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Wednesday, June 7, 2017

Scouting for Thrips in Cotton



Scouting for Thrips in Cotton

               This past week I have received quite a few questions about scouting for thrips in cotton.  The questions have not revolved around so much ‘how’ to scout for thrips as most have already watched our how to scout for thrips in cotton video.  If you have not and would like to do so, the link is here:
               These questions have dealt more with, “How many plants do I check per field for thrips?”  Mostly this is an open-ended question most entomologist in extension do not usually answer directly.  If we do, we must give the answer that guarantees the scout will absolutely know exactly what the pest population in the field is and be able to scientifically defend their findings to a publication review board.  For those that have looked at our new thrips guide you have found this type of answer there: “Randomly select 25 plants from 4 regions of the field and closely go through the plants looking for adult and immature thrips.
If you have not given the new thrips guide a once over, I encourage you to do so now at: http://lubbock.tamu.edu/files/2017/05/Thrips_ENTO-069.pdf.  There are a lot of helpful tips to be found there.
Meanwhile, for those of us scouting lots and lots of fields, that level of pest population precision is not always needed.  Rest assured that for all our research plots and other cases where that level of precision is needed, we are getting it and more.  But for day to day field scouting, I find it to be overkill and too time consuming to practically cover all the acres we must on a weekly basis.  We just need to know if this pest is over economic threshold and at what level are the beneficials helping us out.  So, we need a decision now, based on solid scouting but derived as quickly as possible about whether to spray or not. 
To help fill you in on how our scouting program generates these answers, I have asked our 2017 Plains Pest Management Intern, Trey Buxton, to fill you in on what data I expect of him when he scouts a typical cotton field in Hale, Swisher, & Floyd County.  Trey made a picture perfect scouting in a 30-acre drip field trip last week that gave us great data.  Here is what that path looked like as tracked by his GPS active Strider Tablet:



































Here is Trey in his own words:


My name Is Trey Buxton and I am a summer intern under IPM Agent Blayne Reed out of Hale, Swisher, and Floyd county. I started working for the Plains Pest Management Association in the summer of 2016 as just a summer job and I had no idea what I was doing at first. After working under Blayne for a full summer I feel pretty good about knowing what it takes to scout cotton, corn, and sorghum fields in West Texas and get good data.
When scouting cotton fields early in the growing season the first thing that I do is walk good distance into the field to avoid edge issues, say 50 to 100 steps or so.  These edge areas can catch drift from a neighboring farmer and always have an edge effect with pest, disease and weed populations that do not represent the full field.  When I get to an area that I think is consistent to the rest of the field I start gathering data.  We call each stop we make a data set.  Each data set consists of a stand count (how we calculate plants per acre), record the plant stage in the vicinity, record any weed populations, and conduct 2 whole plant inspections where all thrips, any plant disease, and beneficial populations are recorded. After I have finished recording all my data I start walking to my next data set. You want to make sure that you space your data sets out across the field so you can cover more portions of the field and know what problems you have in those spots of the fields.
Blayne tells me the question is how many plants do we need to get in each field.  Blayne always points to the Texas A&M AgriLife Extension guide.  It says, “Randomly select 25 plants from 4 regions of the field and closely go through the plants looking for adult and immature thrips.” This would be very accurate.  Blayne coaches us that, “More data is always better, but not every field is a research plot.  In day to day scouting, we do not have that much time.”  So, I was trained to scout for thrips on 2 randomly selected plants at each data set and to get them from at least 5 regions of the field. So, in most fields, I am only inspecting 10 total plants throughout the field versus inspection 100 like the Texas A&M AgriLife Extension Handbook says to.  This should not be more accurate than what the handbook says, it just helps to get in and out of fields quicker and allows us to get the minimum amount of data that we need for a field.  In many fields, there is a need to get more data.  Larger fields are a good example.  On really big fields I can easily get 10 data sets.  Another example of needing to get more data in the field would be when thrips populations are very close to averaging around 1 thrips per true leaf stage or when we start seeing thrips larva in the field.  In either of these cases, more data is required to give the producer the best data to help them make tough decisions about spending more money on additional spray. 
I would also like to say that when you are scouting for thrips, you must do a really good job of scouting your 2 plants per data set.  If your data is no good, it does not matter how many plants you check, you have no idea what is happening in that field.  Thrips like to hide on the bottom of the Cotyledon leaves and attach to the veins on the leaves and suck the plant juices out of the leaves. They also like to crawl down into the growing point terminal of the cotton plants and feed down in there which can really turn into a problem because they will damage the terminal and stunt the plants growth. So, whenever I get down check for thrips I make sure that I look the plant over real good and open up the unfurled leaves with my pen or knife. Thrips are really little tan colored insects that have the shape of a grain of rice but they are way smaller.  So, when you are searching for thrips it can be easy to mistake some dirt of a piece of plant that is stuck to the bottom of the cotton leaves for a thrips. To make sure that I don’t get confused I get my pocket knife out and I will poke what I think is a thrips, and if it’s a thrips it will start to crawl around on the leaf.
In the picture shown reveals the path that I took through the field in Swisher County.  My boss, Blayne Reed, considers this a perfect path through a field.  It is considered perfect because I covered enough ground to make sure the data was representative and I didn’t take too long in the field.  In this field, all 5 of my data sets were consistent in weed control, thrips control, and stand count numbers.  Because of the consistency of the thrips, weeds, stand counts, and lack of disease pressure or other issues, the minimum amount of data required from this size field was all that was required and I could move quickly on to my next field to check.

Thanks Trey!
Blayne

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