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Lupin aphid, Essig's lupin aphidIdentification & Distribution Biology & Ecology Damage & Control
Identification & Distribution:Macrosiphum albifrons apterae are large pale bluish grey-green aphids dusted with white wax. Their antennae and legs are pale or dusky with blackish apices. The siphunculi are brownish with dark tips. The siphunculi are 0.21-0.32 times the body length, and 1.6-2.2 times the length of the cauda. The cauda is pale, slender and rather pointed. The body length of adult Macrosiphum albifrons apterae is 3.2-5.1 mm.
The nymphs (see second picture above for the nymph of a future alate) have all dark siphunculi and are dusted with wax. The alates have a dusky head, brown thorax, a bluish green abdomen with small marginal spots, dusky siphunculi and are dusted with wax. The micrographs below are (first) of an aptera in alcohol and (second) of the apex of the siphunculi. Note the polygonal reticulation on the siphunculi - characteristic of the genus Macrosiphum.
The lupin aphid does not host alternate but spends its entire life cycle on Lupin (Lupinus sp). It lives mainly on the leaves, stems and flower spikes. It originates in North America where sexual forms with alate males develop in the autumn, and the aphid overwinters as eggs. In Europe Macrosiphum albifrons was first recorded in England in 1981 where it overwinters as viviparae. It is now widely distributed and considered an invasive pest species over much of Europe.
Biology & Ecology:
We have found the lupin aphid several times in Britain, sometimes in considerable numbers. An adult aptera is shown below giving birth.
Carter & Nichols (1989) reported that, since its first appearance in 1981, Macrosiphum albifrons has recurred on lupin plants in Britain every year up to 1988, in spite of harsh winter weather. Experimental tests of exposure to freezing conditions are reported and indicate that, due to its low-temperature tolerance, this aphid probably survives and reproduces on lupins through most winters in the parthenogenetic viviparous stage.
Further evidence of the low-temperature tolerance of the lupin aphid comes from Frazer & Gill (1989) . They determined the fecundity, survivorship, and rate of development of the aphid Macrosiphum albifrons. These statistics were summarized into life tables and the intrinsic rate of increase computed. The life tables, using a time scale in days, were converted to a variable life table model using a physiological time scale based on an estimated thermal threshold of development of only 3.59°C.
Wink & Witte (1991) identified 31 quinolizidine alkaloids in Macrosiphum albifrons, up to 1.8 mg/g fresh weight. Experimental evidence confirmed that the aphid exploits the dietary alkaloids (which serve as chemical defense compounds in the plant) for their own defense. The recovery of alkaloids in aphids confirms that the alkaloids are transported via the phloem in Lupinus.
Cohen & Mackauer et al. (2010) looked at parasitoids attacking Macrosiphum albifrons in Canada. There it is parasitized by four species of Aphidiidae: Aphidius lupini, Ephedrus californicus, and two unidentified species of Praon. The percentage of parasitism varied seasonally, and between collecting sites. Aphidius lupini was the most common and widespread parasite, killing an average of 5.2, 7.6, and 9.0% of second-, third- and fourth-instar aphids, respectively, over the season as a whole. A fungal pathogen, Entomophthora sp., caused ca. 60% mortality among third- and fourth-instar aphids during rainy periods in late spring and late summer. We have also found Entomophthora attacking lupin aphid colonies (see picture below) in Britain.
In USA Finlayson et al. (2010) found that all coccinellids studied consumed fewer Macrosiphum albifrons compared with three other aphid species, likely because of deterrent compounds sequestered by this species from its host plant. Macrosiphum albifrons is native to the study area and is known to sequester toxic compounds from its host plant that have been shown to cause a "narcotizing effect" on Coccinella septempunctata (Gruppe & Roemer 1988 ). It is thus notable that Harmonia axyridis and Coccinella septempunctata, both introduced species without historical exposure to Macrosiphum albifrons, consumed the lowest numbers of this species. In contrast, Coccinella trifasciata, which is native to the area, consumed the most Macrosiphum albifrons adults. It would seem that Coccinella trifasciata may have evolved the ability to tolerate these compounds, whereas the recently introduced non-native species have yet to do so. By virtue of being able to exploit lupine aphids, Coccinella trifasciata may enjoy a refuge from prey competition with the non-native species. Aphidius lupini was considered as a potential agent for biological control of the lupin aphid in England.
Damage and control
Ferguson (1994) monitored pests on plots of lupins in Hertfordshire and Bedfordshire in Britain between 1986 and 1990. The aphid Macrosiphum albifrons was present each year, and probably overwintered on autumn-sown Lupinus albus in 1989/1990. Its distribution was patchy, and injury was most severe in flowering plants. It was concluded that Macrosiphum albifrons was one of four most damaging pests for lupins.
Natural enemies have been found to attack the lupin aphid (see above), but they often only come in after the damage is done. Most horticulturists consider that insecticide application (deltamethrin, thiacloprid or acetamiprid) is the only option for lupin aphid control (see lupin aphid , but lupins should not be sprayed when in flower (often the first time the aphids are noted) to avoid killing pollinating insects.