Arthropod abundance and diversity in street trees of south Texas, USA

In urban areas, street trees provide a variety of ecological services, including biodiversity conservation. In this study we examined arthropod diversity on native and non-native street trees sampled during the fall of 2010 and spring of 2011 in McAllen, Texas, one of the most rapidly growing urban areas in the country. Eighty-eight street trees were sampled by removing arthropods from the lower canopy foliage using a hand held vacuum. Arthropods were collected into nylon bags, identified to order, and counted by morphospecies. Overall, street trees supported a significant and diverse population of arthropods: a total of 1,971 arthropods were collected, from which 12 different orders and 102 different morphospecies were identified. We found arthropod abundance was higher on street trees native to the Lower Rio Grande Valley compared to non-native trees, especially for beetles, wasps, bees, ants, and spiders. This difference was particularly striking in spring when trees were flushed with new growth. The significant deficiency of arthropods on non-native trees is indicative of their relatively low value for maintaining entomological fauna. Local land managers who aim to include biodiversity conservation in their efforts thus should enhance the urban forest through the conservation of existing native remnant trees and promoting the use of native tree species in landscaping

Host range of Tetramesa romana Walker (Hymenoptera: Eurytomidae), a potential biological control of giant reed, Arundo donax L. in North America

The eurytomid wasp, Tetramesa romana Walker was evaluated as a potential biological control agent of the invasive reed grass, Arundo donax in North America. No-choice tests and timed behavioral studies were used to determine the fundamental host range of two genotypes of the wasp collected from Granada, Spain and Perpignan, France. Thirty-five species, including two genotypes of A. donax and seven ecotypes of Phragmites australis, along with closely related grasses, economic grasses and habitat associates were tested. Complete development of both T. romana genotypes was restricted to A. donax and Arundo formosana. The mean number of offspring produced from individual females was significantly greater on the A. donax genotype from Laredo, TX (12.8 ± 3.2) as compared to the genotype from San Juan, TX (3.9 ± 1.0) and A. formosana (0.8 ± 0.4). In behavioral studies, ovipositor probing was observed on 15 of the 35 species but development only occurred on A. donax and A. formosana. Based on our results, the wasp T. romana appears to be specific to the genus Arundo and is unlikely to harm native or cultivated plants in the Americas

Walking Velocity and Estimated Distance of the Armored Scale Crawler Rhizaspidiotus donacis, a Biological Control Agent for Arundo donax

Arundo scale, Rhizaspidiotus donacis (Leonardi) (Hemiptera: Diaspididae), is an armored scale biological control agent established on the invasive weed, Arundo donax L. (Poaceae; Arundinoideae) at several locations along the Rio Grande in Texas (Goolsby et. al. 2009, Moran and Goolsby 2010, Goolsby et al. 2011, Villarreal et al. 2016). The arundo scale is having significant impact on the target weed in areas where it established (Goolsby and Moran 2019), and no non-target plant use was observed (Goolsby et al. 2020). Armored scale crawlers usually live for less than a day and settle within 1 m of their sessile mother (Beardsley and Gonzalez 1975). Their low level of dispersion led to biological studies of the arundo scale in quarantine before release to quantify aspects of its biology that influenced dispersal. We measured walking velocity, estimated the potential distance a crawler could travel during a 12-hour period, and variations of the attributes for crawlers that emerged over time from different geographical accessions. The information was used to prioritize populations for release at field sites or nearby rearing facility. Three accessions of R. donacis crawlers from France, Italy, and Greece were evaluated (Table 1). Crawlers of each accession were isolated as individuals in gelatin capsules on Monday, Wednesday, and Friday mornings and kept for observation in the laboratory at 23°C and 50% relative humidity. Crawlers in gelatin capsules were observed with the aid of a dissecting microscope (Leica MZ-16). Distances walked were measured using a stage micrometer during 10-second periods. Arundo scale crawlers walked at an average velocity of 0.47 mm per second, which is similar to measurements of crawlers of black scale, Saisettia olea Bern., walking on wax paper at 0.38 mm per second (Quayle 1911). The estimated distance walked by black scale crawlers in 12 hours was 9.1 m, which is similar to arundo scale that ranged from 14.4 to 20.7 m (Table 1). Arundo scale crawlers from different European accessions showed significant differences in mean velocity walked and potential estimated maximum distance during 3 and 12 hours and for days during the week they emerged. Differences might reflect the nutrition of the plant host. All accessions were harvested from A. donax stands with high population levels of R. donacis, so rhizomes and ramets might have been significantly depleted of nutrient reserves which influenced the vigor of crawlers. As expected, crawlers collected on Mondays had the least vigor because some might have been as old as 3 days. Arundo scale crawlers seemed to be capable of traveling as far as 20 m which is the maximum height of an A. donax stem. Although we did not estimate distance for more than 12 hours, the period of time represents the typical life span of an arundo scale crawler (Beardsley and Gonzalez 1975). Dispersal of arundo scale is limited to movement of the crawlers over short distances and displacement of infested rhizomes during flood events. Considering the limited dispersal ability of R. donacis, additional rearing and release might be needed to achieve maximum benefit from this key agent where the weed is invasive and especially over the 350 river miles of the Rio Grande along the Texas-Mexico border

Automatic Camera Trap Classification Using Wildlife-Specific Deep Learning in Nilgai Management

Camera traps provide a low-cost approach to collect data and monitor wildlife across large scales but hand-labeling images at a rate that outpaces accumulation is difficult. Deep learning, a subdiscipline of machine learning and computer science, has been shown to address the issue of automatically classifying camera trap images with a high degree of accuracy. This technique, however, may be less accessible to ecologists, to small scale conservation projects, and has serious limitations. In this study, a simple deep learning model was trained using a dataset of 120,000 images to identify the presence of nilgai Boselaphus tragocamelus, a regionally specific non-native game animal, in camera trap images with an overall accuracy of 97%. A second model was trained to identify 20 groups of animals and 1 group of images without any animals present, labeled as “none”, with an accuracy of 89%. Lastly, the multigroup model was tested on images collected of similar species but in the southwestern United States and resulted in significantly lower precision and recall for each group. This study highlights the potential of deep learning for automating camera trap image processing workflows, provides a brief overview of image-based deep learning, and discusses the often-understated limitations and methodological considerations in the context of wildlife conservation and species monitoring

Development of a remotely activated field sprayer and evaluation of temperature and aeration on the longevity of Steinernema riobrave entomopathogenic nematodes for treatment of cattle fever tick-infested nilgai

A remotely activated field sprayer was developed for application of the entomopathogenic nematode, Steinerne-ma riobrave (Cabanillas, Poinar, and Raulston) for eradication of the southern cattle fever tick, Rhipicephalus microplus (Canestrini) infesting free-ranging nilgai (Boselaphus tragocamelus) in South Texas. The battery pow-ered sprayer is activated by sonic sensors that detect movement of nilgai through fence crossings. An onboard computer operates the sprayer pump and aerator that oxygenates the solution of nematodes. Several types of aeria-tion, agitation, and cooling were tested to prolong the viability of the nematodes in water. Continuous aeration extended the longevity of S. riobrave to more than two weeks as compared to cooling or intermittent agitation. The potential use of nematodes pathogenic to R. microplus dispensed by the remotely activated sprayer to infested nil-gai, and potentially white-tailed deer (Odocoileus virginianus), as part of integrated cattle fever tick eradication efforts is discussed

Development and testing of artificial membranes for rearing of Rhipicephalus microplus, the Southern Cattle Fever Tick

The southern cattle fever tick, Rhipicephalus microplus, is a livestock pest worldwide in tropical and subtropical climates, including South Texas, and can vector Babesia spp., the causal agents of bovine babesiosis. Artificial rearing methods for R. microplus are needed, especially for rearing specialist tick parasitoids that are under evaluation for classical biological control. In this study, we tested the efficiency of artificial feeding of R. microplus larvae, nymphs, and adults on a siliconized substrate (goldbeater’s membrane, lens paper, or Hemotek), or on nonsiliconized goldbeater’s membrane or Hemotek. Other variables tested were a warm water bath, incubator, positioning blood above or below ticks, using various attractants to stimulate attachment to membrane, incubating with or without 5% CO2, changing static blood once a day versus peristaltic pumping of blood, and using heparinized versus defibrinated blood. Peristaltic pumping of blood across the membrane inside the incubator significantly increased larval attachment. We found that up to 25% percent of these life stages would attach to the siliconized goldbeater’s membrane and feed, although none molted or completed their entire life cycle. A red color observable in the “fed” ticks’ legs seemed to indicate that bovine hemoglobin had penetrated the gut and entered the hemolymph of the ticks. We were successful rearing unfed nymphs to the engorged stage, which is the pre-requisite for rearing Ixoidiphagus tick parasitoids. Suggestions for future experimentation for rearing R. microplus on artificial membranes are discussed

Biological Control of Giant Reed (Arundo donax): Economic Aspects

Arundo donax is a large, invasive weed consuming large quantities of water in the riparian area of the Texas Rio Grande Basin. With water availability a concern to the area, the USDA-ARS is investigating biological control agents to increase available water, creating a benefit to both the region’s economy and society in general.Arundo donax, Giant Reed, Water, Economics, Invasive, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Insights into the microbes and nematodes hosted by pupae of the arundo leaf miner, Lasioptera donacis (Diptera: Cecidomyiidae)

The leaf miner Lasioptera donacis Coutin (Diptera: Cecidomyiidae) is a biological control agent of the invasive weed, Arundo donax L. (Poaceae), that was approved for release in the U.S. and Mexico. Pupae are preferred for shipment of living material to quarantine facilities. There is a question of whether emerged females would carry conidia of a potential mutualist fungus, and in particular the saprophyte Arthrinium arundinis, from the pupa or if they would have to acquire the conidia exclusively from the plant to start the oviposition process. We artificially smeared leaf-sheaths of growing plants with A. arundinis before being exposed to female midges, and maintained these host plants until the pupal stage of the midge developed. Polymerase chain reaction methods were applied to detect A. arundinis and any other potential fungi in these pupae. Only 9% of the pupae were infested by fungi or yeast, predominantly belonging to the genus Sarocladium, but not A. arundinis, confirming that the newly emerged females are free of this fungus and will have to acquire conidia present on the leaf-sheath for successful oviposition. We also tentatively tested by PCR for the presence of parasitic nematodes in these pupae. More than 42% of the pupae were shown to be infested specifically by T. gyraloura. Such high infection rate calls for developing methods to eliminate this parasite or to find a parasitefree native population prior to release of L. donacis adults in North America for biological control of A. donax