Influence of Fruit Acidity on Infestation and Damage to Sweet Orange (Citrus sinensis Osbeck)· Varieties by Ceratitis Species (Diptera: Tephritidae) at Ibadan, Nigeria.

Abstract

In 2003 and 2004 fruits of 12 sweet orange varieties: Pineapple, Parson Brown, Hamlin. Washington Navel. Carter Navel, Valencia Late. Lue Gin Gon, Agege, Etinam. Meran, Bende and Umudike were evaluated for susceptibility to fruit fly. Ceratitis spp., infestation. Fruit drop beneath tagged trees (4/variety), resulting from fruit fly damage, was recorded and 10 randomly selected fruits were held in cages for emergence of adult fruit flies. Ten mature fruits of each variety were analyzed for rind and fruit acidity which were correlated with fruit fly infestation. The results showed that Parson Brown, Washington Navel and Carter Navel. which were moderately acidic (PH 4.4 – 4.5), were more susceptible to fruit flies as they had more dropped fruits per tree (2.3 – 3.8) compared to the highly acidic (pH = 3.9), local varieties (Agege, Etinam, Meran. Bende and Umudike) with 0.8 – 1.7 dropped fruits/tree. Positive and significant correlations were respectively established in 2003 and 2004 between fruit fly infestation and acidity of the rind (r = 0.88 and 0.447; P<0.05) and juice (r = 0.88 and 0.655;P<0.05): between fruit fly emergence from infested fruits and acidity of juice (r = 0.905 and 0.90: P<0.01); and between fruit fly infestation and number of dropped fruits (r = 0.76 and 0.77; P<0.05).