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ISSUE 4  June 4, 1998


BUG BRIEFS

    The two most common insect pest concerns around the state are Cutworms and Grasshoppers.

    Cutworm reports are coming in from the Red River Valley to Beach, ND. The cutworms found at this time have most commonly been the Red-backed cutworm (Description: dull gray to brown with dull reddish stripe down the back; 1 to 1 inches long when full grown). There has been quite a range in sizes reported. One sample, late last week, from the Grand Forks area had larvae that were to inches in length. This week, cutworms from south of Fargo were in the 1 to 1 inch length and about to pupate.

    The cutworms have been feeding on a variety of crops. Row crop problems have been most common, with sunflowers and beans mentioned most often. From the Lakota area, barley fields were being severely damaged. Out west, it has been wheat and sunflower. Unfortunately, in several of these cases, the cutworms have been feeding exclusively underground. This makes a control decision very difficult.

    Grasshoppers are causing problems in the southwest, north west and central counties, and the Red River Valley. The young hoppers range in age from first to third instar; the majority are still first and second instar. Most are still in non-crop areas bordering fields, however, movement into fields is beginning. This development has been most important in the southwest where rains have been absent. The vegetation in the those hatching sites is beginning to dry up and the grasshoppers are moving to greener areas next door. Other exceptions include fields where late season crops were planted last year. There, eggs were laid by adults throughout the field and required treatments earlier.

Phillip Glogoza
Extension Entomologist

 

SUGAR BEET ROOT MAGGOT EMERGENCE

    Sticky trap catches of SBRM along with degree-days accumulations indicate that we have already reached peak fly emergence from Foxhome, MN, to Grafton, ND. Peak emergence was in the process of occurring north of Grafton to St. Thomas when windy, cooler weather arrived. As soon as it warms up, the flies that have already emerged and the flies that are going to emerge should result in high numbers on sticky stakes. In other words, one should expect the peak within the next two to three days depending upon location, or when ever temperatures start reaching the 70's from north of Grafton to St. Thomas. Current degree days for St. Thomas are 460. Post applied liquid treatments used where fly pressure is high and no granular insecticides were used at planting should be applied three days ahead of peak fly activity (about 550 degree days).  Keep informed of degree-day accumulations on DTN.  Mike Beltz, American Crystal, provides degree days on DTN.  Thanks Mike!

Scott Armstrong
Entomologist


SUNFLOWER BEETLES MOVING TO NEW FIELDS

    Sunflower beetle adults have been active for several weeks. Movement to new sunflower fields has been very noticeable the past week. The pale yellow to orange eggs on the leaves and stems should be hatching soon. The cool weather should slow the hatch.

    Though we have not had reports of large numbers of adults feeding on seedlings like we have the past few years, it is time to intensify scouting to determine population levels in your fields.

    Scouting Method: Sampling should be 75 to 100 feet from the field’s edges. Adults and/or larvae should be counted on 20 plants at each of 5 sites along an X pattern for a total of 100 plants. Te average number of adults and/or larvae per plant should be determined.

    Economic Threshold: Adult - one to two per seedling. Larvae - 10 to 15 per plant will cause approximately 25 to 30% defoliation if allowed to continue feeding. Control is advised if average defoliation reaches the 25 to 30% level.

 

Insecticides Approved for Sunflower Beetle

Trade Name

Product/Acre

Dosage
(lb AI/acre)

Asana XL*

1.45 - 5.8 fl oz

0.0075 - 0.03

Baythroid*

1.6 - 2.8 fl oz

0.025 - 0.044

Sevin

(varies)

1.5 - 2

Furadan 4F*

0.25 - 0.5 pts

0.125 - 0.25

Lorsban 4E

1 - 1.5 pts

0.5 - 0.75

Scout X-tra*

0.71 - 1.42 fl oz

0.005 - 0.01

Warrior*

1.28 - 2.56 fl oz

0.01 - 0.02

*restricted use insecticide


HESSIAN FLY FOUND INFESTING WHEAT IN STUTSMAN COUNTY

    Hessian fly eggs and maggots were found at the base of small wheat plants from a field in Stutsman County. The eggs are reddish and laid in the grooves on the upper sides of the leaves. The maggots are 3/16 inch long and white in color. Infested plants become thickened and stunted, and take on a bluish-green color. The central growing shoot may be absent. Infested tillers are less than half the size of noninfested healthy tillers. Stunted tillers in young plants often die. If they survive, growth and yield is reduced. Later, infestations and injury become noticeable when infested stems break when heads begin to fill.

    There is no recognized rescue treatment for controlling Hessian fly infestations. Infestations found early, would allow destruction of the wheat, and replant to an alternative crop.

    Hessian fly spend the winter as maggots in a prepupal "flaxseed" stage on early seeded winter wheat and volunteer spring wheat. In the spring, they pupate and emerge from April to May. The warm spring weather has likely contributed to the appearance of these infestations. This year, if Hessian fly become a concern around the farm, be sure to control volunteer wheat to minimize egg laying in August and September.

Phillip Glogoza
Extension Entomologist


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