thanks so much for taking the time to be on the podcast today. Yeah, I’m sure the growers are going to love the recommendations for rootstocks. It’s kind of a black box. Everyone has an opinion.
Gennaro Fazio: All right, thank you. I appreciate you asking me on the podcast.
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, all this information has been aggregated from regional specialists, NEWA and my own observations this week.
Apples are continuing to size in color. Cherry harvest is underway, with most of the tarts just beginning. Sweets are mostly finished and some peaches are harvesting in western New York. So far in the month of July, we’ve had excessive rainfall across most of the state. I’m sure that comes as no surprise. According to the Northeast Regional Climate Center, many parts of the Northeast are in the top five wettest Julys on record. In New York so far for the month of July, parts of the Hudson Valley have recorded over eight inches of rain. Other parts of the state have recorded less than an inch, including places far to the west near Buffalo. Currently, many places are in a D1 moderate drought conditions according to the USDA Drought Monitor. Most places have had in the range of two to three inches so far, and poor air quality is continuing as wildfires from Canada continue, and the smoke is in our area. Looking to the forecast the next couple of weeks don’t look to be much of a break. According to the NOAA Climate Prediction Center, we’re looking for wetter and hotter than average conditions across most of the state. We’ll include links to those weather and climate resources in the Show Notes as usual.
We are continuing to track Degree Day base 43 as an indicator of phenology and insect activity. Both base 43 and 50 are summarized in the table in the Show Notes. Both have been used historically. You can also 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 know, degree days since January 1 isn’t the best predictor of all the apple pests, so we really encourage you to use the models in NEWA that correspond to each pest.
In general this season, according to our trap data and reports that we’re getting from across the state, insect pests are a little bit on the late side within the range of Degree Day averages. Could be related to the cool spring, perhaps the drought last season.
This week we’re seeing in the Hudson Valley first trap captures of apple maggot, but we’re not seeing that yet in the rest of the state. So hopefully you have your red sticky sphere traps hung by now. As the overwintering pupa emerge in the latter half of June or the beginning of July. From wet and dense hedgerows, you’ll be able to detect them. So place traps near the locations you’ve seen them in the past or near these dense wet hedgerows. Three traps should be hung per site, and if an average of five flies are captured per trap using baited traps, that is the threshold.
Brown Marmorated Stink Bug first adult trap captures were recorded this week in western New York.
Woolly apple aphid is peaking across the state, so hopefully you’ve taken Monique’s advice and gotten a systemic on ahead of time.
We’re between flights for some leps, mostly for codling moth and for OBLR, but we’re beginning to see the beginning of the second flight of codling moth this week in the Hudson Valley and potentially some early sites near the Capital Region for OBLR. Be sure to be breaking apart clusters at this time, looking for fruit feeding so you can detect damage.
Early mites are present. We’re seeing European red mite adults present now in the Hudson Valley.
Spotted wing drosophila is present throughout the state at this point in each of the counties where we’ve been monitoring, but it is still in pretty low numbers. We expect those numbers to increase pretty rapidly from now to the end of the season.
Another pest that we are paying attention to is spotted lanternfly. The first adults were reported this week in New York City. They’re present in several places in the Valley and beginning to move toward the northern part of the state, so keep your eyes peeled for those insects, and we’d appreciate reports if you see them.
As far as diseases go, we continue to get reports of fire blight strikes, especially where we had outbreaks in previous season, so stay vigilant and continue to prune out strikes through terminal bud set. Trees become less sensitive once they stop putting on new growth. Scab secondary infections are still popping up in some places that weren’t quite covered. Summer rots are showing up, so stay covered for those as well. We’ve gotten more reports of declining trees from various places across the state. These are new plantings as well as more mature, fully bearing blocks. There are so many possible contributing factors to tree decline, so it’s really important that as part of a good IPM program and successful management, you start with correct ID for the problem so that you can treat it well. Many factors, including phytophthora keeps coming up with all of the rainfall and standing water in orchards. Also, drought and cold damage can cause damage to the cambium or the vascular system, which can lead to tree decline. Fire blight in the rootstocks, herbicide damage, trunk borers, or a combination of all these factors can all be contributors to decline. So make sure you’re looking closely or calling in help if you need a second opinion. Dave Rosenberger provided a great review of possible trunk damage culprits, which he summarized in a blog post, and we can link that in the show notes as well. It’s a nice review.
We’re also starting to see and get reports of sunburn and lenticel break down, some fruit finish disorders, and that’s quite normal for this time of year. Just make sure you’re keeping an eye out.
There are quite a few field days coming up for this time of year. Usually in the month of July when there’s a slower part of the apple season, we tend to schedule those events. So stay tuned to the regional extension teams. In Western New York, next week is the first annual Western New York Fruit Grower Tour on Friday, July 28, brought to you by the Lake Ontario Fruit Team and Lake Ontario AG Consulting. So put that on your calendar. We hope to see you there.
And finally, here’s the rundown of Degree Day base 43 accumulations at newer weather stations throughout the state. As usual. They’re also included in the show notes.
