Thrips control is both interesting and potentially expensive in ultra-narrow-row (UNR) cotton. Because of the importance of establishing and protecting first position fruit in UNR cotton, limiting thrips damage also takes on a greater urgency.

With approximately a five-fold increase in the number of row feet per acre (7.5 inches versus 38) in UNR cotton, rates of at-planting materials must increase proportionally to provide the same amount of insecticide per foot of row.

Thus, a four pound rate of Temik 15G costs approximately $12 per acre on conventional cotton; yet this same amount per row foot would cost almost $60 per acre on 7.5 inch UNR cotton!

With seed treatments such as Adage and Gaucho, the expense increases about three-fold in proportion to the increased plant population in UNR compared with conventional row cotton.

Broadcast foliar treatments for thrips are the same cost per acre with conventional or UNR row spacing, assuming both are Roundup Ready varieties.

To evaluate the economic returns of several thrips control options in UNR cotton, replicated tests were conducted in 1997 and 1998 to evaluate the at-planting insecticide Temik, Gaucho seed treatment, with and without a foliar spray, an Orthene 75S foliar spray treatment and doing nothing.

The Temik 15G was applied at 15 pounds per acre.

This rate provided the same amount of material per row foot as the three pound rate of Temik in conventional, 38-inch row cotton.

All options, except for the Gaucho seed treatment alone and the untreated check, provided adequate thrips control, averaging less than two thrips per plant. One can readily see why the Gaucho seed treatment must often be supplemented with a foliar insecticide spray. The same is true for Adage seed treatment.

Interestingly, the overall economic returns for the Gaucho seed treatment plus an Orthene foliar spray, two Orthene foliar sprays and the Temik treatments were relatively close, despite widely varying control costs.

However, if the price of cotton were set at 55 cents per pound, the two Orthene spray treatment and the Gaucho plus one Orthene spray option would have shown returns of approximately $16 and $13 more per acre then the Temik treatment (approximately $419 and $416 per acre returns versus $403 for Temik), indicating these first two options may be better choices with low cotton prices, at least with this high rate of Temik.

However, given the greater potential for beneficial insect disruption and subsequent outbreaks of secondary pests with the two foliar spray options, Temik might still have been a viable option, at least in higher yield situations, with higher thrips pressure, or at higher cotton prices.

In two 1999 tests in Wilson County, N.C., Temik at the lower eight pound rate (1.2 pounds active per acre) was the most cost competitive, despite the poor uptake and resulting high thrips levels in all treatments. In these tests, all three Temik rates showed the highest yields, although the eight pound product rate showed the greatest net returns.

Table 1: Thrips control in UNR (7.5-inch) cotton; Rocky Mount, N.C. 1997-1998
Treatment Rate
(Active/Acre
Thrips*
5 plants
Cost **
($/A)
Yield
(Lb. Lint/A)
Value
($/A)
Gaucho Seed
+ Orthene
4oz./cwt. +
0.25 lb.
7.3 a 24.90 801 a 536
Orthene
(2 Applications)
0.25 lb. 5.7 a 7.38 775 a 535
Temik 15G 15 lb, 9.8 a 45.00 816 a 526
Gaucho Seed 4 oz./cwt. 41.3 b 19.71 731 a 492
Untreated 49.7 b 693 b 485
* Thrips samples taken four weeks after planting
** Costs and values: Cotton — 70 cents per pound; Temik — $45 per acre; Gaucho — $19.71 per acre; Orthene — $2.19 per acre (when sprayed with Roundup); Orthene plus application costs — $5.19.
Table 2: Economic returns of selected thrips control options in ultra-narrow-cotton near Lucama, N.C., 1999 (Two tests)
Value** @
Treatment Lb.
product/acre
Thrips*
/
5 plants
Yield
(lb. lint/per acre)
$0.5
0
$0.6
0
$0.7
0
Orthene 97S (2X 0.25 27.6 b 638 a 312 375 439
Temik 15G 8.0 67.6 a 744 a 348 422 497
Temik 15G 10.0 53.5 a 718 a 329 401 473
Temik 15G 16.0 53.3 a 759 ab 331 407 483
Check 52.2 a 568 b 284 34 398
Means sharing the same letter are not significantly different (p=0.05; LSD)
* Average of three thrips assessments @ three, four and five weeks after planting.
** Value is the yield at various lint prices minus insecticide cost.

The Temik treatments also showed greater plant heights and stands at seven weeks after planting.

In summary, in comparing the value of various thrips protection options in UNR cotton, 1) an at-planting insecticide treatment, such as Temik, 2) Gaucho seed treatment plus a foliar treatments(s), or 3) foliar sprays — no single option appeared to have a clear advantage.

However, even with expected low cotton prices, whatever the option selected, good thrips management must be taken seriously in UNR cotton.