Fruit Pest News

Volume 4, No. 6   April 21, 2003

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. Captan Label Changes

    3. Peach: Flint Labeled for Scab Control

    4. Grape: Designing an Early-Season Spray Program

    5. Tree Fruit: Oriental Fruit Moth

    6. Tree Fruit: Pheromone Trap Catches and Biofixes

1. Current Conditions

A very warm week has been interrupted by cooler weather, a welcome turn as strawberry harvest begins.  The warm weather allowed some fire blight infections to occur in apples, although none have been reported yet. The MaryBlyt program operated at the PPDC in Nashville indicates that infections took place on April 7, 17, and 18. Whether your trees experienced infection depends on your specific environmental conditions. Blackberries are beginning to bloom. Blackberry growers should see the article below, "Captan Label Changes," for good news on a new fungicide for this crop. Peach growth stages are shuck-off to first cover. Some apple varieties are at petal fall. The cool weather should last for a few more days, with showers Thursday and Friday. (SB)

2. Captan Label Changes

Several long-awaited changes have been made on the Captan 80WDG label.  These changes have not yet been made to other formulations of captan (Captan 50W, Captan 80W, Captec 4L). However, the changes to these other formulations are in the registration process and should be available soon.

Blackberries, raspberries, and dewberries have been added to the Captan 80WDG label. There was a void in anthracnose control on these crops in the absence of Benlate, and the registration of Captan should enhance our control efforts. Botrytis fruit rot and spur blight are also on the label. Captan should also help with cane blight control. Captan 80WDG is labeled at 2½ pounds per acre and has a 3-day preharvest interval. The label allows repeat applications at 10- to 14-day intervals, with a seasonal maximum of 12½ lb per acre. For blackberry anthracnose control, I have obtained the best results when using Benlate by making the first application at early bloom and making two additional applications at two-week intervals.

The lengthy restricted-entry interval (REI) was a hindrance to the use of captan in fruit crops, especially during harvest. The REI was 4 days (96 hr) for apples, stone fruit, blueberries, and grapes. For strawberries, the REI was 24 hr. On the new Captan 80WDG label, the REI is 24 hr for apples, stone fruit, and strawberries. For blueberries, grapes, and brambles, the REI is 72 hr. (SB)

3. Flint Labeled for Peach Scab Control

Peach scab pressure is greatest from shuck split through 2nd or 3rd cover because scab spore counts are high during this time and the cool, wet weather that occurs during this time favors infection. Flint fungicide was recently labeled for use on stone fruit. One of its target diseases is peach scab, for which Flint is very efficacious. The label provides for a rate of 2.0 to 4.0 ounces per acre, with a limit of 4 applications per season. A rate of 2 to 3 oz per acre is probably sufficient for most orchards. The 4 oz rate would only be needed when severe scab pressure is expected (e.g., a severe case the previous year and favorable weather).

The Flint label for stone fruits does not include a statement prohibiting consecutive applications, as it does for most crops. However, it would be prudent to rotate Flint with a non-strobilurin fungicide that has scab activity, such as captan or sulfur. The idea behind rotation is to discourage fungal resistance to reistance-prone fungicides, such as the strobilurins. Flint and Abound are labeled strobilurin fungicides for stone fruit. (SB)

4. Designing an Early-Season Fungicide Spray Program for Grapes

Choose a fungicide(s) based on the history of disease problems in the vineyard, using an efficacy table such as the one on page 17 in the small fruit spray guide, PB1197.  Sterol inhibitor fungicides can be used in the early sprays, but keep in mind that they do not provide control of Phomopsis or downy mildew. The multi-site inhibitors (e.g. captan, mancozeb, maneb, ziram) are better choices for control of Phomopsis, and they also control black rot. The sterol inhibitors (Nova, Elite, or Bayleton) can be tank mixed with the multi-site inhibitors to provide control of powdery mildew and systemic control of black rot. Strobilurins (Abound, Flint, Sovran) have the broadest spectrum of activity, but are more expensive and are limited to 4 applications per year.

Mancozeb and maneb would provide maximum control of black rot if sprays could always be applied as planned. As we all know, however, the weather often prevents that from happening. A rainy period that occurs some time after your last application (e.g. 7 days or later), may allow black rot infections to occur. In that case, a black rot fungicide with good curative activity should be applied as soon as possible. The sterol inhibitors would be good choices. Remember to tank mix them with Phomopsis materials. The strobilurins have some curative activity, but should be used primarily as protectants.

For varieties very susceptible to powdery mildew, a fungicide for powdery mildew control may be needed in the early sprays. The sterol inhibitors and strobilurins are good for this purpose, but many will need assistance from tank mix fungicides for control of Phomopsis and black rot.

Considering the arsenal of fungicides available to the grape grower, it is a good idea to become familiar with the classification of the products, as listed on page 48 of the spray guide. (SB)

5. Oriental Fruit Moth

Oriental fruit moth (OFM) are a damaging pest that looks very similar to the codling moth larv. The mature larva of the OFM has an anal comb found on the last abdominal segment above the anus. The codling moth larva does not have the anal comb. It takes a good hand lens to see this structure. In peach, first generation OFM feed primarily on tender vegetative growth while the following generations feed in the fruit. The up and down spring temperatures cause erratic emergence and egg laying by the first generation.

Oriental fruit moths (OFM) are actively flying now. In Nashville, the biofix (first sustained catch of 2 or more male moths) was April 4. Start accumulating daily degree days (DD) at base 45 degree F on the biofix date for your peach orchard. Note that in addition to the base of 45 degrees F that there is also an upper limit of 90 degrees F. (any temperature above 90 such as 95 is counted as 90 when determining the daily DD). These cumulative degree days will help you time OFM sprays. For first generation OFM, first determine if you have a low-density OFM orchard or a moderate to high-density orchard. Low density orchards are those with less than 0.5 percent of the fruit damaged the previous year and pheromone trap catches do not exceed 10 moths/trap/week anytime before the accumulation of 500 DD after biofix. In low OFM-density orchards, a single application can be applied against OFM at 600 DD after biofix. In moderate to high-density OFM orchards, two insecticide applications are applied 14 days apart, the first at 500 DD after biofix. Refer to the 2003 Southeastern Peach, Nectarine and Plum Pest Management and Culture guide for the timing of subsequent OFM generations utilizing DD accumulations.

Mating disruption for OFM saturates the orchard with pheromone to prevent mating and subsequent laying of fertile eggs. This 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. Accurately time insecticide sprays targeted at 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/acre for OFM (gives 90 days control). A second application of Isomate M100 may be needed by early August. Monitor for fruit damage weekly, especially around the edge of orchards where migrant females (mated outside of pheromone saturated orchard) may lay fertile eggs. Apply insecticides to areas or blocks where you find damage.

Note the first catches of codling moth and tufted apple bud moth (TABM) in Bradley County in April. (FH)

6. Pheromone Trap Catches and Biofixes

Nashville (Davidson County) Pheromone Trap Catches for 2003

* Biofix for RBLR in Davidson County estimated as occurring on March 8

Bradley County Pheromone Trap Catches

*Biofix for redbanded leafroller in Bradley County estimated as occurring on March 8
**Biofix for codling moth in Bradley County was April 5 (2 caught)


Putnam County Pheromone Trap Catches

*Biofix for Putnam County estimated as occurring on March 8


Obion County Pheromone Trap Catches

*Biofix for RBLR occurred prior to trap placement, estimated as occurring on March 8
(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, 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