Help Requested for Nematode Survey

Hi Everyone,

Ever wonder why we only  have one commercial rootstock that we use for Florida peach production?  It’s because of a type of root-knot nematode found only here in Florida.  In fact, it’s scientific name is Meloidogyne floridensis. 

If you have it in your orchard, you might see short shoot growth, early bloom, and a general delay in fruit development (see below). IMG_0680The tree on the right was found to have nematode galls on the root system that was affecting the tree growth.  Successive years of weak growth can cause tree collapse, and will require removal and replanting.

Help Us Out!

So, what can be done?  First things first, we need some help!  Dr. Janete Brito at FDACS, DPI in Gainesville would like to conduct a survey of growers orchards.

Here is her request:

Scientists of FDACS, Division of Plant Industry, University of Florida, IFAS and other research agencies are joining forces through a cooperative Farm Bill agreement to study and identify plant-parasitic nematodes associated with peach trees in Florida peach orchards. So far, the potential risk posed by these nematodes to the new peach industry in Florida has not been fully assessed because of lack of information on their identity and distribution in the state. Scientists involved in this cooperative project are confident that an intensive nematode survey in Florida peach followed by accurate morphological and molecular analyses of plant-parasitic nematodes found will provide precise information on the species that parasitize peach in Florida. Additionally, an associated survey for detection of plum pox virus (PPV) will be carried out. The results of these surveys will provide information about the incidence of these pathogens in Florida peach.

The sites to be surveyed for nematodes will include existing peach orchards, nurseries and land destined to peach production, including abandoned citrus groves. The support and cooperation of the peach growers in the form of access to orchards, nurseries and other sites to be sampled are much needed for the success of this project. As permission and access to the sites to be surveyed is granted, a timetable and strategy will be developed trying to minimize potential interference with the activity of peach growers involved in the survey. Scientists are hoping that this initiative will receive a favorable reception by the Florida peach industry. Peach growers wishing more information about this cooperative project or willing to provide access to their orchards for the survey should contact Dr. Janete Brito, FDACS nematologist; phone: (352)395-4752; e-mail: janete.brito@freshfromflorida. com.

Thank you in advance for helping to figure out where these nematodes are, so that we can target control methods. If you have any questions, please let Dr. Brito know! Cheers, Mercy

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2015 Wet Spring Leading to Potential Brown Rot Issues

Brown Rot in Gulfking
Brown Rot in Gulfking

I hope that everyone is having a good harvest so far, although I will have to say it’s been challenging with all of the rain we have had here in Central Florida.

One issue that we don’t often have to deal with is Brown Rot.  However, with the afternoon rainshowers that we have had (in some cases over 3 inches over the past couple of weeks), it is showing up in some of the harvested fruit, particularly in the bottom part of the fruit.

We are working on an EDIS publication for future reference; however here are some quick points.

Brown Rot

Brown rot is caused by a fungus, Monilinia fruticola and is often an issue in areas with frequent rainfall during fruit development.

Primary infections occur in the spring and can lead to flower death and reduced yield, but secondary infections affect the fruit.  In addition, abortion of mature fruit, e.g., “mummies” that fall to the orchard floor can serve as inoculum for future infections with later ripening periods.

G. England
Brown Rot in Mature Fruit, G. England

Disease Cycle

The continuous production of spores by mummies, cankers, and apothecia fuel the disease cycle and the infection of blossoms and fruit. Brown rot flourishes under conditions of high humidity (>94%) and optimal temperatures occur around 77°F (25°C). Rain, wind and insect activity lead to the release of spores that initiate the infection.

Secondary infection occurs as blossoms and shoots that have been initially infected begin producing spores, and can continue to do so until early June. If secondary spore production can be prevented by the use of effective management techniques, the disease can be more easily contained. The presence of infected fruit and mummies can also act as a source to spread brown rot.

Management

Management for brown rot should begin before anticipated rain events occur, and guidelines for recommended fungicides are listed in the SE Peach Spray Guide: http://www.ent.uga.edu/peach/PeachGuide.pdf.

Please remember to rotate your fungicide chemical classes (as indicated by the FRAC codes) to avoid resistance risk.  There have been races of brown rot that have been identified as resistant to certain classes of fungicides – although there is a fungicide resistance kit that can be ordered to verify that the fungicide is at fault.

Key Points

As always – if you have any questions or concerned, please let me know!

Cheers,
Mercy

Harvesting Good Peaches and Fungicide Management

I love this time of year, as hectic as it is.  For most people in south central/central Florida – things are winding down, while in north central Florida, we are in the midst of harvesting.

Most people this year had a great season, with great fruit quality and flavor.  However, we did have a wet spring (20 inches from January 1 – May 20th) in Citra and north central Florida, while in other years we get less than 10 inches in that same time span.  Cloudy and wet weather affects a number of plant processes such as:

  • Carbohydrate fixation and accumulationaka making sugar in enough quantities to have good brix content in the fruit.  I also saw overripe fruit because growers were waiting for the fruit size to get bigger, but because perhaps of the cloudy/rainy spring, cell division (stage 1) of fruit development wasn’t as good as it has been in years past.  It didn’t help the fruit quality in the store – and this was the result:

IMAG0387

  • Wet feet – in orchards that have poor drainage, you can have problems with leaf drop and/or fruit drop due to damage in the root systems due to suffocation of the roots (anoxia).
  • Increased disease pressure – We also saw a bit of anthracnose ripe rot and botyrosphaeria rot in the fruit after the rains and some of the warm weather we had in the late part of April/early part of May.  It’s important that if we do have successive rain events that you apply fungicides and rotate the chemistries to avoid resistance.  Common fungicides like Abound and Topsin-M are great, but are categorized as medium or high risks for resistance and should be used sparingly or in a diverse rotation of chemicals.

Fungicide management is easy to do – but if you don’t know what a FRAC code is (and no – Battlestar Galactica fans, I’m not swearing…) here is a website that will take you to the codes for each chemical.  http://www.frac.info/publication/anhang/2014%20FRAC%20Code%20List.pdf.  You’ll notice that this chart does not have the company (trade) names of the chemicals so you will have to READ the LABEL to find out what chemical your fungicide contains – and the FRAC code should be listed there as well.

Hints for Next Season

At our winter field day this year in Fort Pierce (typically held the 2nd week of December) we will be talking about thinning.  There was a lot of small fruit put into local supermarkets, and much of this can be alleviated especially in UFSun with more aggressive thinning.  Instead of 6″ between each fruit as is suggested with other Florida peach varieties, UFSun should be thinned to 9-12″ between each piece of fruit.  In addition, anything that can be done to encourage leaf area expansion will be key to getting good fruit size and flavor development.

The use of hydrogen cyanamide is looking promising for peach growers that are down south especially as it appears to help with leaf emergence – an important stage of growth to help fruit develop its maximum potential for fruit size and good flavors.  However, we need more research on timing, and I have some key growers set up around the state this year to look at a couple of different timings and see what the impact is on leaf growth and fruit size/harvest date.  If we can get more uniform leaf emergence and bloom, then we should be able to narrow our harvest window and minimize the number of pickings necessary to harvest the entire crop.  More research to come in 2014-2015!

As always, if you have any questions – please call or email me!

Mercy

 

Phomopsis Constriction Canker

Hello Everyone! I hope that your harvest is going well and that everyone has been getting good prices for their fruit.

Dr. Phil Brannen, pathologist at the University of Georgia sent this along earlier this week, and I thought it would be good to keep an eye out for this in our orchards this year, especially since we have had so much rain and wet weather.

From Dr. Brannen:
I had a call this morning on Phomopsis constriction canker. This is one of the diseases for which we don’t have great answers – certainly not fungicide ones anyway. Some peach varieties are susceptible, and the wet conditions last fall and this winter/spring have likely contributed to the degree of disease observed; the initial infections are thought to occur on buds and leaf scars. The question was asked as to whether pruning out infected tissue would be of value, and the short answer is that I don’t know for sure, but I think it might be for two reasons: carryover inoculum for infections next fall and possible fruit rot.

phomopsis on branch
Phomopsis Canker on Branch (Clemson University)

As far as I know, I have never personally observed Phomopsis fruit rot, but in going over information in my files, I found the following note from George Philley, retired extension pathologist from Texas A&M. He stated, “I saw more Phomopsis fruit rot. It is usually just a novelty type disease, occurring rarely from time to time. Mid to late season I found it in my peaches more often than you would like. It was hot and dry. No brown rot problems at all. I think a good common name for this disease is ” crater rot”. The flesh melts away forming a nice little crater in the fruit. I am unofficially calling it crater rot because I use that terminology in describing the disease to someone. I don’t like using fungal names, like Phomopsis, for common disease names.” I guess “a rose by any other name” comment would be appropriate, but I don’t like the idea of Phomopsis spores raining down on developing fruit. In our 2014 Southeastern Peach, Nectarine and Plum Pest Management and Culture Guide, we state that “Phomopsis or Botryospheria pocket rots are best managed with a tank mix of Topsin-M plus captan, beginning six weeks before harvest.” In reality, I have no idea from where that recommendation was derived, though I have no reason to refute it either. Based on Phomopsis disease recommendations in blueberries, captan does have moderate activity on Phomopsis, so incorporation of captan in cover sprays may be a good recommendation; the addition of a little Topsin would not hurt, assuming that resistance has not occurred to this class. The DMI materials Indar and Quash are also among the best fungicides listed for blueberry Phomopsis twig blight management, as is Pristine; as a result, I am hopeful that Merivon and possibly Orbit (propiconazole) products might have activity as well. Abound has been reported to have activity in peach, as well as captan and DMIs. Therefore, other than adding captan (and possibly Topsin M) to the cover sprays, I think our regular brown rot program will likely be as good as it gets for Phomopsis fruit rot management.

Pruning out diseased tissue does often have value for reducing disease in future years.

It is not perfect, but it does help, and I think it is likely to be beneficial enough that it would pay for itself. Based on one of the attached papers, you don’t need to remove the cuttings from the field to get the benefit of pruning out the infected tissue. I still would prefer that the prunings be flail-mowed as a matter of practice, but there is no evidence that this would benefit Phomopsis canker disease management. Multiple fall applications of fungicides would be required for suppression of the canker stage of the disease, and control through fungicidal means is definitely cost prohibitive.

Additional Comments:

Keep any eye out for sunken lesions that appear silver in the fall – these can lead to spore release if we have a wet spring.  Also – be sure that those with significant fruit on their trees still – keep an eye out for Brown Rot and stay up on your fungicide applications as best you can with the harvest.

If you have any questions, please contact me or your favorite extension agent and we can help!

Happy Harvest!

Images

 

 

Phomopsis Constriction Canker

Bloom and Fungicide Sprays

DSC_0634

As we head into full bloom and early fruit set for the growers down south, please don’t forget about application of your fungicide sprays to combat peach scab.  This, along with peach leaf rust, are our major diseases here in Florida.

UFSun fruit
Peach Scab on ‘UFSun’. Notice scab lesions around the stem area where sprays were difficult to get in.

Please check the latest version of the Southeastern Peach, Nectarine, and Plum spray guide for options.  Please also pay attention to the suggested spray material choices, such as Captan and sulfur.  Sulfur is a good choice for this time of year, because it is relatively inexpensive and does a great job to cover the young fruit and protect it.  The downside is that it has a shorter efficacy length, meaning that you will have to spray more often than if you used a synthetic chemical like Captan.  Additionally, as we head into the bloom period and leaves begin to push open on the tree, be sure to begin your fertilization and irrigation regimes.  We still can get some rain during this time of year, so take that into consideration when you set up or run your irrigation programs.  For help on irrigation requirements, you can check the FAWN site for information on the evapotranspiration (ET) for the day or week.  Although we do not have an irrigation scheduler for peaches at this point, there is a citrus irrigation scheduler that may be helpful.  However, some growers are cutting the recommended amount for irrigation to peaches by various percentages according to their soil type and tree response.

A group at UF have a project in conjunction with the SWFWMD to investigate peach irrigation and reduction of water applications after harvest.  We are working with growers to establish best management practices for irrigation management, knowing that the afternoon thunderstorms often rolling through in June, July, and August can stymy our plans.

As always, be sure to let your county extension agent or myself know of any questions you have!  We are here to help.  Good luck and enjoy the beautiful blossoms!

New 2013 Spray Guide & Nematodes

March 3, 2013

The cooperative effort of several extension specialists throughout the Southeastern U.S. working on stone fruit have contributed to the latest update of the Southeastern Peach, Nectarine, and Plum Pest Management and Culture Guide.  Be sure to download the latest version and use it in your upcoming orchard spray regimens!

Nematodes

As I have traveled over the past six months or so, I have seen many trees that possibly have nematode issues; that is the trees flush out with early growth and sometimes bloom early, yet they lag behind later in the year from normal trees (Figure 1).

Figure 1.  Nematode-affected tree showing reduced growth, due to an outcross of ‘Flordaguard’ rootstock.

Tree affected by Meloidogyne floridensis
Figure 1. Nematode-affected tree showing reduced growth, due to an outcross of ‘Flordaguard’ rootstock.

What do you do if you suspect that nematodes have infected a tree in your orchard?

The first thing that I usually do is politely ask the grower if it’s ok to pull up their tree.  Often you will notice the either early or delayed growth from the rest of the orchard approximately one year from planting, so the trees are easily pulled up from the soil.  In many cases, we end up finding nematode galls throughout the root system (Figure 2).  These root knot galls are caused by the peach root knot nematode (Meloidogyne floridensis).  If you do find these, then dispose of the tree and replant with a new tree that is budded onto “true-to-type” ‘Flordaguard’ rootstock.  Having said this, in a nursery situation, it is often hard to catch those escapes that are outcrosses, and for those nurseries that use seeds to propagate ‘Flordaguard’ rootstock, outcrosses occur approximately 5% of the time, with another 10-15% being rogued out due to slow growth or small diameter caliper.

Figure 2. Root galls on peach root system caused by the peach root-knot nematode, Meloidogyne floridensis.

Solutions?

Unfortunately at this point, we don’t have any good solutions other than planting our varieties on nematode-resistant rootstocks, like ‘Flordaguard’.  We have an ongoing project to figure out why ‘Flordaguard’ is resistant, as well as evaluating other rootstocks that may be resistant from the USDA-ARS Peach Rootstock Breeding program in Byron, GA.  In many cases, fumigation may work – and we have a separate project to examine the effectiveness of the recommended rate as well as a half-rate of Telone II as a pre-plant fumigant in reducing the impact of peach root-knot nematode.

Requesting Help

If you would like to submit a nematode sampling for identification, please send a sample to the UF Nematode Assay Labhttp://edis.ifas.ufl.edu/sr011.  As always, please contact either myself or your local county extension agent regarding orchard issues.  We are always here to help!

A Florida-specific Peach Spray Guide??

October, 2010

I recently returned from the Southeast Professional Fruit Workers Conference held in Asheville, NC last week, and it was beautiful!  There were many great presentations on peach and apple disease management, fruit antioxidant chemistry, postharvest applications to prolong apple shelf life, grapevine evaluations, and apple thinning using a carbon balance approach.

One the major tasks during this conference is to make changes to the regional tree fruit spray guide (http://www.ent.uga.edu/peach/PeachGuide.pdf).  One thing that became clear to me as I brought up several different topics that are specific to Florida growers is that attempting to author a regional spray guide is very difficult.  At least one state has authored their own spray guide for peaches and stone fruit, North Carolina, while other states in the Southeast simply use the regional guide as their go-to resource.

Bacterial Spot on Peach Fruit
Figure 1. Bacterial spot on peach fruit. (Courtesy of forestryimages.org)

In northern states that have significant peach production, a major emphasis  is on preharvest control, specifically brown rot and bacterial spot management.  Of course, these growing areas have a later bloom date, and extended ripening season, with varieties that have longer fruit developmental periods.  Thus, fruit are ripening during prime infection periods for brown rot and significant efforts are made to apply various fungicides to combat this disease.

Many of the varieties developed at the University of Florida in the past 20 years have excellent resistance to bacterial spot (Xanthomonas compestris pv. pruni (Sm.) Young et al.; Figure 1, 2), and thus this particular disease only really affects early varieties TropicBeauty and FloridaPrince.  One grower that I spoke to this year had bacterial spot symptoms show up with a heavy crop load, with no applications for bacterial spot in TropicBeauty.  However, newer non-melting flesh varieties such as UFSun, UFOne, UFGold, etc. have excellent bacterial spot resistance.

Leaves
Figure 2. Bacterial spot leaf symptoms in peach. Courtesy of forestryimages.org

These are just a few examples of diseases that have significant coverage in the Southeastern Peach, Nectarine, and Plum Pest Management and Culture Guide that growers in Florida do not routinely have to control.

We are thinking of authoring a new Florida Stone Fruit Pest Management Guide that focuses on postharvest management of diseases, and contains information on subtropical pests and diseases (such as  Caribbean Fruit Fly, Mediterranean Fruit Fly, etc.).   What do you think?

GO GATORS!

Mercy Olmstead, Ph.D.
352-273-4772
mercy1@ufl.edu