TOXICOLOGICAL STUDIES ON SOME INSECTICIDES AGAINST THE CITRUS .. LEAFMINER, PHYLLOCNISTIS CITRELLA WITH ' SPECIAL REGARD TO SUSCEPTIBILITY OF CULTIVARS TO INFESTATION.

Abstract

The present study was designed to investigate the toxicological effects of some insecticides against the citrus leafminer Phyllocnistis citrella with special regard to susceptibility of cultivars to infestation. The results obtained could be summarized as follows:

1-The insect population usually being to appear in late April, increased rapidly giving two peaks of abundance throughout summer and autumn. It diminished afterwards where disappeared completely during winter season as influenced by unfavorable weather conditions and the rarity of newly formed flushes. 2-All the tested cultivars (lime, mandarin, sour orange, navel orange and sweet orange) are stibjected to attack by the leafminer. The overall percent of infestation showed that mandarin cultivars, as the least susceptible host, displayed 42.4% compared to highly susceptible cultivar sweet orange (50.6 %) i.e. about 16 %decrease in infestation. 3-The oil extracted from lime and mandarin flush leaves were characterised by monoterpene hydrocarbons as main fractions. The esteric structures appeared the most abundant components of sour orange. The two cultivars (navel and sweet oranges) are characterised by the absence of any of sesquiterpens, esters or oxides and high yield of monoterpenes. The relationship between the common features of the phytoconstituents in the citrus leaves and the levels of the leafminer infestation was discussed. 4-The efficiency of some selected compounds applied on navel orange trees was evaluated against the citrus Ieafminer population in Kalyobia Governorate using three different criteria of assessment. 5-The chemical treatments were able to suppress the levels of infestation, to different degrees, in comparison to that of untreated control. The pyrethroid A.-cyhalothrin was the most effective compound followed by the mixture abamectin + KZ oil