Sorghum Midge
Much
of our later planted sorghum will be coming into bloom this week. This means that the long anticipated sorghum
midge season is starting. Today, August
18, 2014, I was in a southwestern Swisher County sorghum field that was at boot
to bloom stage. Only about 5 % of the
heads had blooms yet, but every head with blooms also had a midge. This is not a treatable level of midge… yet. As the field progresses farther into bloom I would
expect to find additional midge infesting an economic level of heads.
Midge are tiny
Dipterans, or flies, that feed exclusively on sorghum type plants. The adult midge only lives less than one day,
just long enough to lay eggs into blooming sorghum. The tiny resulting maggot feasts on a single
developing grain from within consuming it fully only to emerge as an adult a
short time later (usually about 2 weeks) as an adult to start the process
over. Midge cannot overwinter in our
area and must migrate from the south every growing season, usually hopping
generationally from blooming sorghum field to blooming sorghum field. Johnson grass can also harbor the midge life
cycle. Sorghum fields blooming early in
the growing season are normally immune to midge damage, as the midge typically
do not arrive in force until an average date of August 4th.
We have been
finding midge at sub-economic levels in sorghum since late July. So far we have not had any fields reach ET
(economic threshold) for midge but I really think that is about to change. The midge population has been gradually
growing on our early planted sorghum and the abundant Johnson grass population
that our early summer rains have fired.
As sorghum fields enter bloom, I recommend scouting daily, and if your
later sorghum planted sorghum is near a healthy Johnson grass population or an
earlier planted field I recommend extra caution.
When
scouting for midge, I prefer to make use of beat buckets or jugs by placing the
bucket over the blooming head, tiling downward and shaking vigorously. Midge should be shaken loose and
counted. A minimum of thirty plants per
field should be checked, but total number needed to be checked will vary
depending upon field size. Another good
method for use on windy days involves enveloping the blooming head in clear
plastic, disturbing the head and counting midge trying to escape. While in bloom, sorghum should be checked
daily for midge starting about 11AM, temperature depending.
The
ET for sorghum midge at the current market level for grain sorghum should be near
1 midge per head during bloom stage.
This ET level should be slightly lower for seed milo, contracted grain
value depending.
Please call or come by with any
questions,
Blayne
Reed
