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Monellia caryella

Blackmargined aphid, Blackmargined pecan aphid

On this page: Identification & Distribution Biology & Ecology Life cycle Natural enemies Other aphids on the same host Damage & Control

Identification & Distribution

All adult viviparae of Monellia caryella are alate. These alatae are pale lemon-yellow to greenish yellow and hold their wings flat over the back of the body (cf. Monelliopsis species, such as Monelliopsis pecanis, which hold their wings tent-like over the body). The black markings of Monellia caryella are seasonally variable. In spring and early summer they have few black markings (see first picture below for possible spring form). From mid-summer onwards (see second picture below) the most noticeable feature is a broad brown-black band along the anterior margin of the forewing, as well as a continuous broad black band running around the front and sides of the head and down sides of the abdomen as far as abdominal tergite 3 (cf. Monellia microsetosa, which lacks the band on the sides of the abdomen). Autumn forms of Monellia caryella (see third picture below) may also have dark bars across some or all abdominal segments. There are no intense yellow/orange spots visible on the body of the live insect (cf. Monellia microsetosa, which has 2-3 pairs of spots of intense yellow/orange pigment, especially on tergites I-II and V-VI).

First image above copyright Ilona; Second image copyright M.J. Hatfield; Third image copyright Louis Tedders; All under a Creative Commons Attribution 3.0 License.

The antennae of Monellia caryella are banded, and the part of antennal segment III bearing secondary rhinaria is conspicuously swollen (cf. Monelliopsis pecanis, which has that part only slightly swollen). The spinal hairs on abdominal tergites I-IV are all short and fine (cf. Monellia medina, which has at least some of the spinal hairs quite long). The siphunculi are small, pale and tuberculate (cf Melanocallis caryaefoliae, which has truncate black siphunculi). The body length of alatae is 0.9-2.2 mm. Immatures of Monellia caryella (see first picture below) are pale greenish-yellow with paired dusky spinal and marginal rows of tubercles bearing long capitate hairs.

Note: Discrimination of Monellia caryella from Monellia medina and Monellia hispida, all on Carya species, is always difficult and can be especially so in spring.

Both images above copyright Louis Tedders under a Creative Commons Attribution 3.0 License.

Blackmargined pecan aphids live and feed on the leaves of hickory (Carya) spp., especially pecan (Carya illinoiensis) and bitternut hickory (Carya cordiformis). Adults and fourth instar immatures feed on the main leaf veins (see second picture above), with the younger instars feeding on the minor veins. Sexuales occur from mid-October to early December. Monellia caryella is widespread in the USA and in Ontario, Canada, and has been introduced into most pecan growing areas including Spain, Israel, Greece, Turkey and Argentina. It is generally regarded as a serious pest of pecan. Intensive spraying in the United States resulted in the development of resistant strains, and nowadays integrated control is more common.

 

Biology & Ecology

Life cycle

Monellia caryella overwinter as eggs laid in buds and bark crevices of the tree. The eggs generally hatch in late March or early April, and the nymphs move to the undersides of the leaflets and begin feeding on the veins. On reaching maturity, the alate fundatrices produce large numbers of live female offspring which also reproduce viviparously.

Image above copyright Ilona under a Creative Commons Attribution 3.0 License.

There are from 16 to 32 generations per year, with the adults producing from 80 to 215 offspring each. There are two peaks of abundance, in spring/early summer and again in autumn.

As day-length shortens and temperatures fall in late autumn, sexual forms are produced. The oviparae (see picture below) are dark with black dorsal abdominal cross-bands (Quednau 2003).

Image above copyright Louis Tedders under a Creative Commons Attribution 3.0 License.

The oviparae mate with winged males and then lay eggs which overwinter.

Interspecific competition / association

Petersen & Sandstrom (2001) looked at the outcome of indirect competition between two aphid species mediated by responses in their common host plant, pecan (Carya illinoensis). In a greenhouse experiment, performance of two aphid species (Monellia caryella and Melanocallis caryaefoliae) and food quality (phloem amino acid concentration and composition), were measured in leaves after the leaves had been fed upon previously by either conspecifics (= of the same species) or heterospecifics (= of other species). The performance of Melanocallis caryaefoliae was reduced by previous aphid feeding of both conspecifics and heterospecifics. The performance of Monellia caryella was unaffected by prior aphid feeding. Feeding by Melanocallis caryaefoliae induced changes in amino acid content of the phloem. This alteration occurred within infested leaves and did not cause any changes in the phloem of adjacent leaves. Feeding by Monellia caryella did not induce changes in phloem amino acid content, but seemed to inhibit Melanocallis caryaefoliae's ability to alter the phloem.

Natural enemies

Watterson & Stone (1982) surveyed the natural enemies of Monellia caryella in Texas pecan orchards in the USA. One primary parasitoid, Aphelinus perpallidus and 5 hyperparasitoids (Alloxysta schlingeri, Aphidencyrtus sp., Chartocerus sp., Dendrocerus sp., and Pachyneuron sp.) were identified from blackmargined aphids. Aphelinus perpallidus was found in significant numbers, but populations varied greatly among orchards. Below is the characteristic black mummy of an Aphelinus parasitoid, from a Texas pecan orchard.

Image above by permission, copyright Salvador Vitanza, all rights reserved.

During most of the growing season, less than 6% of collected Monellia caryella specimens were parasitized by Aphelinus perpallidus but, in one orchard in October, up to 52% were parasitized. Other species parasitized less than 1% of aphid populations.

Monellia caryella has been (accidentally) introduced to several other pecan growing areas including Israel. Mansour (1988) looked at the impact of native natural enemies on Monellia caryella populations in Israel. He identified one primary parasitoid, the braconid Trioxys pallidus (see picture below) from Monellia caryella in Israeli pecan orchards.

Copyright Centre for Biodiversity Genomics under a Creative Commons Attribution License.

The average total parasitism of Monellia caryella for all locations sampled was 13.5%. Although a hyperparasite, Aphidencyrtus species was present, it had no significantly detrimental effect on the parasite.

Monellia caryella is also invasive in Turkey. Kaya Apak & Aksit (2016) looked at the natural enemies of Monellia caryella in an unmanaged pecan orchard in the Sultanhisar district of Aydin Province, Turkey. There were many species of predators, but few parasitoids. Coccinellidae and Chrysopidae families were the most abundant predator groups. The coccinellid population was highest in spring, and chrysopid populations were highest in summer and fall. Adalia decempunctata was the dominant coccinellid and Chrysopa viridana the dominant chrysopid. Parasitoids comprised a eulophid (Aphelinus sp.), and two braconid species (Aphidius matricariae and Trioxys pallidus). The overall parasitism rate was only 0.85% in 2008 and 0.17% in 2009.

 

Other aphids on the same host

Monellia caryella has been recorded on 7 species of hickory (Carya aquatica, Carya cordiformis, Carya glabra, Carya illinoiensis, Carya laciniosa, Carya olivaeformis, Carya ovata).

 

Damage and control

As per Monelliopsis pecanis.

Acknowledgements

We especially thank Salvador Vitanza for the image of a black mummy shown above.

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Hottes & Frison (1931) and Quednau (2003) as well as Blackman & Eastop (1994) and Blackman & Eastop (2006). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References

  • Kaya Apak, F. & Aksit, T. (2016). Natural enemies and population dynamics of the Blackmargined Aphid (Monellia caryella (Fitch) Aphididae, Hemiptera) on pecan trees in Aydın, Turkey. J. Entomol. Res. Soc. 18(3), 49-60. Full text

  • Hottes, F.C. & Frison, T.H. (1931). The Plant Lice, or Aphiidae, of Illinois. Illinois Natural History Survey Bulletin 19(3), 123-447. Full text

  • Mansour, F. (1988). Parasites of Monellia caryella [Hom.: Aphididae]: Phenology and effect on the aphid population in pecan orchards in Israel. Entomophaga 33, 371-375. Abstract

  • Petersen, M. K. & Sandstrom, J. P. (2001). Outcome of indirect competition between two aphid species mediated by responses in their common host plant. Functional Ecology 15(4), 525-534. Full text

  • Quednau, F.W. (2003). Atlas of the Drepanosiphine Aphids of the World. Memoirs of the American Entomological Institute 72, 51.

  • Watterson, G.P. & Stone, J.D. (1982). Parasites of Blackmargined Aphids and their Effect on Aphid Populations in Far-West Texas. Environmental Entomology, 11(3), 667-669. Abstract