Cotton Insect Newsletter Vol. 22, No. 6, June 23, 2004

Cotton Situation:  I haven't been able to spend much time in cotton fields during the last week, but from what I can see from the road, the crop looks very good.   I have visited a few fields that were planted in April and I didn't have to look very hard to find blooms.  At least 75% of the cotton planted in May either should be producing squares or will begin squaring this week, but less than 10% will have blooms.  Scattered showers are still the norm this week.  If you are in one of those areas where the rain always goes around you--I can sympathize.  I'm no weatherman, but it seems that a dry land mass surrounded by areas that have had adequate moisture may actually repel rain clouds.  How else can you explain those storms that track above and below you on the weather-map, leaving your fields high and dry.   Now that we can actually watch these revolting developments on the weather channel, it's even worse. Cotton Insect Situation:  Second generation bollworm/budworm moth numbers should be peaking this week.  Watch non-Bt cotton fields closely for evidence of feeding in terminals and small squares.   Cotton aphids are showing up in cotton fields throughout the state.  It's way too early to expect any help from the fungus disease.   By mid July, scouts should begin to see evidence of the fungus in many fields.  Aphid populations should begin to crash soon after, as the fungus proliferates throughout the state.   Cotton aphids will attract a wide variety of beneficial insects and spiders.  Lady beetles, big-eyed bugs, pirate bugs, nabids, lacewing larvae, and many others will be attracted to cotton fields.  Many of these beneficials will also be helpful when they attack eggs, bollworms, armyworms and other cotton pests.    Tarnished plant bug activity has been light in the Pee Dee area--in fact they have been hard to find.  Pinhead square set should be running between 85 and 95% during the first couple of weeks of squaring.  A technique developed in Arkansas will help in determining whether or not squares are being damaged by plant bugs.  Lightly tap 100 small squares 1/8" or less in size.  When a square falls off, it shows that an abscission layer was formed due to plant bug injury or a physiological problem.  Slice open damaged squares with a knife or razor blade and look at the immature flower parts; compare to healthy squares.  The reproductive structures in a healthy square will be uniform in shape and color.  If tarnished plant bugs have fed, the internal structure will show brownish, irregularly discolored areas (brownish anthers).   With physiological shed the internal structures are also symmetrical in shape and color, but they tend to shrink evenly, and discolor with time. It's not too early to begin looking for stink bugs in fields that have started blooming.  It is possible for stink bugs to attack tiny bolls and cause them to abort.  As bolls enlarge, stink bug probing will result in hard-locked fibers.  Usually, no more than 1-3 locks are involved, but when infestations are heavy, it is not unusual to see 4-5 hard locks.   The best time to visually check for stink bugs is early in the morning or late in the evening.  They become very elusive and hard to locate at mid day.   Beating plants over a cloth or into a pan will help in finding these secretive critters.  Obviously the brown stink bugs will be easier to eyeball on green plants than will the green and southern green species.    When quarter-sized bolls become readily available for examination, start pulling them and check for damage.  Warts on the inner walls of the bolls are the best indicators stink bug damage.  Tarnished plant bugs are also capable of producing warts.  There will often be black spots on the outer surfaces of the bolls, but these are variable.  In fields where I can easily find evidence of boll damage, I would also want to make sure to find the bug that did the damage.  Use a beat cloth, a beat pan or at least shake the plants on the ground to find the critters, if you are not actually seeing them on the plants.   Here's the bottom line for bugs and damaged bolls.  You need to know the percent of bug damaged bolls (by crushing and examining inner walls of 25 or more), and you need to know which insect did the dirty deed.   Mitchell Roof  Extension Entomologist

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