Bloom and Fungicide Sprays

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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