FARGO, N.D. -- The weekly crop and pest summary from North Dakota, published July 16 by the North Dakota State University Extension Service, has the following highlights:
- Grasshoppers are increasing in central and north-central North Dakota, with conditions favoring an "outbreak." Experts suggest producers do a net sweep with four, 180-degree sweeps equaling a square yard. Threshholds are different based on sampling nymphs adults, says Janet Knodel, NDSU extension entomologist. For example, the "threatening" numbers are 50 to 75 nymphs per square yard in field margins, or 60 to 90 nymphs in a field. It also is threatening with 21 to 40 adults per square yard in a margin or 8 to 14 in a field. Officials have requested Mustang Max is for a Section 24c before the end of July, but approval has not happened.
- Banded sunflower moths have shown up in high numbers in southern Manitoba, north of Walhalla, N.D. Monitor for moths and eggs when sunflowers are in R3 stage. Economic threshold has changed with high market values. When monitoring in the day, one banded moth per 100 plants is a "reasonable threshold given the high 2008 sunflower market prices." The egg count threshold in 2008 is about two to three eggs per six bracts. Chemical is applied in late bud (R4) to early bloom (R5.1). Spraying in early morning or late evening minimizes impact on pollinators. Common control mistakes: not scouting, waiting too long to spray, and perimeter spraying only and not scouting field interior.
- Winter wheat disease trials are ongoing at plots on the Randy Mair farm near Lisbon, N.D. Disease levels were relatively low July 9 but had doubled as of July 14 at late dough stage. Fungicides controlled scab levels by 83 percent leaf rust by 100 percent, and leaf spot diseases by 76 percent. Jagalene and Wesley varieties were most susceptible. Individual varieties such as Radiant, CDC Falcon and Expedition showed leaf rust and/or fungal leaf spotting. Radiant also showed some stem rust infection.
- Sunflower rust has been reported in Renville County, N.D., by crop consultant Mike Hutter and has been seen in other counties. Usually, the disease isn't seen until late July or early August. Rust often starts on the lower leaves and spreads upward. There is little fungicide data from early rust epidemics. Sam Markell, NDSU extension plant pathologist, advises being aggressive in controlling the disease, with weekly scouting. Headline and Quadris are labeled for rust control. If severity on lower leaves is 3 percent to 5 percent or more average for all leaves and prolonged dew and relatively warm days are present, fungicide application may be warranted, and perhaps a follow-up. Preventative treatments probably should wait until early flowering so that upper leaves are protected for a prolonged period.
