Fruit Pest News

Volume 6, No. 2  March 29, 2005

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. Current Conditions

    2. Apple MaryBlyt Program for Fire Blight Management: What to Do Now

    3. Apples: Time for Copper Sprays

    4. Peaches: Use Copper if Bacterial Spot is a Problem

    5. Peaches: Purchase Virus-Tested Trees

    6. Blackberries: Consider Certified Plants

    7. Pheromone Trap Catches and Biofixes

    8. Insecticides: Green Tip to 1/2 Inch Green Sprays on Apples

    9. Oriental Fruit Moth (OFM) on Apple

    10. Oriental Fruit Moth (OFM) Mating Disruption on Peaches, Nectarines and Plums

    11. Thrips on Peaches and Nectarines

1. Current Conditions

Spring is slow this year. O'Neal blueberries began to bloom slightly ahead of normal, around March 1, but the cool weather since then has delayed everything else. Peaches are just beginning to bloom, Golden Delicious trees are at green tip (see MaryBlyt article, below), and Red Delicious trees are still at silver tip. Hopefully, the delay will mean fewer frost problems during bloom. Mild weather is forecast for this week, with occasional thunderstorms. (SB)

2. MaryBlyt Program for Fire Blight Management: What to Do Now

One of the priorities for this newsletter is to provide training and updates for the MaryBlyt program. Fire blight will require increasing attention as time goes by, with the changes that are taking place in apple production.

What it does: The program use temperature and rainfall amounts to tell you when you need to spray with streptomycin and to tell you when to expect fire blight symptoms to appear. The program will improve control efficiency, resulting in better control with fewer sprays than would be obtained by spraying on a fixed schedule. Fewer sprays mean less chance of resistance to streptomycin developing.

For those of you who have begun to use MaryBlyt, here are some points to keep in mind:

• Begin monitoring temperature and rainfall when 50% of the buds show green tissue (Many Golden Delicious plantings are at this stage, now). This is the "biofix," when the program begins calculating pathogen and plant development. In judging when to begin measurements, consider only blossom buds (those at terminals and spurs). Don't consider the leaf buds (those at the nodes).

• You don't need to enter the data into the computer until the blooms begin to open, but you do need to record the measurements every day, and reset the max-min thermometer and empty the rain gauge after the reading. When the first blossom bud opens, the data must be entered into the computer each day.

• The thermometer should be located in the shade, away from the ground. The rain gauge should be located in the open.

• Time of day to take measurements: Can be taken any time, but you should choose a time and be consistent with it each day. I think the most desirable time is late afternoon, because it would allow all of the measurements for that day to be kept together . . . and a spray decision based on that day's data to be made that night (streptomycin applications work well under the slow drying conditions of night). Remember to take note of whether a dew occurred in the morning, since dewfalls are also recorded. (SB)

3. Apples: Time for Copper Sprays

Fixed coppers and Bordeaux mixture are applied at this time of year to reduce fire blight bacterial populations on the surface of apple and pear trees. By doing so, there will be fewer bacteria to be carried to the blooms on the feet of insects or by splashing rain. This job should not be delayed, because application after the 1/2-inch green tip stage can cause fruit russeting in years when there is not enough rain to remove the copper residues before bloom. Don't restrict the copper application to fire blight-susceptible blocks. The fire blight bacteria can be found on the surface of resistant varieties, too. The bacteria don't require a susceptible host to multiply on the surfaces. Fixed coppers and Bordeaux mixture can be mixed with dormant oil if the job is concluded by 1/2-inch green tip. (SB)

4. Peaches: Use Copper if Bacterial Spot is a Problem

In peach or nectarine blocks in which bacterial spot has been a problem, it is a good idea to use some copper sprays in the early season. Since stone fruit trees are quite sensitive to copper, the rate used should be diminished as the season progresses, and green tissue is more prevalent. While 2.0-2.5 pounds of metallic copper per acre is okay at delayed dormant, only 1-2 pounds should be used at pink bud, and no more than 1 pound now (5-10% bloom). One pound of metallic copper would be 1.9 pounds of Basicop (53%) or 2.5 pounds of Kocide DF (40%). At petal fall, the rate should be further reduced to 0.5 pound, and to 0.1-0.25 pounds at shuck split. (SB)

5. Purchase Virus-Tested Peach Trees

When planting that new orchard or replacement trees, buy virus-tested trees from Tennessee nurseries. This the best way to make sure that your trees are free of plum pox and several other viruses. You are already paying 5 cents per tree to support this program, which involves the use of virus-tested budwood. Cooperating nurseries (Freedom Tree Farms, Vaughn, and Cumberland Valley Nurseries) contribute 1% of their gross sales to this program. The proceeds go toward the cosst of testing the budwood used to produce these trees. Testing takes place at Clemson University.

Please support this program by purchasing virus-tested trees. The 5 cent surcharge is assessed on all trees, whether virus-tested or not. Check with the nursery for variety availability. (SB)

6. Planting Blackberries? Consider Certified Plants

If you will be planting blackberries this spring, consider purchasing certified plants. Viruses such as raspberry bushy dwarf virus and tomato ringspot virus can be problems in blackberries, and it is possible to buy infected plants, which will not show symptoms at the time of purchase. Certified plants will also be free of other damaging diseases such as rosette disease. Certified plants have only recently become available. Only one certified nursery, Jones Farms, is licensed to propagate cultivars from the Arkansas breeding program, which produced the major cultivars grown in the South. The plants sold by Jones Farms are derived from tissue culture stock, but come to you after growing in insect-free greenhouses in 3-inch pots since last summer. The plants are inspected and certified by the North Carolina Department of Agriculture. (SB)

Jim and Barbara Jones

c/o Jones Farms

7094 Honeysuckle Lane

Bailey, NC 27807

Home phone: 252-235-3248

Home fax: 252-235-0155

Barbara cell: 252-399-9844

Jim cell: 252-230-2084

email: jonesfarmsnc@aol.com

7. Pheromone Trap Catches and Biofixes

A total of 5 unidentified tortricid moths (family of moths of codling moths, Oriental fruit moths, redbanded leafroller, obliquebanded leafroller etc.) were found in the codling moth (CM) trap and 2 were found in the Oriental fruit moth (OFM) trap at Nashville on March 29. These unidentified moths had a pinkish tinge under the gray scales. They were 8 mm long and had a wing span of 14 mm which was slightly smaller than the CM. An actual codling moth, in contrast, is gray-chocolate brown, crisscrossed with fine alternating white and gray bands. The distal third of the front wings (furthest from head end) has prominent bronzed areas.

The beauty of using pheromone traps is that at best they are only attractive to the target pest and at the worse only a few other closely related insects. It is still too early for much but redbanded leafrollers (RBLR). There have been 76 RBLR caught since the trap was put out on March 11. If you are having problems identifying moths in your traps, check the digital images at a Michigan State University Extension online site at http://www.msue.edu/vanburen/generali.htm (FH)

Nashville (Davidson County) Pheromone Trap Catches for 2005

* Biofix for RBLR in Davidson County estimated as occurring on March 12.

8. Insecticides: Green Tip to 1/2 Inch Green Sprays on Apples

Use a superior-type or highly refined summer oil applied dilute for best results. The oil spray can be used alone or with an insecticide for control of scale, European red mite and rosy apple aphid eggs on apple. If the oil application is delayed until tight cluster to pink, use a refined oil or reduce a superior type to 1/2 to 1 gal/100 gal. Do not use captan within 2 weeks of an oil application because it could cause phytotoxicity. (FH)

9. Oriental Fruit Moth (OFM) on Apple

OFM traps should be put out now because the moths emerge and mate prior to apple bloom. The eggs begin to hatch around petal fall. Mating disruption utilizes larger amounts of pheromone to saturate the orchard with pheromone to prevent egg laying and the subsequent laying of fertile eggs. This can reduce populations below economically damaging levels. While mating disruption of OFM can be initiated now using products such as Isomate Rosso at a rate of 100 dispensers/acre, growers that plan on spraying for plum curculio at petal fall will also control first generation OFM. These growers should thus delay the use of Isomate Rosso until May to target the second generation OFM. (FH)

10. Oriental Fruit Moth (OFM) Mating Disruption on Peaches, Nectarines and Plums

Mating disruption for OFM is effective only in blocks in excess of 5 acres with low populations. A one-year transition from insecticide only to a combination of insecticide and mating disruption may be required in situations with moderate to high OFM pressure. In such cases, accurately time insecticide sprays for OFM larval populations in April and May. Then, before moth flight begins in mid- to late May, place in the upper third of trees 100 Isomate-M100 dispensers/acre for 90 days of control. A second application of Isomate-M100 may be needed in early August. Monitor for fruit damage, especially around the edges of orchards where migrant females may lay fertile eggs. Spray areas where you find damage. (FH)

11. Thrips on Peaches and Nectarines

Thrips can be damaging to nectarines but are seldom damaging to peaches. They cause a rough tan to brown callusing of the skin from feeding at bloom. Thrips sprays are suggested for nectarines at pink and petal fall. Consider treating peaches for thrips at pink if thrips are extremely abundant with SpinTor 2SC or Carzol 92SP. Note that Carzol is highly toxic to bees. Also, do not use Carzol after petal fall. (FH)

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 Unversity 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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