Bastiaan M. Drees

Development of integrated pest management programs for the red imported fire ant (Hymenoptera: Formicidae).

The historic development of integrated pest management (IPM) approaches or programs for the red imported fire ant, Solenopsis invicta Buren, are discussed. Initial attempts to eradicate this species in the U.S. failed. In the early 1980′s site-specific, goal-oriented approaches were developed by adapting IPM concepts to fire ant problem areas. These programs have evolved over time and, more recently, the concept of managing fire ants on an area-wide or community-wide basis has been demonstrated. Currently, efforts are being made to investigate biological control agents to develop biologically-intensive IPM programs.

DEVELOPING FLEXIBLE ECONOMIC THRESHOLDS FOR PEST MANAGEMENT USING DYNAMIC PROGRAMMING

The rice stink bug is a major pest of rice in Texas, causing quality related damage. The previous threshold used for assisting in rice stink bug spray decisions lacked flexibility in economic and production decision variables and neglected the dynamics of the pest population. Using stochastic dynamic programming, flexible economic thresholds for the rice stink bug were generated. The new thresholds offer several advantages over the old, static thresholds, including increased net returns, incorporation of pest dynamics, user flexibility, ease of implementation, and a systematic process for updating.

Foraging Activity and Temperature Relationship for the Red Imported Fire Ant1

The range of temperatures of red imported fire ant, Solenpsis invicta Buren, foraging and food bait removal were examined in laboratory assays for six ant colonies collected from central Texas. Ants were observed crawling from laboratory colonies through clear plastic tubes traversing through a temperature controlled water bath in order to access and remove peanut butter bait. The minimum and maximum critical temperature range for these foraging S. invicta worker ants was 10 and 50°C, respecitvely. The results suggest that exclusion of ant activity can be attained using temperatures outside of this range. Maximum foraging and bait removal in these assays indicate that optimum temperatures for fire ant bait application are between 25° and 35°C. Using video recordings, crawling speed was found to vary for individual ants between the temperature extremes of 10° and 49°C, ranging from 0.21-cm/sec at 10°C to 3.46-cm/sec at 48°C. There was a significant linear relationship between speed and temperature (r2 = 0.71), where Speed = −0.19 + 0.06 × Temperature.

Effect of red imported fire ants on habitat use by hispid cotton rats (Sigmodon hispidus) and northern pygmy mice (Baiomys taylori)

Abstract We examined effects of the exotic fire ant Solenopsis invicta on habitat use by hispid cotton rats (Sigmodon hispidus) and northern pygmy mice (Baiomys taylori) over a 17-month period in an open grassland community in central Texas. We divided the study area into 10 adjacent plots. Five alternating plots were treated with an ant-toxic bait to reduce density of S. invicta. The remaining 5 plots were left untreated. We trapped small mammals monthly and calculated capture per unit effort (CPUE) for each small mammal species in each of 3 treatments (treated, untreated, border) each month. Trap months were partitioned into 2 seasons, summer and winter. Sigmodon hispidus altered habitat use, as indicated by CPUE, in the presence of S. invicta during summer, and B. taylori did not alter habitat use in the presence of fire ants during either season.

Indirect effects of red imported fire ants on Attwater's prairie-chicken brood survival.

ABSTRACT The invasive red imported fire ant (Solenopsis invicta) has negatively affected a host of taxonomic groups throughout its acquired North American range. Many studies have hypothesized indirect trophic impacts, but few documented those impacts. We evaluated invertebrate abundance as a factor limiting juvenile survival of the endangered Attwaters prairie‐chicken (Tympanuchus cupido attwateri), and whether fire ants reduce invertebrate numbers and biomass. From 2009–2013, we monitored survival of Attwaters prairie‐chicken broods (n = 63) with radio telemetry during the first 2 weeks post‐hatch and collected daily invertebrate samples at brood sites. Broods located in areas with the highest median invertebrate count (338 invertebrates/25 sweeps) had a survival probability of 0.83 at 2 weeks post‐hatch compared to 0.07 for broods located in areas with the lowest median invertebrate count (18 invertebrates/25 sweeps). During 2011–2012, we evaluated the reduction of fire ants on invertebrate numbers and biomass by aerially treating areas with Extinguish Plus™ in an impact‐reference study design. Treated fields had 27% more individual invertebrates and 26% higher invertebrate biomass than reference fields. Our results clearly document that invertebrate abundance affects Attwaters prairie‐chicken brood survival and that fire ants may indirectly contribute to low brood survival by suppressing invertebrate abundance. We posit that within the fire ants acquired North American range, fire ants are likely contributing to declines of other insectivorous species. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Seeing Fire Ants Smell: Olfaction of Solenopsis invicta

Abstract. Foraging workers of the red imported fire ant, Solenopsis invicta, were observed to respond to the presence of hot dog slices. The ants detected the odor of this food lure from an overhead distance of at least 3 cm and possibly as far as 5 cm. In addition, more foraging ants accumulated over time underneath the lures compared to the nontreated check (no hot dog slice). The technique used could help develop food lures detectable by ants at greater distances to improve detection and management programs.

Worker Ant Foraging Response on and Near Mounds of the Red Imported Fire Ant, Solenopsis invicta Buren 1

Abstract. Red imported fire ants, Solenopsis invicta Buren, are an invasive species that has infested more than 145 million hectares in the southern United States. Management of this insect pest often relies on the use of food lures and granular bait insecticides. This experiment was conducted to determine the response of red imported fire ant workers when a food lure was placed on the center of a mound or 0.3, 0.9, and 1.8 m from a mound. Percentage of foraging worker ants after 60 minutes of exposure to the food lure was 31.7 to 36.0 at the mound center, 24.5 to 22.3 at 0.3 m, 19.6 to 21.4 at 0.9 m, and 24.2 to 20.4 at 1.8 m. These results demonstrate that red imported fire ants forage on top of their mounds. These data should help convince insecticide manufacturers to allow placement of granular baits on top of nondisturbed mounds in addition to scattering bait around the mound.

Subsurface Temperature Profile and Red Imported Fire Ant1 Foraging and Sampling by Food Lures, Coachella Valley, California

Abstract The effect of surface soil temperature on attraction of foraging red imported fire ants, Solenopsis invicta Buren, to a food lure in centrifuge vials with access 2.54, 5.08, and 7.62 cm below the surface compared with vials horizontally at the soil surface or in the soil with the opening at the soil surface was monitored in the Coachella Valley of California. Analysis of variance showed no significant differences in the mean numbers of ants collected in the three strata, indicating a 2.54-cm opening as preferable, or when compared with vials horizontally placed at the soil surface or with the opening at the soil surface. However, during summer days, vials baited with subsurface food lure attracted 10–30 more foraging worker ants compared with vials horizontally placed at the soil surface or with the opening at the soil surface. Use of this method could provide more consistent data on monitoring ant foraging and result in fewer false negatives.

Rapid Assessment Survey of the Ant Fauna of Green Island, Cameron County, Texas

Abstract. We did a rapid assessment of ants on Green Island, a strategic nesting location for colonial waterbirds on the Texas coast. We found 10 ant species by using bait or collecting by hand. The tropical fire ant, Solenopsis geminata (F.), was the most common species, accounting for 42% of the ants collected. We found the area free of the red imported fire ant, Solenopsis invicta Buren, a potential threat for the native ant assemblage and conservation of colonial waterbirds. We recommend more surveys and adoption of surveillance protocols to prevent introduction of invasive species.