Components of the essential oil of three citrus species in correlation to their infestation with scale insects

Abstract

Twenty components of the essential oil encountered in the oil glands of 3 citrus species with different degrees of susceptibility to infestation with the red scale Aonidiella aurantii Maskel. have been identified through GLC. Citrus species with higher hydrocarbons content are more susceptible, while those with higher alcoholic terpenes content are more resistant to insect infestation. The behavioural response of the crawlers of this scale insect to the individual components of the essential oil support to a great extent this view, where the crawlers were attracted to the hydrocarbons and but they avoided or showed no obvious response to the acoholic terpenes. The correlation between this insect species and citrus trees has been discussed. Zusammenfassung Komponenten des Öls von drei Citrus‐Arten in Beziehung zum Schildlausbefall Es wurden 20 Komponenten des von den Öldrüsen dreier Citrus‐Arten produzierten Öls mit unterschiedlicher Wirkung auf den Befall durch die Rote Schildlaus, Aonidiella aurantii Mask. identifiziert. Citrus‐Arten mit höherem Hydrocarbon‐Gehalt zeigten sich empfindlicher, solche mit höherem Gehalt an alkoholischen Terpenen dagegen resistenter gegen den Schildlausbefall. Das Verhalten der Schildlauslarven gegenüber den einzelen Komponenten des Öls wies in dieselbe Richtung: die Larven wurden von den Hydrocarbonen, nicht jedoch von den alkoholischen Terpenen angezogen. Die Beziehungen zwischen der Schildlaus und den Citrus‐Bäumen werden erörtert.

Toxicity of citrus essential oils against Ceratitis capitata (Diptera: Tephritidae) larvae

“…Habib et al (1972) found a negative correlation between the concentration of essential oils in leaves and fruits of citrus and their susceptibility to red scale Aonidiella aurantii (Maskell). Moreover, Salama & Saleh (1984) found that citrus species with higher hydrocarbon content are more susceptible to red scale infestation compared to those with higher alcoholic terpenes. Caccioni et al (1995 and 1998) have reported the inhibitory effects of citrus essential oils and their components against the fungal pathogens Penicillium digitatum (Pers.)…”

“…Citrus species have developed several mechanisms to defeat infestations of fruit flies as well as infestations by other insect species. The chemical properties of fruits, especially the peel essential oils are considered to be the most important resistance mechanism of citrus fruits against fruit flies (Greany et al , 1983; Aluja et al , 2003; Birke et al , 2006; Aluja & Mangan, 2008; Papachristos et al , 2008) and also against a wide range of other insects and plant pathogens (Habib et al , 1972; Salama & Saleh, 1984; Caccioni et al , 1995, 1998; Kuate et al , 2006).…”

Estimation of secondary compounds content of some citrus leaves and their relationship by dietary preference for yellow scale insect Aonidiella. Orientalis (Hemiptera: Diaspididae)

“…The highest concentration of alkaloids in sour orange leaves was (22.69%) compared to the lowest concentration in lemon leaves (11.58%), while the highest concentration of total terpenes in lemon leaves was (25.44%) and the lowest concentration was in orange leaves (7.46%). The results of [24] showed when they studied twenty aromatic compounds in oil glands of three types of citrus fruits, which are, baladi oranges, sugar oranges and lemons (benzhair), as the types with high content of terpene alcohols are more resistant to infection by red scale insect crawler Aonidiella aurantii. while citrus species with a higher hydrocarbon content were more sensitive to insect infestation.…”

Insecticidal properties of monoterpenoids and their derivatives as a new natural means of crop protection

“…" Thymyl ethyl ether is a thymol derivative synthesized in our laboratory. reviewed in recent literature in chemical ecology (Salama and Saleh 1984, Sheppard 1984, Moleyar and Narasimham 1987, Sangwan et al 1990, Watanabe et al 1990. Consequently, several monoterpenoids have been considered as alternatives to conventional pesticides for a more natural means of control.…”