2016 University of Minnesota Cooperative Black Cutworm Trapping Network Report #6

Week of April 23-April 29, 2016

This newsletter is also available in a print-friendly pdf format: 2016 Black Cutworm Network Issue 6

bcw2016_06mapa.pngLast week's weather systems brought additional black cutworms into the state. Fourteen trap locations reported moth captures from April 23-29, most occurring April 24-26.

Rock County trap had a significant capture of 22 moths from April 24-25. Because of rains, this area is behind in corn planting. This is the second significant flight of black cutworm moths that this trap has captured this spring.

Meeker County had 9 on the same date range.

A Brown county trap captured 6 moths on the 25-26.  

Otherwise low numbers of moths.

The weather system that brought rains into the southern part of the state, particularly on April 25th, brought moths as well. Pay close attention when scouting late-planted corn and sweet corn in, and around, those areas where heavy rainfall occurred on this date.

Leaf feeding from the earliest flights should be starting while any eggs produced from the later flights have not yet hatched (Table 1). Remember, small broadleaves like sugar beets can be cut by relatively small cutworms.

Date* of significant trap capture Trap Location Degree Days/Estimated Development Stage Projected date to corn cutting
28-Mar Swift Co. 190 DD/Leaf feeding 16-May
12-Apr Rock Co. 137 DD/Leaf feeding 21-May
19-Apr Murray Co. 61 DD/Egg 29-May
20-Apr Sibley Co. 67 DD/Egg 29-May
24-Apr Rock Co. 29 DD/Egg 31-May
24-Apr Meeker Co. 29 DD/Egg 1-Jun
*first date if two night significant flight
Table 1. Dates and locations of significant 2016 captures of black cutworm moths in 2015. The estimate of projected cutting date is based on accumulating 300 Degree Days (base 50ºF) after a significant capture. It uses 30-year historical temperature data for projecting future degree-days. Projections run with temperature data current to May 3, 2016. Source: https://mygeohub.org/groups/u2u/gdd.



Figure 2. Greatest cumulative two night black cutworm moth capture by county through April 29.

Figure 2 shows the counties where significant captures (eight or more moths over two consecutive nights) and lesser captures occurred. You will notice that most of the moth captures are in a band from the SW corner of Minnesota to the Northeast.

This echoes the spring rainfall pattern shown in figure 3. Those areas within the trapping network with less rainfall, SE MN for example, have captured moths but in lower numbers.  The Swift county capture in March is somewhat of an anomaly, being earlier than other captures. These moths probably arrived on March 26th and 27th. This system stretched into Kandiyohi County where we did not have any traps. I suspect moths dropped there as well. This map also roughly illustrates areas of SW and SC Minnesota with delayed planting.

Only six traps have had significant captures this spring. I would use flights in nearby counties for other counties with or without traps. I highlighted my perception of the areas of most concern for black cutworm damage.

We should be scouting all corn, whether or not you think you will have a cutworm problem. Look for leaf feeding initially including on emerged weeds. I have received several photos of cutworms this spring. It is important to know which cutworm you have when you are making a treatment decision. For example, dingy cutworms, while devastating to dicotyledonous crops by cutting below the cotyledon, rarely cut corn below the growing point.

Corn ground (2015 soybeans) that is worked and planted is a low risk from any later flights. It is now a race between corn and black cutworm development in planted fields. Unplanted fields may still seed additional flights and, of course, may have already been visited by egg-laying females. Cooperators may continue to monitor traps in areas with unplanted corn or sweet corn.

See scouting for black cutworms for more information.

bcw 2016 06

Figure 3 . Spring rainfall patterns. Source: http://water.weather.gov/precip/.