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Syngenta Receives Callisto Registration

June 8, 2001
Callisto 4SC (mesotrione) recently received a label for use in corn. The active ingredient belongs to the callistemone herbicide family and controls susceptible species by inhibiting the 4-HPPD (4-hydroxyphenylpyruvate dioxygenase) enzyme. This enzyme is essential in the biosynthesis of carotenoids, making this herbicide's mode of action a pigment inhibitor. Symptoms observed on susceptible species are bleached or whitened leaf tissue. Callisto may be used as a soil-applied or postemergence herbicide on field corn, production seed corn, and corn grown for silage. Soil-applied Callisto rates range between 6 and 7.7 fluid ounces per acre alone and may be tank-mixed with preemergence grass herbicides for grass control. Postemergence applications of Callisto should be made at 3 fluid ounces per acre and must always include a crop oil concentrate (do not use methylated seed oil) and a spray-grade nitrogen source (either 2.5% v/v of 28% UAN or 8.5 lb per 100 gal of AMS). Corn may be treated up to 30 inches tall or up to the 8-leaf stage. Callisto may be used more than once a year. However, do not make the second application of Callisto within 14 days of the first application. Do not apply more than 10.7 fluid ounces of Callisto per season per acre.

Callisto has good activity on a number of broadleaf weed species; however, it is not effective for the control of most grass weeds. Table 2 contains Callisto efficacy ratings on various broadleaf weed species taken from research trials conducted at the University of Illinois and other Midwest universities. Precautions that should be observed include the following: (1) do not apply Callisto postemergence if the crop was previously treated with Counter or Lorsban insecticide, as severe injury may occur; (2) do not make postemergence applications of Callisto in a tank mix with any organophosphate or carbamate insecticide, or any emulsifiable concentrate grass herbicide, or injury may occur; and (3) do not make a postemergence application of any organophosphate or carbamate insecticide within 7 days before or 7 days after a Callisto application, or severe injury can occur.--Christy Sprague and Aaron Hager

Author: Aaron Hager Christy Sprague

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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