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Lettuce seed-stem aphidOn this page: Identification & Distribution Other aphids on the same host Damage & Control
Identification & Distribution
Adult apterae of Acyrthosiphon lactucae (see first picture below) are pale yellowish green or pink. The dorsal surface has a pale grey wax bloom, often appearing as pale transverse stripes. The head is smooth, and the antennal tubercles are well developed with smooth broadly-divergent inner faces. The terminal process is less than 7.5 times as long as the base of antennal segment VI. Antennal segment III has secondary rhinaria and bears hairs that are less than 0.7 times the diameter of that segment. The fused apical rostral segment (R IV+V) is 0.6-0.7 times the length of the second hind tarsal segment (HTII), and has 16-25 accessory hairs (cf. Acyrthosiphon ilka, which has RIV+V 0.8-0.9 times the length of HTII, with 6-8 accessory hairs). There are no dark markings on the dorsum (cf. Nasonovia ribisnigri, which on the secondary host - lettuce - has dark intersegmental sclerites between each abdominal segment). Abdominal tergites I and VII usually have no marginal tubercles. The siphunculi are long and tapering with no polygonal reticulation (cf. Hyperomyzus lactucae, which has distinctly swollen siphunculi). The cauda is finger-shaped, clearly longer than its basal length. The body length of adult apterae is 1.7-2.9 mm. Immature apterous Acyrthosiphon lactucae (see second picture below) resemble the adult apterae, but have shorter siphunculi and cauda.
Both images above by permission, copyright Claude Pilon, all rights reserved.
Acyrthosiphon lactucae alatae (see picture below of immature and adult alate) show the same two colour forms as the apterae, but have somewhat dusky siphunculi.
Image above by permission, copyright Claude Pilon, all rights reserved.
Images above by permission, copyright Claude Pilon, all rights reserved.
Images of Acyrthosiphon lactucae copyright CBG Photography Group under a Creative Commons - Attribution Non-Commercial Share-Alike License.
Acyrthosiphon lactucae feeds on stems and undersides of leaves of lettuce (Lactuca species). It does not host alternate, remaining on lettuce year round. Sexuales develop in autumn, with alate males. Acyrthosiphon lactucae is a native Eurasian species and is found throughout Europe, the Middle East, Kazakhstan and Pakistan. In Britain the lettuce seed-stem aphid has only been found in southern counties. It was introduced to North America many years ago and is now widely distributed there. More recently Acyrthosiphon lactucae has been recorded from Argentina (Mier Durante et al. 2011) and Chile (Nieto Nafría et al. 2018).
Other aphids on the same host
Damage and control
Lettuce is attacked by several different aphid species, the most important of which are Acyrthosiphon lactucae, Aulacorthum solani, Macrosiphum euphorbiae, Myzus persicae and Nasonovia ribis-nigri. There are also several root aphids, for example Pemphigus bursarius, Trama caudata and Trama troglodytes. Which species is the most important varies within and between countries.
Palumbo (2004) describes insecticide alternatives for aphid management in head lettuce in Arizona, USA. Two insecticides have both contact and systemic activity - pymetrozine (pyridine azomethine) and acetamiprid (a neonicitinoid). A newer insecticide, flonicamid is a nicotinamide with systemic activity. All these products have been shown to provide good efficacy against lettuce aphids if applied at low aphid densities before head formation begins. Palumbo (2018) gives a more up-to-date account of aphid control on lettuce including cultural management, encouragement of natural enemies, scouting for aphids, aphid identification and early application of foliar insecticides.
Mifsud et al. (2011) notes that Acyrthosiphon lactucae is frequently damaging to cultivated lettuce in Italy, preferentially infesting the inflorescence. It is also a vector of Lettuce Mosaic Virus.