REDUCING TREATMENT COSTS FOR FIRE ANT SUPPRESSION IN TEXAS CATTLE PRODUCTION SYSTEMS
 
Bastiaan M. Drees, Professor and Extension Entomologist
Charles L. Barr, Extension Associate
Michael E. Heimer, County Extension Agent, Agriculture - Montgomery County,
and Ronald Leps, County Extension Agent, Agriculture - Williamson County
 

Treatment programs conducted to suppress populations of the red imported fire ant, Solenopsis invicta Buren, can be expensive and time consuming. Short of subsidizing the cost of fire ant insecticides by government programs, potential techniques for reducing treatment costs include: 1) develop economic injury levels and implementation of economic thresholds or action levels; 2) use modified treatment patterns; 3) reduce equipment requirements; 4) treat for ants while conducting other field operations such as fertilizing; and 5) adjust treatment timing to optimize residual effectiveness (i.e. fall broadcast insecticide bait applications provide suppression of fire ants during early spring months). Methods (2,3 and 4) were investigated in the trials reported below.
 

I. EVALUATION OF ALTERNATIVE RATES AND TREATMENT PATTERNS FOR RED IMPORTED FIRE ANT BAIT PRODUCTS, LOGIC® AND AMDRO®.
 
Previous studies (Drees et al. 1992; Drees et al. 1993) showed that the effects of a spot application of Logic® Fire Ant Bait (containing fenoxycarb, also sold as Award®) affect more than one fire ant mound. Broadcast application, applied as a "skip swath" pattern (0.75 lbs./acre), provided suppression of fire ant mound numbers similar to that obtained using conventional, full coverage (1.5 lbs./acre), treatment. In the trial reported in 1993, swaths were 35 ft. wide. In addition, the application of a 1.5 lbs. mixture of Amdro® Fire Ant Granules/Insecticidal Bait (hydramethylnon, 0.75 lbs. of formulation) plus Logic (0.75 lbs.) provided quick initial fire ant suppression, characteristic of the effects of an Amdro treatment, and long (over 1 year) suppression, characteristic of a Logic treatment. The trial reported here is a replication of this earlier study and included a spot treatment applied without a manual or electric seeder.
 

Materials and Methods
 
This trial was established behind the earthen dam at Granger Lake in Williamson County, Texas. This area is routinely mowed and has restricted access to U. S. Army Corps of engineers personnel, only. No livestock was grazed in this area and cut grass was not harvested for hay. Plots, 150 by 300 ft. (1.03 acres), were established with 30 ft. buffer areas. Active fire ant mounds were counted in each plot by using a 30 ft. long pole (made from 0.75 inch diameter PVC pipe reinforced internally with 0.5 inch electrical metal tubing (EMT)). This pole was carried by at least two people and walked lengthwise across 260 ft. of each plot on each side of the centerline (0.36 acre sample area). Active ant mounds were counted using the minimal disturbance method. Mounds were disturbed with a pointed stick and considered to be active when 25 or more worker ants emerged from the mound within 30 seconds.
 
Resulting ant mound counts were arrayed by plot and blocked into 4 blocks (replicates) of eight treatments each. Treatments (Table 1) were randomly assigned within each block. Full rate broadcast and strip treatments were applied using a tractor mounted Herd® Model GT-77 seeder, July 1, 1993. Reduced rate (0.75 lb./acre) Amdro and Logic broadcast applications were applied using a hand held Cyclone® Model 1C1 seeder, July 2. Periodically after treatments (4 weeks, 3 months, 6 months, 12 months and 18 months), fire ant mounds were monitored using the technique described above. Results were analyzed using analysis of variance (ANOVA)(P < 0.05) and means were separated using Tukey's Studentized Range test.
 
 

 
 Table 1. Treatments evaluated for red imported fire ant suppression, Granger Lake, Williamson Co., Texas, 1993.
 
Treatment
Pattern
Rate
1. Amdro® (hydramethylnon) complete coverage broadcast
1.50 lbs./acre
2. Amdro® (hydramethylnon) complete coverage broadcast
0.75 lb./acre
3. Logic® (fenoxycarb) complete coverage broadcast
1.50 lbs./acre
4. Logic® (fenoxycarb)
complete coverage broadcast
0.75 lb./acre
5. Logic® (fenoxycarb)
skip swath broadcast
0.75 lb./acre
6. Logic® (fenoxycarb)
spot application
 2 Tbsp./spot on a 30 by 30 ft. grid pattern (1.424 lbs./acre)
7. Logic® plus Amdro®
 
 
(fenoxycarb plus hydramethylnon)
complete coverage broadcast
0.75 + 0.75 lb./acre
8. untreated control
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Back to Materials and Methods

Results

This site did not receive rain from 26 June 1993 until well into September. This dry weather suppressed ant mounding activity in all plots, including the untreated control plots (Table 2). The full Amdro and Amdro plus Logic treatments numerically reduced active ant mound numbers relative to other treatments by four weeks after treatment. However, significant differences between treatments did not occur until 3 months following treatment with all treatments except Amdro® having significantly fewer active ant mounds than untreated plots. Statistically, all Logic®-based treatments performed similarly throughout this trial. The mound numbers in Logic skip swath and spot treatment plots began to increase after 12 months and all treatments approached or exceeded pre-treatment levels after 18 months. Although results obtained from this trial were not as clear as those documented in the trial conducted at Lake Conroe Dam (Drees et al. 1993), the trends obtained from treatments remained the same.
 


 
 Table 2. Number of active red imported fire ant mounds per 0.36 acre subplot and total ant mounds per treatment (for four replications) before and after treatment, Granger Lake, Williamson County, Texas, 1993.
 
Mean no. active fire ant mounds/0.36 acre*
TREATMENT
0 week
4 week
3 month
6 month
12 month
18 month
Untreated 57.75a 20.75a 20.00a 36.75a 50.00a 60.50a
Amdro, full rt 55.00a   7.00a   6.25abc   6.25b 24.75ab 61.50a
Amdro, half rt 56.75a 13.50a 15.5ab 25.25ab 35.25ab 74.50a
Amdro:Logic 55.00a   6.75a   1.50bc   2.00b 15.50b 49.25a
Logic, full rt 58.25a 13.50a   0.25c   2.50b 13.50b 67.25a
Logic, half rt 56.00a 17.50a   5.75abc   2.75b 14.50b 71.00a
Logic, skip 55.00a 19.75a   4.50bc   1.75b 16.75ab 61.25a
Logic, spot 54.75a 15.50a   4.25bc   1.25b 16.00ab 60.25a
F
29.49
4.19
4.11
4.66
2.74
0.96
P
0.0001
0.0028
0.0031
0.0015
0.0247
0.5003
R sq.
0.9335
0.6659
0.6620
0.6894
0.5662
0.3147
MSE
123.74
43.293
39.429
125.57
220.281
426.756
Crit. val.
4.743
df
21
Min. Sig. Dif.
26.383
15.605
14.843
26.577
35.201
48.995
 

* Means followed by the same letter(s) are not significantly different using analysis of variance and Tukey's Studentized Range Test (P < 0.05).

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