Fruit Pest News

Volume 6, No. 20  September 6, 2005

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.

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. Strawberries: First Report of Anthracnose

    2. Cucurbits: Downy Mildew

    3. Vegetables: Phytophthora Blight

    4. Apples: Prevent Storage Decays

    5. Stone Fruits: American Plum Borers

    6. Other Pheromone Trap Catches

Strawberries: First Report of Anthracnose

The first report of anthracnose was confirmed in the plant diagnostic lab on September 6. Tips were stuck on August 14 and symptoms were noticed in the plant bed by the grower last week. Buds were turning black and dieing, and the necrosis advanced up the leaf petioles, causing the leaves to collapse due to the weakness at the base of the petiole. Some petioles had discrete black lesions. The disease was present throughout the bed.

Be on the lookout for these symptoms. When found in a plug bed, it is often preferred to discard all the plants and replace them, if disease-free plants can be located. Fungicidal control is difficult, and the planting would be facing an uphill battle all year. Captan sprays can be used in rooting beds. (SB)

Downy Mildew of Cucurbits

Downy mildew has become widespread on cucurbits throughout the state, with some serious cases. Hopefully, you have using a basic fungicide such as chlorothalonil or mancozeb so that the first spore shower of downy mildew to hit your field doesn't hit so hard. When downy mildew does appear (tiny yellow leafspots turning necrotic, on pumpkins and squash), add a more specialized fungicide such as Acrobat or Tanos to your basic fungicide. Another option is to substitute Cabrio, Pristine, Gavel, or Ridomil Gold Bravo for the tank mix. Whatever your choice is, you need to choose two of them.  That is because any of these specialized fungicides need to be rotated with another one that is not related to it. It's okay to apply chlorothalonil or mancozeb continuously, but not so for the specialized fungicides. There are many downy mildew fungicides on the market now; choose two that you like. Others that are not mentioned above are provided in UTAES PB1282.

Another thing to remember about cucurbit downy mildew: Although it needs moisture for infection, rainfall is not needed. If spores are present when a good, heavy dew forms, one night (8 hours, at typical temperatures) is all that is needed for infection. Also remember that, unlike most downy mildew species, high temperatures do not inhibit cucurbit downy mildew. It can be perfectly happy in mid-summer. (SB)

Phytophthora Blight of Vegetable Crops

There has been a rash of Phytophthora capsici outbreaks this year. This disease has the potential to really shake up the way we farm, with its devastating capacity and its long-lived nature in the soil. We need to gather as much information as we can about the P. capsici populations occurring in Tennessee, so that we will be in a better position to deal with the disease in the future. You will be hearing more about this as we go. (SB)

4. Prevent Apple Storage Decays

The previous article discussed cosmetic apple storage diseases. Other storage diseases such as blue mold, caused by Penicillium expansum, and gray mold, caused by Botrytis cinerea, involve decays that actually reduce marketable yields. Unlike the cosmetic storage diseases, most of the decay disease infections occur in storage, mostly through wounds. Control tactics differ for the two types of storage diseases. However, certain late-season fungicide sprays in the orchard can help reduce both types. Applied at 14 days before harvest, a tank mix of Topsin M with either captan or ziram helps control storage decays and sooty blotch and flyspeck. Chemical control after harvest has become extremely limited. Sanitation practices are more important now than ever.

If you have had problems in the past with storage decays, you are encouraged to visit http://www.nysaes.cornell.edu/ent/scaffolds/2002/8.19.html#d1 for details on control. The article was written by David Rosenberger, Cornell University. (SB)

5. Stone Fruits: American Plum Borers Caught in Pheromone Trap
The American plum borer is a pyralid moth (same family of moths as the European corn borer). The female moth is attracted to open wounds and sap to lay her eggs. Black knot infested plums are also very attractive to egg laying. It is a pest of plum, peach, cherry (especially mechanically harvested since they lay eggs near wounded bark), persimmon, sycamore, basswood, tuliptree, sweetgum, oak and others. It and another closely related borer, the root collar borer, can be a serious pest of tuliptree, especially in the landscape or tree plantation.

The first generation American plum moths were caught on April 20 and the moth flight continued into May and June. The second generation moths were caught on September 1. This generation will be laying eggs over the coming weeks on the bark of host trees. Sprays applied for peachtree borer after harvest in early to mid-August will help prevent damage from this pest. (FH)

6. Other Moth Catches
A flight of cabbage looper moths, beet armyworm moths and armyworm moths were caught on September 1 and 6. Fall armyworms were caught for the first time on September 1. Inspect crops in the weeks ahead for these caterpillar pests.

Beet armyworms often lay their egg masses on weeds such as pigweed in addition to cultivated host plants. The beet armyworm moves up into Tennessee from the deep South where it overwinters. Thus it is usually a just a fall pest in Tennessee. Vegetable crops attacked include asparagus, bean, beet, brocoli, cabbage, cauliflower, clery, chickpea, corn, cowpea, eggplant, lettuce, onion, pea, pepper, potato, radish, spinach, sweetpotato, tomato and turnip. It can be as much a threat this time of year to tomatoes as corn earworm (tomato fruitworm).

Cabbage loopers are primarily pests of cabbage, brocoli, collards and cauliflower but can also attack potato, spinach, lettuce, parsley, tomato, cucumber and geranium.

Armyworms are pests of corn, cereal grains, pasture and lawn grasses. When populations are high, the caterpillars will devour the plants on which they developed and then crawl off in mass in search of more food and laying waste to susceptible crops like a maurading army. (FH)

Nashville (Davidson County)
Oriental Fruit Moth (OFM), Redbanded Leafroller (RBLR), Obliquebanded Leafroller (OBLR), Codling Moth (CM), Grape Berry Moth (GBM), Variegated Leafroller (VLR), Black Cutworm (BCW)

* Biofix for RBLR in Davidson County estimated as occurring on March 12.
**Biofix for GBM in Davidson County is April 4.
***Biofix of BCW in Davidson County on April 12.
****Biofix for OFM in Davidson County on April 12.
*****Biofix for OBLR in Davidson County on May 13.
"Biofix for VLR in Davidson County on July 12

Bradley County

*Biofix for RBLR in Bradley County on March 12.
**Biofix for OFM in Bradley County on March 25.
***Biofix for CM in Bradley County on April 16.


Putnam County

*Biofix for RBLR in Putnam County on March 21.
**Biofix for OFM in Putnam County on April 6.
***Biofix for OBLR in Putnam county on May 11.

Obion County

*Biofix for RBLR in Obion County estimated to be on March 12 (trap not out early enough).
**Biofix for OBLR in Obion County on April 4 (waiting for confirmation since this was much earlier than other locations).
***Biofix for CM in Obion County on April 4 (waiting for confirmation).
****Biofix for OFM in Obion County on April 11.
*****Biofix for VLR in Obion County on May 3 (waiting for confirmation).

Other Pheromone Trap Catches for Davidson County
Diamondback Moth (DBM), American Plum Borer (APB), Cabbage Looper (CL), Armyworm (AW), Sod Webworm (SWW)

* Biofix of DBM in Davidson County probably earlier than April 20
**Biofix of APB in Davidson County probably earlier than April 20
***Biofix of CL in Davidson County on April 29
****Biofix of AW in Davidson County on May 2
*****Biofix of SWW in Davidson County on May 9
^Biofix for BAW in Davidson County on September 1
"Biofix for FAW in Davidson County on September 1
Knox County*
Tufted Apple Budmoth (TABM)

*The Knox County traps were put out by a first time cooperator still learning to identify. the moths. Correspondingly, the trap counts for May 2 remain suspect. We do know that the traps were put out too late to accurately determine a biofix for Oriental fruit moth (OFM) and redbanded leafroller (RBLR). The obliquebanded leafroller (OBLR), codling moth (CM), variegated leafroller (VLR) and tufted apple budmoth (TABM) catches are possible biofixes or at least early in their moth flights.

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

Copyright 2005 The University of Tennessee. All rights reserved. This document may be reproduced and distributed for nonprofit educational purposes provided that credit is given to University of Tennessee Extension.

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