Volume
5 Issue 10
July 22, 2008
“It's always something…”: Sunflower Bud Moth
 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 (figure
1A). 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
insecticides 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 geneneration 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 then tunnel into
the plant; the entrance hole is surrounded by black frass. The
larvae feed inside stems and complete their development inside the
plant (figure
1B). They return to a location near the entry hole to pupate.
Most of the current, observed bud moth stage are older larvae
(and even
pupae) in stalks, indicating
the damage has already been done. Generally, sunflower bud
moth larvae
feed 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 (figure
1D), from which an adult will eventually emerge.
Dr. Ian MacRae
U of Minnesota Entomologist
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