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Brachycaudus amygdalinusShort-tailed almond aphid, Leaf-curling almond aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Natural enemies Other aphids on the same host Damage & ControlIdentification & DistributionIn spring Brachycaudus amygdalinus colonies cause rolling of young almond or peach leaves, and stunting of new growth, to produce pseudogalls (see pictures below). Each leaf is rolled somewhat obliquely with respect to its mid-rib.
Images above copyright Dr László Érsek, all rights reserved. On their primary host the apterae (see first picture below) of Brachycaudus amygdalinus are squat-bodied and green with rather short pale legs and antennae. The adults have a variably fragmented black dorsal patch with dorsal bars anteriorly and posteriorly (cf. Brachycaudus helichrysi, which is yellow-green with no dark dorsal patch; Brachcaudus schwartzi, which is shiny yellow brown to dark brown with an extensive black dorsal patch; and cf. Brachycaudus persicae, which is shiny dark brown to black). The antennae are 6-segmented. The apical rostral segment (R IV+V) is only about 0.8 times as long as the second hind tarsal segment (HT II) and bears 4 accessory hairs (cf. other Brachycaudus, spp. on Prunus which have RIV+V at least 0.9 times the length of HTII and bearing at least 5 accessory hairs). Abdominal tergite VII (or VII and VIII) has spinal tubercles. The siphunculi are pale with dusky tips (cf. Brachycaudus schwartzi, which has black siphunculi). The cauda is very broadly rounded, with its length less than half its basal width (cf Brachycaudus helichrysi, which has a cauda about as long as its basal width). The body length of adult Brachycaudus amygdalinus apterae is 1.6-2.1 mm.
Images above copyright Dr László Érsek, all rights reserved. Alatae of Brachycaudus amygdalinus (see second picture above) have a dark central abdominal patch. Spring migrant alatae have secondary rhinaria on their antennae; with 12-21 on segment III, and 0-1 on segment IV.
Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved. Brachycaudus amygdalinus apterae, on their secondary host, are smaller and somewhat more elongate (see third picture above). They are brown to dark green in colour with dusky siphunculi and 5-segmented antennae. Brachycaudus amygdalinus host alternates from Prunus species (especially almond, Prunus dulcis, or peach, Prunus persica) to various Polygonaceae (especially horsetail knotweed, Polygonum equisetiforme), prostrate knotweed, Polygonum aviculare, redshank, Persicaria maculosa, and tall buckwheat, Fagopyrum cymosum). It may also be anholocyclic on Polygonaceae (the knotweed or smartweed-buckwheat family). Brachycaudus amygdalinus is found in Europe, especially southern Europe, the Middle East, North Africa Central Asia, Pakistan, and has been introduced into South Africa. Biology & EcologyLife cycleGhorbali et al. (2008) looked at the life cycles of the aphids Brachycaudus amygdalinus and Hyalopterus amygdali on almond trees in Najafabad Region, Iran. For both species egg hatching was in late winter but population increase of Brachycaudus amygdalinus occurred two weeks earlier than was observed for Hyalopterus amygdali. The fundatrices fed on the young foliage, inducing gall formation. In early spring damage signs of Brachycaudus amygdalinus were expressed on almond twigs as serious leaf curling (see picture below) followed by retarded growth of twigs and shortened internodes.
Image above copyright Dr László Érsek, all rights reserved. The fundatrices and their offspring reproduce parthenogenetically, leading to rapid increases in population size during spring. The picture below shows a group of immature Brachycaudus amygdalinus.
Image above copyright Dr László Érsek, all rights reserved. With the onset of warm season, both species moved from almonds to their secondary hosts, which left the almonds free of these pests during summer. In late summer gynoparae migrated back to almond, followed later by the males. The oviparae produced by gynoparae on almond mated with these males and laid their eggs near the buds. Natural enemiesTalhouk (1977) recorded the natural enemies of Brachycaudus amygdalinus and Brachycaudus helichrysi in Lebanon. The two species of Brachycaudus had many natural enemies, including the coccinellids Scymnus subvillosus (=Pullus subvillosus), Synharmonia conglobata (=Harmonia conglobata) and Exochomus quadripustulatus, at least one species of Leucopsis, the cecidomyiid Aphidoletes aphidimyza, the syrphids Syrphus ribesii and Episyrphus balteatus, the braconid Aphidius matricariae and the mirid Deraeocoris pallens. Pterochloroides persicae, on the other hand, had few natural enemies. Almatni & Khalil (2008) carried out a survey of the natural enemies of Brachycaudus amygdalinus in southern Syria. 30 species of natural enemies were recorded: including 15 Coccinellidae, 4 Anthocoridae, 4 Miridae, 3 Syrphidae, one species of Chrysopidae, one Chamaemyiidae, and one beetle, plus one parasitoid. Some arachinids also preyed on this aphid. The most numerous predator at the beginning of the season was Coccinella septempunctata, followed later by Scymnus (Pullus) subvillosus and Hippodamia variegata. The most numerous predatory bug was Orius horvathi. Other aphids on the same hostPrimary hostsBrachycaudus amygdalinus has been recorded on 12 species of Prunus (Prunus amygdalus, Prunus armeniaca, Prunus brahuica, Prunus bucharica, Prunus cerasifera, Prunus domestica, Prunus ledebouriana, Prunus mahaleb, Prunus melanocarpa, Prunus nana, Prunus persica, Prunus petunnikowii).
Secondary hostsBrachycaudus amygdalinus has been recorded on 3 species of Polygonum (Polygonum aviculare, Polygonum ellipticum, Polygonum equisetiforme).
Brachycaudus amygdalinus has been recorded on 1 species of the Persicaria genus (Persicaria maculosa).
Damage and controlThe feeding of Brachycaudus amygdalinus on young almond leaves causes their curling and premature drop, twig growth is retarded and the internodes are shortened. In areas of the Eastern Mediterranean the pest causes severe damage to almonds. Gerson & Applebaum (2019) summarize the biology and management of Brachycaudus amygdalinus. They state that an early spring application of a systemic pesticide often controls this aphid. There are numerous natural enemies that feed on these aphids, such as the braconid parasitoid Ephedrus persicae, the anthocorid Anthocoris minki and the entomopathogenic fungus Erynia radicans, in addition to the natural enemies mentioned above. However, in Syria the recorded natural enemies could not achieve adequate control nor any kind of limitation of the development of the aphid populations in the area studied. Gerson & Applebaum recommend releasing some successful natural enemies or testing natural insecticides like Neem in order to keep aphid population in almond and peach orchards below damage threshold. Baspinar et al. (2018) discuss pest management in organic almond orchards. They note that growers should avoid application of excess nitrogenous fertilizer and irrigation to control shoot flushing and leaf formation where there are high numbers of colonizing aphids. They also noted that enhancing the numbers of natural enemies in the spring may help to control Brachycaudus amygdalinus populations.
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