Aphid Alert: Region-wide virus vector surveillance for
the Minnesota and North Dakota potato industry
Edward B. Radcliffe, radcl001@umn.edu
|
Aphid
Alert 2001, No. 10,
August 24
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:
Minnesota State Legislature,
Rapid Agricultural Response Initiative &
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
|
 |
Publication of
this issue of Aphid Alert 2001 was
delayed due to our webmaster attending the 6th International Aphid
Symposium in Rennes, France, 3-7 September, and our aphid identifier
developing pneumonia. Not much question who had the better time. However, we are both back
at work and expect to soon have Aphid Alert back on
schedule. |
| Aphid
captures, week ending August 24.
The week ending 24 August saw continued decline
in aphid flight activity. Again, no green peach aphid was captured in the
trapping network. Captures of aphid species that are potential PVY vectors
declined to 6.80 per trap compared to 11.23 the previous week. Across all
sampling dates, captures of potential virus PVY vectors in 2001 have been
only 1/3 of what they were in 2000. This difference is even more dramatic
when we consider green peach aphid flight activity. Green peach aphid
captures in 2001 are only 1/180 of what they were in 2000. This should
translate into fewer seed lot rejections for virus, especially PLRV this
winter.
Locations for which data were not available when this page was
created will be updated as results are received. One suction trap and two pan traps are operated at each
location, except at Crookston, Rosemount and Thief River Falls which have
more. Data are
reported as total aphid captures per three traps.
|
 |
Captures of green peach aphid per trap, 1992-1994,
1998-2000 (click on figure on left to view larger image).
Abundance of green peach aphid
has differed greatly from one year to the next. In the years
1992-1994 (green lines), captures of green peach aphid were
consistently low; in 1993 only 7 were captured all year. In 1998
and 1999 (red lines) , mean weekly captures were 6 times that of
1992-1994. In 2000 (yellow line), the mean weekly capture rate
was comparable to that of 1992 and 1994. Peak green peach aphid
flight activity occurs in early-mid August, about one week after peak
flight activity of other
potential PVY vectors.
|
|
 |
Comparison of captures of green
peach aphid per trap in 2000
and 2001.
We can now say that 2001
was a repeat of 1993, a year with essentially no green peach
aphid flight activity. The canola is mostly harvested and
never supported the large populations of green peach aphid or turnip
aphid that were common in 1998-2000.
|
|
 |
Captures of PVY vectors other
than green peach aphid per trap, 1992-1994,
1998-2000 (click on figure on left to view larger image).
Abundance
of potential PVY vectors other than green peach aphid have differed
greatly from year to year. Total captures in 1998 were 20 times that
of 1993, and 2-3.5 times that of other years. Species
predominance differed among the years but there were also differences
among locations. Combining data from all dates and trap locations, the
most abundant aphid in 1998 was the sunflower aphid complex, (70% of total captures). In 1999 the most
abundant species was the turnip aphid, (25% of total captures). In 2000 the corn leaf
aphid
comprised 35% of total trap captures.
|
|
 |
Comparison of captures of
potential PVY vectors (other than green peach aphid) per trap in 2000
and 2001.
Corn leaf aphid continues
to be the most abundant aphid in trap captures. We are capturing only small numbers of
bird-cherry oat aphid, English grain aphid, greenbug, and
sunflower aphid. We have captured very few turnip aphids.
|
|
|
|
|
|
|
|
|
|
LATE BLIGHT
SUMMARY
|
Minnesota & North
Dakota, Aug.
31: Congratulations to all producers for an almost late blight
free season. Only three small outbreaks were reported. Much of
the credit goes to all of you for following integrated late
blight management recommendations all season. Tuber infection
and storage problems due to late blight should be minimal, but
tuber infection could still be present, so continue late season
sprays and monitor the harvest
Wisconsin, Sept
3: The past two weeks has
seen a resumption of conditions favorable for late blight.
The total number of severity values rose considerably since
August 15 and with extensive dew each night, we see additional
severity values accumulating each day. In fields in
central WI where symptoms of late blight were detected in late
June, leaf and stem lesions remained dormant until the past two
weeks. Sporulation on some lesions has resumed and
secondary spread is being observed where fungicide coverage is
not adequate. Many fields have already been treated with
vine desiccant in preparation for harvest. Pockets of
green leaves and stems remain in many fields, so this is a
gentle reminder that late blight is still active and growers
need to continue fungicide spray programs as long as foliage and
vines remain green. Remember that even small pockets of
green foliage infected with late blight pose subsequent risks to
stored tubers. The last thing growers need is to inoculate
tubers at harvest by running the harvester through these pockets
of green vines that have become infected with the late blight
fungus late in the growing season. For those fields that
will not be vine killed for another two weeks, growers should be
especially careful in maintaining a tight fungicide program with
thorough coverage of stems and leaves.
|
|
| To
subscribe
or unsubscribe to Aphid Alert 2001
To become an e-mail subscriber send us an
e-mail message with the word "subscribe"
in subject line. We
have taken the liberty of adding many names to our e-mail subscriber
list. 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 want to receive
messages in HTML format; if so, reply with "TXT"
in the subject line..
|
|
Send comments or inquiries regarding this page to Ted Radcliffe.
Return to top of this page
Return to opening menu of Radcliffe's IPM World Textbook
The University of Minnesota is an equal opportunity educator and employer.
Last modified: Thursday, September 13, 2001
© Regents of the University of Minnesota, 2001
|
