Fruit Pest News

Volume 8, No. 22  September 26, 2007

An online newsletter whose goal is to provide all interested persons with timely information on diseases and insects of commercial fruit and vegetable crops 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.

This is the last issue of Fruit Pest News for 2007. The next issue will be posted at this web site in mid-March, 2008.

This issue of Fruit Pest News contains a subject index for all issues to date for this year. The opening page of the Fruit Pest News web site contains a list of all of the issues. You can connect to the issue of interest there.

We want to take this opportunity to thank you for your readership. Suggestions for topics to address are very welcome. We're grateful for the insect trap counts that some of you have been sending us. We would like to hear when you see a disease or insect for the first time for the year, or if you are experiencing a severe outbreak. The weekly format of this newsletter is designed for reporting such time-sensitive news. Try to phone or e-mail us your news. Of course, all reports are kept anonymous (unless you want us to use your name!). (SB)

In This Issue:

    1. Fruit Pest News Subject Index, 3/14/07-9/26/07

    2. Fall Vegetable Insect Pests

    3. Reduce Apple Scab with Fall Urea Sprays

    4. Peach Leaf Curl and Plum Pockets

    5. Nematode Samples

    6. Orange Rust Sprays in Fall

    7. Cobalt Insecticide Registration

    8. Pheromone Trap Catches

 Fruit Pest News Index, 3/14/07 through 9/26/07

2. Fall Vegetable Insect Pests

There is a whole complex of caterpillar pests of cole crops including imported cabbageworm, cross-striped webworm, cabbage webworm, garden webworm, diamondback moth caterpillar, and cabbage looper. The imported cabbageworm is a green caterpillar with short, dense hairs that give it a velvety appearance. It also has a light yellow stripe down the back and is sluggish if prodded. It can grow to 1.25 inches and the adult is not a moth but a white, day flying butterfly. The diamondback moth larva is much smaller (1/3 inch long full grown) green caterpillar that is tapered at both ends. It will wiggle vigorously if prodded. While these two caterpillars can be found throughout the season, the cabbage looper larva tends to be found more late in the season. The cabbage looper is 1.5 inches full grown and attacks most leaf crops. This looper only has three pair of fleshy prolegs while the imported cabbageworm and diamondback moth larva both have five pair. Feeding by these caterpillars can cause holes in leaves, cabbage heads, or florets of broccoli and cauliflower. Lots of messy, wet frass (excrement) is often seen with their feeding.

Fall armyworm, beet armyworm and corn earworm can also be late season pests of leaf crops. Beet armyworms spend the winter in the Gulf coast states and can not overwinter in Tennessee. They are slow to move into the state and are mainly a fall pest. The beet armyworm moths can lay their eggs on pigweed and other plants. The resulting larvae can then move from the weeds to susceptible crops. Besides their feeding damage, caterpillars and other insects can be a big problem in processing vegetables if they are harvested with the crop. Insecticides with a relatively short preharvest interval such as SpinTor (1 day), Avaunt (3 days), Asana XL (3 days), Ambush and Pounce (1 day), Lannate (1 day), Mustang Max (1 day), Warrior (1 day), Proaxis (1 day), and Intrepid (1 day) for cole crops are useful in keeping these crops clean prior to harvest. The pyrethroids (Mustang Max, Warrior, Proaxis, Ambush, Pounce, Asana XL) have activity against many types of insects and thus are a particularly good choice for quickly knocking down a variety of pests prior to harvest.

Continue to scout crops each week for insect pests. Keep on the lookout for stink bugs and corn earworms on tomatoes, European corn borer and beet armyworm on pepper, crucifer flea beetles on cole crop transplants, European corn borer, corn earworm, and fall armyworm on sweet corn, and rind feeding by cucumber beetles on maturing pumpkins. (FH)

3. Reduce Apple Scab with Fall Urea Spray

Apple scab inoculum can be reduced by applying urea in the fall. This treatment works by inhibiting the development of scab fruiting bodies in the fallen leaves and by hastening the decomposition of the leaves. Apply 5 pounds of low-biuret urea per 100 gallons of water when about 75% of the leaves have fallen. If you apply too early, too much of the nitrogen moves out of the leaves into the tree and the scab suppression effect is reduced. Fallen leaves can also be shredded with a flail mower. As with urea, this practice has also been shown experimentally to reduce scab inoculum the following spring. Escaped leaves can also be mowed in the spring. (SB)

4. Peach Leaf Curl and Plum Pockets

Peach leaf curl is a disease of peaches and nectarines that must be controlled during the dormant season. Shortly after leaf drop in the fall is a good time for the fungicide application. Infections can take place any time after the buds begin to open, so you may get some unexpected infections if you wait until late in the dormant season to spray. Leaf bud scales can begin to separate during warm periods of the dormant season. A single preventive spray applied before infection occurs will provide good control of leaf curl. However, if the disease was severe, consider using two sprays -- one in the fall and a second in early spring prior to bud swell.

The most effective material for peach leaf curl prevention is ferbam. This product is limited in distribution, so you may have to use an alternative product. Copper, chlorothalonil, ziram, and thiram are labeled for this use and are moderately effective. If you choose to make your leaf curl application at the delayed dormant stage, copper provides the advantage of bacterial spot control at that time. Applied in the fall, the bacterial spot control effect of copper would not be expressed.

Plum pockets is a disease of plums caused by a fungus related to the peach leaf curl fungus. Where plum pockets is a problem, apply chlorothalonil or copper as described for peach leaf curl. As with leaf curl, there is no control once the disease shows up during the growing season. (SB)

5. Nematode Samples

For those of you who conduct soil sampling for nematode testing, fall is the time of year to do it. The reason is that your chances of detecting damaging types of nematodes are best after they have had a growing season to build up (although, your chances would be even better if there were some soil moisture). To further improve your recovery of damaging types, take your cores from the plant root zone. I.e., take the sample from the rows of annual crops before scattering them by discing. Try to collect 15-20 cores per field in a bucket, then pulverize and mix them. This is a very important step, because the lab will not mix them for you. Place 1/2 to 1 pint in a plastic bag, label it, and keep it out of the sun.

Samples may be sent to A&L Labs in Memphis, for $26 per sample. The lab at Mississippi State University may also accommodate you, but it is recommended that you first contact the lab, at 662-325-2146. (SB)

6. Orange Rust Sprays in Fall

Orange rust is not quite the problem it used to be because of the prevalence of resistant blackberry varieties today. However, the popular variety Navaho and most black raspberry varieties are quite susceptible. There was not much spread this year because of the weather. However, if you have observed orange rust on your plants previously, some protective sprays of Nova, Cabrio, Pristine, or Abound may be in order. For home gardeners, fixed coppers may be helpful.

The systemic infections that cause this disease to be so troublesome take place in the fall as the temperatures decline. These infections are caused by teliospores and basidiospores. The sprays that are applied in the spring for orange rust are aimed at aeciospore (the orange spore) infections. While fully developed leaves are the most susceptible to aeciospore infections, it is the young leaves and buds near the ground that receive the systemic infections. Likely sites are young primocanes (new shoots) and buds on cane tips that are in the process of rooting. Thus, make sure your spray is reaching the lower parts of the plants.

Cultural controls, such as removing wild brambles from areas near the planting, and removing infected plants early in the season should be used to the greatest degree possible. Improving air circulation be controlling weeds, and using good pruning practices will decrease the duration of leaf wetness. (SB)

7. Cobalt Insecticide Registration

Cobalt Insecticide contains both an organophosphate insecticide (chlorpyrifos) and a pyrethroid insecticide (gamma-cyhalothrin) as active ingredients. This new Dow Agrosciences insecticide is labeled for use on a number of crops including alfalfa, Brussels sprouts, corn (field, sweet, and corn grown for seed), tree nuts, grain sorghum (milo), cotton, sunflower, and wheat. This broad-spectrum insecticide should provide fast knockdown with a relatively long residual. Note that the preharvest intervals, which vary by crop, tend to be fairly long. (FH)

8. Pheromone Trap Catches for 2007

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), diamondback moth (DBM), armyworm (AW), cabbage looper (CL)

* Biofix for RBLR in Davidson County was February 28.
** Biofix for OFM in Davidson County was March 26.
*** Biofix for GBM in Davidson County was April 10.
**** Biofix for OBLR in Davidson County was April 25.
^ Biofix for DBM in Davidson County was April 25.
+ Pheromone lure missing

Bradley County

Putnam County

*Biofix for RBLR in Putnam County estimated as March 2 (trap not out early enough).
**Biofix for OFM in Putnam County March 21.
***Waiting to verify biofix for CM, many unknown moths being caught in these traps that can easily be mistaken for CM.
**** Biofix for OBLR in Putnam County for OBLR was April 25.

Obion County

* Biofix for RBLR in Obion County estimated to be on March 2 (trap not out early enough).
** Biofix for OFM in Obion County on March 26.
*** Biofix for OBLR in Obion County on April 30.
**** Biofix for VLR in Obion County on April 30.

(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

Soil, Plant and Pest Center

5201 Marchant Drive

Nashville, TN 37211

Copyright 2007 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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