Tar Spot Of Corn Confirmed In NE Missouri

Sep 05, 2022

By Linda Geist

University of Missouri’s Plant Diagnostic Clinic confirmed tar spot in three corn samples collected in the northeastern Missouri counties of Lewis and Holt on Aug. 30, according to Peng Tian, the clinic’s lab director.

Tar spot of corn is an emerging disease threat. In 2018, yield losses of 20-60 bushels per acre were reported during a severe outbreak in Indiana, says Mandy Bish, coordinator of the MU Integrated Pest Management program. Corn leaves can senesce prematurely when infected during critical grain fill stages.

Tar spot appears as circular or oval raised black dots (stromata) on both sides of leaves. A brown or tan halo may surround the spots, which can also appear on the sheaths and husks. Tar spot can appear on brown and green tissue, alone or in numbers.

“Insect frass, Physoderma brown spot and black micronutrient foliar fertilizers may be mistaken for tar spot,” says Bish. “Insect frass and foliar treatments can typically be scraped off the leaf surface with a fingernail. Physoderma brown spot has many small, brownish lesions on the leaf and dark lesions that are restricted to the midrib. Tar spot lesions will not be restricted to the midrib.”

Tar spot can also be confused with southern corn rust. Unlike the pustules of southern corn rust or common rust, the stromata of tar spot do not break through the leaf’s surface.

The fungal pathogen can infect multiple times in a single season. It overwinters on soil surface residues and spreads by wind and heavy rain. Prolonged periods of leaf wetness favor infection.

In 2019, the Plant Diagnostic Clinic confirmed tar spot in nine northeastern Missouri counties. Tar spot has spread through the Midwest, including Iowa, Illinois, Wisconsin, Ohio and Michigan.

This is the first confirmation of tar spot in Holt County. MU Extension agronomist Wayne Flanary has followed up on multiple reports from Holt County. “Tar spot is a new pest to this region of the state and obviously a concern for our producers,” he says.

If you suspect tar spot, submit samples to the diagnostic clinic for confirmation. Visit plantclinic.missouri.edu(opens in new window) for instructions on submitting samples. You also may take photos of your plants and send them to plantclinic@missouri.edu(opens in new window).

Photos available:

https://extension.missouri.edu/media/wysiwyg/Extensiondata/NewsAdmin/Photos/2020/20200810-TS-Fig3.jpg
Stromata of tar spot covering a leaf with both green tissue and brown senescing tissue. Multiple diseases can occur with tar spot. These black raised dots are the stromata of the tar spot pathogen, which overwinters on residues at the soil surface. File photo by K. Wise.

https://extension.missouri.edu/media/wysiwyg/Extensiondata/NewsAdmin/Photos/2020/20200810-TS-Fig4.jpg
A single stroma of the tar spot pathogen on a brown senescing leaf. At low levels, tar spot can be difficult to detect, as it is only a single spot on a single leaf. File photo by K. Bissonnette.

Source : missouri.edu

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Agricultural Market Update: Grain Prices, Crop Conditions, and Weather Impacts

Welcome back to our channel where we provide comprehensive updates on the latest trends and changes in the agricultural sector. This week, we're looking at significant movements in grain prices, crop conditions, and the effects of weather patterns. Let's dive into the details:

Grain Price Decline Grain prices have fallen to their lowest levels since 2020, with December corn down 4.3% and November soybeans losing 3.1%. This decline is partly due to the beneficial moisture brought by Hurricane Beryl to the Midwest, which has improved crop conditions significantly. The USDA reported that corn and soybean crops are in their best condition in four years, contributing to the downward pressure on prices.

Record Short Positions and Market Sentiment Fund traders have increased their net short positions in the corn market to a record level, with a net short of 347,000 contracts of corn. This reflects a bearish sentiment in the market, further influencing grain price dynamics. Similar selling trends were observed in soybeans and SRW wheat, indicating broad market caution.

Weather Impact and Forecast Hurricane Beryl has brought significant rainfall across Arkansas, Missouri, western Tennessee, western Kentucky, and southern Illinois, with more expected over Missouri, Illinois, and Indiana in the coming days. Despite this, the market is currently more focused on the moisture benefits rather than potential heat risks forecasted in the 6-10 and 8-14 day periods.

US Crop Conditions Corn and soybean conditions have shown slight improvements last week, with corn rated 68% good to excellent and soybeans at 68%. These are among the best ratings for this time of year since 2020, suggesting robust crop health that could continue to influence grain prices.

Winter Wheat Harvest and Spring Wheat Conditions The US winter wheat harvest is progressing well, ahead of schedule with significant portions already harvested in Kansas and Texas. Spring wheat conditions are also favorable, with 75% rated good to excellent, although there have been some declines in states like Idaho, South Dakota, and Washington. Brazil's Corn Harvest and US Exports Brazil's second corn crop harvest is advancing rapidly due to favorable hot and dry conditions, with 63% of the crop already harvested. Meanwhile, US corn shipments saw a substantial increase last week, indicating strong export demand, which contrasts with the recent drop in domestic grain prices.

Ongoing Developments Lastly, the USDA reported a flash sale of corn, with significant quantities sold to unknown destinations, scheduled for delivery over the next two marketing years. This could signal ongoing international demand for US corn despite lower prices.

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