NDSU Crop and Pest Report

Entomology


ISSUE 13  July 24, 2003

SOYBEAN APHID ALERT!

Soybean aphid populations are increasing. There are reports of some initial treating of fields in the Fergus Falls to Lake Park, Minnesota areas. In eastern North Dakota, we continue to find colonies of aphids, still most often along shelterbelts or protected areas. But, colonies are increasing from the 4 to 5 of last week to double that number this week. Several northeastern counties have soybean aphids present in fields, also, but the NDSU IPM survey does not have those locations for the map at this deadline.

In addition, while inspecting fields and plots earlier this week, we were finding many winged soybean aphids sitting on plants near field and plot edges. Southern Minnesota soybeans have had many more soybean aphids than we’ve had and winged aphids are being produced there. No doubt, we are seeing the movement of those aphids into our area, much like our cereal aphids move through the region.

Soybean fields should be scouted. All soybean fields inspected are in the R1 to R2 growth stage. Closely monitor aphid situations through the R4 (pod set stage).

See Issue 11 for more details on soybean aphid management.

Soybean aphid map

Winged soybean aphid image
Winged soybean
aphid on leaf

 

APHID ALERT: Potato insect update for the Northern Great Plains, week ending July 18

(source: Edward B. Radcliffe, Department of Entomology, University of Minnesota)

Aphid flight activity throughout the Northern Great Plains continued to be light during the last week. Bird cherry_oat aphid captures declined from the previous week, but again this was the species most abundantly represented in our trap captures. Soybean aphid populations are building rapidly on soybean throughout Minnesota and the Red River Valley. This aphid can reach very high densities on soybean and has a great propensity to produce winged adults when crowded. Previous experience suggests that soybean aphid tends to be under represented in our trap captures. Soybean aphid does not colonize potato, but we have shown that it can acquire and transmit PVY. Buckthorn aphid continues to be commonly represented in the trap captures from Manitoba. In Minnesota and North Dakota, potato aphid was captured at most locations and is a common colonizer on potato throughout the region. Only one green peach aphid was captured during the past week.

Potato leafhopper continues to be the insect pest of greatest immediate concern to Northern Great Plains potato growers. Some growers have reported potato leafhopper pressure above the economic threshold even after the application of foliar insecticides.

Colorado potato beetle remains a control concern for some growers, particularly in more northerly locations. In southern and central Minnesota the first summer generation of larvae have finished feeding and most have entered the soil to pupate. The summer adults have not yet emerged. Results from the 2003 University of Minnesota insecticide efficacy trials targeting Colorado potato beetle can be found on the Aphid Alert Web site at:

http://ipmworld.umn.edu/alert.htm

Three experiments were conducted, 1) Systemic insecticides applied at planting or hilling, 2) Systemic insecticides applied at planting but with varying seed piece row spacing, 3) Foliar insecticides applied when late instar (3rd and 4th) larvae first appear.

 

BANDED SUNFLOWER MOTH VERY ACTIVE IN SOUTHEAST

Sorry that it seems there are so many warnings about major insect activity this week, but the numbers of Banded Moth being observed in Cass and Richland Counties are quite alarming. I suspect there are great numbers in other counties as well.

Observations around commercial fields and research plots spotted numerous banded moth resting on plants adjacent to the sunflower fields. The moths stage in these border areas to mate before moving into the field to lay eggs. Egg laying has begun, though, on bracts of plants in the mid to late bud stages.

Banded Sunflower image

The 2002 National Sunflower Association coordinated survey found banded sunflower moth damage generally distributed across the Dakotas. There was one particular area of heavier feeding damage in the southeast. Based on the survey information, all sunflower growers should be monitoring for moths at this time.

2002 Sunflower Survey map

Banded sunflower moths begin to emerge from the soil about mid-July and are present in the field until mid-August. Although some moths are in the sunflower field during the day, many rest in vegetation along field margins. At twilight, females move into the field to deposit eggs. Moths flutter from plant to plant but do not feed.

Moths lay eggs on the bracts of the sunflower heads in the late bud stage. Females oviposit more eggs on pre-bloom to bloom stage sunflower heads (R4-5) than on early bud (R2-3) or post-bloom (R6) sunflower heads. The majority of eggs are deposited on the outer whorl of bracts, and some eggs are laid on the underside of the sunflower head.

Newly emerged larvae are usually found on the bracts later moving to the disk flowers where they feed on pollen. Third and later instars tunnel through the disk flowers and feed on young developing seeds. As the seeds mature and harden, larvae chew into the seeds to feed. Each larva penetrates and consumes the contents of several seeds. The maximum density of larvae in the sunflower head occurs in mid-August. After feeding to maturity, larvae drop to the ground and spin cocoons in the soil where they pass the winter.

Banded sunflower moth larvae normally consume the entire kernel, whereas seed weevil larvae consumes only about one-third of the kernel. Also, the exit hole in the seed created by the banded sunflower moth is slightly larger than the one made by the seed weevil larva and is usually located on the top rather than on the side of the seed.

A treatment guideline of 1 moth per 2 plants when scouting at dusk or later has been used for a number of years.

INSECTICIDE

DOSAGE IN LB
AI/ACRE

PRODUCT
PER ACRE

Asana XL
RUP

0.03 - 0.05

5.8 - 9.6 fl oz

Baythroid
RUP

0.031 - 0.044

2.0 - 2.8 fl oz

Furadan 4F
RUP

0.5

1 pt

Lorsban 4E
RUP

0.5 - 0.75

1 - 1.5 pts

Scout X-TRA
RUP

0.014 - 0.0164

2 - 2.33 fl oz

Warrior
RUP

0.02 - 0.03

2.56 - 3.84 fl oz

Phillip Glogoza
Extension Entomologist
pglogoza@ndsuext.nodak.edu


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