Fruit Pest News

April 23, 2001

A weekly, 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.

Text appearing in blue or red can be clicked to link to other web sites. Be aware that much of the linked information is produced in other states and may not be applicable to Tennessee.

In This Issue:

    1. Benomyl Fungicide To Be Discontinued

    2. Tree Fruit: Insect Update

    3. Apple: Fire Blight "Strikes"

1. BENOMYL FUNGICIDE TO BE DISCONTINUED

Dupont has announced a business decision to discontinue the manufacture of the widely-used fungicide benomyl throughout the global market by the end of this year.  The company indicates that it expects to phase out distribution and sales of all benomyl products by the end of 2002.  EPA stands ready to assist Dupont in carrying out the company’s request for voluntary cancellation and phase-out of benomyl, often marketed under the trade name Benlate here in the U.S.

Benomyl is approved for use on about 70 fruit, nut, vegetable, and field crops.  No residential uses are approved.  EPA has been in the process of reviewing the human health and ecological effects of benomyl in order to complete a reregistration eligibility decision (RED) on the pesticide next year.  

On April 18, 2001, Dupont formally requested voluntary cancellation of all of their benomyl technical, end use, and special local need product registrations.  The next step under FIFRA will be for EPA to publish a Section 6(f) Federal Register notice announcing receipt of the request for voluntary cancellation, and inviting public comment for 30 days. (Adopted from an article by Gene Burgess and Darrell Hensley, of the Entomology and Plant Pathology Department, University of Tennessee.)

2. TREE FRUIT: INSECT UPDATE

Plum curculio feeding and oviposition damaged peaches and apples can be found at our Nashville (Davidson Co.) location. Our petal fall spray on April 20 was possibly a bit late for this pest so some damage occurred prior to the spray. The petal fall spray is very important for this pest. The first cover spray is also important for this pest.

Oriental fruit moth (OFM) and codling moth (CM) adults are being caught in our traps but there are no signs of larvae yet. The biofix for Oriental fruit moth (trap catches exceed 5 moths per trap per week) has occurred April 9 for Putnam Co., April 12 for Bradley Co., and probably around April 9 (caught 23 moths between April 6 and 12) for Davidson Co. The Obion Co. traps were just recently put out. No OFM were caught on April 9 while 6 OFM were caught on the 20th.

Oriental fruit moth DD models use a base temperature of 45F. First generation egg laying is usually low on apple, and only one insecticide application 500 to 600 DD after biofix is necessary. As of April 23 there are 282.8 DD accumulated at our Davidson County location since the April 9 biofix.

In peaches the biofix for Oriental fruit moth (OFM) begins with the first sustained catch of 2 or more moths in the spring. The biofix was April 6 for the Putnam Co. orchard and the estimated biofix was April 9 (0 caught on April 6 and 23 found in trap when checked on April 12; I should have checked trap more often) for Davidson Co. Low OFM density orchards are those with less than 0.5 percent of fruit damaged the previous year and pheromone trap catches not exceeding 10 moths/trap/week anytime before the accumulation of 500 DD after biofix. There were 23 OFM in trap on April 12 in Davidson Co. so this would be a moderate to high OFM density orchard which would require two insecticide applications applied 14 days apart, the first at 500 DD after biofix for first generation OFM. As of April 23 there were 282.8 DD accumulated since the April 9 biofix so we still have some time before the first spray for this pest. For your information, a low density OFM density orchard would require a single insecticide application at 600 DD after biofix.

The biofix for codling moth (the first sustained catch of 2 or more moths in the spring) was April 13 (possibly earlier) for Obion Co. and April 4 for Davidson Co. A biofix was not determined yet for the other sites. Codling moth DD models use a base temperature of 50F. As of April 23 there were 311.5 DD accumulated at the Davidson Co. location. At low density orchards (less than 0.5 percent of fruit damaged the previous year and pheromone traps that do not exceed 10 moths per trap anytime before the accumulation of 200 DD after biofix) a single insecticide application can be made at 350 DD after biofix. Moderate to high density orchards will have had higher fruit damage the previous year or higher pheromone trap catches than with low density orchards. In the Davidson Co. trap we had a catch of 12 codling moths on April 4 and one on April 6 so we are in the moderate density orchard category. In moderate to high density orchards, two insecticide applications are applied 14 days apart, the first at 150 to 250 DD after biofix. Treat beginning at 150 DD if using a product which is primarily ovicidal (i.e., Confirm or Intrepid), and begin treatments at 250 DD if using a product which has contact activity against larvae (i.e., organophosphate or pyrethroid). We used a pyrethroid on April 20 for our petal fall spray when we had 253 DD, which is about as close as you can get to our 250 DD target. If we had not caught so many codling moths on April 4 (12 caught) and instead not exceeded 10 moths per trap per week we would call this a low density orchard and could get by with a single insecticide application at 350 DD after biofix.
(FH)

                                                    Obion Co.(traps put out April 9)

Bradley Co.

Putnam Co.(traps put out 4-4-01)

Davidson Co. (OFM and RBLR traps put out 3-26, The 8 RBLR on 3-26 were found in last years trap. The OBLR and CM traps put out 4-2)

3. FIRE BLIGHT "STRIKES"

Fire blight blossom blight appeared on Saturday, April 21 on Golden Delicious at Nashville and at Franklin. A couple of initial strikes were followed by several the following day. According to the MaryBlyt program, the infections occurred 12 days earlier, on days that had moderate dews in the morning and high temperatures in the 80's during the day. No streptomycin was used in the orchard.

Many varieties are at petal fall and, as a result, are no longer susceptible to blossom blight infections. However, streptomycin applications are needed on those varieties if any tag-on blooms are present. Tag-on blooms are quite susceptible to fire blight infection because of the warmer weather that usually accompanies them. Loosing a few late blossom clusters to fire blight may not seem important, but the bacteria produced by just a few infected blossoms can result in a significant shoot blight epidemic. The time to prevent shoot blight is during bloom (with streptomycin applications) and during the dormant period (by removing cankers). Attempting to control shoot blight by applying streptomycin after the bloom period is usually futile, and not recommended. (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