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

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.
 

Twenty seven seed potato fields volunteered by Minnesota and North Dakota growers were used in this research. Each of the 27 potato fields was sampled for aphids in the first 18 meters at either end and in the field interior (24 hours prior to treatment, 72 hours post-treatment and 7-days post-treatment). A single aerial application of Monitor 4 was applied in an 18 m spray swath at each end of the field (where the crop and headland interface was most obvious and where we expected to find most green peach aphids). Each border area was sampled by selecting one leaf from 30 randomly selected plants in the 18 m border area for 60 leaves total. The field interior, defined as the area beginning at least 30 m from the field edges, was sampled by selecting one leaf from 40 randomly selected plants throughout the interior area. Aphid species, numbers and forms (winged or wingless) were recorded for all samples.

Pretreatment samples of green peach aphid in 27 seed potato fields indicate that of the 1,432 green peach aphids recorded, 91% were encountered in the border area (Figure 1).  Samples collected 72 hours post-treatment found 265 green peach aphid in the border area and 111 in the interior of the field (Figure 1). Samples collected from 24 fields 7 days after application detected 475 green peach aphids in the border areas and 406 in the field interior (Figure 1). 

Our results indicate that for at least the first application of Monitor 4, a border application would effectively control colonizing green peach aphids in seed potato fields and would benefit the grower through reduced application costs.

A fifth consecutive week of hot, dry weather has produced abnormally dry soils and stressed nonirrigated crops throughout the Northern Great Plains.  While such conditions might seem unfavorable for development of Potato Late Blight, new infections were reported last week in Pembina County, North Dakota.  There were no new reports of Late Blight in Manitoba this week.  Thus far, Minnesota and Wisconsin have escaped without any reported Late Blight this year.  Wisconsin's Walt Stevenson notes that “If this holds true for the remainder of the season, 2003 will be the first year in the last decade with no late blight.”  Still the advice of Philip Northover to Manitoba growers bears repeating here. “Scouting for Late Blight should be continued. If Late Blight is found, plants should be destroyed immediately to prevent damage to the rest of the field. If fields with late blight are near yield and quality objectives, consider top-killing immediately.”  And again from Walt Stevenson, “As we enter the last month of canopy maintenance, growers should continue protective fungicide programs that will also manage early blight.  Weather conditions can change rapidly so stay alert to changing conditions."
 

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