Aphis gossypii (Glover)

Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Aphidoidea, Aphididae.

Common name: Cotton aphid; Melon aphid.

Geographical distribution: Wide-spread in the warm temperate regions of the world, restricted to greenhouses in colder regions, absent only in parts of Canada and Asia. CIE Distribution Map #A18.

Host plants: Polyphagous, feeding on many crop plants in the families Cucurbitaceae, Crucifereae, Solanaceae, Malvaceae and other cultivated orchard, vegetable crop plants and weeds. A recent study suggests that there are two widely distributed host races or subspecies of A. gossypii, with different host plant family associations.

Morphology: The adult body is about 2 mm in length. The head and thorax of the pear-shaped alate adult is black. The color of the body is variable, yellow-green to dark green, sometimes almost black, with its siphunculi, cauda and the apical part of the antennae and rostrum brown or dusky. The apterate adult is of variable color too. There is an elongated dark spot on each of the forewings. The body color of the nymphs vary from very pale yellow to pale green and they are smaller that the adults. Aphis gossypii is phenotypically plastic; its morphology and color variations may depend on the host plant and the physiological state of the individual aphid.

Life Cycle: Aphis gossypii is viviparous throughout the year. It is relatively insensitive to the Khamsin winds prevalent during spring in the Middle East and may be dispersed by them. The mean threshold for development is estimated at 6.2ºC; generational time is 4.5 days at the optimal temperature of 30ºC, 12 days at 15ºC. Adults live for 2-3 weeks and may deposit 2-5 eggs daily, completing about 20 annual generations.

Economic importance: Aphis gossypii is a major pest of glasshouse cucurbit crops, mainly cucumber and melon, in many Mediterranean countries. In the eastern Mediterranean, it is also a serious pest of cotton and vegetable crops. The aphid has been reported to cause damage to tomato, cucumber and pepper crops in Jordan. The pest is a phloem-feeder, excreting honeydew that serves as a substrate for sootymold. In addition, the aphid is a vector of non-persistent plant viruses in the eastern Mediterranean, including Plum Pox Virus (PPV) (see also Myzus persicae (Sulzer) and Aphis spiraecola Patch ), Tristeza Citrus Fruit Virus, Cucumber mosaic virus (CMV), Zucchini yellow mosaic virus (ZYMV), and of some persistent viruses.

Management: Wherever low pest levels can be tolerated, natural enemies control them. Aphys gossypii is of quarantine concern in countries which import plants that host this pest in the countries of origin. Zero-tolerance is then essential, and control measures are mandatory.

Cultural control: Cucumber varieties resistant to A. gossypii may seriously reduce the reproduction of the aphid and enable even small populations of natural enemies to control the pest.

Chemical control of A. gossypii is similar to that of other aphid pests and is periodically updated as new compounds are approved for the various crops. A decisive factor in the choice of insecticides for controlling this pest is its ability to develop resistance to specific insecticides during the warm season, which can, in some cases, increase by almost 2 orders of magnitude. In cotton production, part of the resistance that had developed during the previous season is lost, probably due in part to re-infestations by wind-borne aphids.

Biological control: Aphis gossypii is the only aphid found on cucurbits and on cotton, with relatively low parasitism rates (usually less than 10%) on cotton. The primary parasitoids, (mainly Lysiphlebus spp., Aphidiidae) are abundant at the beginning of the season but hyperparasites increase thereafter.

References:

Hill, D.S. 1983. Aphis gossypii Glover. In: _Agricultural Insect Pests of

the Tropics and Their Control_, 2nd Edition Cambridge University Press. p. 201.

Ishaaya, I. and Mendelson, Z. 1987. The susceptibility of the melon aphid,

Aphis gossypii, to insecticides during the cotton growing season. Hassadeh

67:1768-1772 (in Hebrew, with English summary).

Kersting, U., Satar, S. and Uygun, N. 1999. Effect of temperature on

development rate and fecundity of apterous Aphis gossypii Glover (Hom.,

Aphididae) reared on Gossypium hirsutum L. Journal of Applied Entomology

123: 23-27.

Leclant, F. and J.-P. Deguine. 1994. Aphids (Hemiptera: Aphididae). In:

Matthews, G.A. and Tunstall, J.P. (eds), Insect Pests of Cotton. CAB

International, Wallingford, UK., pp 285-323.

Margaritopoulos, J.T. Tzortzi, M., Zarpas, K.D., Tsitsipis, J.A. and Blackman,

R.L. 2006. Morphological discrimination of Aphis gossypii (Hemiptera:

Aphididae) populations feeding on Compositae. _Bulletin of Entomological

Research_ 96:153-165.

Swirski, E. and Amitai, S. 1999. Annotated list of aphids (Aphidoidea) in

Israel. Israel Journal of Entomology 33: 1-120.

van Steenis, M.J. and El-Khawass, A.M.H. 1995. Life history of Aphis gossypii on cucumber: influence of temperature, host plant and parasitism. _Entomologia

Experimentalis et Applicata_ 76: 121-131.

Websites:

http://influentialpoints.com/Gallery/Aphis_gossypii_melon_or_cotton_aphid.htm