ble 3. A second view of particle size distribution was obtained from the
D. Reichard and T. Ladd (LPCAT faculty) showed that there were little or
Data obtained in the high-density apple management system experiment showed that average permethrin deposits were highest in the trellis system (Fig. 2). Strong relationships were noted between deposition and the dis- tances from the nozzles to tree midline, tree height, and tree spread. In addi- tion, permethrin deposits tended to follow canopy volume characteristics (Fig. 2). In the case of slender spindle trees, the relatively narrow tree struc- ture may have allowed more of the spray to pass on through the canopy, thus
TABLE 1—Seasonal savings intermittent sprayer versus boom sprayer.
• in pesticides:
conventional
% Savings in Insecticide Use, Intermittent Sprayer over
Conventional Year Cabbage 1 43 2 34 3 44 4 40 5 ^ ^
Avg. 40
Peppers 50 46 30 46 43
HALL ON LPCAT: A NEW APPROACH 127
Avg permethrin pgm/site
Pyramid
Intersfem
Trellis Stand Spin.
f33.5gL ^4.8
33.5a 19.8b 17.8b 10.4c Avg canopy volume/tree (m^)
FIG. 2—Spray deposition in apple management systems with permethrin at 6.88 L/min on each system.
decreasing impingement values. The second trial, where spray volume was adjusted for each planting density and system characteristics, resulted in a more even deposition pattern (Fig. 3). However, leaf area, tree (system) struc- ture still accounted for significant differences in spray deposition between plantings. New high-density apple orchards are easier to spray than the larger standard plantings but require careful manipulation of existing equipment.
Thus, adjustments can be made for these geometric differences in plant cano- pies as well as differences in pest densities. Dose targeting can aid IPM and reduce the potential for resistance; more active molecules enhance the feasi- bility of this approach to pest control.
At this time, the implementation of the dose targeting protocol appears limited by: (1) the lack of practical flexibility of current spray equipment, (2) inadequacy of basic information on biological targets, and (3) the lack of in- formation on "placement" rules.
Two-spotted spider mite adults on lima bean plants sprayed with
Avg carbaryl ugm / site
Pyramid
Intersfem
Stand. Spin.
FIG. 3—Spray deposition in apple management systems with carbaryl at 467 L/ha in each system.
pyrethroids moved from the normal lower surfaces to the opposite (untreated) leaf (Table 2). Adult TSSM on leaf surfaces with either phosmet or water did not exhibit hyperactivity or dispersal responses.
Feeding studies of TSSM also demonstrated a distinct reduction in percent of feeding time in response to a mist treatment of pesticides (Table 3). Addi- tional studies of mist treatments to Jeaf disks showed a difference between two pyrethroids in oviposition behavior as well as feeding potential (Table 4).
Where droplets of two formulations of permethrin were placed on leaf disks in
TABLE 2—Effects of an aerosol mist of pesticides on the behavior of TSSM at 48 h after treatment.
No. of Adults at 48 h on Plant Surface Treatment and Rate, g AI/L Lower Left Upper Left Lower Right" Upper Right"
Mavrik, 2 EC 0.06 20 3 7 0 S-3206, 2.4 EC 0.06 16 4 0 0
0.06 0.06 0.6 0.3
20 16 0 9
Imidan, 5 0 W P 0.6 0 0 39 0 Plictran, 50 WP 0.3 9 0 20 0 Water . . . 8 0 14 0
"Treated surfaces.
TABLE 3—Feeding time of TSSM in response to pesticide residues.
Mist Treatment Pydrin, 2.4 EC Carzol, 92 SP Kelthane, L6 EC Water
Untreated
Rate, g A I / L
0.06 0.45 0.48
LSD (0.05 level)
Mean Percent Feeding Time
0.0 21.2 48.2 47.4 66.7 12.5
TABLE 4—Effect of pesticides on TSSM mortality dispersal, oviposition, and feeding responses.
Treatment and Rate, g Mavrik, 2.0 EC Ambush, 2.0 EC Check
AI/L 0.06 0.06
Live 4.1a 3.5 b 5.0 a
Average No. of TSSM/Disk Off the Disk Eggs
1.0 a 1.1c O.Ob 3.9 b 0.0 b 23.1 a
in 24 h"
Feeding Scars 0.0 c 45.0 b 245.0 a
"Means in each column followed by the same letter are not significantly different at the 0.05 level (DNMRT).
HALL ON LPCAT: A NEW APPROACH 129
a random manner in different density patterns, TSSM exhibited a change in behavior according to drop density (Table 5). Permethrin in four drops per disk did not eHcit a change in proportion of feeding time (compared to water checks). However, permethrin, as an ED deposit, caused a reversal of the proportion of time spent feeding compared to water checks and permethrin EC droplets. A decrease in TSSM feeding scars resulted from the increase in the number of ED droplets per disk (Table 6).
In summary, the laboratory data showed some significant responses of TSSM depending on coverage (i.e., density of droplets). As the deposition pattern changed, the mortality, dispersal, feeding, and oviposition responses were different according to dose delivery. In the case of the Electrodyn®, the responses of TSSM to droplets were even more dramatic. As noted in other studies [5-7], this repellency (hyperactivity) is particularly prevalent with some pyrethroids and is thought to be partially the cause of mite resurgence in some fruit orchards.
TABLE 5—Examination of droplet density and formulation on behavioral responses of TSSM."
Treatment Ambush, 3 ED*
Ambush, 2 E C Water
1 Droplet/Disk Walk Feed
45.7 254.3
4 Droplets/Disk Walk Feed 251.8 48.1
63.8 236.2 59.9 240.1
"Data in seconds.
*ED = Electrodyn®-generated permethrin at 0.1 mL/s flow rate.
••EC used at concentration of 0.06 g AI/L.
TABLE 6—Response of TSSM to Electrodyn® droplets of cypermethrin."
Average No. of Feeding Scars/Disk Drops per
1 2 3 4 5
Disk Water Check
192.5
Tracer 134.2 165.0 215.0 150.1 149.1
Cypermethrin 84.2 48.3 21.6 31.2 25.0
"Electrodyn® with cypermethrin 3 ED at 0.1 mL/s flow rate.
Summary
Dose targeting encompasses the definition of the biological target (crop and pest) and dictates the subsequent dose delivery protocol. Some recent resistance (R) models show coverage is a major factor in the development of R. Current studies of grower applications show unacceptable levels of preci- sion which can aggravate the R problem. Correct coverage is dictated by the proper match of equipment, transport processes and physiochemical proper-
ties, pest, target, and population identification by the well-trained operator.
Implementation of dose targeting protocols appears limited by lack of flexi- bility in current equipment, basic information on biological targets, and in- formation on placement rules.
The delivery of pesticides to plant surfaces is a very inefficient process. The development of more active agents as well as environmental concerns make it imperative that we increase this efficiency. Unfortunately, the recent USDA- ARS six-year plans call for a 42% reduction in applied research in agricul- tural chemical technology.
Biologists and engineers need to work together to provide the necessary information for the rapid implementation of dose-targeting and other tech- niques designed to increase the efficiency of the pesticide application process.
This will require increased team research on basic mechanisms of delivery, impingement, and dose responses of pests to dose/drop density coverage pa- rameters.
The advantages of the LPCAT program include the sharing of techniques and equipment with active communication in problem solving, development engineering, and advanced computer model projections of spray particle de- livery—all within the diverse area of application technologyj LPCAT repre- sents a unique effort to actively integrate and link the biologist and the engi- neer for advancement of spray technology.
References
[/] Graham-Bryee, J., Philosophical Transactions, Royal Society of London, Vol. B, No. 281, 1977, pp. 163-179.
[2] Geisbuhler, H., Philosophical Transactions, Royal Society of London, Vol. B, No. 295, 1981, pp. 111-123.
[J?] Reichard, D. and Ladd, T. J., Transactions, American Society of Agricultural Engineers, Vol.24, 1981, pp. 893-896.
[4] Ferree, D. and Hall, F., Acta Horticultura, Vol. 114, 1980, pp. 91-99.
[5] Hall, F., Journal of Economic Entomology, Vol. 72, No. 3, 1979, pp. 441-446.
[6] Iftner, D. C. and Hall, F., Journal of Economic Entomology, Vol. 76, No. 4, 1983, pp. 687- 689.
[7] Iftner, D. C. and Hall, F., Environmental Entomology, Vol. 12, No. 6, 1983, pp. 1782- 1786.
Granules
Development of Toxic Baits for Control of Imported Fire Ants
REFERENCE: Banks, W. A., Lofgren, C. S., and Williams, D. F., "Development of Toxic Baits lor Control of Impoiied Fire Ants," Pesticide Formulations and Application Systems: Fourth Symposium. ASTM STP 875, T. M. Kaneko and L. D. Spicer, Eds., American Society for Testing and Materials, Philadelphia, 1985, pp. 133-143.
ABSTRACT: Toxic baits for control of the red and black imported fire ants, Solenopsis invicta Buren and S. richteri Forel, respectively, were developed by incorporating an ef- fective toxicant into a liquid food material and absorbing this into a granular carrier for distribution in the field. Screening tests with worker ants and laboratory colonies showed that of more than 4400 chemicals tested only three primary toxicants and four insect growth regulators demonstrated promise for control of field populations of the fire ants.
Effective bait formulations that gave good control of the ants were produced by incorpo- rating the amidinohydrazone toxicant, AC-217300, or the insect growth regulator. Pro- drone, into soybean oil and impregnating the oil solution onto pregel defatted corn grits.
KEY WORDS: imported fire ant, Solenopsis invicta, Solenopsis richteri, toxic baits, chemical control, formulations, toxicants, granular carriers, food attractants
The red imported fire ant, Solenopsis invicta Buren, and the black im- ported fire ant, Solenopsis richteri Forel, were accidentally introduced into the United States at Mobile, Alabama, approximately 45 and 65 years ago, respectively. Through natural flights and inadvertent transport by man the ants, from this point of entry, have infested about 100 million hectares of land in nine southern states and Puerto Rico. Public demand for relief from the stinging and mound-building habits of the ants prompted the U.S. Congress in 1957 to appropriate funds and authorize the U.S. Department of Agricul- ture (USDA) to cooperate with the affected states in efforts to control them.
Chemical control was begun in the fall of 1957 with large-area applications of the residual chlorinated hydrocarbons heptachlor and dieldrin. A research and methods development laboratory to improve existing or develop new
'Insects Affecting Man and Animals Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Gainesville, FL 32604.
1 3 4 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM
methods of control was established at the same time. The development of mirex bait by this laboratory and its extensive use for control of the imported fire ant (IFA) has been well documented [1-8] and will not be considered here.
In subsequent years, the discovery that residues of mirex were present in a wide variety of organisms in the environment [9-12] and that mirex was highly toxic to estuarine organisms [13-17] led the Environmental Protection Agency (EPA) to severely restrict its use. When information became available indicating that mirex was also a potential carcinogen [18], the EPA in 1978 cancelled registrations for all products containing mirex. These cancellations left no registered chemicals available for fire ant control except on an individ- ual mound basis; however, this method is too labor intensive and costly for large agricultural areas. The need for suitable control chemicals to replace mirex resulted in intensified efforts by USDA scientists to develop new con- trol agents. Williams [19] reported that of more than 4400 primary bait toxi- cants evaluated subsequent to 1976 only three were sufficiently promising to warrant extensive field testing. Banks et al [20] reported that only four of fifty five insect growth regulators (IGR) demonstrated potential for control of IFA. We present here the procedures we have used to develop effective baits using our studies with Amdro® fire ant bait as an example.^
Development of Amdro Bait
The design of a toxic bait for area-wide applications requires three basic components: a food or other type attractant, a toxicant, and a granular car- rier. Prior studies with food attractants had established that vegetable oils were readily accepted by the worker ants [/]. They provide water repellency to the bait formulation, which is a great advantage in large-scale applications, and they are not attractive to most beneficial insects. Soybean oil has been the material of choice since mirex was developed because it is readily available at a moderate price. Because of these many desirable properties, it was selected also as the food attractant for Amdro bait in all laboratory and field tests.
The toxicant in Amdro fire ant bait is American Cyanamid AC 217300, (tetrahydro-5,5-dimethyl-2(l/f)-pyrimidinone, (3-[4-(trifluoromethyl)phe- nyl]-l-(2-[4-trifluoromethyl)phenyl]ethenyl)-2-propenylidene)hydrazone). It was the most effective of a group of nine similar amidinohydrazones [21], exhibiting delayed toxicity at 0.1 and 1.0% in laboratory tests (Table 1). Ac- tivity of the chemical was initially hampered by its poor solubility in soybean oil (ca. 1.0% or less); however, it was determined that addition of oleic or linoleic acid at 50% of the toxicant concentration increased solubility without
^This paper reports the results of research only; mention of pesticides in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended. Also, mention of a commercial or proprietary product does not constitute an endorsement of this product by the USDA.
TABLE 1—Effectiveness of AC 217300 against red imported fire ant workers (average of 9 replications with 20 workers each replication).
Chemical AC 217300
Mirex (standard)
Soybean oil (check)
Concentration,
%
0.01 0.1 1.0 0.01 0.1 1.0
1 1 1 19 1 0 3 0
Percent Mortality on 2
1 1 63 1 2 71 1
3 1 4 87 1 45 96 1
6 2 49 100 11 84 100 3
Indicated Day 8
5 68 28 91 4
10 7 73 50 93 5
14 7 82 67 100 7
seriously reducing acceptability of the oil solution to the ants at concentra- tions up to 5.0%. The oil-cosolvent solutions of AC 217300 were very effective in tests against whole laboratory colonies [19] (Table 2), causing high level worker mortality and death of the queen in all colonies treated at concentra- tions of toxicant in the solution of 2.5, 5.0, and 10.0%. Colonies treated at 20% concentration survived due to apparent repellency of the higher concen- tration.
Initial field tests with AC 217300 were conducted with the toxicant-soybean oil bait impregnated on corn cob grits (CCG). This carrier had proven very successful with mirex, since it was readily available, the particles were easily sized and durable, and the final formulations could be applied with ground or aerial equipment. The test formulations were made by dissolving the toxicant at a concentration of 4.0% in the soybean oil-cosolvent system and impreg- nating it on the CCG at 15% by weight of the formulation to produce a 0.6%
bait. (This is the maximum absorption capacity of the grits.) The bait was applied at the rate of 3.7 kg/ha (22.2 g/ha active ingredient (AI)) with trac- tor-mounted granular application equipment to 2.0 ha plots in nongrazed permanent pasture. Three 0.16 ha circular subplots were established in each treatment plot for pre- and posttreatment evaluation of ant activity. Each mound within the subplots was examined at each interval and rated as alive or active if 20 or more live ants were present.
The initial tests were disappointing (Table 3), with a maximum kill of only 34% versus 96% for the mirex standard. Since the oil solutions containing AC 217300 had given good results in laboratory tests, we concluded that in- sufficient toxicant was reaching the ants in the field colonies because of the low absorption rate on CCG. We reasoned that more oil-toxicant could be delivered to the ants by increasing toxicant concentration in the soybean oil, increasing the bulk rate of application of bait, or using a more absorptive carrier that would carry and deliver more oil-toxicant per particle than the 15% possible with CCG.
136 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM
TABLE 2—Mortality in laboratory colonies of the red imported fire ant treated with indicated concentrations of AC 217300 in soybean oil baits."
Concentration, %, AC 217300 in Soybean Oil
2.5 5.0 10.0 20.0
2.5 5.0 10.0 20.0
1
90QD 80 90 75
58 50 30 10
Percent Mortality in Each Colony at Indicated Number of Weeks Posttreatment''
2 3
Gulfport, Mississippi 98
lOOQD 90 75
100 lOOQD
85 Gainesville, Florida
88 73 55 13
90 75 64 18
4
CN
93QD 79QD 66QD 20CN
8
95 91 66
16
97 95 75
20
98 100 80
24
100 100
"Tests at Gulfport, Mississippi, were with colonies with 10 000 to 20 000 workers and 10 to 20 mL of brood; tests at Gainesville, Florida, were with colonies with 60 000 to 120 000 workers and 50 to 60 mL of brood.
' Q D = queen dead; CN = colony normal (queen alive with eggs and all stages of brood);
colonies receiving only soybean oil and either cosolvent or untreated checks remained norma) throughout the test.
TABLE 3—Effectiveness of corncob grit-soybean oil baits containing AC 217300 against natural infestations of red imported fire ants.
Toxicant and Percent Concentration
Rate of Application Bait,
kg/ha
Toxicant, g/ha
Pretreatment Count of Active IFA Colonies
Percent Reduction in Active Colonies After Indicated Weeks"
4 9 15 AC 217300, 0.6%
Mirex 10-5,0.1%
Check
3.7 4.6
22.2 4.6
39 33 33
34 51 17
27 93 8
34 96 3
"Corrected for check mortality by Abbott's formula.
All three approaches had merit, so we decided to investigate all. The first two were accomplished easily; however, a search for more absorptive carriers proved to be more difficult. Our studies with mirex had shown that a com- pletely inert carrier was needed to reduce the potential for the soybean oil to become rancid. Rancidity could have two undesirable effects: reduced feed- ing by the ants and breakdown of the chemical toxicant. Of all the material tested, only puffed cereal-type pellets of corn, rice, or wheat consistently sat- isfied these requirements, absorbed 30% or more oil, and flowed readily
through apphcation equipment. Baits were thus formulated on extruded corn pellets (ECP), with 30% soybean oil containing 1.25, 2.5, 5.0, and 10% AC 217300 producing baits containing 0.375, 0.75, 1.5, or 3.0% AI. Formula- tions on CCG for comparison were made with 15% oil containing the same toxicant concentrations, but produced baits containing 0.1875, 0.375, 0.75, and 1.5% AI. The CCG baits were applied at rates ranging from 2.8 to 8.07 kg/ha (5.25 to 121.0 g/ha AI) and the ECP baits at rates ranging from 1.4 to 4.03 kg/ha (5.25 to 121.0 g/ha AI). Application and evaluation techniques were the same as for the initial tests, except plots were 1.2 ha in size with 0.15 ha evaluation subplots. Results from these tests were somewhat better (Table 4) than in the initial tests although quite erratic. When data from all the tests were combined it was seen (Fig. 1) that 10 to 15 g Al/ha was the optimum dosage and at those rates the corn pellet bait was decidedly superior to the CCG baits. No consistent correlation between application rate and control was discernible.
Further tests were considered necessary to fully determine the best carrier and formulation; thus larger-scale tests were conducted in Alabama, Louisi- ana, and Texas. It became apparent as these tests were planned that the ECP used in the previous tests would no longer be available and an alternative mate- rial would be necessary. Therefore studies were conducted to compare the ECP with defatted and degermed corn grits, a new type of carrier produced as a by- product of the cereal industry (Lauhoff Grain Company, Danville, Illinois). All the formulations contained 2.5% toxicant in the oil solution which was applied to the carriers at 30% by weight of the formulation. The baits were applied with fixed-wing aircraft to 40.5 ha plots on noncultivated areas. Since the earlier laboratory and field tests had shown evidence of eliminating the queens even though all workers in the colonies were not killed, a new system of evaluating the treatments was developed that took into account effects of the toxicants other than total colony mortality. In this new system, circular subplots were established, as previously, the entire area within each subplot was searched, and each nest found was opened with a spade and examined carefully. A nest rating of 1 to 10 was assigned as shown in Table 5.
The interaction of population density and colony class was then used to establish a population index that can be expressed mathematically by
10
Population index (PI) = E K{Nt)
where N^ is the number of ant colonies in a given area comprised of colony classes having the value of K, where (10 < K > \).
The changes in population indices offered a more realistic means of assess- ing effects of the chemical. Comparison of the reductions in population indi- ces obtained in the aerial treatment tests showed that all the baits were 80 to 90% effective in reducing populations of the ants (Table 6). The formulations
1 3 8 PESTICIDE FORMULATIONS: FOURTH SYMPOSIUM
TABLE 4—Effectiveness of baits containing AC 217300 for control of red imported fire ants (each test consisted of three replications at three sites).
Formulation (Carrier and
Toxicant Concentration)
0.1875%
0.375%
0.75%
L 5 %
0.375%
0.75%
1.5%
3.0%
Mirex (standard), 0.1%
On corncob grits
Application Rate Bait,
kg/ha
Active Ingredient, g/ha Corncob Grits 2.8
5.6 2.8 4.03 5.6 8.07 2.8 4.03 5.6 8.07 4.03 8.07
5.25 10.5 10.5 15.1 21.0 30.2 21.0 30.2 42.0 60.5 60.5 121.0 Extruded Com Pellets 1.4
2.8 1.4 2.02 2.8 4.03 1.4 2.02 2.8 4.03 2.02 4.03 1.12 1.37
5.25 10.5 10.5 15.1 21.0 30.2 21.0 30.2 42.0 60.5 60.5 121.0 1.12 1.37
% Control Obtained"
Test 1
33 55 51 56 39 47
84'' 47"
55' 55' 49'- 57' 97
Test 2
52 67 45 72 63 70
66 87 79 82 72 71
86
"Data corrected for untreated check mortality by Abbott's formula.
'Data for one replicate.
' Data for two replicates.
on pregel defatted corn grits were slightly more effective than those on pregel degermed corn grits. The data obtained in these studies provided the basis for conditional registration by the EPA of AC 217300 in a pregel defatted corn grit formulation under the trade name Amdro. This bait has gained good acceptance by the homeowner and is being widely used for IFA control on lawns, playgrounds, and other areas frequented by people. It can also be used for IFA control in pastures, range grass, and nonagricultural land.