Fruit Pest News

Volume 5, No. 11  May 25, 2004

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. First Reports

    2. Tree Fruit: Fruit Damage by Insects

    3. Tree Fruit: Pheromone Trap Catches

    4. Vegetable Corner

        4.a. Cucurbits: Planning for Powdery Mildew Season

        4.b. Tomatoes: Pythium Stem Rot

1. First Reports

First reports of the year during the past week: leaf scorch of strawberry -- May 14, Dickson County; green fruit brown rot of peach -- May 19, Davidson County; bitter rot of apple (walnut sized fruit) -- May 23, Williamson County.

2. Fruit Damage by Insects

In our unsprayed fruit block at the Ellington Agricultural Center, the crescent-shaped plum curculio oviposition scars can be seen on apples, nectarines, and peaches. While the larvae do not develop in apples remaining on the tree, the scar gets larger as the fruit grow. The plum curculio larvae can develop in the softer flesh of peaches, plums, cherries and nectarines still on the tree. The legless larva (6-9 mm) is whitish with a brown head and a light brown shield behind the head. One found in tart cherry this weekend was 8 mm long. Catfacing from plant bugs is particularly bad on both peaches and nectarines, usually with a gum in the center. The nectarines especially have lots of gummosis (oozing of clear gum caused by insect feeding punctures). (FH)

3. Pheromone Trap Catches

Nashville (Davidson County) Pheromone Trap Catches for 2004
OFM RBLR OBLR CM GBM
3-4 (put out RBLR trap) 0 3* 0 0 0
3-5 (put out new traps) 0 15 0 0 0
3-8 0 29 0 0 0
3-10 0 4 0 0 0
3-15 0 10 0 0 0
3-17 0 11 0 0 0
3-19 0 13 0 0 0
3-22 1 25 0 0 0
3-24 0 14 0 0 0
3-29 25** 62 0 0 0
4-1 0 17 0 0 6***
4-2 0 9 0 0 0
4-5 1 24 0 0 0
4-7 14 10 0 0 1
4-8 1 5 0 0 2
4-12 12 15 0 0 2
4-15 0 6 0 0 0
4-19 36 6 0 0 6
4-21 18 2 0 0 3
4-27 35 2 0 0 1
4-30 26 1 0 0 0
5-5 8 0 0 0 0
5-10 9 1 3**** 0 2
5-17 18 2 3 0 0
5-19 5 0 0 0 0
5-21 6 3 0 0 0
5-24 12 15 6 0 0

* The three RBLR caught in trap left over from last year. New RBLR trap put out 3-4-04. Biofix for RBLR in Davidson County estimated as occurring on February 29.
**Biofix for OFM estimated to have occurred on March 26.
***Biofix for grape berry moth (GBM) estimated as occurring on 3-30.
****Biofix for obliquebanded leafroller.


Bradley County Pheromone Trap Catches
  OFM RBLR CM TABM
3-10 new traps put out 0 4* -- 0
3-13 0 59 (catch for now on from 2 traps) -- 0
3-19 2** 43 -- 0
3-26 put out CM traps 2 28 -- 0
4-2 21 25 0 0
4-9 7 26 0 0
4-16 9 9 0 0
4-23 22 26 2*** 2****
4-30 5 2 1 1
5-7 1 0 0 0

*Four RBLR moths caught in trap from last year. Biofix for redbanded leafroller in Bradley County estimated as occurring on February 29.
**OFM biofix on March 19.
*** CM biofix on April 23.
**** TABM biofix on April 23.


Putnam County Pheromone Trap Catches

3-8 set out OFM RBLR OBLR CM
3-12 0 31* 0
3-19 0 51 0
3-26 0 49 0 0
4-2 0 73 0 0
4-9 13** 37 0 0
4-16 7 35 2*** 0
4-23 8 16 0 0
4-30 2 12 3 0
5-8 12 1 1 1****
5-14 4 0 2 0
5-21 2 18 2 0

*Biofix for RBLR in Putnam County estimated as occurring on February 29.
**Biofix for OFM estimated as occurring on April 7.
*** Biofix for OBLR on April 16 (waiting for confirmation).
****Biofix for CM.


Smith County Pheromone Trap Catches (Two orchards, a set of traps at each site))
Traps put out 3-9 OFM RBLR OBLR CM
3-18 0 89* 0 0
3-24 0 63 0 0
4-1 0 140 0 0
4-7 0 90 0 0
4-14 6** 47 0 0
4-21 7 21 0 3***
4-28 6 1 7**** 0
5-5 3 0 2 0
5-12 0 0 25 0
5-20 0 49 17 1

* Biofix for RBLR estimated as occurring on February 29.
** Biofix for OFM estimated as occurring on April 9.
*** Biofix for CM on April 21(waiting for confirmation)
**** Biofix for OBLR on April 28 (waiting for confirmation)

(FH)

4.a. Planning for Cucurbit Powdery Mildew Season

Cucurbit powdery mildew typically does not begin until mid-summer, but it is not too early to plan your fungicide program and make sure the products you wish to use are available from the dealers. The big news for this year is the occurrence of strobilurin-resistant powdery mildew. Resistant strains began appearing across the country in 2002, and now appear to cause a re-thinking of powdery mildew control plans. You will not know whether the powdery mildew you get in your field is resistant to the strobilurins (Quadris, Cabrio, Flint) until it is too late, when you fail to get good control. If that is too big a risk for you, use sulfur or a sterol inhibitor (Nova or Procure).

Since resistance to the sterol inhibitors is also a threat, you should rotate occasionally to sulfur. Remember that sulfur is strictly a surface protectant and coverage of both sides of the leaves is needed for good control. The strobilurins provide control of other diseases such as microdochium blight and downy mildew and, because of this property, are usually applied alone. Sulfur and the sterol inhibitors are specific to powdery mildew and should be tank mixed with broad-spectrum fungicides such as chlorothalonil or mancozeb. (SB)

4.b. Pythium Stem Rot of Tomatoes

We are seeing quite a few tomato samples with Pythium stem rot.  Young plants are pale and stunted and some become chlorotic and die.  The lower stem shows a dark rot and the roots are not developed.  Pythium stem rot is a young plant disease - - if the plant survives, it will develop tolerance to the fungus and produce a normal plant.  Gardeners can mound some soil up around the stem to encourage root development above the rot.  There are no effective chemical treatments for homeowner use.  Commercial growers can use Ridomil Gold or Ultra Flourish injected into the drip system or as a directed spray to the base of the plants.  This treatment will not rescue infected plants, but will protect uninfected plants.  Pythium stem rot is usually found in poorly-drained areas of the field. (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, Professor and Extension Entomologist

fahale@utk.edu

 

Both authors available at:

615-832-6802

fax 615-781-2568

Plant and Pest Diagnostic Center

5201 Marchant Drive

Nashville, TN 37211