Local Aphid Species Infestation on Invasive Weeds Affects Virus Infection of Nearest Crops Under Different Management Systems – A Preliminary Study

Abstract

In the present study, we conducted field surveys to detect the population density of the most important invasive weed species and their associated virus vectoring aphids in crops grown under high input field (HIF) vs. low-input field (LIF) conditions, with and without fertilizers and pesticides. The most frequent invasive weed species were annual fleabane, Erigeron annua (L.), Canadian horseweed, Erigeron canadensis (L.) and Canadian goldenrod, Solidago canadensis (L.). These species were predominantly hosts of the aphids Brachycaudus helichrysi and Aulacorthum solani under both management systems. The 13% higher coverage of E. annua under LIF conditions resulted in a 30% higher B. helichrysi abundance and ∼85% higher A. solani abundance compared with HIF conditions. To reveal the incidence of virus infection in crop plants and invasive weeds, high-throughput sequencing of small RNAs was performed. Bioinformatics analysis combined with independent validation methods revealed the presence of six viruses, but with strikingly different patterns under LIF and HIF conditions. Their presence without symptoms in invasive weeds and crop plants supports the necessity of employing new approaches to those currently employed in invasive weed management. These findings also suggest that invasive weeds could serve as hosts for local aphid species and reservoirs for plant pathogenic viruses, both under low and high input management systems. In this light, as here demonstrated, viruses transmitted by local aphid species were found to differ between the management systems; hence, the importance of B. helichrysi and A. solani as virus vectors in particular clearly needs to be re-evaluated. Altogether, we accept that the present study is a pilot one and individual virus vectoring of aphids still needs to be directly tested. Even so, it represents one of the first contributions to this particular area, and thereby paves the way for further similar applied research in the future.

Diversity and Functional Roles of the Gut Microbiota in Lepidopteran Insects

“…Lepidoptera is one of the most widespread and diverse insect clades in terms of the number of species and biomass [1,2]. Approximately 180,000 species of lepidopteran insects have been described all over the world, some of which act as forestry and agricultural pests, such as butterflies, moths, and skippers.…”

Millet Could Be both a Weed and Serve as a Virus Reservoir in Crop Fields

“…Analysis of their virome, which is a new area of investigation [49], can add new insights to this field. As weeds can both host aphid vectors and viruses, they could play a key role in virus distribution [50]. To determine the spread of this mechanism, and identify the agronomically important viruses that could use this strategy further, directed surveys should be conducted in the future.…”

Associational susceptibility of crop plants caused by the invasive weed Canadian goldenrod, Solidago canadensis, via local aphid species

“…), the HIF by large monocultures with a low density of natural vegetation, situated about 5,500 km 2 in area at an altitude of 220-750 m a.s.l. (Szabó et al, 2019(Szabó et al, , 2020. Around 200 km separated the areas with no direct connections between them via main roads or railways.…”

“…The weed assessment method here used has earlier been detailed by Szabó et al (2019Szabó et al ( , 2020. In brief, two sample areas each of around 10m 2 were selected in both LIF and HIF regions.…”

“…To date, the fact that invasive weeds may act as virus reservoirs and hence pose a potentially serious threat via local migrating winged aphid species in terms of virus vectoring has yet to be tested under different crop management systems (Bell, 1983;Popkin et al, 2017). Having said that, several local aphid species, notably the leaf-curling plum aphid, Brachycaudus helichrysi Kaltenbach and the glasshouse-potato aphid, Aulacorthum solani (Kaltenbach), have already been tested to determine whether invasive weeds such as annual fleabane, Stenactis (= Erigeron) annua (L.) and Canadian horseweed, Erigeron (= Conyza) canadensis can act as summer 'reservoir' hosts for pest aphids, thereby allowing transmission of pathogenic crop plant viruses from these plants to adjoining crop plants (Szabó et al, 2019(Szabó et al, , 2020.…”