Aphid Alert: a research/outreach program providing region-wide virus vector surveillance
to
the Northern Great Plains potato industry
Aphid
Alert 2002, No. 9,
August 30
Published cooperatively by
the
Department of Entomology,
College of Agricultural, Food & Environmental
Sciences,
University of Minnesota, the
University of Minnesota Extension
Service,
and the State Seed Potato Programs of Minnesota and North Dakota
Project funding
provided by:
the Northern Plains Potato Growers Association,
the Minnesota State Legislature,
Rapid Agricultural Response Initiative
&
the
United States Department of Agriculture,
Cooperative State Research,
Education and Extension Service,
Integrated Pest Management Program, North Central Region
WWW address:
http://ipmworld.umn.edu/alert.htm
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Contents
Aphid
Situation in Week Ending August 30 |
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Aphid
Situation in Week Ending August 30
Aphid flight activity remained high across the Northern
Great Plains in the week ending August 30. Captures of green
peach aphid per trap were slightly higher than in the previous
week in Manitoba, but were down by a third in Minnesota and North
Dakota. This regional difference may reflect the earlier
maturing of green peach aphid host plants in more southern
locations. Turnip aphid continued to be the most abundant
aphid in Minnesota
and North Dakota traps, representing 55% of the week's captures,
but numbers were down from over 80% the week before. The decline of
turnip aphid is associated with the maturation and harvest of
canola. Bird cherry-oat aphid numbers remained high this
week even though much of the small grain acreage has been
harvested. Cumulative numbers of bird cherry-oat aphid
are higher than in any of the seven previous years of the Aphid Alert
network. The exceptional abundance of this aphid is of
particular concern because bird cherry-oat aphid is an efficient
vector of PVY and was implicated as a primary contributor to
previous PVY epidemics in the northern great plains. The
recent wet weather experienced in much of the northern great
plains has provided favorable conditions not only for late blight,
but also for fungal aphid pathogens. Mycoses (fungal
infection) appear to be prevalent in green peach aphid on potato
and colonizing populations are generally in decline. Potato
fields with green peach aphid infestations are now producing large
numbers of winged aphids. This greatly increases the risk of
virus being spread from production fields to seed potatoes.
Seed potato fields should be vine-killed as soon as economically
and practically feasible to minimize risk of virus spread.
If the crop must be permitted to grow, mineral oil sprays are the
most effective means of minimizing PVY spread. |
| Weather Conditions and
Late
Blight
Heavy rains blanketed much of northern great plains during the past week. Crops were damaged by water logged fields and even standing water in many locations in southern Manitoba, eastern North Dakota and northwestern Minnesota. Counties in northeastern North Dakota that had largely escaped damage from earlier storms were hit hard this time. Six or more inches of rain was not uncommon, and Park River, N.D., received 12. In addition to direct damage, the soggy fields provide highly favorable conditions for development of potato late blight. The past week brought the year's first report of late blight in northwestern Minnesota. Growers should continue fungicide applications and scout fields for the presence of late blight. Late season late blight and rain can cause serious tuber infection and decay in storage. It is important to continue fungicide application until vine kill to limit tuber infection. Data show that late season application of the fungicides Gavel and Omega provide the best protection from late blight tuber infection. Dead vines do not support late blight, but green vines and partially dead vines should continue to be sprayed with fungicide to protect against late blight. Potato late blight status reports |
| Subscriber
Alert This is the ninth issue of Aphid Alert 2002. This newsletter is intended to alert seed potato producers in the Northern Great Plains to flight activity by aphid species that are known to be potential vectors of potato viruses. We report results weekly on the WWW, by e-mail to subscribers, and by surface mail to all Minnesota and North Dakota seed potato growers. The hard copy and e-mail versions of Aphid Alert report aphid capture data available as of the date they are mailed. The WWW version is updated as additional data becomes available. To become an e-mail subscriber, send us an e-mail message with the word "subscribe" in subject line. If you have no interest in receiving this newsletter by e-mail, please reply with the word "unsubscribe" in the subject line. Some e-mail subscribers may not wish to receive messages containing graphics. If so, reply with the the words "no graphics" in the subject line. |
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Minnesota locations: mean aphid captures per
trap during the week ending August 30 |
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North Dakota locations: mean aphid captures per trap during the week ending August 30
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Manitoba locations: mean aphid captures per trap during week ending August 30 (see Manitoba Agriculture and Food Website)
Note: aphid species ID has yet to be completed for Glenboro and Kemnay. |
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Wisconsin, South Dakota and Nebraska locations: mean aphid captures per trap during the week ending August 30
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Figure: Trap locations in the Aphid Alert network in 2002
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Figure: Cumulative captures of green
peach aphid (per trap), 1992-1994, and 1998-2001. Three
distinctly different seasonal patterns of green peach aphid
abundance have been observed. In 1998 and 1999 green peach
aphid were abundant with total captures approximately an order of
magnitude greater (10X) than that of 1992, 1993 and 1994, and two
orders of magnitude greater (100X) than that of 1993 and 2001.
For the Minnesota and North Dakota seed potato industry, low
green peach aphid pressure in 1994 coincided with the end of a
multi-year PVY epidemic and the low green peach aphid pressure of
2001 coincided with the end of a multi-year epidemic of PLRV.
During the week ending August 30, green
peach aphid flight activity increased 80% over the previous
week, but overall, 2002 has been a year of only moderate green
peach aphid pressure.
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Figure: Cumulative captures of bird cherry-oat aphid (per trap), 1992-1994, and 1998-2001. This aphid comes off wheat and other cereals. The species is typically abundant in the Northern Great Plains. In our area, green peach aphid and bird cherry-oat aphid appear to be the two most important vectors of PVY. Lowest abundance of bird cherry-oat aphid during the years the Aphid Alert network has operated was in 1994, which, coupled with low green peach aphid pressure, coincided with the end of a multi-year epidemic of PVY. Bird cherry-oat aphid flight activity has been higher in 2002 than in previous years of the Aphid Alert network.
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Figure: Cumulative captures of bird cherry-oat aphid and green peach aphid (per trap), 1992-1994, and 1998-2001. These two aphids have been implicated as the primary vectors of PVY in the Northern Great Plains (see Aphid Alert 2002, no. 2). Other potential vectors of PVY, e.g., greenbug and turnip aphid are also abundant this year.
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Ted Radcliffe Last modified: Friday, August 30, 2002 © Regents of the University of Minnesota, 2002
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