Right now, we have seeing both Lygus
and fleahoppers in our Hale & Swisher County program fields, but not at economic
threshold (ET) yet. Because several of
our program cotton fields have been so close to economic levels, it is likely
several other area fields are nearing or are at ET. We have been finding some high beneficial
populations and they have probably kept the fleahoppers from reaching ET so far
in our fields. We recommend keeping a
very close eye on your cotton’s square drop percent and plant bug populations.
Cotton
fleahoppers are very flighty, small, pale green to whitish color. The adults can fly, and the wings rest flat
across the back. The nymphs are pale
green and very small, ranging from the size of a grain of dust to almost the
size of the adults. Feeding with their
stylet-like sucking mouthparts fleahoppers can kill a square on a cotton
plant. The ET for these insects is 25%
to 35% plants infested or roughly 1fh. / 1.5 - 2 ft., with square drop
considerations. In match head squaring
stage cotton, this would be about 10% square drop, while in three fourths grown
square cotton it would be 15 - 20% drop.
Once a cotton field’s stage can be measured by nodes above white flower
(NAWF) fleahoppers are rarely an economic concern.
Lygus
are larger than a cotton fleahopper, and can range in color from pale green or
almost yellow. They always have a
distinct triangle on the thorax, which is made by the crossing of their wings
across their ‘backs’. The larvae tend to
be greenish and have dark, distinct black spots on their backs. The ET for Lygus also requires similar fruit
drop considerations, but their ET is usually considered in Lygus per row ft. The official Lygus ET is 1 Lygus / 2 ft. but
in most entomologists consider this per foot ET something of a sliding scale
with crop stage as well as fruit retention considerations. If you have 1 Lygus / 3.5 ft. in a field with
match head squares and a significant amount of dropped squares, it may be time
to consider spraying. One Lygus / 2.5
ft. for blooming cotton with the same square drop considerations seems to be a
practical ET. Lygus do cause economic
injury to developing bolls causing drop and/ or damage to the boll up to 350
heat units. For fields nearing cut-out,
an ET of one Lygus per 1.5 ft. seems to work well. Adult Lygus can fly in and out of a cotton
field, and often will when they are just passing by. It is not uncommon to find a sharp increase
in square drop, but not find any Lygus present.
This usually indicates that Lygus stopped briefly in route for a more
preferred host. In these situations keep
an eye out for Lygus nymphs soon as it is possible that the passing Lygus
adults laid eggs in the cotton.
Unfortunately, the eggs are too small to be found. The nymphs lack wings and cannot easily leave
the area.
We
prefer to use drop cloths in conjunction with whole plant inspections to
evaluate in field plant bug populations and influence upon fruit loss. Drop cloths can be used to find both of these
true bugs and, if the insects are sufficiently stunned from the ‘thrashing’ of
the cotton plants, can provide a good platform to identify these pest’s rather
distinctive appearance. We are keeping a
very close watch on these guy’s populations now and would be surprised if no
area fields are at currently at ET. We
recommend or area producers and consultants stay vigulant. Lygus bugs and fleahoppers are both hazards
for developing squares and we have both of them here now.
Good Luck!
Please call or come by the office if you have any questions. Thanks!
Kate
Blayne
Written
by Kate Harrell, Intern with the Plains Pest Management Association and Texas
A&M AgriLife Extension – IPM, Hale & Swisher County.
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