ISSUE 12 July 22, 2004
BLISTER BEETLES IN FLOWERING CANOLA
Reports from canola production areas of North Dakota and Manitoba indicate that blister beetles, particularly the black blister beetle, are noticeable in many fields. Populations are not at treatable levels, but their presence may be alarming when and if the populations congregate in the field as they often do.
Every year we expect to see some blister beetles in canola, as well as alfalfa. Typically, we see the Nuttall blister beetle in canola. This is the bright metallic, purple to green to blue beetle that often is sighted. However, reports indicate the most common species observed is the black blister beetle. The larvae of this species eats grasshopper eggs, and its populations tend to increase in times when grasshopper populations are also increasing. Larvae of the Nutall blister beetle do not feed on grasshopper eggs, and are thought to live in the nests of ground-nesting bees, feeding on eggs, larvae, and stored food. Therefore, their populations have not increased or decreased in relation to grasshopper populations.
Nuttall Blister Beetle
(Photo courtesy the Canola Council of Canada)
WHEAT INSECT UPDATE: Wheat Midge, Armyworm, and Aphid
The degree day accumulations for wheat midge in the northern counties range from 1500+ in the central counties to 1400+ in the northen counties. This means we are at peak emergence of females in the north and almost complete emergence in the central areas. Reports indicate that midge can be observed in fields but the numbers are below treatment levels. It is strongly recommended that if fields are in the boot to early flowering, they should be scouted to determine whether midge levels are economic or not. Weather conditions, calm and balmy, are very favorable for midge.
There have been some questions about feeding damage observed in grain fields that sounds suspiciously like armyworm. Damage reports includ clipped awns, chewed kernels, and leaf feeding. These reports have been few, but range from eastern ND to central Manitoba. The storm patterns during the past weeks often transport the armyworm moths to the region. The late arrival though is nor likely to cause any significant problems. While walking fields, look in these areas to see if armyworms are present, particularly if you are seeing evidence of feeding that seems hard to explain. Armyworms tend to feed at night and hide under debris on the soil during the day. The easiest way to look for armyworms is to shake the vegetation and count the larvae on the ground or under the debris on the ground. Larvae like to hide under debris or even clumps of soil during the day, so look under these for evidence of larvae as well.
Aphid numbers continue to be low. Some recent scouting reports from the NDSU IPM crop survey found some fields with a higher incidence of infested stems, but generally the fields have still been well below 25% of the stems with aphids present. It takes an infestation of 85% infested stems prior to heading to justify treatment in our region.
Sunflower beetle has been about the only insect present, and generally at low numbers. Some adults, numerous eggs, and low levels of larvae can be found in most fields. Larval infestations reported in the NDSU crop survey have mostly been in the 1 to 5 larvae per plant range. We need 12 to 15 larvae per plant for treatments to be warranted.
There were some earlier reports regarding Spotted stem weevil, but treatment decisions were largely being made on infestations that were observed last year. Treatments in Emmons and McIntosh counties were based on stalk lodging last year, particularly areas where stalk infestations were in the 75+% range.
Banded moth have typically begun to emerge by this time. Check field margins for the presence of these moths as they congregate in these areas to mate before moving into sunflower fields. A current NDSU research project on banded moth reports having found eggs of this insect already being laid on bracts of the developing buds.
Banded Sunflower Moth
CORN BORER UPDATE
Emergence of the univoltine flight is underway throughout the eastern areas of the state. In southern counties, peak emergence has passed. A few reports from observers who have seen moths in fields, but reports of eggs or any larval feeding have not been heard. It is time to scout for eggs and larvae and see if there will be any treatable populations developing in the region.
SOYBEAN APHID UPDATE
A few scattered reports from the Red River Valley of people finding aphids . . . but still very small populations. The NDSU crop survey has not scouted any fields where aphids were found. The Minnesota crop survey did find last week three fields near Crookston with aphids, but again very low numbers.
The temperature outlook appears to be favorable for aphid reproduction the next week. However, there still is not a lot of aphids out there to grow this population quickly, and we do not have the populations to the south and east to produce large numbers of migrant aphids into the area.
Things continue to look favorable. The next two weeks will be the key. Continue to scout and reports of aphid populations and how they progress are welcome.