INTRODUCTION
The red imported fire ant, Solenopsis invicta Buren, was first introduced into the United States in or near Mobile, Alabama sometime between 1933 and 1945 and has since proliferated throughout much of the southern USA. The red imported fire ant now occupies over 285,000 acres throughout the southeastern United States and can be found in each of South Carolina’s 46 counties. Fire ants can be both beneficial and a pest problem to the region’s row-crop farmers. Fire ants are predators of other insects, helping farmers by attacking and killing pest insects that come near their mounds or feeding territory. On the other hand, farm equipment, such as combines, can be damaged by fire ant mounds while operating in the field. Disking the soil disrupts and may destroy fire ant mounds. As more farmers convert to conservation tillage systems, there is concern that fire ants will proliferate and the problems associated with fire ant mounds will increase proportionately. Fire-ant queens can fly several miles when leaving the mound in search of establishing a new colony. Therefore, many fire ant colonies in homeowner yards or rural housing developments may originate from fire ant queens leaving agricultural fields.
OBJECTIVE
To determine the influence of new cropping practices on the number and distribution of red imported fire ant colonies.
APPROACH
A split landscape study has been established at the Pee Dee Research and Education Center in Florence, SC, with half the 14-acre field being produced using traditional cropping practices and the other half innovative cropping practices (Table 1). The innovative cropping practices are designed to result in higher productivity while, at the same time, be more environmentally friendly. The field was split in half so that both halves have similar soil types (Fig. 1).
| Table 1. Treatments imposed on split landscape study. |
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Traditional
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Innovative
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Disk, Cultivate
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No Surface Tillage
|
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Bulk Soil Sample
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Grid Sample, Precision Apply
P
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Broadcast Apply P
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|
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In-Row Subsoiled for Deep
Tillage
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Deep Tilled with a ParaTill
(Broadcast Deep Tillage)
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Wide Rows (>30 inches)
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Narrow Rows (Except Cotton)
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Conventional Varieties
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Transgenic Varieties
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Fig.1. Soil types found in the split landscape field NoA=Norfolk loamy sand 0-1% slope, NoB=Norfolk loamy sand 1-3% slope, NiA=Nobocco sandy loam 0-1% slope, OcB=Ocilla sand 0-3% slope, BoB=Bonneau sand, Co=Coxville sandy loam, Ra=Rains sandy loam). |
Traditional Innovative |
Using GPS, red imported fire ant mounds that showed active signs of colonization were mapped twice per year to examine the number and distribution of the mounds under the two different cropping systems (Fig. 2). This research began in 1998 following soybean planting and continued with corn in 1999, cotton in 2000 and corn in 2001. Ant mounds were determined after planting and harvesting each crop. A similar crop rotation will be used in the future.
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Fig. 2. Red imported fire ant mound locations were marked using a portable GPS unit. |
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RESULTS
Mound densities for each year are shown in Table 2. Red imported fire ant mound densities were at their lowest level after soybean planting (spring) in 1998. However, by the end of the growing season (fall), mound density had increased almost 9 fold on the innovative side of the field, but only doubled on the traditional side. Mound numbers were high on both sides of the field at the beginning of the corn growing season in 1999. Mound numbers stayed about the same during the 1999 growing season on the innovative side, but decreased on the traditional side. Mound numbers after planting cotton were low on both sides of the field in 2000. Aldicarb insecticide was applied to both sides of the field at planting, which may have resulted in fire ant mortality. Fire ant mound numbers increased during the 2000 growing season on both sides of the field, although mound numbers in the fall were still higher on the innovative side than on the traditional side.