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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #179536
Title: NEOZYGITES FRESENII (ENTOMOPHTHORALES: NEOZYGITACEAE) PREVALENCE IN APHIS GOSSYPII (HOMOPTERA: APHIDIDAE) IN THREE SOUTH CENTRAL GEORGIA COTTON FIELDS

Author
item Marti, Orville
item Olson, Dawn

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2005
Publication Date: 1/1/2006
Citation: Marti, O.G., Olson, D.M. 2006. Neozygites fresenii (Entomophthorales: Neozygitaceae) prevalence in Aphis gossypii (Homoptera: Aphididae) in three south central Georgia cotton fields. Journal of Entomological Science. 41(1):22-32.

Interpretive Summary: Cotton aphids (Aphis gossypii) are a common pest of commercially grown cotton (Gossypium hirsutum) and many other plants. The cotton aphid is attacked by a fungus, Neozygites fresenii, which kills many of the aphids in late June and early July. The numbers of aphids on cotton plants in three south Georgia (USA) fields were monitored by plant sampling in 2002. The percentage of aphids that were positive for the fungus was monitored by the use of two kinds of traps, sticky traps and pan traps. Aphids were found in pan traps as early as 4 May, but all the aphids were negative for the fungus until 10 June. After this date, the percentage of infected aphids increased rapidly to a peak of more than 60% by 27 June. The increase in the aphid population between 3 June and 8 July was also rapid, but declined sharply after the fungus became established in the aphid population. Since the fungus has a short life cycle lasting only a few days, several generations of the fungus are able to develop between the time it is first detected and the time of the decline of the aphid population in early July.

Technical Abstract: The presence of cotton aphids, Aphis gossypii, and the incidence of its fungal pathogen, Neozygites fresenii, were monitored with pan traps, plant sampling, and sticky traps in three south central Georgia cotton fields in the early part of the 2002 growing season. Aphids were trapped in low numbers (<10/trap/sampling date) in fields 1 and 2 until 17 June, when the aphid population increased appreciably (to >60/trap/sampling date). A similar increase was observed in field 3 after 21 June. Differences observed in the three fields were attributed to differences in planting date. Aphids in sticky traps were counted but not examined for pathogenic fungi. Aphids were detected in pan traps as early as 4 May but all were negative for N. fresenii until 10 June, after which the mean incidence of the fungus increased rapidly to a peak of >60% by 27 June. The aphid population as determined by plant sampling increased logarithmically between 3 June and 8 July, whereas the increase in incidence of N. fresenii was exponential, with all of the observed increase occurring after 10 June. Multiple generations of the fungus develop between its first detection in aphids in mid-June to the peak of the epizootic on or after 8 July.