Erik R. Echegaray

Virulence Analysis of Hessian Fly Populations From Texas, Oklahoma, and Kansas

ABSTRACT In recent years, the number of wheat, Triticum aestivum L., fields heavily infested by Hessian fly, Mayetiola destructor (Say), has increased in the Great Plains of the United States. Historically, resistance genes in wheat have been the most efficient means of controlling this insect pest. To determine which resistance genes are still effective in this area, virulence of six Hessian fly populations from Texas, Oklahoma, and Kansas was determined, using the resistance genes H3, H4, H5, H6, H7H8, H9, H10, H11, H12, H13, H16, H17, H18, H21, H22, H23, H24, H25, H26, H31, and Hdic. Five of the tested genes, H13, H21, H25, H26, and Hdic, conferred high levels of resistance (>80% of plants scored resistant) to all tested populations. Resistance levels for other genes varied depending on which Hessian fly population they were tested against. Biotype composition analysis of insects collected directly from wheat fields in Grayson County, TX, revealed that the proportion of individuals within this population virulent to the major resistance genes was highly variable (89% for H6, 58% for H9, 28% for H5, 22% for H26, 15% for H3, 9% for H18, 4% for H21, and 0% for H13). Results also revealed that the percentages of biotypes virulent to specific resistance genes in a given population are highly correlated (r2 = 0.97) with the percentages of susceptible plants in a virulence test. This suggests that virulence assays, which require less time and effort, can be used to approximate biotype composition.

Haplotypes of the Potato Psyllid, Bactericera cockerelli, on the Wild Host Plant, Solanum dulcamara, in the Pacific Northwestern United States

Abstract‘Candidatus Liberibacter solanacearum’ (Lso) is a bacterium that infects solanaceous crops and causes plant decline and yield losses, especially in potato and tomato. Lso is transmitted to these hosts by the potato psyllid (Bactericera cockerelli Sulc) vector. B. cockerelli host plants are not limited to crop plants, but also include many wild, solanaceous weeds. These wild hosts could potentially impact overwintering and breeding of the psyllids and serve as reservoirs for Lso. In the Pacific Northwestern United States, B. cockerelli was recently reported to overwinter on bittersweet nightshade (Solanum dulcamara L.). The present study utilized high resolution melting analysis of the B. cockerelli mitochondrial cytochrome c oxidase I gene to assess the psyllid populations occurring on S. dulcamara during the summer and winter months in Washington, Oregon, and Idaho. This technique has previously been used to analyze the cytochrome c oxidase I gene of B. cockerelli, and has identified four psyllid haplotypes. Lso infection was also determined for the psyllids collected from S. dulcamara. During both the summer and the winter months in the Pacific Northwest, the Northwestern psyllid haplotype was the predominant population found living on S. dulcamara. However, low levels of the Western psyllid population were also present in Washington and Oregon during the same period. No overwintering psyllids tested were Lso-infected, suggesting that these populations do not pose an imminent threat of Lso transmission to newly emerging potatoes and other solanaceous crops in the region, unless a source of Lso becomes available.Resumen‘Candidatus Liberibacter solanacearum’ (Lso) es una bacteria que infecta a cultivos de solanáceas y causa abatimiento y pérdida de cosechas, especialmente en papa y tomate. Lso se transmite a estos hospedantes por el vector psílido de la papa (Bactericera cockerelli Sulc). Las plantas hospederas de B. cockerelli no se limitan a especies cultivadas, sino que también incluyen muchas malezas silvestres solanáceas. Estas hospedantes silvestres pudieran impactar potencialmente la invernación y apareamiento de los psílidos y servir como reservorios para Lso. En el Noroeste del Pacífico de los Estados Unidos de América se ha reportado recientemente a B. cockerelli invernando en la planta “uva del diablo”, “dulcamara” o “matagallinas” (Solanum dulcamara L.). En el presente estudio se utilizó un análisis de fusión de alta resolución del gen mitocondrial del citocromo c oxidasa de B. cockerelli para analizar las poblaciones del psílido que se presentan en S. dulcamara durante los meses del verano e invierno en Washington, Oregon y Idaho. Se ha utilizado previamente esta técnica para analizar el gen mencionado, y ha identificado cuatro haplotipos del psílido. También se determinó la infección por Lso en psílidos colectados de S. dulcamara. Durante los meses de verano e invierno en el Pacífico del Noroeste, el haplotipo del psílido del Noroeste era la población dominante que se encontraba viviendo en S. dulcamara. No obstante, también se encontraba, aunque en bajos niveles de la población, el psílido del Oeste en Washington y Oregon durante el mismo período. Psílidos no invernantes probados estaban infectados de Lso, sugiriendo que estas poblaciones no representan una amenaza inminente de transmisión de Lso a papas de nueva emergencia y a otros cultivos de solanáceas en la región, a menos que una fuente de Lso estuviera disponible.

Life History Characteristics of the Rove Beetle, Dalotia coriaria (Coleoptera: Staphylinidae) under Laboratory Conditions

Abstract Rove beetles (Coleoptera: Staphylinidae) have been reported as predators of animal and human disease vectors and of insect pests associated with field and greenhouse crops including species in the genera Aleochara, Holobus, Paederus, Dalotia, Staphylinus and Philonthus; however, there is limited information on their life history parameters. The rove beetle Dalotia coriaria (Kraatz) is a predator of greenhouse pests including fungus gnats. In this study, stage-specific and total development, fecundity, longevity, and sex ratio were investigated under laboratory conditions using growing medium as a substrate, which was designed to simulate what rove beetles would experience under greenhouse conditions. Duration of life stages was 2.2, 7.1, and 7.8 days for egg, larva and pupa respectively, whereas total development time from egg to adult was 17.0 days. Average fecundity was 90.2 eggs per female and the number of adults produced per female was 69.1. In addition, D. coriaria male and female adult longevity was 60.3 and 47.8 days. The sex ratio was 1∶1 (females∶males). These results will be helpful in improving augmentative biological control and mass-rearing.

Assessment of Potato Psyllid Bactericera cockerelli (Hemiptera: Triozidae) and Zebra Chip Disease in Four Commercial Potato Varieties in the Columbia Basin

Potato varieties may respond differently to the occurrence of arthropod pests including plant-pathogen. Although the potato psyllid, Bactericera cockerelli Sulc. (Hemiptera:Triozidae), the putative vector of Zebra Chip (ZC) disease, has been historically reported in the southern, central and western United States, the occurrence of the disease in the Pacific Northwest (PNW) is relatively new. Thus, there is a lack of information about infestation levels in commercial varieties, including russet potatoes, the predominant variety type of the region. In addition, susceptibility of russet varieties to ZC, which has become a serious production threat for the PNW since 2011, has not been thoroughly investigated. In the current 2-year study, the level of potato psyllid infestations and the impact of ZC disease in four commercial potato varieties, Ranger Russet, Russet Burbank, Umatilla Russet and Premier Russet, was evaluated. Psyllid adults were collected using a vacuum sampler based on an inverted leaf blower design, and leaf samples were used to collect eggs and nymphs. Also, ZC incidence and severity in fresh tubers was determined. The number of naturally occurring adults, nymphs and eggs per sample was similar among varieties suggesting a lack of affinity for any given variety. There was a positive relationship between the number of infective psyllids and disease incidence in 2011, while no relationship was detected in 2012. Although all varieties were equally susceptible to the disease, Ranger Russet numerically had the highest ZC incidence in tubers and Umatilla Russet the lowest.ResumenLas variedades de papa pudieran responder de manera diferente a la incidencia de plagas artrópodas que incluyan fitopatógenos. Aun cuando el psílido de la papa Bactericera cockerelli Sulc. (Hemiptera: Triozidae), el supuesto vector de la enfermedad de la papa rayada (Zebra Chip, ZC), ha sido reportado históricamente en el sur, centro y occidente de los Estados Unidos, la ocurrencia de la enfermedad en el noroccidente Pacífico (PNW) es relativamente nueva. De manera que hay un vacío de información sobre los niveles de infestación en variedades comerciales, incluyendo las russets, el tipo de variedad predominante en la región. Además, la susceptibilidad de las variedades russet a ZC, que se ha convertido en una seria amenaza a la producción para el PNW desde el 2011, no ha sido investigada a fondo. En el estudio actual de dos años, se evaluaron los niveles de infestación del psílido de la papa y el impacto de la enfermedad de la ZC en cuatro variedades comerciales, Ranger Russet, Russet Burbank, Umatilla Russet y Premier Russet. Se colectaron adultos del psílido utilizando un muestrador de vacío, basado en un diseño invertido de una barredora de hojas de aire, y las muestras de hoja se usaron para colectar huevecillos y ninfas. También se determinó la incidencia y severidad de ZC en tubérculos frescos. El número de adultos que se presentó naturalmente, de ninfas y de huevos por muestra, fue similar entre variedades, lo que sugirió una carencia de afinidad para una variedad cualquiera. Hubo una relación positiva entre el número de psílidos infectivos y la incidencia de la enfermedad en 2011. No se detectó esta relación en 2012. Aun cuando todas las variedades fueron igualmente susceptibles a la enfermedad, Ranger Russet tuvo numéricamente la mayor incidencia de ZC en tubérculos y Umstilla Russet la más baja.

Incidence of Bactericera cockerelli (Hemiptera: Triozidae) Under Different Pesticide Regimes in the Lower Columbia Basin

Abstract Zebra chip is a potato disease transmitted by the potato psyllid Bactericera cockerelli (Šulc) and distributed across several regions of the United States. Because of its potentially devastating effects, the disease represents a threat to the potato production and the industry particularly in the Pacific Northwest, where it was first detected in 2011. Efforts to control the disease primarily focus on managing the vector using pesticides. In this study, the effectiveness of two pesticide spray programs in 2012 (“FULL” and “REDUCED”) and three in 2013 (“FULL 1,” “FULL 2,” and “REDUCED”) against the potato psyllid was evaluated. Yellow sticky cards were used to monitor the adults, whereas immatures were evaluated by sampling the leaves. Overall, the vector infestation level in both years was low. The mean total number of adults per trap in 2012 was 1.5, 5, and 12 for “FULL,” “REDUCED,” and the control, respectively, while in 2013 was 10.3, 20.7, 17.7, and 52 for “FULL 1,” “FULL 2,” “REDUCED,” and the control, respectively. For each particular year, season-long regimes were most effective at controlling the pest than targeted applications; however, there was no statistical difference among regimes (“FULL” or “REDUCED”) after early July, when the first psyllids were detected, until mid-August. Moreover, this number was similar to the control. Also, psyllid density was uniform across sticky traps, and no clear relationship was found between the proportion of Lso-infective psyllids and zebra chip disease intensity.

Potato Psyllid (Hemiptera: Triozidae) Response to Insecticides Under Controlled Greenhouse Conditions.

Abstract Bactericera cockerelli (Šulc) is a common pest of solanaceous crops largely known for vectoring “psyllid yellows” in potatoes. In recent years, however, this pest has attracted considerable attention for vectoring Zebra Chip, a devastating bacterial disease that was first reported in the United States in 2004 and has spread across the southern and northwestern states, causing significant economic losses to potato growers and the industry. Management of the disease is mainly achieved by reducing the psyllid population using insecticides, including pyrethroids and neonicotinoids; however, new insecticides with different modes of action are needed to avoid the acquisition of resistance. In the current study, the immediate and residual effects of conventional and new materials were tested under greenhouse conditions against adults and nymphs. Cyantraniliprole at a high rate and spinetoram showed the highest immediate and residual activity against adults, whereas cyantraniliprole and oxamyl (low and high rates) were effective against nymphs, with no differences between rates. Soil applications of cyantraniliprole, oxamyl, and imidacloprid were still toxic to adults and nymphs 7 and 14 d after treatment. Also, cyantraniliprole and tolfenpyrad were detrimental to psyllid reproduction. The incorporation of new chemistry in rotation programs may provide a useful management tool against this pest.