NDSU Crop and Pest Report

Entomology


ISSUE 2  May 9, 2002

 

ARMY CUTWORM WAITING FOR WARM WEATHER IN SOUTHWEST ND

The first reports of Army cutworm concerns have come in from the southwest part of the state. No losses, but it should serve as a wake up call that damage is likely. Monitor newly seeded fields, as well as alfalfa, for activity. This cutworm overwinters as partially grown larvae and becomes active when soil temperatures reach 40 F. Army cutworm infestations in winter wheat were reported in mid-April from south central and southwestern South Dakota where these cutworms get started a little earlier.

With planting delays in the east due to cool, wet conditions, there arenít significant crop acres where the Dingy cutworms can cause harm. The dingy cutworm also overwinters as a partially grown larva and begins feeding with warming soils. Monitor stand emergence for this and other insect concerns in the next few weeks.

As in previous years, here is some reference information for cutworms, though we hope the need is limited.

Action Thresholds for Cutworms by Crop:
Canola 1 per square foot
Small Grain 4 to 5 cutworms per square foot
Corn 3 to 6% of plants cut and small larvae less than 3/4 inch present
Sugarbeets 4 to 5% of plants cut
Soybean/Drybean 1 or more larvae per three feet row or 20% of plants cut
Sunflower 1 per square foot ore 25 to 30% or plants cut
Forage 5 or more pre square foot

Insecticides labeled for treating the above crops for cutworm control include:

Canola ........ Capture
Wheat ......... Lorsban 4E-SG, Mustang, and Warrior.
Corn ........... permethrin (Ambush, Pounce), Asana, Lorsban, Mustang, Sevin, and Warrior.
Sugarbeets .. Asana, Lorsban, Mustang, and Sevin.
Soybean ...... Asana, Lorsban, Mustang, Pounce, Scout X-tra, Sevin and Warrior.
Dry Bean .... Asana, Mustang, Sevin, and Orthene.
Sunflower ... Asana, Baythroid, Lorsban, Sevin, and Warrior.
Alfalfa ........ permethrin (Ambush, Pounce), Baythroid, Lannate, Lorsban, Mustang, Sevin, and Warrior

The newest insecticide product available for cutworm control in the above crops is Mustang, a pyrethroid insecticide known as zeta-cypermethrin.

 

SOYBEAN APHID WATCH - 2001

You may recall that at the end of last year, it was reported that the Soybean aphid, Aphis glycines, had been found in the eastern counties of North Dakota. There will be a concerted effort to monitor for this new insect pest this spring. As progress develops, watch for news in the newsletter and other information sources. Information on the web is available through the NDSU Insect Updates page:

http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/index.htm

There are several web links that will be of interest. One is the 2002 Soybean Aphid Watch. Maps in the midwest will be updated by state representatives that will provide information on detection, population levels, and other comments as the season progresses. This effort is being coordinated by the North Central Pest Management Center and the North Central Integrated Pest Management Program.

Identification:

The soybean aphid is yellow-green with black cornicles ("tail-pipes") and a pale colored cauda (tail projection). As with other aphids, the soybean aphid is small, about the size of a pinhead. Nymphs would be smaller.

Soybean Aphid

The soybean aphid is the only aphid that will colonize soybean. Because there are no other aphid species that develop on soybean, it is safe to assume that if you see colonies of tiny, yellow aphids on soybean plants, it is Aphis glycines.

It is reported that this aphid feeds specifically on soybean (plants in the Genus Glycine). This aphid is not expected to colonize dry bean varieties (Phaseolus spp.). There are other aphids that may be found on dry beans, specifically the Bean aphid, Aphis fabae. This aphid is blue_black in color and has not been an economic problem in North Dakota.

 

FOREST TENT CATERPILLAR OUTBREAKS ANTICIPATED

(see article in Horticulture section)

 

Phillip Glogoza, Extension Entomologist
pglogoza@ndsuext.nodak.edu

 

WATCH FOR SEEDLING SUGARBEET INSECT PESTS IN THE SOIL

Slow sugarbeet germination and seedling development rates are consequence of the extended cool and wet conditions that are persisting throughout the Red River Valley this spring. These conditions can result in sugarbeet seedlings being vulnerable to attack by early-spring feeders such as wireworms, springtails, and white grubs.

Local white grub populations are not expected to be a major threat this year in most RRV sugarbeet fields because the majority will not be in the economically damaging stage until next season. However, wireworm infestations are reported in pockets throughout the Valley on an almost-annual basis. Also, larvae observed in a few eastern ND sugarbeet fields last year were very young, and could pose problems again during the 2002 season. Depending on the species, wireworms can spend 2 to 6 years in the larval stage before they develop into their adult stage, the "click beetle." Therefore, one cannot assume that risk has passed after experiencing wireworm problems in a given year. Springtails could also be problematic for sugarbeet producers this year due to extended cold and moist soil conditions. They pose the greatest threat in fields with heavy soils and high organic matter content.

Growers and agricultural professionals associated with sugarbeet production should carefully monitor fields for failure of plants to emerge and for wilted seedlings. Affected areas are typically in patches. It is fairly rare for entire fields to be taken out by these pests. Although other agronomic factors can result in similar symptoms, seedling soil insects could be causing the problem. Unfortunately, fields that did not receive a planting-time insecticide or seed treatment are particularly vulnerable to seedling insect pests, and rescue treatment are not effective. If an infestation is confirmed, prompt replanting and application of a registered soil insecticide or simply accepting the plant stand reduction are the only management options.

For more information regarding wireworms, consult extension circular no. E-188 (revised) entitled "Wireworm Management for North Dakota Field Crops." It is located on the web at:

http://www.ext.nodak.edu/extpubs/plantsci/pests/e188-1.htm

To learn more about springtails, see extension circular no. E-1205, "Springtails in Sugarbeet: Identification, Biology, and Management." It is also located on the web at:

http://www.ext.nodak.edu/extpubs/plantsci/rowcrops/e1205w.htm

Mark Boetel
NDSU Research & Extension Entomologist
mboetel@ndsuext.nodak.edu

 

WHAT MILD WINTERS MIGHT MEAN

Diamondback moths, an insect pest of crucifers, have been observed around outdoor lights in the city of Fargo since April 14. What makes this interesting is that these were newly emerged individuals. This observation suggests that diamondback moth pupae successfully overwintered in the region. Normally, the diamondback moth populations are the result of spring migrating moths. Our extremely mild winter was probably a contributing factor to their survival. What is not known is how extensive this survival may have been around the canola production areas.

The bigger question would be how many other insects that donít normally overwinter here have made it through the winter ?

Dr. Gerald Fauske
NDSU Entomology Research Specialist
Gerald.Fauske@ndsu.nodak.edu


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