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ISSUE 3  May 20, 1999


    The Environmental Protection Agency granted a section 18 to North Dakota for the application
of Folicur fungicide on sunflower to control sunflower rust. The use rate is 4 fl oz/A. A maximum of
2 applications is allowed; there should be a 14 day interval between applications. There is a 50 day
PHI; i.e. do not apply within 50 days of harvest. Do not apply directly to water or to areas where
surface water is present or to intertidal areas below the mean high-water mark.

    Sunflower rust was observed by crop consultants and area extension specialists primarily in the north
central portion of the state. Some fields were sprayed with Folicur last year (we had a section 18 last
year, too) while many others had rust present, but no action was needed. Warm weather this summer
in areas where rust was present in 1998 could result in an increase in rust severity in 1999.

    Research data indicates that rust infections from the bud stage to 27 days after initiation of flowering
have the greatest effect on yield. If rust severity averaged over the top four leaves reaches 3% prior to
the 27th day after initiation of flowering, it is likely that an application of Folicur will be economic. Ray
petal wilt occurs approximately 27 days after the initiation of flowering. In most years the crop is not
ready to harvest until approximately 50 days after ray petal wilt. Thus, it is not economic to apply after
ray petal wilt and this should also assure compliance with the PHI stated on the label.

    NDSU Extension Circular PP-998, Sunflower Rust, provides information on the biology of sunflower
rust. It also contains drawings depicting various rust severities.



    The Environmental Protection Agency granted a section 18 to North Dakota for the application
of Tilt fungicide on dry edible beans to control rust. The use rate is 4 fl oz/A. A maximum of 3
applications is allowed, with applications on a 14 day interval. The PHI is 28 days, i.e. do not apply
within 28 days of harvest.

    Rust has been a common problem in recent years and there is plenty of rust carryover to start
infections in 1999 if weather conditions favor rust. Nights with at least 8-10 hours of dew and
moderate temperatures favor rust.

    Small red and pink classes are generally susceptible to rust. Most older pinto varieties are
susceptible, but many of the newer pinto varieties are resistant to the most common races currently
present in North Dakota. Most navy varieties are resistant to the current races, as well. Cranberry,
black, and dark red kidney are resistant to current races. Some light red kidney varieties are resistant,
but others are susceptible. Information on common field reactions to rust are given in the back of
NDSU Extension Circular A-654, North Dakota Dry Bean Performance Testing, 1998.

    Once the lower pods of susceptible beans have fully formed beans (lower pods are striping in the
case of pinto beans), a fungicide is no longer needed. This stage corresponds closely to the PHI of
28 days that is on the section 18 label.

Art Lamey
Extension Plant Pathologist



    Early season tan spot was observed the last few days on spring wheat, by Greg Endres at
Carrington and by me at Fargo. The spring wheat was in the one to two leaf stage and planted into
wheat stubble. The disease will continue to develop with high humidities and saturated soils. Early
season fungicide use was discussed in the previous Crop and Pest Report issue.

    The USDA Cereal Rust Bulletin #3, May 10, 1999, said that wheat leaf rust in Texas and
Oklahoma is more severe than last year. Kansas State Plant Pathology Dept.’s Disease Alert,
dated May 10, 1999, said that the recent cool weather in Kansas has slowed progress of most
wheat leaf diseases, but rust may become more noticeable in the next 10 days. With our recent
rains, late seeding of some wheat crops will occur, increasing the risk of exposure of these later
maturing crops to high populations of leaf rust spores. In 1998, leaf rust was hard on certain
spring wheat varieties at Carrington and in the NE part of the state, varieties such as ACBarrie,
2375, Ingot, ACMajestic, and Lars. We will have to keep close track of leaf rust development
on the wheat crops to our south.

    The accepted scientific name of wheat leaf rust has recently been changed from Puccinia
f. sp. tritici to Puccinia triticina. Because of the rules of scientific taxonomy and
nomenclature, the P. recondita name should technically be reserved for leaf rust on rye. Most
current publications still have the name Puccinia recondita f. sp. tritici associated with wheat
leaf rust, until those publications are revised.

    Cereal Rust Bulletin #3 also reported that crown rust of oats was severe in plots of susceptible
cultivars but light in commercial fields in the southern US. The alternate host of oat crown rust,
the buckthorn, was showing some early stages of the aecial cups of crown rust in Brookings, SD,
in early May. Barley leaf and stem rust has been pretty minimal in southern plain states.



    Pest Management Specialists from Colorado, Wyoming, Nebraska, and Montana have
joined resources and recently published an Integrated Pest Management Guide for the High Plains
regions of Colorado, Western Nebraska, Wyoming and Montana. Much of the information within
could be useful to pest managers in the western half of North Dakota, as well. The cost of the
publication is $24, and it is available from the Univ. of Nebraska Panhandle Research and Extension
Center, 4502 Ave. I., Scottsbluff, NE 69361 (Phone 308-632-1230), or from the University of
Wyoming, Ag. Communications Resource Center, P.O. Box 3313, Laramie, WY 82071-3313
(Phone 307-766-2115). A free yearly update also is available.

    The Guide is in a loose-leaf format, with several hundred pages, and it covers primarily insect and
disease pests and management recommendations for the following: alfalfa, field corn, small grains,
dry beans, sunflower, sorghum, millet, safflower, amaranth, and canola insects, range/pasture,
sugarbeets, potato, cole crops, tomato, pepper, eggplant, onion, sweet corn, lettuce, carrot, spinach,
and cucurbit crops.

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Source: USDA Cereal Rust Bulletin No. 3

Marcia McMullen
Extension Plant Pathologist/IPM Coordinator



    The sugarbeets are starting to come up, and now is the time to be on the look out for root rot and
damping off diseases such as Pythium, Rhizoctonia, and Aphanomyces. There are two species of
Pythium that cause seedling disease in sugarbeets. P. ultimum is a fairly widespread organism causing
mainly preemerge damping off in sugarbeets. Infection is most likely to occur under conditions of high
soil moisture and at temperatures most favorable for germination. The other species of Pythium,
P. aphanidermatum, is more likely to infect under conditions of high soil moisture and warmer soils.

    Rhizoctonia solani is more likely to infect emerged seedlings. Infection usually begins below the
soil line and extends up the hypocotyl. There is often a distinct line between infected and healthy tissue.
Sugarbeets may continue to thrive with only light infections of R. solani, but under the proper conditions,
later season infections may occur.

    Aphanomyces cochlioides causes a disease called Black Rot on sugarbeets. Like Rhizoctonia,
Aphanomyces more often infects emerged seedlings causing a black lesion on the hypocotyl, The
most characteristic symptom of this disease is a narrow, sometimes shriveled, blackened taproot.
This root rot pathogen is capable of causing serious yield losses and is long lived in the soil.

    The NDSU Plant Diagnostic Lab will culturally confirm the presence of any of these root rot
pathogens on plants suspected of being infected. If you are interested in more information on these
seedling diseases of sugarbeets and many other issues related to sugarbeets, call the lab, or check
out the following websites:


    Samples coming into the Plant Diagnostic Lab this week include: Cytospora canker and winter
injury on spruce, salt injury on pine, Pythium root rot on sugarbeet, abiotic disorder on tomato,
canker on cottonwood, winterkill on alfalfa.

Cheryl Ruby
Plant Diagnostician

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