Non-target Insect Populations Research Articles

Survey of Mosquito Larvae for Potential Nematode Parasitic Biological Control in Alachua County

There is an obvious and considerable interest in developing novel methods to control mosquito-borne diseases due to their impacts on mammalian hosts. Biological control practices are sustainable alternatives to chemical control of mosquito populations. Some nematodes are efficient insect parasites and represent a potential source of novel biological control agents. Such beneficial nematodes are potent biological control agents that can remove harmful pests whilst also preserving non-target insect populations. One such nematode, Romanomermis culicivorax, is a parasite of mosquito larvae, inducing paralysis and eventually killing its host. The potential success of a biological control agent can be informed from the current prevalence of native populations. Thus, we conducted a survey of parasitic nematodes in mosquito larvae in Alachua County. Twenty-five samples were obtained from all around Alachua County, with assistance from the Gainesville Department of Public Works Mosquito Control Section. Subsequent visual inspection and PCR for R. culicivorax were conducted to detect the presence of mosquito and nematode DNA in each sample. Out of the twenty-five mosquito samples tested, only one sample tested positive for the presence of the beneficial nematode. This sample was found in an apartment complex in proximity to Devil’s Millhopper Geological State Park. This work demonstrates the presence of mosquito parasitic nematodes in Alachua County, but at very low levels, potentially discouraging the use of such biological control practices. In addition, the proximity of the positive sample to the natural area may indicate the need to preserve such habitats for effective biological control measures.

Acttra SWD Bait Formulation Against Drosophila Suzukii and its Compatibility with Berry Pollination by the Honey Bee, Apis Mellifera

Abstract Crop protection substances are continuously developed to prevent the decimation of non-target insect populations through insecticide use. The bait formulation Acttra SWD was created to attract the adult spotted-wing drosophila, a generalist pest of berries, and when mixed with insecticide would cause a reduction in the volume of insecticide applied, thus avoiding a complete coverage of crops and resulting in economic and ecological benefits to society. However, Acttra SWD has some compounds, including sugars and fruit odors, that might attract non-target fauna, especially insect pollinators. Therefore this study aimed (1) to investigate if Acttra SWD mixed with the recommended pesticide, i.e. spinosad (Entrust), is attractive to the honey bee, which is extensively used for berry pollination and (2) to evaluate the insecticidal activity of Acttra/Entrust in oral and contact tests on the same species. In all replicates, most foragers rejected feeders that offered Acttra/Entrust, and some switched to Acttra/Entrust-free feeders. Accordingly, mortality caused by this mixture in oral tests was low and did not differ from control, since the majority of bees did not consume the Acttra/Entrust treatment. However, mortality caused by this mixture was higher than in control groups in topical tests. Our results indicate that honey bees will not be attracted to and poisoned by crops sprayed with Acttra/Entrust, but contact with the bait would result in lethal or sub-lethal effects.

Increasing neonicotinoid use and the declining butterfly fauna of lowland California.

The butterfly fauna of lowland Northern California has exhibited a marked decline in recent years that previous studies have attributed in part to altered climatic conditions and changes in land use. Here, we ask if a shift in insecticide use towards neonicotinoids is associated with butterfly declines at four sites in the region that have been monitored for four decades. A negative association between butterfly populations and increasing neonicotinoid application is detectable while controlling for land use and other factors, and appears to be more severe for smaller-bodied species. These results suggest that neonicotinoids could influence non-target insect populations occurring in proximity to application locations, and highlights the need for mechanistic work to complement long-term observational data.

Pheromone Lure and Trap Color Affects Bycatch in Agricultural Landscapes of Utah.

Aerial traps, using combinations of color and attractive lures, are a critical tool for detecting and managing insect pest populations. Yet, despite improvements in trap efficacy, collection of nontarget species ("bycatch") plagues many insect pest surveys. Bycatch can influence survey effectiveness by reducing the available space for target species and increasing trap screening time, especially in areas where thousands of insects are captured as bycatch in a given season. Additionally, bycatch may negatively impact local nontarget insect populations, including beneficial predators and pollinators. Here, we tested the effect of pheromone lures on bycatch rates of Coccinellidae (Coleoptera), Apoidea (Hymenoptera), and nontarget Lepidoptera. Multicolored (primarily yellow and white) bucket traps containing a pheromone lure for capturing one of three survey target species, Spodoptera litura (F.), S. littoralis (Boisduval), or Helicoverpa armigera (Hübner), were placed in alfalfa and corn fields, and compared to multicolored traps without a pheromone lure. All-green traps with and without H. armigera lures were employed in a parallel study investigating the effect of lure and trap color on bycatch. Over 2,600 Coccinellidae representing seven species, nearly 6,400 bees in 57 species, and >9,000 nontarget moths in 17 genera were captured across 180 traps and seven temporal sampling events. Significant effects of lure and color were observed for multiple taxa. In general, nontarget insects were attracted to the H. armigera lure and multicolored trap, but further studies of trap color and pheromone lure specificity are needed to better understand these interactions and to minimize nontarget captures.

Side effects of fungicides on the abundance and the species diversity of the natural populations of Drosophila and their hymenopterous parasitoids in orchards

Within entomophagous insects, hymenopterous parasitoids are important regulators of natural populations of insects including pests. Pesticide treatments are largely used in orchards for economic reasons. These treatments allow for greater productivity, but they may also impact upon non-target insect populations. Drosophila and their hymenopterous parasitoids are abundant in orchards and are not direct targets of pesticide treatments. In this work, natural populations of Drosophila and their parasitoids were monitored from June to November, and their abundance was reported from two types of orchards. One type was under conventional pesticide treatments, mostly fungicides (“Treated plot”), and the other was under low-input treatments (“Low-input plot”). Five Drosophila species and five parasitoid species were present in both types of orchards. A time effect on abundance was found with two peaks of abundance, one in August and the other in autumn (October), corresponding to a fluctuation of numbers depending on the availability of resources. When comparing insect abundance between the two types of plots, the abundance in the Treated plot was found to be lower than or equal to that in the Low-input plot. Furthermore, a significant decrease in the abundance of two scarce parasitoid species (Leptopilina heterotoma and Asobara tabida) that could lead to their disappearance was also observed. The results are discussed in the context of the diverse lethal and sub-lethal effects of pesticides on the development and reproduction of natural populations of insects and their importance as natural enemies.

Isolation of transcripts from Diabrotica virgifera virgifera LeConte responsive to the Bacillus thuringiensis toxin Cry3Bb1

Crystal (Cry) proteins derived from Bacillus thuringiensis (Bt) have been widely used as a method of insect pest management for several decades. In recent years, a transgenic corn expressing the Cry3Bb1 toxin has been successfully used for protection against corn rootworm larvae (genus Diabrotica). The biological action of the Bt toxin in corn rootworms has not yet been clearly defined. Because development of resistance to Bt by corn rootworms will have huge economic and ecological costs, insight into larval response to Bt toxin is highly desirable. We identified 19 unique transcripts that are differentially expressed in D. virgifera virgifera larvae reared on corn transgenic for Cry3Bb1. Putative identities of these genes were consistent with impacts on metabolism and development. Analysis of highly modulated transcripts resulted in the characterization of genes coding for a member of a cysteine-rich secretory protein family and a glutamine-rich membrane protein. A third gene that was isolated encodes a nondescript 132 amino acid protein while a fourth highly modulated transcript could not be further characterized. Expression patterns of these four genes were strikingly different between susceptible and resistant western corn rootworm populations. These genes may provide useful targets for monitoring of Bt exposure patterns and resistance development in pest and non-target insect populations.

Major effect genes or loose confederations? The development of insecticide resistance in the malaria vector Anopheles gambiae

Insecticide use in public health and agriculture presents a dramatic adaptive challenge to target and non-target insect populations. The rapid development of genetically modulated resistance to insecticides is postulated to develop in two distinct ways: By selection for single major effect genes or by selection for loose confederations in which several factors, not normally associated with each other, inadvertently combine their effects to produce resistance phenotypes. Insecticide resistance is a common occurrence and has been intensively studied in the major malaria vector Anopheles gambiae, providing a useful model for examining how insecticide resistance develops and what pleiotropic effects are likely to emerge as a consequence of resistance. As malaria vector control becomes increasingly reliant on successfully managing insecticide resistance, the characterisation of resistance mechanisms and their pleiotropic effects becomes increasingly important.

Toxicidade de Substâncias Isoladas de Simarouba versicolor St. Hil. (Simaroubaceae) para Formigas Cortadeiras Atta sexdens L. (Hymenoptera: Formicidae) e para o seu Fungo Simbionte Leucoagaricus gongylophorus (Singer) Möller

Leaf-cutting ants' control by means of insecticide application can cause harmful effects to the environment, non-target insect populations and human health. Vegetal products toxic to insects may represent an alternative way for controlling economically important insects for the reason that they may be more selective, besides a less residual effect. In order of this, the aim of the current study was to evaluate the toxicity of crude extracts, fractions and isolated substances from Simarouba versicolor St. Hil. (Simaroubaceae) to Atta sexdens L. (Hymenoptera: Formicidae) workers and its symbiotic fungus, Leucoagaricus gongylophorus (Singer) Moller. Leaf-cutting ants' toxicity was determined by ingestion bioassays, while the activity against the symbiotic fungus was evaluated by its development in a culture medium containing vegetal extracts. Dichloromethane fractions derived from S. versicolor methanol crude extracts showed biological activity to leaf-cutting ants and its symbiotic fungus. From these fractions, two alkaloids were isolated, 4,5-dimethoxycanthin-6-one and 5-methoxycanthin-6-one, being the first toxic only to the symbiotic fungus and the other to fungus and the ant. Purified triterpenoids from others S. versicolor extracts didn’t show deleterious effect to both leaf-cuttings ants and the symbiotic fungus.

Host Specificity of Microsporidia (Protista: Microspora) from European Populations ofLymantria dispar(Lepidoptera: Lymantriidae) to Indigenous North American Lepidoptera

Results of traditional laboratory bioassays may not accurately represent ecological (field) host specificity of entomopathogens but, if carefully interpreted, may be used to predict the ecological host specificity of pathogens being considered for release as classical biological control agents. We conducted laboratory studies designed to evaluate the physiological host specificity of microsporidia, which are common protozoan pathogens of insects. In these studies, 49 nontarget lepidopteran species indigenous to North America were fed five biotypes of microsporidia that occur in European populations ofLymantria disparbut are not found in North American populations ofL. dispar.These microsporidia,Microsporidiumsp. from Portugal,Microsporidiumsp. from Romania,Microsporidiumsp. from Slovakia,Nosema lymantriae,andEndoreticulatussp. from Portugal, are candidates for release as classical biological control agents intoL. disparpopulations in the United States. The microsporidia produced a variety of responses in the nontarget hosts and, based on these responses, the nontarget hosts were placed in the following categories: (1) no infection (refractory), (2) atypical infections, and (3) heavy infections.Endoreticulatussp. produced patent, host-like infections in nearly two-thirds of the nontarget hosts to which it was fed. Such generalist species should not be recommended for release. Infections comparable to those produced inL. disparwere produced in 2% of the nontarget hosts fedMicrosporidiumsp. from Portugal, 19% of nontarget hosts fedMicrosporidiumsp. from Romania, 13% fed spores ofMicrosporidiumsp. from Slovakia, and 11% of nontarget species fedN. lymantriae.The remaining nontarget species developed infections that, despite production of mature spores, were not typical of infection inL. dispar.We believe it is very unlikely that these atypical infections would be horizontally transmitted within nontarget insect populations in the United States.

John N. Couch: A Founder of Entomological Mycology

Results of traditional laboratory bioassays may not accurately represent ecological (field) host specificity of entomopathogens but, if carefully interpreted, may be used to predict the ecological host specificity of pathogens being considered for release as classical biological control agents. We conducted laboratory studies designed to evaluate the physiological host specificity of microsporidia, which are common protozoan pathogens of insects. In these studies, 49 nontarget lepidopteran species indigenous to North America were fed five biotypes of microsporidia that occur in European populations ofLymantria disparbut are not found in North American populations ofL. dispar.These microsporidia,Microsporidiumsp. from Portugal,Microsporidiumsp. from Romania,Microsporidiumsp. from Slovakia,Nosema lymantriae,andEndoreticulatussp. from Portugal, are candidates for release as classical biological control agents intoL. disparpopulations in the United States. The microsporidia produced a variety of responses in the nontarget hosts and, based on these responses, the nontarget hosts were placed in the following categories: (1) no infection (refractory), (2) atypical infections, and (3) heavy infections.Endoreticulatussp. produced patent, host-like infections in nearly two-thirds of the nontarget hosts to which it was fed. Such generalist species should not be recommended for release. Infections comparable to those produced inL. disparwere produced in 2% of the nontarget hosts fedMicrosporidiumsp. from Portugal, 19% of nontarget hosts fedMicrosporidiumsp. from Romania, 13% fed spores ofMicrosporidiumsp. from Slovakia, and 11% of nontarget species fedN. lymantriae.The remaining nontarget species developed infections that, despite production of mature spores, were not typical of infection inL. dispar.We believe it is very unlikely that these atypical infections would be horizontally transmitted within nontarget insect populations in the United States.

Ecological strategies of forest insects: the need for a community-level approach to reforestation

The traditional, single-species approach to forest pest management is considered in light of the range of ecological strategies respresented in forest arthropod communities. Insect population growth and impact depend on host variables subject to silvicultural manipulation, especially during early stages of forest development, but silvicultural practices often induce undesirable responses from non-target insect populations. A suggested approach to forest pest management involves consideration of arthropod community structure, life history traits, and interactions among arthropod and plant species in order to anticipate insect responses and refine silvicultural recommendations accordingly.

Velvetbean Caterpillar and Bean Leaf Beetle Control on Soybeans with Microbial Insecticides, 1979

Abstract A small plot field trial was initiated on October 3 at the Black Belt Substation of the Auburn University Agricultural Experiment Station near Marion Junction, Alabama. Significant numbers of both velvetbean caterpillar and bean leaf beetles were found at this date on a small field of late planted Bragg variety soybeans. Plots measuring 4 x 50 ft (36 in row spacing) were treated with materials applied with a CO2 powered knapsack sprayer, 3 nozzles/row, calibrated to deliver 20 gal/acre at 30 psi with TX 4 cone spray tips. A randomized complete block field plot design with 4 replications was utilized. Prespray larval and beetle counts were taken on the day of treatment, and evaluation counts were taken at 2 and 5 days post-spray. All samples were made by the shake cloth method and consisted of 3 3 ft samples/plot. D-vac samples were also taken on the 3 sampling dates for determining non-target insect populations. Eight 10 row ft samples were taken from random locations over the entire field just prior to treatment application, and one 10-ft sample was taken in each plot at 2 and 5 days post-spray.