| SUMMARY OF OBSERVATIONS FOR WEEK ENDING 8 SEPTEMBER. Green peach aphids per trap averaged just 0.55
per trap during the week ending 8 September. Other aphids species which can vector
PVY averaged 8.00 per trap. Thus, aphid numbers are lower than last week, and
especially so for green peach aphid which was down 73%. Today, trap capture data is
reported for only 9 of the 14 stations in the network. Missing data will be added to
this WWW report as it becomes available and associated files will be updated accordingly.
PCR data for green peach aphids captured during the week ending 2 September is also
not yet available.
Last week, heavy rains were widespread. Some
locations where we have traps received 3 or more inches of rain. Not only was the
weather unfavorable for aphid flight, but some of the traps filled with water probably
resulting in some loss of aphids that had been captured. Given the prevalence of
late blight and the dire consequences of the wet weather, aphids probably were not the
most immediate concern of most potato growers. However, the aphid and virus
situation may be better than we earlier expected.
In early summer 1999, green peach numbers
were considerably higher than on the same dates last year, but for the past two weeks
numbers have been lower than last year. Over all dates, green peach aphid captures
per trap are 49.4% higher than in 1998. Captures of PVY vectors other than green
peach aphid are down 75.5% from 1998.
This summer, we have yet to detect our
first PLRV-positive green peach, whereas last year 59% of green peach aphids captured in
August 1998 were positive for PLRV. Our
PCR tests have also been negative for PVY. PVY. However, IC-PCR data for PVY may
less useful because PVY is non-persistent in the aphid, so non-detection only means that
that aphid was not infected when captured. The data for PLRV is greater biological
significance, because an aphid once infected with PLRV remains so for life.
Table 2. IC-PCR test results for week ending 30
August
Location |
End date for collection |
Number of green peach aphids tested |
Baker |
8/30 |
11 |
Cando |
8/30 |
2 |
Climax |
8/25 |
13 |
Gully |
9/02 |
61 |
Karlstad |
8/31 |
2 |
Rolette |
8/27 |
2 |
Walhalla |
8/27 |
14 |
Williams |
8/31 |
5 |
Total |
|
102 |
Our most abundant potential PVY vector in 1999 has been
turnip aphid, which reproduces on canola. A search of the literature has not
provided much information as to the importance of this aphid as a PVY vector. This
species is known to transmit PVY, but it appears that its efficiency as a vector is not
established.
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those of you interested in receiving updates about this research or any resulting
advisories sooner than this information can be delivered by mail or even before it is
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In the message, write "Aphid Alert subscribe." ERRORS: If you find errors, typographic or factual, we would appreciate having
them called to our attention so they can be corrected. Phone: Robert Suranyi (218)
773-3346 or Ted Radcliffe (612) 624-773 or send an e-mail to radcl001@umn.edu.
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