Early Pride is a relatively new licensed citrus variety that’s being planted more often in Florida. It’s popular as a fresh fruit because of its early season maturity, large fruit size, deep orange color and sweet flavor. If you’re thinking about working with Early Pride, there are some things you need to know about its tendency for dieback in leaves, twigs and shoots. From our recent experience, the dieback seems manageable, but there are some things you should do to treat and prevent it. I tracked the development, causes, treatment and recovery of dieback in one of our groves over a year from when the trees first went into the ground to determine what are the causes and treatments for Early Pride dieback. Almost all the trees eventually recovered by following the practices we worked out.

This is Part 1 of two posts on managing dieback in Early Pride citrus. This first post discusses symptoms and disease progress, and Part 2 will cover causes, treatment and recovery. This post will be updated as more information comes in. The last updates were on September 17, 2014.

Download a PDF of this report.

You have to be able to recognize dieback symptoms and differentiate them from similar-appearing problems. Up-close symptoms, which I’ll show through the photography below and in my next post, are a good diagnostic. From a cursory point of view, the dieback can appear to have different causes. But over several surveys, we found most of the dieback could be traced to some sort of physical trauma.

Sometimes this trauma was obvious, as in the case of a large wound. I think the trauma can also be unnoticeable, as could be the case with a slitting of the bark when a tree is whipped about in the wind. Working along with the USDA, we also found infection by secondary pathogens seemed to have exacerbated the issue.

We discovered it’s important to act quickly after you first see dieback if you are to intervene and successfully treat the physical injuries leading to more dieback. Acting quickly is relative and depends to some extent on how widely spread and severe is the problem. If the problem is pervasive, you may want to act right away, but you have a little more time if the problem has just appeared on only a few trees.

I doubt you can completely eliminate dieback in young Early Pride groves, but the framework I outline below could help you from ending up with a problem worse than it has to be. All things considered, I think initial tree planting size may be one of the most important factors in preventing the problem from rearing its ugly head in the field.

About Early Pride

Early Pride is a low-seeded mutant of the Fallglo mandarin hybrid {‘Bower’ [Citrus reticulata Blanco × (C. paradisi Macf. × C. reticulata) × ‘Temple’]}. The variety originates from budwood Dr. Jack Hearn irradiated in 1991. Since Early Pride is licensed, you have to contract with the New Varieties Management and Development Corporation (NVDMC) for propagation and planting. You can find more information about Early Pride in the USDA’s description of the variety.

Because of it’s Fallglo heritage, Early Pride seems to have similar dieback issues as does Fallglo. Dr. Greg McCollum from the USDA in Ft. Pierce provided me these examples of dieback on Fallglo from his lab. (Note that these photos are Fallglo and not Early Pride, but the symptoms are similar.) Several growers are dealing with the dieback issue in new Early Pride plantings, and it looks like the extent of the disease varies from grower to grower. Some growers hardly consider it an issue, while others are dealing with significant dieback and tree attrition. One purpose for my report is to look into the reasons why this seems to be the case.

The information in this article is provided “as is” and should be considered a “work in progress”. Grovetracks and the author of this article disclaim any loss or liability, either directly or indirectly as a consequence of applying any information herein, or in regard to the use and application of this information for any purpose whatsoever. No guarantee is given, either expressed or implied, in regard to the merchantability, accuracy, or acceptability of the information.
History of the Dieback Problem in Our Grove

In September 2013, we planted the first large Early Pride setting in this area on Kuharski rootstock. A month or so after planting, we noticed dieback appearing similar to one I had seen before on Fallglo. This was a serious cause for concern for us, because it wasn’t clear at that time whether the trees would survive the dieback problem or not. Most all the trees eventually did recover.

Before you read further, take 3 minutes now and check out this video, which summarizes the progress of the disease in our block. The video shows resulting tree condition as of September 2014 after our interventions to control the disease. This is illustrated through several maps in which individual trees showing dieback were geotagged and tracked. I monitored the change in disease severity on those trees over time. As shown in the video, the number of trees showing dieback decreased from October 2013 to September 2014. Scroll to the last half of the video for a quick drive-through of what used to the worst section of the grove. As you’ll see, the trees look good today (September 2014).

Tree Condition–Before and After

It helps to have an idea of the general tree condition from planting through to today (September 2014). As you can see in the four images below, I selected two representative trees showing dieback when the problem was severe, and two representative trees after the trees recovered. Whether or not many of the trees with some of the worst dieback from a year ago would recover was questionable when we first started out. However, with the treatment program, most of them eventually grew out of the problem. The top two photos are the “before” images and the bottom two are the “after” images. Note these are not the same trees, but rather are representative trees from the worst affected area of the grove. You can see a broader view of this area in the drive-through video I shot last week. I have little doubt that the dieback problem would be much worse today had we not aggressively treated the problem.

(Click on the images to view larger versions.)


• Aperture:ƒ/5.6• Credit:STEVE ROGERS• Camera:DMC-LX7• Taken:September 15, 2014• Flash fired:no• Focal length:4.7mm• ISO:160• Shutter speed:1/640s


 

Practices for Managing Early Pride Dieback
It appears that if caught early, Early Pride dieback can be managed and trees can recover.

This section covers practices we used to intervene with the dieback problem in our grove. (In the next post, I’ll go into more detail on exactly what symptoms we saw, what we thought caused them, and how we arrived at our management approach.) This is not to say the techniques we developed will work for everyone. Nevertheless, I think what we arrived at should be a good starting point for you to troubleshoot your dieback issues and arrive at appropriate interventions to contain the disease in your groves. Regardless of how light or severe your dieback problem is, it’s important to not delay taking action–you have to act as soon as the dieback is recognized. Here are some of the most important practices and safety precautions we worked out to help contain dieback in Early Pride. These suggestions are based on observations from our first Early Pride planting. I’ll update this list later as I get more information about what works and what doesn’t, and what’s need and what isn’t.

  • In the nursery, avoid ties that are too tight.
  • Don’t plant trees in the grove that are too small. Trees should be of sufficient size to avoid being easily injured.
  • Look for well-wooded bark on nursery trees before taking delivery.
  • Handle your trees carefully when loading and picking them up at the nursery to minimize physical injury.
  • When transporting trees from the nursery to the grove, secure them so they don’t get blown or knocked about by the wind (in the back of a truck, for example).
  • Immediately remove binding ties that are too tight when the trees are set in the grove. Retie with looser ties, if necessary.
  • If trees need to be staked in the field, avoid tight ties.
  • Prune dead tissue in the field at the time of planting.
  • Avoid trunk wraps that are too tight and that don’t allow moisture to escape. If using trunk wraps of any kind, make sure the trunk can be aerated and stay dry.
  • Individual trees should be inspected for signs of dieback at 2, 4 and 6 weeks. Note that initial stages of the dieback can be difficult to see, especially if the dieback is a small proportion of the canopy.
  • Prune parts of the tree showing dieback as soon as possible after the thorough inspection.
  • Disinfect pruning shears when moving from tree to tree.
  • Burn or dispose of pruned debris off site. (This is a safety precaution.)
  • Treat with a broad-spectrum fungicide (such as Helena ProPhyte or a similar material) after the trees are set in the grove. I think this is a good prophylactic measure. Use a surfactant, such as Helena Dyne-Amic, with the fungicide. (We didn’t do this initial fungicide treatment step as we weren’t fully aware of the dieback issue at first.)
  • Treat with a broad-spectrum fungicide, such as Helena Pro-Phyte, after any pruning on small trees. We spot treated using a hand sprayer.
  • Periodically inspect the trees for additional dieback and prune as needed. Do this at least for the first 6- to 9 months the trees are in the grove. The proportion of dieback to healthy canopy decreases as the trees get larger.
  • It’s possible on larger trees that small amounts of twig dieback might be the norm. (I’m not sure how aggressive removal of tissue dieback needs to be on larger trees.)
  • Apply sufficient fertilizer, including liquid and slow release, to coerce the canopy to “grow out” of the problem.
  • Although root problems don’t seem to be correlated with the dieback we saw, I think soil-applied products such as Ridomil, KPhite, AgPhite or similar materials are helpful.

Once we realized that physical injuries were related to much of the dieback issue, it became clear what kinds interventions would help prevent the problem from getting worse. I’ll emphasize again that it might not be possible to completely eliminate dieback in this variety, but it can be greatly reduced by minimizing injuries and treating as needed.

Variations in Early Pride Dieback Symptoms

As I showed in my earlier post on December 9, 2013, dieback symptoms can vary from tree to tree. It can appear on first survey as if the dieback is due to different causes. Dieback can show up on some trees, but not others. And it can be worse on some trees moreso than others. As I surveyed our grove on different dates for changes in tree appearance, I began to pick up on the different kinds of dieback symptoms that can develop. The eight photos below give you an example of the range of symptoms that can appear.

The patterns of dieback that were developing appeared most likely due to the same ultimate cause–physical trauma. But the manifestations of the disease can vary quite a bit. In some trees, the dieback was constrained to the outer twigs. Some trees had only few leaves decline. And other trees had dieback extending all the way from outer branches down into the trunk. Nevertheless, almost all the symptoms I saw ultimately seemed have the same basic cause of being related to some sort of physical trauma. In some cases this trauma was easily recognized, as was the case with girdling due to tight ties. In other cases, the reason for the trauma was less obvious, but it was trauma nonetheless. In the next post, I’ll show close-ups of the different kinds of symptoms, injuries and infections that developed to give you a better feel for what to look for.

At this time, I have some reason to believe the dieback symptoms on Early Pride are a little different than the ones on Fallglo, but this is a preliminary opinion. For example, there seems to be less “gumming” in Early Pride as compared to that of Fallglo. Also, I seem to recall that the dieback and gumming on Fallglo was more difficult to relate to specific physical traumas. It’s possible that while the symptoms of dieback on the two varieties are different, the basic causes on both will be traceable back to some sort of injury. We’ll need more information before we can determine how different the Fallglo and Early Pride really are from each other.

(Click on any image to view the gallery.)


• Aperture:ƒ/2.8• Credit:Steve Rogers• Camera:DMC-LX7• Taken:October 16, 2013• Copyright:© 2013 Steven Rogers Photography All Rights Reserved• Flash fired:no• Focal length:4.7mm• ISO:80• Location:27° 56.255′ 0″ N 81° 53.309′ 0″ W• Shutter speed:1/320s• Title:Early Pride Dieback


Early Pride Dieback Disease Progress

The spread of the dieback had us a bit confused at first. As shown in the geotagged map below, the disease initially appeared clustered around a flush out valve. (Note the aerial image does not correspond to the planting of a young grove. This base map is from an earlier date when an older grove occupied this location, but it’s the most recent aerial available in our Cartographica GIS mapping application.)

(Click image for larger view.)

 

October 2013. Initial map of Early Pride dieback clustered near a flush-out valve.

Initial map of Early Pride dieback clustered near a flush-out valve.

 

We thought at first the dieback issue may have been related to some kind of flooding, such as when valves were flushed out during irrigation maintenance. This had us thinking that there may have ultimately been a root issue involved, but inspection of the roots showed no clear reason for the decline. After ruling out root issues, we thought we might be dealing with a nutrient or salt burn issue, such as might result from fertigation practices. These, too, proved not to be the case. We also looked at soil types, pH, and even the possibility that a group of weak trees had coincidentally been planted around the flush out valve. None of these ideas panned out, either.

Since we had no clear lead early on about the cause of the disease, the best course of action was to track the progress of the disease over time and hope that important keys to solving the problem would emerge by spatial mapping and photographing the patterns of development.

The technologies I used for tracking disease progress consisted of those in the list below. Although we could have done this with more sophisticated technologies (Arc GIS, drones infrared imaging, etc) I decided on this project to work with tools that are generally available to consumers for a fairly reasonable cost.

 

I photographed most of the time in Camera Raw format using the Nikon or a Panasonic LX-7, followed by geotagging using the Garmin GPX data merged using Photo Mechanic 5. Images were post-processed for color correction, saturation and sharpening in Adobe Photoshop CC (Creative Cloud) on a Mac Pro running OSX Mavericks 10.9.2. I optimized the photos for the blog using Adobe Photoshop’s Save for Web feature into JPG format, at a quality setting of 10, progressive rendering, Adobe (1998) sRGB color space, 72 ppi and using 600 x 600 px maximum dimensions. The Save for Web feature was invoked using a custom action, then applied using Photoshop’s Batch and Droplet automations.

 

Geotagged Photos Showing Change in Tree Condition

To track change in the patterns of disease, I used the Garmin Oregon 650t with included camera to geotag each tree that showed signs of dieback. I resolved the position of each tree to within about 15 feet, and photographed affected trees. To follow up, I went back on several other occasions over from October 2013 through September 2014 and image mapped the grove in the same way. This allowed me to track individual trees over time and determine to what extent, if any, they succumbed to or recovered from the dieback.

As shown in the map below, each point represents a geotagged photograph of an individual tree on a particular date. I shot two photos of each tree, including one from a distance and another close up. The actual photographs are automatically positioned onto the map below by Cartographica based on embedded geocoordinates. The image data can be explored in the desktop Cartographica app by clicking on any photo to enlarge the different views of the trees at a location. This makes is easy to go back later and check on disease development and compare overall tree condition.

(Click image for larger view.)

 

Photographic map of Early Pride dieback.

Photographic map of Early Pride dieback.

 

Disease Progress Over Time

To summarize the result of all this mapping, it appears that the disease incidence and severity decreased over time. You can see this graphically in this video, but following is a more detailed explanation of the same information as is in the video.

In the map below, the white diamonds represent the incidence of Early Pride dieback as counted in November 2013. There was a fairly rapid increase in dieback between October 2013 and November 2013, but that was during a time that it was untreated. We intentionally left it untreated in the early stages to help us establish that it was a problem that would spread rather than naturally decrease. At that time, there were about 118 trees affected with some sort of dieback issue. This included trees with variations in disease severity ranging from mild to severe. I mapped the disease again in February 2014 and counted 96 trees that showed signs of dieback. Although there appeared to be some reduction in the amount of dieback, whether or not this trend would continue wasn’t clear at that point.

The most recent mapping is from September 2014 (represented by the green diamonds). I mapped about 68 trees in the latest map that showed signs of dieback. It is possible that the 68 represents a slight underestimate, since some trees may have had canopy that outgrew the dieback, obscuring the dieback and making it difficult to rate. Despite my concern about underestimation, it looks like the decrease in dieback incidence and severity is real.

I also mapped the dieback at other times throughout the past year, each time photographing trees and categorizing the type of dieback that occurred. This allowed me to classify the nature of leaf, twig and stem dieback into about six symptom categories. From this information, we were able to determine exactly what was inducing the dieback in this grove. I’ll provide more details on this analysis in the next post covering causes and treatments.

In any case, even considering that the 68 counted this month may be a slight underestimate, it appears that the incidence and severity of dieback in Early Pride decreased over time. It’s important to note that this decrease was the result of a pruning and treatment program. We don’t know how bad the dieback would have become if it were left untreated. More on the causes and treatment of the problem in the next post.

(Click image for larger view.)

 

Map showing change in disease progress over time.

Map showing change in disease progress over time.

• Aperture:ƒ/8• Credit:Steve Rogers• Camera:DMC-LX7• Taken:November 27, 2013• Copyright:© 2013 Steven Rogers Photography All Rights Reserved• Flash fired:yes• Focal length:4.7mm• ISO:100• Location:27° 56.251′ 0″ N 81° 53.307′ 0″ W• Shutter speed:1/80s• Title:Early Pride Dieback