NF526 Spring Millers

Biology, migration, and management of spring millers. Millers can be abundant in and around homes each year, especially in May and early June. At this time of year, the moths are most likely the adult stage of the army cutworm, a common pest of wheat and alfalfa. When millers emerge and begin to move westward in the spring, area residents have little recourse but to patiently await their departure. There are a few tactics, however, that can help lessen moth activity in and around homes: Keep outside lighting to a minimum. These night-flying moths are attracted to lights. A porch light, inadvertently left on, can attract hundreds or even thousands of these pests. Where lighting is necessary, use yellow light bulbs. Yellow light will not attract as many moths because insects do not sense this color very well. Seal cracks and crevices with caulking. Place weather stripping around doors and windows. Repair all screens in windows, doors, attic vents, etc. Consider using a landscape that minimizes flowering plants and dense vegetation near houses

Ecology and Management of \u3ci\u3ePemphigus betae\u3c/i\u3e (Hemiptera: Aphididae) in Sugar Beet

Pemphigus betae Doane (Hemiptera: Aphididae), is a sporadic pest of sugar beet (Beta vulgaris L. var. vulgaris) in all major sugar beet production regions of North America. These oval-shaped, pale-yellowish insects, with a body length ranging from 1.9–2.4mm, secrete a waxy material, giving their subterranean colonies a moldy appearance. Poplars in the genus Populus L. are the preferred primary hosts, while sugar beet and certain weed species, such as common lambsquarters (Chenopodium album L.) and kochia (Kochia scoparia (L.)), are among the secondary hosts. Pemphigus betae has a complex and varied life cycle and is usually heteroecious and holocyclic, although anholocyclic apterae are known to overwinter in the soil. Heavy infestations of this aphid can induce significant reductions in yield, sugar content, and recoverable sugar. Under conditions of extreme stress and heavy infestations, the alienicolae can induce stunting, chlorosis, wilting, and even death of sugar beet plants. Accurately establishing population densities for sugarbeet root aphids presents a challenge, because the economic important stage of this insect is subterranean. However, use of a fall root rating index aids in estimating relative population densities. Furthermore, root aphids are especially difficult to control by means of conventional insecticides. For this reason, integrated pest management tactics, including the use of host plant resistance, cultural control techniques, and the use of natural enemies, should take precedence

The Interface Between Wheat and the Wheat Curl Mite, \u3ci\u3eAceria tosichella\u3c/i\u3e, the Primary Vector of Globally Important Viral Diseases

Wheat production and sustainability are steadily threatened by pests and pathogens in both wealthy and developing countries. This review is focused on the wheat curl mite (WCM), Aceria tosichella, and its relationship with wheat. WCM is a major pest of wheat and other cereals and a vector of at least four damaging plant viruses (Wheat streak mosaic virus, High plains wheat mosaic virus, Brome streak mosaic virus, and Triticum mosaic virus). The WCM–virus pathosystem causes considerable yield losses worldwide and its severity increases significantly when mixed-virus infections occur. Chemical control strategies are largely ineffective because WCM occupies secluded niches on the plant, e.g., leaf sheaths or curled leaves in the whorl. The challenge of effectively managing this pest–virus complex is exacerbated by the existence of divergent WCM lineages that differ in host-colonization and virus-transmission abilities. We highlight research progress in mite ecology and virus epidemiology that affect management and development of cereal cultivars with WCM- and virus-resistance genes. We also address the challenge of avoiding both agronomically deleterious side effects and selection for field populations of WCM that can overcome these resistance genes. This report integrates the current state of knowledge of WCM–virus-plant interactions and addresses knowledge gaps regarding the mechanisms driving WCM infestation, viral epidemics, and plant responses. We discuss the potential application of molecular methods (e.g., transcriptomics, epigenetics, and whole-genome sequencing) to understand the chemical and cellular interface between the wheat plant and WCM–virus complexes

P7 and P8 proteins of High Plains wheat mosaic virus, a negative-strand RNA virus, employ distinct mechanisms of RNA silencing suppression

High Plains wheat mosaic virus (genus Emaravirus), an octapartite negative-sense RNA virus, encodes two RNA silencing suppressors, P7 and P8. In this study, we found that P7 and P8 efficiently delayed the onset of dsRNA-induced transitive pathway of RNA silencing. Electrophoretic mobility shift assays (EMSA) revealed that only P7 protected long dsRNAs from dicing in vitro and bound weakly to 21- and 24-nt PTGS-like ds-siRNAs. In contrast, P8 bound strongly and relatively weakly to 21- and 24-nt ds-siRNAs, respectively, suggesting size-specific binding. In EMSA, neither protein bound to 180-nt and 21-nt ssRNAs at detectable levels. Sequence analysis revealed that P7 contains a conserved GW motif. Mutational disruption of this motif resulted in loss of suppression of RNA silencing and pathogenicity enhancement, and failure to complement the silencing suppression-deficient wheat streak mosaic virus. Collectively, these data suggest that P7 and P8 proteins utilize distinct mechanisms to overcome host RNA silencing for successful establishment of systemic infection in planta

Mixed Infection of Hard Red Winter Wheat with High Plains Virus and Wheat Streak Mosaic Virus from Wheat Curl Mites in Nebraska

A new disease of wheat and corn caused by the High Plains virus (HPV) has been observed in the High Plains region of western United States. HPV is transmitted by the wheat curl mite, Aceria tosichella, which is also the vector of wheat streak mosaic virus (WSMV). In the field it is extremely difficult to visually differentiate plants infected with WSMV from those with HPV. An indirect protein-A sandwich enzyme-linked immunosorbent assay (PAS-ELISA) and Western blot analysis were used to identify WSMV and HPV. Samples of wheat curl mites were collected from arbitrarily chosen sites from commercial wheat plantings in 1995 and 1996 and used to infest caged wheat plants. After 3 weeks, leaf samples were harvested and assayed. Both Western blot analysis and PAS-ELISA were effective at identifying samples positive for WSMV and HPV, both alone and in mixed infections. Western blot results showed that over the 2 years, 65% of the samples were positive for WSMV, 46% were positive for HPV, and mixed infections were found in 40% of the samples. HPV presence was verified with similar results from field collected plant samples. These levels of virus indicate an unexpectedly high incidence of HPV in wheat curl mite populations in Nebraska

Nested deletion analysis of Wheat streak mosaic virus HC-Pro: Mapping of domains affecting polyprotein processing and eriophyid mite transmission

A series of in-frame and nested deletion mutations which progressively removed 5′-proximal sequences of the Wheat streak mosaic virus (WSMV) HC-Pro coding region (1152 nucleotides) was constructed and evaluated for pathogenicity to wheat. WSMV HC-Pro mutants with 5′- proximal deletions of 12 to 720 nucleotides systemically infected wheat. Boundary sequences flanking the deletions were stable and unaltered by passage through plants for all deletion mutants except HCD12 (lacking HC-Pro codons 3–6) that exhibited strong bias for G to A substitution at nucleotide 1190 in HC-Pro codon 2 (aspartic acid to asparagine). HC-Pro mutants with 5′-proximal deletions of up to 720 nucleotides retained autoproteolytic activity in vitro. In contrast, 5′-proximal deletion of 852 nucleotides of the HC-Pro coding region (HCD852) abolished both infectivity and in vitro proteolytic activity, confirming that the proteolytic domain of WSMV HC-Pro resides within the carboxy-terminal third of the protein and includes the cysteine proteinase motif (GYCY) conserved among four genera of the family Potyviridae. Inoculation of wheat with HC-Pro deletion mutants also bearing the GUS reporter gene revealed that HCD852 was unable to establish primary infection foci in inoculated leaves, indicating that processing of the P3 amino-terminus was essential. Deletion of as few as 24 nucleotides of HC-Pro (codons 3–10) eliminated transmission by the eriophyid mite vector Aceria tosichella Keifer. Collectively, these results demonstrated similar organization of proteinase and vector transmission functional domains among divergent HC-Pro homologues encoded by potyviruses and tritimoviruses. Published by Elsevier Inc

Ecology and Management of Pemphigus betae (Hemiptera: Aphididae) in Sugar Beet

Published ArticlePemphigus betae Doane (Hemiptera: Aphididae), is a sporadic pest of sugar beet (Beta vulgaris L. var. vulgaris) in all major sugar beet production regions of North America. These oval-shaped, pale-yellowish insects, with a body length ranging from 1.9–2.4mm, secrete a waxy material, giving their subterranean colonies a moldy appearance. Poplars in the genus Populus L. are the preferred primary hosts, while sugar beet and certain weed species, such as common lambsquarters (Chenopodium album L.) and kochia (Kochia scoparia (L.)), are among the secondary hosts. Pemphigus betae has a complex and varied life cycle and is usually heteroecious and holocyclic, although anholocyclic apterae are known to overwinter in the soil. Heavy infestations of this aphid can induce significant reductions in yield, sugar content, and recoverable sugar. Under conditions of extreme stress and heavy infestations, the alienicolae can induce stunting, chlorosis, wilting, and even death of sugar beet plants. Accurately establishing population densities for sugarbeet root aphids presents a challenge, because the economic important stage of this insect is subterranean. However, use of a fall root rating index aids in estimating relative population densities. Furthermore, root aphids are especially difficult to control by means of conventional insecticides. For this reason, integrated pest management tactics, including the use of host plant resistance, cultural control techniques, and the use of natural enemies, should take precedence

Nested deletion analysis of Wheat streak mosaic virus HC-Pro: Mapping of domains affecting polyprotein processing and eriophyid mite transmission

A series of in-frame and nested deletion mutations which progressively removed 5′-proximal sequences of the Wheat streak mosaic virus (WSMV) HC-Pro coding region (1152 nucleotides) was constructed and evaluated for pathogenicity to wheat. WSMV HC-Pro mutants with 5′- proximal deletions of 12 to 720 nucleotides systemically infected wheat. Boundary sequences flanking the deletions were stable and unaltered by passage through plants for all deletion mutants except HCD12 (lacking HC-Pro codons 3–6) that exhibited strong bias for G to A substitution at nucleotide 1190 in HC-Pro codon 2 (aspartic acid to asparagine). HC-Pro mutants with 5′-proximal deletions of up to 720 nucleotides retained autoproteolytic activity in vitro. In contrast, 5′-proximal deletion of 852 nucleotides of the HC-Pro coding region (HCD852) abolished both infectivity and in vitro proteolytic activity, confirming that the proteolytic domain of WSMV HC-Pro resides within the carboxy-terminal third of the protein and includes the cysteine proteinase motif (GYCY) conserved among four genera of the family Potyviridae. Inoculation of wheat with HC-Pro deletion mutants also bearing the GUS reporter gene revealed that HCD852 was unable to establish primary infection foci in inoculated leaves, indicating that processing of the P3 amino-terminus was essential. Deletion of as few as 24 nucleotides of HC-Pro (codons 3–10) eliminated transmission by the eriophyid mite vector Aceria tosichella Keifer. Collectively, these results demonstrated similar organization of proteinase and vector transmission functional domains among divergent HC-Pro homologues encoded by potyviruses and tritimoviruses. Published by Elsevier Inc

Differential Spatial Gradients of Wheat Streak Mosaic Virus into Winter Wheat from a Central Mite-Virus Source

The wheat curl mite (WCM), Aceria tosichella Keifer, transmits three potentially devastating viruses to winter wheat. An increased understanding of mite movement and subsequent virus spread through the landscape is necessary to estimate the risk of epidemics by the virus in winter wheat. Owing to the small size of WCMs, their dispersal via wind is hard to monitor; however, the viruses they transmit produce symptoms that can be detected with remote sensing. The objective of this study was to characterize the spatial dispersal of the virus from a central mite-virus source. Virus infection gradients were measured spatially by using aerial remote sensing, ground measurements, geostatistics, and a geographic information system between 2006 and 2009. The red edge position vegetation index as measured via aerial imagery was significantly correlated with in-field biophysical measurements. The occurrence of virus symptoms extended differentially in all directions from mite-virus source plots, and predictions from cokriging revealed an oval pattern surrounding the source but displaced to the southeast. The variable dispersal in different directions appeared to be influenced by the mite source density and wind direction and speed, but temperature also seemed likely to have affected mite spread. The spatial spread revealed in this study may be used to estimate the potential sphere of influence of mite-infested volunteer wheat in production fields. These risk parameter estimates require further validation, but they may potentially aid growers in making better virus management decisions regarding differential virus spread potential away from a central source

Octapartite negative-sense RNA genome of \u3c/i\u3eHigh Plains wheat mosaic virus\u3c/i\u3e encodes two suppressors of RNA silencing

High Plains wheat mosaic virus (HPWMoV, genus Emaravirus; family Fimoviridae), transmitted by the wheat curl mite (Aceria tosichella Keifer), harbors a monocistronic octapartite single-stranded negative-sense RNA genome. In this study, putative proteins encoded by HPWMoV genomic RNAs 2–8 were screened for potential RNA silencing suppression activity by using a green fluorescent protein-based reporter agroinfiltration assay. We found that proteins encoded by RNAs 7 (P7) and 8 (P8) suppressed silencing induced by single- or doublestranded RNAs and efficiently suppressed the transitive pathway of RNA silencing. Additionally, a Wheat streak mosaic virus (WSMV, genus Tritimovirus; family Potyviridae) mutant lacking the suppressor of RNA silencing (ΔP1) but having either P7 or P8 from HPWMoV restored cell-to-cell and long-distance movement in wheat, thus indicating that P7 or P8 rescued silencing suppressor-deficient WSMV. Furthermore, HPWMoV P7 and P8 substantially enhanced the pathogenicity of Potato virus X in Nicotiana benthamiana. Collectively, these data demonstrate that the octapartite genome of HPWMoV encodes two suppressors of RNA silencing