Fruit Pest News

Volume 4, No. 22    September 30, 2003

An online newsletter whose goal is to update Extension agents and growers of commercial tree fruit and small fruit crops

on diseases and insects in Tennessee.

This is the last issue of Fruit Pest News for 2003. The next issue will be posted at this web site in early March, 2004.

The focus of this issue of Fruit Pest News is a subject index for all issues to date for this year.  This index will allow you to review a topic, and there should be new readers (hopefully) who might wish to read certain topics that they missed. The opening page of the Fruit Pest News web site contains a list of all of the issues. You can connect to the issue of interest there.

We want to take this opportunity to thank you for your readership. Please help us spread the word to other interested readers. This newsletter is for you, so please let us know how we can improve it to serve you better. Suggestions for topics to address are very welcome. The greatest need I see is for more scouting reports from across the state. We're grateful for the insect trap counts that some of you have been sending us. We would like to hear when you see a disease or insect for the first time for the year, or if you are experiencing a severe outbreak. The weekly format of this newsletter is designed for reporting such time-sensitive news. Try to phone or e-mail us your news. Of course, all reports are kept anonymous (unless you want us to use your name!). (SB)

In This Issue:

    1. Subject Index for 2003

    2. Strawberry Anthracnose Update: Should You Spray?

    3. Peach: Items from S.E. Regional Newsletter (Plum Pox Virus, Halford Seed Purity)

 1. Subject Index for Fruit Pest News, 3/10/03 through 9/29/03

2. Strawberry Anthracnose Update: Should You Spray?

As discussed in the two previous issues of Fruit Pest News, several growers received anthracnose-infected tips from a nursery. The disease appeared in the plug beds in which these tips were used. Remedial options are limited, since there are no clean tips available, and the use of bare root plants is not feasible for most Tennessee growers. Roguing of infected plants is not practical because anthracnose levels in the affected beds are too high. Most growers in this predicament have elected to proceed with field planting, using contaminated plants, even those showing symptoms. How should these anthracnose-infected plants be treated, to optimize chances for a successful crop?

The first reaction would be to spray. A research trial conducted last year in North Carolina by Dr. Frank Louws indicated that a fungicide application on infected plants in the plug bed did not reduce damage in the field. Plant mortality and stunting was as great in the sprayed as in the unsprayed. It is not known whether a fungicide spray schedule during the fall would have been beneficial. I think it is rather unlikely, based on the experience I have had with attempts to control anthracnose during the summer in matted row plantings.

Fall applications of fungicides are not recommended because they may not provide any benefit and they should be reserved for use during the spring, when we know they will be effective. All fungicides have a labeled limit on the number of times they can be applied; these limits would be exceeded if the materials were used both in the fall and spring. The manufacturers limit the number of applications to avoid residues on the harvested product that exceed the tolerance level, and to avoid encouraging the development of resistance in the fungal population.

Furthermore, a fall fungicide program would do little to protect the berries next spring, even if it prevented spread of the disease. With favorable weather during harvest, a severe outbreak of berry rot can result from a small amount of inoculum. Abide by the label, spend less money on fungicides, and spray next spring, when we know the fungicides will be effective. (SB)

3. Peach: Items from Southeastern Regional Peach Newsletter

In the survey and eradication program in Pennsylvania this year, plum pox virus (PPV) was found in 6 homeowner sites, 2 commercial orchards, and one fruit tree nursery. The nursery is the most troubling site, since the implications are obvious. Investigations are underway to determine whether budwood or rootstocks played a role in this case. Our nurseries must be protected. The Southeastern Budwood Testing Program is reportedly going well, and budwood stocks for southeastern peaches should be relatively clean of viruses. However, some viruses can enter a nursery through seed stocks as well. There appears to be a need for a controlled seed stock. This is illustrated by the PPV case and by the recent discovery by Dr. Simon Scott, Clemson University, that 'Halford' seed stocks are of mixed genotype and prone to infection with prunus necrotic ringspot virus (PNRV). More news will be reported as it becomes available. (SB)

The Fruit Pest News URL is: http://web.utk.edu/~extepp/fpn/fpn.htm

Contacts:

Steve Bost, Professor and Extension Plant Pathologist

scbost@utk.edu

Frank Hale, Associate Professor and Extension Entomologist

fahale@ext1.ag.utk.edu

Both authors available at:

615-832-6802

fax 615-781-2568

Plant and Pest Diagnostic Center

5201 Marchant Drive

Nashville, TN 37211