ndsucpr_L_sm.jpg (11690 bytes)

ent_Logo_Lg.jpg (12173 bytes)


ISSUE 8  June 22, 2000

SUGARBEET ROOT MAGGOTS: What’s the rain doing to them, and is my insecticide
going to work?

    Extremely high sugarbeet root maggot (SBRM) fly activity has been recorded on NDSU sticky stakes in the Cavalier, St. Thomas, and Minto areas of the northern Red River Valley. Counts in those areas ranged from 132 to 320 flies per stake immediately prior to the anticipated peak fly activity period. However, the cool and very windy conditions that existed immediately following those counts resulted in very low fly numbers on stakes during the latter part of last week. The return of dry, warmer conditions could result in an extended or a second peak in SBRM fly activity. The likelihood of high activity will be
largely dependent on how well the adults withstood the heavy rainfall that fell on much of the northern Valley during the past few days. In addition, prolonged periods of standing water or saturated soil could result in some degree of larval mortality.

    Several questions have surfaced regarding remaining active ingredient from planting-time insecticide applications following prolonged dry periods and extended windy conditions. Although early-season winds may have moved banded granules slightly off of the target zone, planting-time insecticides that were applied using the modified in-furrow method should have been protected from the wind and will most likely provide control of the early wave of maggot feeding.

    As suggested in earlier reports, soil moisture would be key to good activity from granular materials. Rainfall was very sparse during much of April and May for many growers in the northern Valley. Much-needed rainfall was received throughout the northern areas of the Valley over the weekend of June 10-11 in varying amounts from 0.15- to 0.75-inches. In addition, bands of extremely heavy rain moved across the area Monday evening, and many areas received additional rainfall periodically throughout the following week. Postemergence granular and liquid insecticides should have been activated and sufficiently rain-incorporated to prevent runoff losses that would have otherwise occurred during the heavy rainfall events of Monday evening. However, data regarding leaching losses due to extreme rainfall is lacking. Thus, only time will tell how well the post treatments will have performed.

    Currently, the larvae that have already hatched are remaining fairly high in the soil profile due to the very moist sub-soil conditions that exist in many fields. Therefore, tap roots will not be at as much risk of being severed as a result of maggot feeding injury. Also, the rainy and cool weather has delayed egg laying and subsequent larval establishment, whereas beets have progressed well in their development during the past 10 days. The combination of shallow larval feeding injury and well-developed beets may result in limited impact by the sugarbeet root maggot in many areas of the Valley.

    A few growers are still considering application of a postemergence insecticide. Growers planning on using a liquid material will likely get activity on the adult flies that are still active in fields and may get some larval control if they are able to incorporate it or if more rainfall is received within a few days of application. Incorporation will also be critical to granular applications, and the soil surface should be dry to ensure good incorporation.

Mark Boetel
Sugarbeet Entomologist
NDSU Department of Entomology

 

ARMYWORM BEING FOUND IN GRAIN FIELDS

    From southeast North Dakota, reports of Armyworm feeding in small grains were coming in June 19 - 20. There were varying levels of injury. Damage symptoms included clipping of wheat and barley stems. By these preliminary descriptions of damage, I suspect there are some fields with levels exceeding the treatment threshold of 4 to 5 armyworm per square foot.

Treatment options in wheat are:

Insecticide

Product per Acre

ethyl parathion 8EC

8 fl oz

Lannate

12 to 24 fl oz

Lorsban 4E-SG

1 pint

methyl parathion 8EC

8 fl oz

Penncap-M

2 to 3 pints

Warrior

2.56 to 3.84 fl oz

 

Treatment options in barley are:

Insecticide

Product per Acre

ethyl parathion 8EC

8 fl oz

Lannate

12 to 24 fl oz

methyl parathion 8EC

8 fl oz

Penncap-M

2 to 3 pints

For more information on armyworms, NDSU extension circular E-830 can be found at:

http://www.ext.nodak.edu/extpubs/plantsci/pests/e830w.htm

 

CEREAL LEAF BEETLE FOUND IN WESTERN NORTH DAKOTA

    In May (C&PR, Issue 2) we put out information regarding the Cereal Leaf Beetle (CLB) and its expanding range of infestation. The insect is established in numerous areas of Montana and was moving eastward. The earlier heads up was to alert everyone to the potential for CLB to be found in North Dakota this season.

    Well, it happened this past week. Active infestations were detected in both McKenzie and Williams counties. This discovery of infestations will have regulatory implications for moving grain and hay to California. Dave Nelson, ND Department of Agriculture, will be notifying elevators in affected counties this week regarding the requirements for transport to California.

    In the mean time, producers in western counties should be closely monitoring fields for the presence of CLB to determine if treatable levels are present in fields. At greatest risk will be irrigated fields in the general vicinity of the Missouri and Yellowstone Rivers. Boot stage is a critical point in plant development and impact of cereal leaf beetle feeding damage can
be felt on both yield and grain quality. Before boot stage, the threshold is: 3 eggs and larvae or more per plant (including all the tillers present before the emergence of the flag leaf). Larvae feeding in early growth stages can have a general impact on plant vigor. When the flag leaf emerges, feeding is generally restricted to the flag leaf which can signficiantly impact grain yield and quality. The threshold is decreased at the boot stage to: 1 larvae or more per flag leaf.

Treatments are:

For wheat, barley and oats:

Insecticide

Product per Acre

Lannate

0.75 to 1.5 pints

Malathion 5EC

1 to 2 pints

Malathion ULV

4 to 8 fl oz

 

Wheat ONLY:

Insecticide

Product per Acre

Sevin

1 lb active ingredient
(rate varies by formulation)

Warrior

2.6 to 3.8 fl oz

For more information on CLB, follow the links from the NDSU Entomology Updates under wheat at:

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

 

DEAD FLIES ON FOLIAGE

    Several reports of dead flies from eastern ND counties showing up on trees and shrubs have been received. These flies have distinctive white bands across the abdomen. These white bands are spores of the fungal disease known as Entomophthora muscae. The fungus kills the flies. Infected flies use stems and twigs of trees or shrubs as a site to die. Flies commonly affected by E. muscae are the common house fly, and the adult of the seed corn maggot.

    Production of E. muscae fungal spores appears to greatest at a relative humidity of 55% or higher. Flies usually succumb to the disease before they can produce eggs so the fungus apparently can play a role in reducing future populations of the fly species mentioned.

 

WHEAT MIDGE EMERGENCE

    With the disruption in internet service, a degree day update is not possible at this writing. The valley and southcentral counties will be approaching the point when emergence gets underway this week. Keep in touch with your local extension office for alerts on when this point is reached though there information will also be limited. Information from campus will resume as soon as possible.

Phillip Glogoza
Extension Entomologist
pglogoza@ndsuext.nodak.edu


cprhome.jpg (3929 bytes)topofpage.jpg (3455 bytes)tableofcontents.jpg (4563 bytes)previous.jpg (2814 bytes)next.jpg (1962 bytes)