Susceptibility of Selected Grape Varieties to Arthropod Infestation in Salah Al-Din Governorate, Iraq

Grapevines are essential to Iraq's horticultural economy, as the Salah Al-Din region is considered the leading producer. However, grapevines are susceptible to arthropod pests, which threaten yield and quality. This study evaluated the infestation levels on Shada, Beadh Al-Hamam, and Faranci Asoud grape varieties, focusing on pest populations, associated predators, and the role of leaf nutrient content in pest resistance. Biweekly leaf samples were taken using a microscope for pest and predator checks and counts. Leaf NPK content was determined using standard chemical methods. The highest population peak of the mite Tenuipalpus granati was recorded at the end of August, reaching 100.27 and 156.87 individuals/leaf on the Shada and Beadh Al-Hamam varieties, respectively. Meanwhile, the Faranci Asoud variety exhibited the highest density, with 385.80 individuals/ leaf in early September. For the black vine thrips Retithrips syriacus, infestations occurred at the end of July, reaching 17.33, 19.07, and 26.00 insects/leaf on the Shada, Beadh Al-Hamam, and Faranci Asoud varieties, respectively. The citrus mealybug Planococcus citri reached 4.00, 11.67, and 7.33 insects/leaf on the same varieties by the end of September. Predators such as Amblyseius sp., Chrysoperla carnea, and Scolothrips sexmaculatus correlated significantly with mite and thrips populations, but not with mealybugs, this could be due to the low population density of mealybugs. Nutrient analysis revealed a strong positive correlation between nitrogen content and pest density, a non-significant positive correlation with phosphorus content, and a negative correlation with potassium content. These findings suggest that varietal differences in pest susceptibility are influenced by leaf nutrient composition and predator presence. The study demonstrates an approach to vineyard management by leveraging natural plant defenses and natural enemies to mitigate pest damage without relying on harmful chemicals. Keyword: Grapevine, pests infestation, Retithrips syriacus, Tenuipalpus granati, biological pest control, sustainable agriculture.