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Sources Of Variability In Agronomic Weed Seed Predation: Time, Space, Habitat, And Hyperpredation, Sonja K. Birthisel

Electronic Theses and Dissertations

Weed seed predation is an ecosystem service that benefits farmers by decreasing seedbank inputs, thereby reducing weed pressure in subsequent growing seasons. Seed predation can be considerable, but is highly variable. Sources of variability may include time, space, habitat, and trophic interactions such as hyperpredation. Two experiments were conducted to measure the impacts of these sources of variability on weed seed predation rates in Maine mixed vegetable agroecosystems.

Chapter One of this thesis describes a series of landscape-level field experiments conducted to quantify the effects of time, space, and habitat on seed predation rates. Seed assays, with and without vertebrate …

Assessment Of Factors Affecting Establishment Of Biological Control Agents Of Hemlock Woolly Adelgid On Eastern Hemlock In The Great Smoky Mountains National Park, Abdul Hakeem

Doctoral Dissertations

Eastern hemlock in the Great Smoky Mountains National Park (GRSM) is threatened by hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). To manage this invasive pest in GRSM, ca. 550,000 Sasajiscymnus tsugae (Sasaji and McClure) (Coleoptera: Coccinellidae) and 7,857 Laricobius nigrinus Fender (Coleoptera: Derodontidae) have been released. Limited information is available on their establishment in GRSM. To fill this gap, a study was initiated to assess establishment of these predators and their impact on hemlock health. To determine factors affecting establishment of these predators, 65 release sites were sampled from 2008 to 2012. Several factors were evaluated for their …

The Life History Of Larinus Minutus, A Biological Control Agent Of Invasive Knapweeds, And Its Dispersal From Release Sites In Arkansas, Adam M. Alford

Graduate Theses and Dissertations

Larinus minutus Gyllenhal, a biological control agent of invasive knapweeds, has become established in several states and provinces since initial North American introduction in 1991. In order to reduce growing spotted knapweed populations in Northwest Arkansas, Larinus minutus (a biological control agent of spotted knapweed) was released annually from 2008-2011. Little is known about the larval development of this species, although the widespread use of this insect has provided research describing detailed host range and generalized life history. The speed and extent of the spread of this weevil from release sites following introduction have not been reported. This research described …

An Ecological Assessment Of Insect Diversity At Organic Central Coast Vegetable Farms On Two Spatial Scales, Emily Musgrave

Master's Theses

Modern industrial agriculture is the principal cause of anthropogenic land use changes for terrestrial ecosystems. Approximately 40% of the planet's land surface, or half of the habitable area, is now composed of agricultural landscapes. The simplification and industrialization of agriculture are the biggest drivers of global biodiversity loss, especially on Californian's Central Coast. Diversified organic agriculture, however, may offer some refuge for non-crop species. In this study we analyzed insect and plant biodiversity on and adjacent to organic vegetable farms on the Central Coast of California at two spatial scales, the landscape-scale and a smaller within-farm scale. At the landscape-scale, …

A Phylogenetic Analysis Of Species Diversity, Specificity, And Distribution Of Mycodiplosis On Rust Fungi, Donald Jay Nelsen

LSU Master's Theses

There are more than 7800 species of Pucciniales (rust fungi) described. Aeciospores and urediniospores of rust fungi are a food source for the larval stage of members of the fly genus Mycodiplosis, hence these could be of interest as potential biological control agents. Currently, Mycodiplosis contains 49 described species based on adult male morphology. A survey of 1,350 rust-infected plants from 44 countries was recently conducted to assess the occurrence of Mycodiplosis fly larvae across a broad spectrum of Pucciniales. Larvae were found on 261 collections from 25 countries. Statistical analyses explored the distribution of larvae in relation to host …