Grain sorghum fields range in maturity from nearing bloom to soft dough and all of these fields need to be scouted frequently.
Blooming sorghum is susceptible to sorghum midge and field scouts are finding more midge in the fields this week. Scout sorghum fields 2-3 times per week until past bloom.
Start by scouting fields on the south side (downwind) as the midge is a poor flyer and will be found on the field margins first. When you are finding them on field margins, move 150-200 feet into the field and check again.
Look for adults on the yellow blooms by inspecting carefully and at close range all sides of randomly selected flowering grain heads. The reddish, gnat-like adults crawl on or fly about the flowering heads. During inspection, handle the grain heads carefully to avoid disturbing the adult midges.
Clapping your hands on the sorghum head can be useful to find large numbers of midge but may not find the midge if there are only 1-2 per head.
The economic threshold can be determined by this equation: Click HERE for ET calculator
Number of sorghum midges/flowering heads = Cost of control as $A × 33256 / Value of grain as $ per cwt × Number of flowering heads
My current economic threshold for sorghum midge is 0.5 midge per head (or 1 midge per 2 heads).
Once fields have bloomed, sorghum should be scouted for headworms and stink bugs. Headworms include the fall armyworm, corn earworm and occasionally the sorghum webworm.
Scout these fields by beating heads in a bucket. We use a 2-gallon bucket for scouting sorghum. Look here for a brief video.
Using the bucket you can find how many headworms and stink bugs are in your field.
I addressed stink bugs in sorghum last week HERE.
Also, we have not found fields with concerning numbers of sugarcane aphids yet, but continue to watch for them.
Economic thresholds for grain sorghum are as follows: