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Plant Bug Situation Heating Up in Cotton

Things are heating up in the cotton patch, and I don’t mean just the temperatures. We still have some thrips on some of the late planted cotton, but as thrips are not of concern on most of the cotton, the plant bug numbers are beginning to increase, and in some cases the numbers are quite high. It appears that numbers are going from just a few, to as many as 60 plant bugs per 100 sweeps. Remember, our threshold is 9-12 per 100 sweeps. I have had several reports from all over the cotton region of counts from 15-20 to 40-60 per 100 sweeps, and the scenario is always the same–the cotton is around the 8th node, has about 4 squares on it, and there is a corn field nearby. In some cases, you can substitute the corn field for fields with large areas of blooming weeds nearby too. Anyway, these fields went from just a few plant bugs a week ago to up to 5x threshold this week. In most cases, the corn is beginning to tassel and silks are out. Adult plant bugs are alternating their time between the corn fields and the cotton fields.  When corn tasseling and silk emergence coincides with cotton squaring, it creates the “perfect storm” for plant bug problems. As those silks begin to brown, we will see mass movement into cotton too. Quite frankly, this is way too many plant bugs to be seeing this early, and it means to me that we are really going to be battling plant bugs this season. Usually plant bug numbers like this start when cotton begins to bloom.

Another consideration is the hot dry weather for much of the growing region. I know the folks in Northeast Arkansas have received some rain (and bad wind), but in most of the state, it’s getting dry. Soon, when the weeds dry out, we will get an influx of plant bugs from this source too. We have been sweeping flowering weeds on field edges the last couple of weeks, and I assure you, there are very big numbers of plant bugs on daisy fleabane and other flowering weeds right now.

The question we are getting is how to handle these plant bugs at this point. If numbers are not just terrible, just threshold or above, consider a first shot of a neonicitinoid like imidacloprid (Trimax, Couraze, Alias, etc), thiamethoxam (Centric), or flonicamid (Carbine). See the chart below for rates as there is more than one rate for some of the imidacloprid products (these are courtesy of Dr. Scott Stewart in Tennessee).  Prices are reasonable on imidacloprid (and the other neonic products), and higher-end rates should be considered, particularly when numbers are moderate or high.

Comparable Rates of Imidacloprid Products Applied as Foliar Spray for Tarnished Plant Bug

Lb Active Ingredient per Gallon

(trade names)*

Suggested Rates (lb ai/a) Suggested Rates (oz/a) Labeled Maximum Rate (oz/a)
1.6  (Nuprid 1.6F) 0.047 – 0.062 3.75 – 5.0 5.0
2.0  (Couraze 2F) 0.047 – 0.062 3.0 – 4.0 4.0
4.0  (Alias 4F, Couraze 4F, Nuprid Max) 0.047 – 0.062 1.5    – 2.0 2.0
4.6  (Admire Pro) 0.047 – 0.062 1.3 – 1.7 1.7

* The trade names listed are labeled for foliar use on cotton.  However, not all imidacloprid products are labeled for foliar application. Be sure to check the label, and do not exceed the maximum application rate.

Alternative Foliar Treatments for Tarnished Plant Bug Prior to Flowering

Trade Names (active ingredient) Suggested Rates (lb ai/a) Suggested Rates (oz/a) Labeled Maximum Rate (oz/a)
Centric 40WG (thiamethoxam) 0.0375 – 0.0625 1.5 – 2.5* 2.5
Carbine 50WG   (flonicamid) 0.081 – 0.089 2.6 – 2.8 2.8
Intruder 70WSP (acetamiprid) 0.05 1.1 1.1

* Do not use lowest suggested rate except during early season and only when populations do not greatly exceed threshold levels.

In those areas where plant bugs bounce back quickly from this first application and numbers start rising quickly, you may want to consider Diamond (6 oz) with knockdown material, the next time plant bug numbers reach threshold.  We will discuss those options in the next newsletter. Some of the oldest cotton is near this point now and I know some Diamond is going out with the second plant bug shot right now.  I would save my orthene for later, and Bidrin can’t be used until bloom, so the neonicitinoids are the products of choice. Whatever you do, stay away from pyrethroids for now because spider mites are beginning to pop up everywhere, and you don’t want to make that situation worse.

Also, don’t forget to monitor square retention. I think it is just as critical as plant bug number, and maybe more so. We want to maintain 80% square set or above. Remember, our research shows that 80-85% square set is better than 95%+ square retention, particularly this time of year, because it allows the plant to overcompensate and avoid overloading the plant, setting it up for a big shed later on when it hits a little stress (too hot, too dry, cloudy weather, etc).

In summary, watch fields closely as they reach about 8 nodes, particularly those fields with corn nearby (or other plant bug host areas—CRP, levees, etc.). Watch square retention closely, and don’t let numbers drop below 80%. Treat with a neonicitinoid when thresholds are reached. Don’t rush it.  Trust me.  You’ll get your chance to spray plant bugs before this is all over. Remember, for maximum yields, a little square shed is better than no shed at all.

 

 

 

 


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