CURRENT SEASON – 2008

"It's always something..." Sunflower Bud Moth – July 18, 2008.

            As usual, what started as a slow bug year has thrown me a spitball.  Sunflower bud moth has been reported from numerous locations in eastern ND and western MN.  What has been showing up is black, granular material on the stalk or around the base of the developing head – this is frass (bug poop), and a sign that sunflower bud moth larvae are feeding.  Historically, even high populations of sunflower bud moth do not usually cause serious economic loss.  The exception is when they attack the head, preventing normal head and seed development (which we've seen in some cases this year).  Unfortunately, there's little to be done about this particular insect problem, mostly because of where it's located.  Like sunflower midge, these insects are inside the plant making it extremely difficult to get chemistry to them, and even long residual chemistries might not be that effective as we don't have good information on their developmental rate (i.e when the adults will emerge, etc).

        Sunflower bud moth have 2 generations in the northern plains, the current one is probably gen. 1.  In Minnesota, North Dakota and up into Manitoba, the 2nd generation is not generally economically important because the plant has outgrown it's susceptibility to yield loss (head is already developed).  Adults emerge from overwintering pupae in May/June (but we're a bit late in everything this year...) and lay eggs on terminals of immature sunflower and leaf axils.  The newly hatched larvae them tunnel into the plant, the entrance hole is surrounded by black frass.  The larvae feed inside stems and complete their development inside the plant.  They return to a location near the entry hole to pupate.  Most of the current observed insects are older larvae (and even pupae) in them, indicating the damage has already been done in these cases.  Generally, sunflower bud moth feeds in the backs of developing heads in later planted sunflowers.  This also is what we're mostly seeing, which makes sense - even if they got in early, most sunflowers in the region emerged later. 

           

In the images, the small brown capsule is a pupa, from which an adult will eventually emerge.  In the image on the left, you can see where a sunflower bud moth caterpillar has burrowed and fed upon the developing head – this is the situations which will result in yield loss.  Click on the images for higher resolution pictures…

 

There are a couple of good websites with more info on sunflower bud moth:

From North Dakota State University

From Manitoba Agriculture

From Kansas State University

 

 

Grasshoppers – Jumping onto the scene… - July 02, 2008

Several locations in NW MN have reported grasshoppers.  Surveys have turned up a mixed bag of species, most of which are not usually agriculturally damaging species but a couple of the species typically thought of as agricultural pests have been recovered as well.  What is of greatest concern is the timing of the hatch; there were a number of very young nymphs of species that should be older by this date.  In other words, we’re seeing delayed hatching of some species which usually hatch out earlier in the season.  While concerning, it’s not surprising, the different species we’re discussing all overwinter as eggs in the soil and their development is strongly influenced by soil temperature (which were not exactly blistering this spring!)  The reason delayed hatching is of concern is because, today’s temperatures aside, we’re entering a warmer, drier period.  Warmer, drier weather does not favor the development of the naturally occurring fungal diseases which infect and kill grasshoppers.  Consequently, grasshopper populations hatching into and developing during warmer periods are not subjected to as much natural mortality from these fungal diseases and will have better survival.  Scouting fields adjacent to CRP or other areas in which grasshopper populations develop is a good idea.

            Grasshoppers don’t like to lay eggs in tilled soil, consequently, most of the agriculturally damaging species will lay eggs outside of tilled fields; meaning they attack the edges of fields first.  The exception is in no-till systems where grasshoppers will lay eggs within the field.  To scout for grasshoppers, walk the field (early in the season start along the field’s edge) and visualize a 1 ft2 area along your path. As you come to the 1 ft2 area, count the number of grasshoppers within it (this is usually best done by counting the number of grasshoppers that hop out of the area or are moving within it); sample 20 locations and calculate the average no. grasshoppers per ft2.  Because thresholds are based on numbers per yd2 (see Table below), convert the average number of grasshopper per ft2 area by multiplying by 9.  One ft2 samples are used because it would be too difficult to count the number of grasshoppers in a square yard when populations are very high.

Grasshopper Populations – Treat At/Above ‘Threatening’ Levels

 

Rating

Nymphs per square yard

Adults per square yard

Margin

Within Field

Margin

Within Field

Light

25-35

15-25

10-20

3-7

Threatening

50-75

30-45

21-40

8-14

Severe

100-150

60-90

41-80

15-28

Very Severe

200+

120+

80+

29+

 

            For lots more information on grasshoppers in Minnesota, see our grasshopper page here.

 

 

Soybean Aphid Surveys in NW MN – June 25, 2008

            We scouted several soybean fields in the area today and didn’t find much more than yesterday – aphids can be found in very low numbers in certain fields and the plants are still relatively young.  The fields most likely to have aphids right now are those in which they generally show up first (i.e. if you’ve got a field that usually has early aphids, go take a peek!).  Based on the stages we’re seeing, it does look like we’re starting to get our 2nd generation of nymphs but the populations are still pretty small….

 

 

 

First Soybean Aphids of the Season – June 24, 2008

 

Very low levels of soybean aphid have been reported from west Polk county (we found some yesterday in our plots at the NWROC in Crookston).  Populations are very low so far.  Ardell Knudsvig, field scout for MDA, reports finding aphids in several fields, aphids were on less than 10% of plants with low numbers where they did occur.  Most of the aphids we’re finding in NW MN are all young nymphs, no winged ones (although this could be because we’re not really finding many aphids of any kind yet!), and no alatoid nymphs (these are the nymphs with ‘should pads’, destined to turn into winged aphids. 

This coincides with reports from SE & SW MN that aphids are starting to be show up in fields there.  They've been reported from Rosemont, Becker, Morris and SW MN.  They've also been found in very low numbers in the SE.  This isn’t that surprising; we generally start to pick up some aphids in fields in late June/early July.  

            So, bottom line, soybean aphids are showing up on schedule, they’re not widely distributed yet and where they are found, they’re only at low numbers.  So they’re definitely NOT a problem yet.  It's probably a good idea to check those fields traditionally at highest risk just for presence and serious scouting will likely start in most locations within the next couple of weeks. 

           

Selected Past IPM Updates

Summary of 2007 Season

August 3, 2006 - Tank Mixing Insecticides & Fungicides in Sugarbeet

July 25, 2006 - Two-Spotted Spider Mite Feeding Damage

July 19, 2006 - Soybean Aphid regional Update

June 16, 2006 - Orange Wheat Blossom Midge in Southern MN?  Let’s Find Out!

May 30, 2006 - Soybean Aphid Makes A VERY Early Arrival

May 19, 2006 - Cutworms in Sugarbeet

June 16, 2006 - Orange Wheat Blossom Midge in Southern MN?  Let’s Find Out!

May 30, 2006 - Soybean Aphid Makes A VERY Early Arrival

May 19, 2006 - Cutworms in Sugarbeet

July 05, 2005 – Armyworm Flight, Crookston

June 06, 2005 – Soybean Aphids – they’re back

May 23, 2005 – Cutworms in Sugarbeets

July 2003 - Leafminer in Sugarbeets

July 2002 - Armyworms in Small Grains
July 2002 - Grasshoppers in The Red River Valley
May 2002 - Cutworms in Sugarbeets
Fall, 2001 - Soybean Aphid in NW Minnesota
August, 2001 - Lygus in Sugarbeets
July/Aug, 2000 - Armyworm Outbreak in RRV
Fall, 2000 - Soybean Aphid, A New Insect Pest in Minnesota Soybeans
June 20, 1999 - Potato Leafhopper, Grasshoppers, Cereal Insects
Sept 12, 1999 - Impact of Aster Yellows on Canola May be Greater Than You Think
Aug 31, 1998 - Lygus in Sugarbeets

Publications Available for Download

Insects

Grasshoppers -
Minnesota Grasshopper Management - 2002 with color graphics
Minnesota Grasshopper Management Brochure with scouting and control information (available as a PDF file designed to be a tri-fold brochure).

Scouting -
Scouting for Insects in Wheat, Alfalfa, and Soybeans - a manual prepared for the University of Minnesota Extension Service Field School, held at the Northwest Experiment Station, Crookston, MN, July 7-8, 1998.
Early Season Scouting for Soybean Aphids - A guide to scouting early season soybeans for soybean aphid.

Questions? Comments? E-mail us at:

imacrae@umn.edu