Population trends and chemical control of citrus leafminer Phyllocnistis citrella Stainton on citrus in Jordan Valley
1996
Ateyyat, M.A.
Several ecological and chemical experiments have been conducted on citrus leafminer (CLM) between Nov., 1994 and Oct., 1995 in five citrus orchards at diffrent sites in Jordan Valley(JV). In addition, a survey of CLM in Jordan was also done during the research period. The survey of CLM showed that it was widely distributed in Jordan. It was found attacking citrus trees in the JV sites, Amman, Zarqa, Rusaifa, Salt, Madaba, Jarash, Mahis, Fhais, Baqa'a, Karak, Irbid, Ramtha, Aqaba and Ajlun. Percentage of infested succulent lemon leaves in JV in Aug., 1995 was highest in Baqura and Adaseyya in the north of JV and decreased gradually as moving toward the south. Although, CLM was reported to attack succulent tender leaves and twigs, it was observed attacking pummelo fruits in Al-Masalha citrus orchards in Oct., 1995. Studies on the preferable citrus species and microclimate to CLM infestation in Al-Masalha citrus orchards showed that lemon and pummelo were highly susceptible, while clementine and mandarin were highly resistant. The lower surface of leaves, the lower parts of the trees, the center and southern sides of trees and the peripheral trees in the field were highly susceptible. Population trend studies on CLM on lemon trees in Deir-Alla Agricultural Station (DAAS) and Wadi Al-Yabis Agricultural Station (WYAS) between Nov., 1994 and Oct., 1995, showed that the highest peak of alive larvae was in early May, 1995 in both stations. The highest peak of alive pupae was in early May, 1995 in WYAS, and in Sep. in DAAS. Thirteen overlapped generations were recorded in DAAS, and 14 overlapped generations in WYAS. Larval mortality was mainly due to overcrowding in both DAAS and WYAS especially in May, 1995. Natural enemies also played a role in CLM immature mortality. The highest percentage of infested lemon leaves recorded was in May in WYAS and in Jul., Aug. and May, 1995 in DAAS. The highest percentage of infested lemon new growths was in Nov., 1994 and from May to Sep., 1995 inDAAS. Seven eulophid parasitoids reared from CLM immatures were identified as: Pnigalio sp. A, B, and C, Ratzeburgiola incompleta Boucek, Cirrospilus quadristriatus (Subba, Rau and Rarnamani), Cirrospilus pictus (Nees) and Neochrysocharis formosa (Westwood). The most common parasitoid was Pnigalio species. A, in addition to one predator identified as Chrysoperla carnea. The larvae of this predator were found feeding on CLM larvae. Chemical control experiments were conducted by testing 15 pesticides against CLM. Pirate, Vapcocidin, Evisect, Vertimic, Confidor, Acifon, Nomolt and Mimic were highly effective; and more effective as larvicides, especially on the first and second larval instars.
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