VegNet Vol. 15, No. 4. April 29, 2008
Ohio State University Extension Vegetable Crops
On the WEB at:  http://vegnet.osu.edu
If experiencing problems receiving this fax, Call 614-292-3857

In This Issue

1.Freeze Watch Tonight

2. Section 18 Emergency Exemption for Topsin M Use on Tomatoes andPeppers in Ohio Approved

3. Copper Applications and Oxidate

4. Sweet Corn Hybrid Tolerance Ratings to Accent and Callisto

Freeze Warning for Tonight, Wednesday Morning B. Precheur
Dewpoints in teens and dying winds will support good radiational cooling tonight especially with the surface high centered just southeast of our area. This location favors strong radiational cooling and enhanced with continued building of high pressure. Expect subfreezing temperatures for most of the north and central regions and possibly a good portion of parts of southern OH. Areas south of US 24 should be mostly a frost event. The freeze watch goes from late tonight through Wednesday morning. Strawberry and vegetable growers should be prepared for this event.

Section 18 Emergency Exemption for Topsin M Use on Tomatoes and 

Peppers in Ohio Approved by Sally Miller

A Section 18 Emergency Exemption for use of Topsin M WSB fungicide in Ohio for management of Sclerotinia white mold in tomatoes (also known as timber rot) and peppers has been approved by the U.S. Environmental Protection Agency.  The label may be downloaded from the OSU Extension Pesticide Education Program website (http:// pested.osu.edu/section18.htm).  You must have this label in your possession if you use Topsin M on peppers or tomatoes. This exemption is in effect from April 24 until November 1, 2008.

Topsin M WSB (United Phosphorus, Inc.) may be applied at a rate of 0.5 - 1.0 lb product/acre, with a maximum of four applications and 3.5 lbs product/acre/crop.  The product must be applied by ground application;  the pre-harvest interval (PHI) is 2 days.  Chemigation with this product is prohibited.  Topsin M may be applied on a 7-14 day schedule beginning when white mold/timber rot appears.  The worker re-entry interval (REI) is 12 hours.

White mold can be a problem in Ohio under cool, moist conditions. Peppers or tomatoes following soybeans, cabbage, or other crops in which significant white mold pressure was observed in the last 3-5 years should be scouted for white mold when environmental conditions are favorable.  Tomatoes or peppers in high tunnels are particularly vulnerable in some areas, especially in the spring and fall.

Copper Applications and Oxidate

Andy Wyenandt, Ph.D., Specialist in Vegetable Pathology and Michelle Infante-Casella, Gloucester County Agricultural Agent. From Plant and Pest Advisory, April 9, 2008. Rutgers Cooperative Extension

[Editors Note: Here is an very interesting article from The Garden State. Please note the information in the second paragraph which should shed some light on the many instances of foliar burning we see every summer.]

Heavy rain and winds can all cause injury to vegetable plantings. Some injury is quite noticeable, such as hail damage; however, other injury may go unnoticed. Cultural practices such as tying, staking, cultivation and pruning can also create entry ways for bacterial infections. Many growers may plan on applying copper fungicides in tank mixes. High temperatures increase the possibility of phytotoxicity when using copper-based fungicides. In order to avoid this problem, growers should watch the daytime temperatures closely and avoid spraying if temperatures remain high. Simple management strategies to help avoid bacterial problems include not working in fields when the foliage is wet. Additionally, if overhead irrigation is used, try to irrigate in the morning so foliage dries quickly. Remember that bacterial diseases thrive and spread when foliage remains wet for long periods of time.

Additionally, the product Oxidate is a management option for control of bacterial diseases, especially in tomatoes. However, remember that Oxidate has no residual activity and should be used accordingly. Take caution when using this product on any crop and make sure to read the label. According to the product MSDS Oxidate contains hydrogen dioxide (synonym for hydrogen peroxide) and peroxyacetic acid. The MSDS also states that the pH is 1.33 and that combinations of Oxidate with either bases or metals should be avoided due to reactivity issues and product instability. Mixtures of Oxidate and copper hydroxide may possibly produce soluble copper which is known to be phytotoxic.

Sweet Corn Hybrid Tolerance Ratings to Accent and Callisto

C. Boerboom and J. Bollman, University of Wisconsin-Madison in collaboration with R. Becker, University of Minnesota, R. Bellinder, Cornell University, D. Morishita, University of Idaho, E. Peachey, Oregon State University, and M. VanGessel, University of Delaware

The tolerance of these sweet corn hybrids to postemergence applications of Accent and Callisto was evaluated in field trials from 2005 to 2007 at multiple locations across the US. These tolerance ratings are based on early season visual ratings of injury. The ratings are provided as a guide to understand the risk of potential herbicide injury. Herbicide labels, herbicide companies, and seed companies may also make herbicide use recommendations that should be followed. Always read and follow the herbicide label and follow the label's precautions to reduce the risk of herbicide injury.

This publication is now available at the VegNet website. Click on the link below or go to the fist listing under Research Results: Sweet Corn Hybrid Tolerance Ratings to Accent and Callisto[PDF file]