Low and high input agricultural fields have different effects on pest aphid abundance via different invasive alien weed species

Abstract

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 Stenactisannua, Erigeroncanadensis and Solidagocanadensis. These species were hosts predominantly for the aphids Brachycaudushelichrysi and Aulacorthumsolani in both management systems. The 13% higher coverage of S.annua under LIF conditions resulted in a 30% higher B.helichrysi abundance and ~85% higher A.solani abundance compared with HIF conditions. Host plant quality was assessed by measuring peroxidase enzyme activity. There was a significantly increased POD activity at 10 μmol min−1 mg protein−1 unit in S.annua under LIF conditions, suggesting a higher stress by aphids under this management regime. The high colonization intensity of B.helichrysi on maize, potato and alfalfa crops were detected from both S.annua and E.canadensis. We conclude that new and faster methods need to be used to prevent colonization of such virus vectoring aphids and their host plants, even under low input regimes.

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

“…This is undoubtedly due to two principal reasons: (1) The technique used may be fundamentally unsuited for virus detection from aphid stylets or (2) it may simply be that the titre of virus within the aphid stylets is very low, whereas in the plant itself, it is very much amplified, allowing detection. The previous colonization experiment (Szabó et al, 2019) clearly demonstrated that with both aphid species here studied, virus transmission definitely occurred during the insects' movement from weeds to crop plants and the colonization of these.…”

“…The same trend was observed for A. solani, where a 13% higher coverage of E. annua resulted in an increase of about 85% for this aphid under LIF compared to HIF regimes (Figure 1). In our previous experiments testing colonization abilities of these particular aphids (Szabó et al, 2019), it was also shown that E. annua and E. canadensis are suitable weed hosts for both species but especially for B. helichrysi. Significant colonization of B. helichrysi from both weeds toward the crop plants maize, alfalfa, and potato was detected (Szabó et al, 2019).…”

“…In our previous experiments testing colonization abilities of these particular aphids (Szabó et al, 2019), it was also shown that E. annua and E. canadensis are suitable weed hosts for both species but especially for B. helichrysi. Significant colonization of B. helichrysi from both weeds toward the crop plants maize, alfalfa, and potato was detected (Szabó et al, 2019). Therefore, virus transmission from invasive weeds to crop plants by these aphids is highly probable.…”

“…Significant colonization of B . helichrysi from both weeds toward the crop plants maize, alfalfa, and potato was detected ( Szabó et al, 2019 ). Therefore, virus transmission from invasive weeds to crop plants by these aphids is highly probable.…”

“…Field surveys were conducted over a 2-year period during the crop growing seasons of 2015 and the 2016 in Central and Eastern Transylvania, Romania. The methods used have also been described by Szabó et al (2019) . Assessments were run under two different input management regimes (low and high), carefully selected to take into consideration similar geographic and climate regions (see also / Supplementary Figure S1 ).…”