Aphids Down, Plant Bugs Still Around

Cotton 003

Cotton is looking good in the county. This morning I looked at fields anywhere form 3 weeks to 6 week bloom. Older

Aphid Fungus

Aphid Fungus

cotton is producing heavy boll load. Aside from applying PGR’s, we’re still looking for insects. Many fields have been sprayed for stink bugs. Brown and Southern Green stinkbugs are present. Most checks are showing 10% – 20% boll damage. The aphid fungus has set in, and aphids are pretty much gone. Many cast skins are seen under the leaves, and some of them have a green to brown wooly fungal mass. This is not the fungus that killed the aphid, but is a secondary fungus that grows on the dead ones (above).

Something we are still aware of is immature tarnished plant bugs in some fields which is rarely observed. We’ve sprayed more for them this year also. Below is an update from UGA Extension Cotton Entomologist, Dr. Phillip Roberts:

“Our primary method for scouting plant bugs is square retention.  Our goal is to retain 80 percent of all first positions as we enter bloom.  The square retention technique works well in pre-bloom cotton but is not as a reliable technique in blooming cotton as physiological shed confounds counts.

Effective use of the sweep net becomes difficult after bloom due in part to plant size and more emphasis should be placed on use of a drop cloth.  Also be observant for both adult and immature plant bugs when making visual plant inspections; examine terminals and inside the bracts of squares, blooms, and small bolls.  Also be observant for “dirty blooms”, blooms in which many of the anthers are dried and brown.  Dirty blooms are an indication that plant bug (especially nymphs) are feeding on larger squares which the plant did not shed.”

Clouded Plant Bug Nymph - Photo by Andrew Taylor

Clouded Plant Bug Nymph – Photo by Andrew Taylor

We have also seen clouded plant bugs in addition to tarnished plant bugs. Clouded plant bugs will feed on squares similar to tarnished plant bugs but will also more readily feed on small bolls. To the left is an immature clouded plant bug taken by scout, Andrew Taylor. The antennae of immature clouded plant bug nymphs are horizontally striped with red and white.  A dark-colored spot on the dorsal surface of the abdomen is visible in larger nymphs.

“We do not have recommended thresholds for use of drop cloths, visual inspections, or sweep nets in Georgia.  However, entomologist in the Mid-South have developed solid workable thresholds when using these sampling techniques which should be applicable to Georgia cotton:

Mid-South Plant Bug Thresholds: Tarnished plant bug thresholds can be used for clouded plant bugs, but clouded plant bugs should be counted 1.5 times when using a sweep net. Note that the threshold is higher during the third week squaring and bloom compared with the first two weeks of squaring.

Third week of squaring through bloom: Drop Cloth: 3 plant bugs/6 row feet, Visual: 10 plant bugs/100 plants, Sweep Net: 15 plant bugs/100 sweeps

First 2 weeks of squaring: Drop Cloth: 1 plant bug/6 row feet, Visual: 5 plant bugs/100 terminals, Sweep Net: 8 plant bugs/100 sweeps.”

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