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ISSUE 13   July 25, 2002




Reports of damage from sunflower beetles continue to come in throughout North Central Region. If fields are getting close to flowering and sunflower beetle damage is below 25% defoliation (economic threshold level), spraying should be delayed in these fields. Then, rechecked during early flowering (R5.1) to see if head insect pests, like sunflower seed weevil or banded sunflower moth are present. In other words, one insecticide sprayed at early flowering could be control all of these insect pests. Banded sunflower moth and sunflower moth are flying and will be attracted to the early flowering fields. Scout fields for damaging levels of 1 moth per 2 plants at dawn. Sprays should include the grassy field borders where banded sunflower moths are active during the day, as well as sunflower fields. No red sunflower seed weevil reports yet.

Numerous Lygus bugs have been observed this year. So, confection sunflower growers should remember to spray for Lygus bug at early flowering (R5.1) and a second spray 7 days later to minimize brown "spot" damage.



Trap counts of Bertha armyworm have decreased the last two weeks of July. Cumulative trap catches are below the 900 mark in the "hot" spot in Bottineau-Renville Counties from Mohall to Bottineau. This indicates that larval infestations will not be widespread. However, fields that were flowering during peak moth flight, the week of July 1-8, may become infested at economic levels. These fields should be scouted for bertha armyworm larvae (caterpillar). If 22-28 larvae are found per square yard, yield loss will occur to the field and a foliar insecticide, Capture, should be applied at 2.1-2.6 fl oz/A. Good coverage is essential for effective control, so donít cut gallonage (minimum of 3 gal per A for air and 10 gal per A for ground). Remember, bertha armyworm will feed on mustard and canola. Other trapping areas of NC, NW, and SW Regions are at low risk for larval infestations with cumulative trap catches below 300 moths.



The wheat midge flight is near the end - thanks to the hot weather! Degree day accumulations are as follows for the NC and NW Regions as of July 23, 2002: Bowbells=1635; Bottineau=1767; Mohall=1771; Berthold=1755; Hofflund=1869; Minot=1894; Towner=1896; Karlsruhe=1908; Watford City=1938 and Williston=1963. Some localized spraying has been reported in the North Central Region, especially from north of Carpio to Lansford to Mohall. The hot, dry weather may have shortened the life span of the adult wheat midge.



There are many fields of small grains, flax, and sunflowers that are being threatened by high populations of hungry grasshoppers. Some fields have been sprayed already. We had some relief with the cooler weather. However, when it gets hot, the grasshoppers will become more active again. Adult grasshoppers to third instar nymphs are present now. So, continue to keep a watch on your fields for grasshopper damage and apply the insecticide quickly after initial damage, like clipping off flax bolls, chewing on grain/sunflower heads.

Jan Knodel
Area Ext. Specialist/Crop Protection

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