Aphid Alert 2001, No. 1, June 20

Subscriber Alert

This is the first issue of Aphid Alert 2001. This newsletter is intended to alert Minnesota and North Dakota seed potato producers to flight activity by aphid species that are known to be potential vectors of potato viruses. The trapping network has resumed operation and we will soon be reporting results weekly on the WWW, by e-mail to subscribers, and by surface mail to all Minnesota and North Dakota seed potato growers. 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 wish to receive messages containing graphics, if so reply with the the words "no graphics" in the subject line.

Background

The 1998-2001 Aphid Alert project has much in common with a 1992-1994 research project of the same name. During that time, our focus was on vectors of PVY. In the mid 1980s, Minnesota and North Dakota experienced a persistent PVY epidemic that grew increasing severe each year, until ended in 1992 by the almost complete absence of potential PVY vectors throughout the region. Data from 1991-1994, provide useful baselines we can compare with present vector abundance and phenologies to identify possible differences in that may account for present severe problems with both PVY and PLRV.

Figure: The proportion of Minnesota seed potato acreage rejected for certification because of excess prevalence of virus infection increased from 6% in 1993 to 57% in 1998 and 1999. In 2000, the situation was marginally better with 46% of acreage rejected.

graph showing the proportion of rejected seed potato acreage from 1993-2000

Figure: The recent crisis in the Minnesota seed industry has been caused by both PLRV and PVY. Decrease in PLRV in 2000 compared to 1998 and 1999 is presumed to reflect the reduced abundance of green peach aphid in 2000. Both PLRV and PVY remained high probably reflecting the large amount of virus inoculum that must yet be flushed from the potato production system.

table showing potato seed lot rejections from 1998-2001

Figure: Trap locations in Aphid Alert network in 2000.

graphical map illustrating trap locations in the Aphid Alert Network in 2001

Figure: In 1998 and 1999, green peach aphid, the most important vector of PLRV, was much more abundant than it had been in 1992-1994. This increase may be related to the great expansion of canola acreage that has occurred in the region since the earlier study. Canola can produce large populations of green peach aphid that take wing in mid-summer as the canola matures.

graph of green peach aphids captured per trap from 1992-1994 and 1998-2000

Figure: PVY can be transmitted by many different aphid species. Some of these vectors are very inefficient compared to green peach aphid, but often they are much more abundant. The complex of aphid species associated with small grains were implicated as important PVY vectors in 1992-1994.

graph showing PVY vectors other than the green peach aphid, from 1992-1994 and 1998-2000