Harlan G. Thorvilson

Seasonal Changes in Bait Preference by Red Imported Fire Ant, Solenopsis Invicta (Hymenoptera: Formicidae)

Bait stations were established in four different vegetational habitats near Houston, Texas, to attract Solenopsis invicta Buren, the red imported fire ant (RIFA). Bait preferences were compared in each habitat for each monthly 24-h sampling period. Foragers located both the high carbohydrate and high protein baits, but greater numbers were recruited to the carbohydrate bait during the sampling periods of the year registering lower temperatures (mean = 17@*C). In contrast, when the seasonal temperatures were greater (mean = 25@%C), RIFAs were collected in higher numbers on the proteinaceous bait. These findings must be considered when planning a field research project to collect RIFAs.

Field Applications of Bait-Formulated Beauveria bassiana Alginate Pellets for Biological Control of the Red Imported Fire Ant (Hymenoptera: Formicidae)

Abstract The red imported fire ant, Solenopsis invicta Buren, is an important pest in the southern United States, in part because few natural enemies exist. Beauveria bassiana is an entomopathogenic fungus that holds great promise as a biological control agent against S. invicta. In previous studies, B. bassiana was effective in laboratory trials, but field applications were less effective. In the current study, we compared the efficacy of different application methods of B. bassiana mycelia encapsulated in alginate pellets against S. invicta in heavily infested areas. Direct insertion of pellets into S. invicta mounds caused some reduction in activity rating. However, observations of ants removing pellets from mounds shortly after insertion led to the development of a bait system to encourage pellet retention in the mounds. Broadcast applications and individual mound treatments of B. bassiana alginate pellets coated with peanut oil reduced activity ratings of S. invicta populations.

Detection of magnetism in the red imported fire ant (Solenopsis invicta) using magnetic resonance imaging

Red imported fire ant (Solenopsis invicta) workers, queens, and alates were analyzed by magnetic resonance imaging (MRI) for the presence of natural magnetism. Images of ants showed distortion patterns similar to those of honey bees and monarch butterflies, both of which possess ferromagnetic material. The bipolar ring patterns of MRI indicated the presence in fire ants of small amounts of internal magnetic material, which may be used in orientation behaviors, as in the honey bees.

A preliminary mathematical model of the apple twig borer (Coleoptera: Bostrichidae) and grapes on the Texas high plains

Abstract The apple twig borer, Amphicerus bicaudatus (Say), has a major economic impact on the developing vineyard industry of the Texas High Plains. The life history of this insect has been studied and the potential damage caused by beetles has been calculated. From these data a mathematical model of the interaction of the apple twig borer (ATB) and grape vines has been produced. The model assumes three periods during the year which account for major changes in the ATB-grape vine system. A simple model is presented in which specific functional forms for the relationships between the population densities of ATBs and grape vines are given. Numerical solutions of the model are presented and reflect vineyard practices regarding the removal of pruned canes. The results are discussed in terms of the qualitative behavior of the system.

Red imported fire Ant (Hymenoptera : Formicidae) populations in Texas highway rights-of-way and adjacent pastures

Abstract Do disturbed habitats along highway rights-of-way encourage the establishment and spread of the red imported fire ant, Solenopsis invicta Buren, in Texas? The objective of this study was to determine if highway rights-of-way harbored S. invicta populations that were significantly different from those in adjacent pastures. Data on S. invicta populations were collected from three transects along highways within S. invicta-infested areas of Texas. One north–south transect, a southern east–west transect, and a northern east–west transect were established in Texas and extended 1,678 km. Twenty-eight sites, ≈80 km apart along transects, were visited between 14 May and 1 June 1996. Numbers of S. invicta mounds, mound vitality ratings, ants collected in bait cups, and vegetative characteristics were measured in rights-of-way and in adjacent pastures at each site. No significant differences in pooled (n = 28) mean numbers or vitality of S. invicta mounds were detected in rights-of-way as compared with those of adjacent properties. However, significantly more S. invicta colonies than expected were found on roadbeds (≤1.0 m from paved surfaces) as compared with the remainders of rights-of-way and to adjacent pastures. Roadbed colonies were also smaller, which suggested that colonies were more recently founded than in the remainders of rights-of-way. Mound population densities and numbers of ants in bait cups were not well correlated with vegetative characteristics measured in this study. In Texas where S. invicta is well established, S. invicta is in a population equilibrium between highway rights-of-way and adjacent pastures. However, highway roadbeds may offer an early successional habitat for S. invicta colonies and may require special survey and pest management attention, especially along the frontiers of infestation in Texas.

The Straw Itch Mite, Pyemotes Tritici (Acari: Pyemotidae), as a Biological Control Agent of Red Imported Fire Ants, Solenopsis Invicta (Hymenoptera: Formicidae)

The straw itch mite, Pyemotes tritici (Lagreze-Fossat and Montane), is a parasitic pyemotid mite that has generated considerable interest as a biological control agent of the red imported fire ant, Solenopsis invicta Buren. To evaluate the efficacy of this mite against S. invicta under the conditions of central Texas, a large-scale field trial was conducted during 1985. A total of 244 S. invicta colonies was mapped and colony size and activity ratings recorded. During May, two applications of mites cultured on Angoumois grain moth-infested wheat kernels were introduced into 103 colonies, and 141 control colonies were treated with Angoumois grain moth-infested wheat kernels not infested with mites. The colonies were also twice treated in October. Throughout the test period, colonies were periodically inspected and rated. Analysis of the data using t-tests did not reveal significant differences in ratings between mite-treated and control colonies. Therefore, the straw itch mite, P. tritici, was not found to be an effective biological control agent of the red imported fire ant.

Comparison of Lygus elisus Van Duzee and Lygus hesperus Knight (Hemiptera: Miridae) Feeding Injury to Pre-bloom Cotton

Feeding injury and abscission of 6th, 9th and 11th node, first-position cotton squares exposed to Lygus hesperus Knight and L. elisus Van Duzee for 24 h were investigated in field and laboratory st...

AN INSECT GROWTH REGULATOR (PRO-DRONE) FOR EFFECTIVE MANAGEMENT OF THE RED IMPORTED FIRE ANT (HYMENOPTERA: FORMICIDAE)

Pro-Drone, an insect growth regulator (IGR) with juvenile hormone activity, was aerially applied twice at the rates of 11.86 g AI/ha in large-scale field trials for control of the red imported fire...

Beauveria bassiana (Ascomycotina: Hypocreales) Dry Mycelium in Soil Exhibits No Adverse Effects on Bermudagrass and Pinto Bean Plants

Infective spores, primarily conidia, have been used historically in insect biocontrol efforts employing entomopathogenic fungi as microbial agents (Magalhães and Boucias 2004, J. Orthoptera Res. 13: 155–159). Indeed, Humber (1991, In Proc. Aphid-Plant Interactions: Populations to Molecules Oklahoma State Univ. Agric. Exp. Station MP-132. Pg. 45–56) noted that only spores (conidia or blastospores) are capable of successfully invading the host insect body. While fungal mycelium is not infective per se (i.e., cannot invade live insect hosts), the use of mycelia artificially produced as dry granules or pellets has been explored. Such mycelial preparations placed in the field or greenhouse with environmental conditions conducive for fungal growth will grow and eventually produce infective spores that insect pests may contact. Use of dry mycelial preparations may circumvent technical difficulties inherent in the industrial production and the commercial application of aerial fungal spores (Jackson et al. 1997, Mycol. Res. 101: 35–41) while capitalizing on the relatively simple production of filamentous stages (mycelium) using equipment from industrial biotechnology (i.e., fermentation). Dry mycelium formulations have been tested against insects on foliage and in other environments (Rombach et al. 1986, Environ. Entomol. 15: 1070–1073; Wraight et al. 2003, Biol. Control 28: 60–77). Sanchez-Peña and Thorvilson (1991, Pp. 94–105, In Proc. 1991 Imported Fire Ant Conf., Univ. Georgia, Athens) successfully used dry mycelium of Beauveria bassiana (Balsamo) Vuillemin sensu lato against red imported fire ant, Solenopsis invicta Buren, queens. Krueger et al. (1992, J. Invertebr. Pathol. 59: 54–60) reported shorter lethal times of grubs of the