Aphid Alert 2003, No. 11, August 29

Potato insect update for the Northern Great Plains, week ending August 29

Total aphid captures in Minnesota and North Dakota during the past week were little different from the week before. Only 5 green peach aphid were captured, 4 at Walhalla, ND and 1 at Williams, MN. Captures of bird cherry-oat aphids declined to 20, compared to 48 the week before. Turnip aphids were again the most abundant aphid, 317 captured. Captures of sunflower aphid (317) and soybean aphid (59) were double that of the week before, while captures of corn leaf aphid (247) were only half.

In Manitoba, total aphid captures were more than double that of the previous week. Twenty five green peach aphid were captured, compared to 12 the week before. Captures of potato aphid (29) also doubled. Buckthorn aphid continued to be the species most abundant in the Manitoba traps accounting for 92% of aphids identified. Bird cherry-oat aphid (68) declined only slightly from the week before (78).

The cartoon (below) shows cumulative capture of winged green peach aphid as mean number per trap (Minnesota and North Dakota data only) for the years 1992-1994, and from 1998 to the present. The gold line represents cumulative mean captures per trap to date for 2003. In the years we have operated the Aphid Alert trapping network, there were two with exceptionally high green peach abundance (1998 and 1999) and two with very few green peach aphids (1993 and 2001). It now appears certain that high green peach aphid numbers will not be exceptionally high in 2003. This year, there appears to be a greater risk of mosaic spread than of leafroll virus because of the abundant inoculum present in the crop and because the former can be spread by other aphids in addition to green peach aphid.

graph showing green peach aphid trap captures for the week ending August 27, 2003

Note that the data is plotted in this cartoon on a logarithmic scale.

Minnesota-North Dakota aphid data, week ending Aug. 27

table showing Minnesota and North Dakota aphid data for the week ending August 27, 2003

Manitoba aphid data, week ending Aug. 28

table showing Manitoba aphid data for the week ending August 28, 2003

Additional information on the aphid situation in Manitoba can also be found at www.gov.mb.ca/agriculture/crops/insects/index.html, and the Manitoba Agriculture and Food potato hotline at 1-800-428-6866.

Late Blight Situation

Report taken from the NDSU Bravo/Quadris Blightline for August 27th sponsored by Syngenta and the Quadris/Bravo Performance Pak.

During the past week Potato late blight was confirmed from a field in Walsh County, ND. Conditions for spread and development of late blight have not been favorable in most of the region, but the high humidity and resulting dew on the foliage can aid in the in-field spread and development of disease. The forecast for the coming week is for cooler temperatures and scattered thunderstorms, which would provide conditions favorable for late blight and increase chances of field-to-field spread. If these conditions occur, growers should scout fields for late blight and maintain an active fungicide program. Growers in northeastern North Dakota should continue protectant fungicide applications for the remainder of the season on a weekly schedule until the vines are completely dead. If disease pressure increases because late blight is present, or the weather becomes cool and wet, consider a five-day interval between spray applications. Late season infection by late blight can result in tuber infection and tuber decay in storage, so growers should consider fungicides that provide tuber blight protection such as Gavel or Omega, or applications of chlorothalonil plus tin to reduce late season inoculum. These fungicides should be applied as the final two or three sprays of the season for best tuber protection. Good vine kill of fields destined for storage will reduce the chance of late blight tuber infection and subsequent problems in storage.

Potato late blight status reports

 

Guide to the Field Identification of Wingless Aphids on Potato

(click here for a PDF of the Guide)

photo of a potato aphid photo of a buckthorn aphid photo of a foxglove aphid photo of a green peach aphid photo of a cotton aphid
Potato Aphid, Macrosiphum euphorbiae (Thomas) Buckthorn Aphid, Aphis nasturii (Kaltenbach) Foxglove Aphid, Aulacorthum solani (Kaltenbach) Green Peach Aphid, Myzus persicae (Sulzer) Cotton (=melon) aphid, Aphis gossypii (Kaltenbach)

Subscriber Alert

This is the eleventh issue of Aphid Alert for the 2003 growing season. This newsletter is intended to alert seed potato producers in the Northern Great Plains to flight activity by aphid species 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 will be updated as additional data becomes available. To become an e-mail subscriber to Aphid Alert 2003, send us an e-mail message with the word "subscribe" in subject line. Note that current subscribers need not resubscribe. If you have no interest in receiving this newsletter by e-mail, please reply with the word "unsubscribe" in the subject line.