Document Type : Original Article
Authors
1
Plant Prot. Res. Inst., Dokki, Giza, Egypt
2
Plant Prot. Dept., Fac. Agric., Zagazig Univ., Egypt
Abstract
This investigation was carried out to study the relationship between citrus leafminer (CLM) Phyllocnistis citrella Stainton and some factors i.e. flushes (growth cycles), leaf area, leaf age, citrus varieties, some chemical contents in leaves and storage fruits of six citrus varieties and species at El-Kassasien District, Ismailia Governorate and Minia El-Kamh District, Sharikia Governorate orchards for three successive seasons 2013, 2014 and 2015. The results could be summarized as follows: infestation started to appear in small leaves (0.4-0.9, 1.8-2.7, 1.1-1.7 cm2 for orange varieties) and (0.3, 0.9, 0.8 cm2 for mandarin) in different emerged flushes (spring, summer and autumn), respectively during seasons 2013 and 2014. Also, leaf blade was not infested when area reached more than 3.2- 3.8, 6.5- 7.6 and 6.5- 7.0 cm2 in orange varieties as well as 1.6, 2.9 and 2.0 cm2 in mandarin through spring, summer and autumn flushes, respectively. The young leaves less than three days old were subjected more to highly infestation rate than old ones. Percentage of infestation, significantly decreased in descending order (autumn, summer and spring flushes cycle, respectively). The new sprouted growth in spring flush (March) were least damaged and escaped from CLM infestation. The tested citrus species and varieties showed significant differences in infestation rates with CLM, where navel orange recorded the highest followed by valencia orange, mandarin, sweet orange, baladi orange and sour orange. The effect of certain chemical contents (volatile oil contents, phenols, total carbohydrates, total protein and pH level) in some citrus varieties leaves on infestation rate of CLM was investigated. Total content of volatile oils in citrus leaves was affected by diversity of varieties. Differences of citrus infestation rates with CLM depend on total content of volatile oils in some citrus leaves of tested varieties and other varieties have no relation with volatile content. The present study demonstrates the effect of phenols content on insect infestation rate. Meanwhile, high total carbohydrate in leaves of citrus varieties showed a significantly lower infestation with CLM. Total proteins and pH level in citrus leaves showed no relation with CLM infestation. Fruits storage on trees after the normal date of harvesting increased significantly CLM infestation, where infestation in navel orange reached 42.88 and 47.44% after storage 90-120 days compared with 31.72 and 34.83% in normal date of harvesting, Also, infestation in mandarin reached 38.66 and 41.55% after storage compared with 24.00 and 27.33% in normal harvesting date.
Keywords
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