Abstract
Spring and autumn flushes are generally the most infested periods by citrus aphids. Nevertheless, the role of citrus foliar minerals on aphids is not clear. Thus, this paper aims to study the correlation between certain minerals and the infestation degree of citrus varieties by Aphis spiraecola. Aphid counting was carried out on 12 leaves for each of the six species retained (clementine, lemon, grapefruit and three varieties of mandarin), during autumn (October 2014) and spring (April 2015) flushes. In addition, mineral contents of the leaves in P, K, Na, Ca and Li were measured for the same periods. The results showed that the infestation levels of the studied varieties were higher in the spring flush than in the autumn one. Moreover, analyzes of young leaves showed an important intraspecific (mandarin varieties) and interspecific differences in the mineral composition between the examined citrus trees. The study of the relationship between infestation levels by A. spiraecola and mineral content of the six examined species showed no significant correlation, suggesting a marginal role of the five analyzed minerals in the relation citrus – A. spiraecola.
Highlights
Herbivorous insects identify their host plants through the morphological aspect, chemical signals and sometimes by the combined action of all these factors (Städler & Reifenrath, 2009)
450 Acta agriculturae Slovenica, 115/2 – 2020 entine clone 63, lemon ‘Eureka’, grapefruit ‘Shambar’ and three varieties of mandarin: ‘Ortanique’, ‘Carvalhal’ and ‘Commune’), aphid counting was carried out on 12 randomly chosen young leaves belonging to 4 trees for each of the retained varieties, at the rate of 3 leaves / tree, distributed over the different cardinal directions
It was noticed that the infestation levels of these varieties were higher in the spring flush than in the autumn one (Table 1)
Summary
Herbivorous insects identify their host plants through the morphological aspect, chemical signals and sometimes by the combined action of all these factors (Städler & Reifenrath, 2009). The performance of insects is determined directly by the quality of host plants (Sun & Ge, 2011). The main nutritional needs of insects are amino acids, vitamins, minerals, carbohydrates, lipids and sterols (Silva et al, 2005). Khattab (2007) reported that potassium may play a role in the defense mechanism of aphidinfested plants. Pests need adequate quantities of several minerals to grow and reproduce (Wigglesworth, 1966). Components such as carbon and nitrogen act directly on the fertility of the pest (Awmack & Leather, 2002)
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