Interactions of Amphorophora agathonica Hottes with raspberry viruses and resistant red and black raspberry

In recent years, red raspberry production in Washington and British Columbia has been severely limited by a newly emerged virus complex that causes symptoms of crumbly fruit. The complex is comprised of three viruses: Raspberry bushy dwarf virus (RBDV), Raspberry leaf mottle virus (RLMV) and Raspberry latent virus (RpLV). Both RLMV and RpLV are transmitted by the aphid Amphorophora agathonica Hottes. The objectives of this work were to monitor seasonal phenology of A. agathonica and study the aphids' behavior on infected plants as well as resistant red and black raspberry cultivars. The lower developmental threshold of A. agathonica was calculated to be 2.7°C and field populations in northern Washington began increasing rapidly at approximately 800 growing degree days and peaked at approximately 1000 degree days. Evaluations of aphid performance on infected plants revealed that single infection plants (RLMV or RpLV) and co-infected plants (RLMV+RpLV) significantly increased aphid longevity over the healthy controls, while the co-infected plants also significantly increased aphid fecundity. Electrical penetration graph (EPG) studies of A. agathonica feeding behavior showed no differences in feeding between healthy and infected plants. However, EPG studies revealed two distinct mechanisms of resistance against A. agathonica in red and black raspberry. The red raspberry resistance gene Ag₁ results in extended periods of salivation in the phloem sieve elements with little subsequent phloem ingestion, a behavior commonly associated with plant defense mechanisms related to a phloem recognition factor. Three novel aphid-resistant black raspberry selections were also studied. Aphids feeding on the resistant black raspberries were unlikely to salivate in the phloem sieve elements, which may point to a mechanism that causes aphids to be unable to recognize when they have punctured the sieve elements. Overall, this research discovered new information about A. agathonica biology, feeding behavior, and interactions with viruses that can be incorporated into future management strategies

Raspberry viruses affect the behavior and performance of Amphorophora agathonica in single and mixed infections

Pathogens may alter their hosts, which consequently increases transmission efficiency by vectors. We examined the effects of Raspberry leaf mottle virus [RLMV; Closterovirus (Closteroviridae)] and Raspberry latent virus [RpLV; Reovirus (Reoviridae)], alone and in a co-infection in raspberry, Rubus idaeus L. (Rosaceae) cv. Meeker, on the behavior and performance of its vector, Amphorophora agathonica Hottes (Hemiptera: Aphididae). Longevity was increased in aphids feeding on all infected-plant treatments compared with healthy plants, but aphid fecundity only increased in the co-infection treatment. In a two-way choice study between infected and healthy plants, aphids showed no difference in preference between plants after 30 min of exposure. After 24 h, aphids significantly preferred to settle on plants infected with RLMV over healthy, but healthy plants over plants infected with RpLV. There were no differences in settling preferences between healthy and co-infected plants. An electrical penetration graph study showed no differences in aphid feeding behavior on plants infected with RLMV and RLMV+RpLV when compared with healthy controls. Our results are consistent with past findings that infected plant’s impact vector performance and behavior, but also highlight the need to further investigate greater virus diversity and effects of mixed infections.Keywords: Co-infection, Rubus idaeus, Behavioral manipulation, Raspberry leaf mottle virus, Aphididae, Hemiptera, Rosaceae, Raspberry latent virus, Reoviridae, Closteroviridae, Large raspberry aphi

New Reports of Exotic and Native Ambrosia and Bark Beetle Species (Coleoptera: Curculionidae: Scolytinae) From Ohio

In a 2007 survey of ambrosia and bark beetles (Coleoptera: Curculionidae: Scolytinae) along a transect in northeastern Ohio, we collected six exotic and three native species not previously reported from the state. These species include the exotic ambrosia beetles Ambrosiodmus rubricollis (Eichhoff), Dryoxylon onoharaensum (Murayama), Euwallacea validus (Eichhoff), Xyleborus californicus Wood, Xyleborus pelliculosusEichhoff, and Xylosandrus crassiusculus (Motschulsky). The native ambrosia beetle Corthylus columbianus Hopkins, and the native bark beetles Dryocoetes autographus (Ratzeburg) and Hylastes tenuis Eichhoff are also reported from Ohio for the first time. Our study suggests a northward range expansion for five of the six exotic species including, X. crassiusculus, which is an important pest of nursery and orchard crops in the southeastern United States

Transmission Biology of Raspberry latent virus, the First Aphid-Borne Reovirus

Raspberry latent virus (RpLV) is a newly characterized reovirus found in commercial raspberry fields in the Pacific Northwest (PNW). Thus far, all members of the plant reoviruses are transmitted in a replicative, persistent manner by several species of leafhoppers or planthoppers. After several failed attempts to transmit RpLV using leafhoppers, the large raspberry aphid, commonly found in the PNW, was tested as a vector of the virus. The virus was transmitted to new, healthy raspberry plants when inoculated with groups of at least 50 viruliferous aphids, suggesting that aphids are vectors of RpLV, albeit inefficient ones. Using absolute and relative quantification methods, it was shown that the virus titer in aphids continued to increase after the acquisition period even when aphids were serially transferred onto fresh, healthy plants on a daily basis. Transmission experiments determined that RpLV has a 6-day latent period in the aphid before it becomes transmissible; however, it was not transmitted transovarially to the next generation. To our knowledge, this is the first report of a plant reovirus transmitted by an aphid. Phylogenetic analyses showed that RpLV is related most closely to but distinct from Rice ragged stunt virus (RRSV), the type member of the genus Oryzavirus. Moreover, the conserved nucleotide termini of the genomic segments of RpLV did not match those of RRSV or other plant reoviruses, allowing us to suggest that RpLV is probably the type member of a new genus in the Reoviridae comprising aphid-transmitted reoviruses.Keywords: Plant viruses, Identification, Whitefly bemisia tabaci, Myzus persicae, RT-PRC, Vector interactions, Mottle viru

Sugar in moderation: sugar diets affect short-term parasitoid behaviour

The biological control potential of parasitic wasps in the field is expected to increase with the provisioning of sugar sources, which increase longevity and replenish carbohydrate reserves. Apanteles aristoteliae is an important parasitoid of Argyrotaenia franciscana, the orange tortrix, an economic pest in fruit crops. In the present study, the effect of sugar diet on the physiological status of A. aristoteliae is investigated in the laboratory, as well as the effects of nutritional status on short-term olfactory orientation and parasitism behaviour, and the association between olfactory orientation and immediate parasitism activity. Levels of glycogen, fructose, total sugars, proportional weight gain and volume consumed are higher among females fed 25% sucrose solution than 10% sucrose solution, and lowest for those fed water. Sugar feeding also affects behaviour: wasps with higher levels of fructose or weight gain have a lower probability of making a choice in the olfactometer. Wasps with intermediate fructose levels or weight gain have a higher probability of orienting towards hosts than wasps with low or high levels. Among wasps that make a choice in the olfactometer, wasps fed 10% or 25% sucrose significantly prefer host versus food cues, whereas starved wasps are just as likely to select food cues as host cues