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American large raspberry aphidOn this page: Identification & Distribution Biology & Ecology Population dynamics Other aphids on the same host Damage & Control
Identification & Distribution
Adult apterae of Amphorophora agathonica (see first picture below) are pale green. The apical rostral segment (R IV+V) is 1.05-1.85 times the length of the second hind tarsal segment (HT II) (cf. Amphorophora sensoriata and Amphorophora rubicumberlandi, which have RIV+V 0.6-0.8 times the length of HTII). The siphunculi are pale greenish at the base, shading to dark brown towards the apices (cf. Amphoropha idaei and Amphorophora rubi, which have entirely pale siphunculi apart from a darker apical rim, and Amphorophora tigwatensa, which have the siphunculi dusky or dark). The cauda and legs are light to medium brown. The siphunculi are swollen on the distal half (cf. Aphis rubicola, which have siphunculi tapering from base to flange). The siphunculi have no zone of polygonal reticulation (cf. Illinoia rubicola, which have a sub-apical zone of polygonal reticulation). The cauda is 1.5-2.7 times R IV+V and 2.2-3.4 times the base of antennal segment VI. The body length of adult Amphorophora agathonica apterae is 2.4-4.7 mm. Immature American large raspberry aphids (see second picture below) are whitish-yellow.
Both images above by permission, copyright Claude Pilon, all rights reserved.
Amphorophora agathonica alatae have a pale brown head and thorax with a pale green abdomen.
First image above Stephen Ausmus, USDA in public domain;
Amphorophora agathonica feeds on the young stems and undersides of leaves of red raspberry (Rubus idaeus var. strigosus), and occasionally in small numbers on other Rubus species such as black raspberry Rubus occidentalis. These aphids do not host alternate, but remain all year on raspberry. Sexuales develop in autumn with oviparae and alate males. The species is widely distributed in North America north of about latitude 38 ° N, including Alaska and Nova Scotia.
Biology & Ecology
Kennedy & Schaefers (1974) looked at the distribution and phenology of Amphorophora agathonica on red raspberry crops. Most Amphorophora agathonica observed during 1971 and 1972 on red raspberry were located on the primocanes (first year canes). Relatively few were seen on the floricanes (second year canes). Alatoid nymphs were most abundant in late June, several weeks before the peaks in population density. Their appearance at this time implies that the greatest natural primary spread of raspberry mosaic from cultivated plantings may be expected in late June and early July. Nymphs collected in the field in late September developed into oviparae.
Lightle et al. (2014) looked at the seasonal phenology of Amphorophora agathonica in commercial fields of red raspberry of northern Washington state, USA. The lower developmental threshold of the species was estimated to be 2.7°C. In the field, apterous and alate aphid populations began rapidly increasing at about 800 growing degree-days and peaked at 1,050 growing degree-days.
Other aphids on the same host
Amphorophora agathonica occurs on 7 species of Rubus (Rubus idaeus var. melanolasius, Rubus occidentalis, Rubus odoratus, Rubus parviflorus, Rubus phoenicolasius, Rubus procerus, Rubus strigosus).
Damage and control
Amphorophora agathonica is the principal vector of raspberry mosaic virus complex (RMoV) in North America. This complex includes many viruses including Rubus yellow net, black raspberry necrosis, raspberry leaf mottle and raspberry leaf spot viruses. It is apparently not a vector of raspberry leaf curl or vein chlorosis.
Lightle et al. (2014) monitored the spread of raspberry viruses (raspberry latent virus - RpLV and raspberry leaf mottle virus - RLMV) to determine how rapidly fields became infected and whether there was a relationship between Amphorophora agathonica presence and infection. RLMV spread rapidly, with 30-60% of plants in four different commercial fields testing positive after three growing seasons. Surprisingly there was no discernible relationship between the presence or abundance of aphids based on 10 leaves sampled per plant location, and the odds of that plant becoming infected with RLMV.
Schaefers (1968) reported on the control of the Amphorophora agathonica in raspberry nursery stock in New York. To assure that virus-free raspberry varieties remain virus free during field propagation of planting stock requires the application of an effective program for the control of the mosaic vector Amphorophora agathonica. In New York the aphid is present in the field from mid-May through late October and control is needed throughout the entire period. Several foliar spray materials were investigated and were found to lack the needed persistence for a continuous protective program. of those tested, Niagara 10242 was the most effective. Granular systemic materials applied over the row provided greatly improved control in comparison with the foliar spray applications, of the materials tested, Temik, was consistently the most effective. The results suggest that two applications of Temik, one in mid-May and one in early August, will provide effective season-long control of the aphid.
Host plant resistance is considered a practical and cost-effective approach for growers to manage insect pests. Lightle et al. (2015) looked at the effects of three novel resistant black raspberry selections on Amphorophora agathonica feeding behavior and performance. Aphids were more attracted to the susceptible cultivar 'Munger' (control) than the resistant selections. Parturition occurred on the resistant selections, but fewer nymphs were deposited on resistant lines relative to the susceptible control. Nymphs survived much less time on resistant selections, whereas nearly all were still alive after 11 days on the control. The tissues responsible for resistance appeared to be the mesophyll and phloem sieve elements. Aphids had a reduced probability of salivation into the phloem sieve elements of resistant selections.