Side-dress Temik® Effects on Lint Yields

Stephen H. Husman, Pinal County Cooperative Extension

Abstract

Temik 15G was side-dressed at a rate of 7 lb./acre and 14 lb./acre and compared to an untreated check in 4 experiments in 1996 and 1997 in Buckeye, Az. Treatments were made just prior to early bloom. Lygus counts were taken using a sweep net on weekly intervals for four to six weeks post application. A net positive return on investment (ROI) ranging from $34.79/acre to $48.19/acre was realized in three of the four experiments with the seven lb./acre rate. One experiment resulted in a net economic loss of $24.84. A net positive ROI was experienced in two of the four experiments ranging from $23.31 to $50.11 using the fourteen lb./acre Temik rate. Two of the four experiments resulted in a net loss ranging from $28.28 to $93.27 using the fourteen lb./acre rate. It appears that lint yield increase responses are due in part to a plant response to Temik, not necessarily related to lygus density as evidenced in part by the lack of measured sweep count populations.

Introduction

Temik 15G has been widely used for both in furrow at plant and side-dressed in season serving as a systemic insecticide for insect control. However, general sentiment amongst producers is one of uncertainty relative to consistency of return on input investment. Temik 15G is a material often used for future insect damage prevention. With today's current economic conditions, cotton producers must maximize on production efficiency and provide cost effective inputs in order to consistently realize a net positive return on investment.

Temik 15G is a water soluble, granular soil applied material with systemic insecticide properties. In addition to the systemic insecticide property, Temik oftentimes results in a plant growth and yield response. A couple objectives of these experiments were to document through sweep net sampling and fruit form damage assessments, the plant bug control component of yield response in contrast to yield response from a possible plant growth regulator response.

Materials and Methods

Four replicated experiments were conducted on a commercial farm in Buckeye, Az. Temik 15G was side-dressed prior to the second post plant in-season irrigation at both a 7 lb./acre and a 14 lb./acre rate compared against an untreated check. Timing of treatment applications were made just prior to early bloom (Table 1). The experiments consisted of three treatments replicated four times arranged in a randomized complete block design with each plot consisting of twelve rows running the entire field length.

In season lygus counts per 100 sweeps were made weekly for a four to six week post application period for both nymphs and adults in 1996. In 1997, both internal and external fruit form damage evaluations were conducted from 10 plants per plot. Fruit forms from a square to a five day old boll were excised from individual plants and examined for both internal and external lygus damage. The results of the fruit form assessment are not yet completed and will be reported in a later document. Plant mapping measurements were made to evaluate plant bug effects on fruit retention and height:node ratios in 1996. Plant mapping measurements were not initiated in 1997. Yields were measured by harvesting the center four rows of each twelve row plot and weighing with portable electronic scales placed under a cotton trailer tires. Yield data was statistically analyzed.

Results and Discussion

The results of the 1996 experiments (Baseline, Broadway) were consistent in that the seven lb./acre rate resulted in significantly higher lint yields of 100 - 120 lb./acre contrasted against the untreated check. At the Baseline experimental site, both the seven and fourteen lb./acre resulted in a 120 lb./acre lint increase when compared to the untreated check. At the Broadway test site, the seven lb./acre rate had a significant lint yield increase of 102 lbs./acre compared to the untreated check. However, the fourteen lb./acre rate was not significantly different than the untreated check. Explanation for this is unknown. The 1997 results of test site Sec. 24-2 were consistent with 1996 tests in that the seven lb./acre rate resulted in a significantly higher lint yield of 100-120 lb./acre contrasted against the untreated check; however, the fourteen lb./acre rate which was not significantly different than the seven lb./acre rate had a yield increase of 163 lb./acre compared to the untreated check. The test conducted on Sec. 30W-12 resulted in no significant lint yield differences between the seven lb./acre rate and the untreated check and a significant yield decrease for the fourteen lb./acre rate compared to the seven lb./acre rate and the check (Table 2). Reasons for the results documented on Sec. 30W-12 are not understood.

Lygus counts/100 sweeps at the Baseline site in 1996 were under a 15 count/100 sweeps from 0-30 days after treatment (DAT) in all treatments (Figure1a). The recommended thresholds for treatment consideration is 15/100 sweeps. However, final lint yields were increased in the Temik treatments when compared to the untreated check suggesting the possible plant based Temik yield response.

The Broadway test site lygus counts are more difficult to interpret (Figure 1b). 14 DAT, the untreated check and the seven lb./acre rate were at or above a treatable lygus population threshold. However, populations declined across all treatments up to 30 DAT. Lint yields were significantly higher in the seven lb./acre treatment than the untreated check with the fourteen lb./acre rate statistically the same as the untreated check.

Plant mapping measurements of height:node ratios and fruit retention measurements were unable to numerically discern differences across all treatments at both test sites (Figure 2). Explanation may include variability of plants sampled within differing sampling periods and lack of lygus population differences and resultant fruit damage and shed.

In 1997, both experiments had sweep count based lygus populations under a treatable threshold up to 30 DAT (Figure 1c and Figure 1d). Again, in spite of lygus populations under the treatment threshold, significantly higher lint yields were measured in both the seven and fourteen lb./acre treatment at Sec 24-2. The experiment in Sec.30W-12 resulted in no significant lint yield response with the seven lb./acre treatment with a significant lint response decline in the fourteen lb./acre rate treatment.

Summary

As indicated previously, these experiments will be repeated for the next three years to develop long term return on investment data. To date, a net positive return on investment was measured in three of the four experiments with the seven7 lb./acre rate side-dressed at early bloom. The positive rate of return ranged from $34.79 to $48.19 /acre. One experiment resulted in a net loss of $24.84/acre with the fourteen lb./acre treatment. A net positive return ranging from $23.31 to $50.11/acre was experienced two of four times with the fourteen lb./acre treatment. Two of the four experiments resulted in a net loss ranging from $28.28 to $93.27/acre with the fourteen lb./acre treatment. It appears that much of the lint yield increase response is due to a plant response to Temik, not necessarily a lygus control response as evidenced in part by the lack of measured sweep count populations. Again, a more detailed and complete fruit form damage assessment will reveal more definitively the relationship of insect induced losses in contrast to plant based Temik application yield response.

Acknowledgments

The author would like to express his sincere appreciation to Rhone-Poulenc for their financial support and H-4 farms for their cooperation and assistance with this research.


This is a part of publication AZ1006: "Cotton: A College of Agriculture Report," 1998, College of Agriculture, The University of Arizona, Tucson, Arizona, 85721. Any products, services, or organizations that are mentioned, shown, or indirectly implied in this publication do not imply endorsement by The University of Arizona. The University is an Equal Opportunity/Affirmative Action Employer.
This document located at http://ag.arizona.edu/pubs/crops/az1006/az10067w.html
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