Chemical composition of corn leaf essential oils and their role in the oviposition behavior of Sesamia nonagrioides females.

The chemical composition of the volatile oils collected by steam distillation from leaves of seven corn hybrids and their effect on the oviposition behavior of Sesamia nonagrioides females was studied. Samples of the volatile oils from each of the hybrids were analyzed by capillary gas chromatography-mass spectrometry (GC-MS) and several major compounds were identified. The major compound found in all seven hybrids was 3,7,11,15-tetramethyl-2-hexadecen-1-ol (phytol), ranging from 38.3 to 64.9% of the total quantity. Compounds detected in significant proportions include (Z)-3-hexenol (3.1 to 8%), nonanal (4.9 to 14.5%), pentadecanal (1.8 to 5.8%), neophytadiene (5.5 to 12.9%), (Z)-3-hexenyl acetate (2.5 to 8.9%), and an analogue of 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3-(4H)-one (DIMBOA) (2.4 to 9.3%). The analysis showed no qualitative differences among the chemicals identified while quantitative differences were detected. Among the volatile oils, the significant difference was in the quantity of aldehydes present. In two-choice bioassays, filter paper sticks treated with volatile oils containing higher quantity of aldehydes received fewer eggs than those with lower aldehyde quantity. Bioassays with synthetic aldehydes of a chain length C9-C14 confirmed the above results.

Comparative studies of female sex pheromone components and male response of the corn stalk borer Sesamia nonagrioides in three different populations.

Studies to determine possible differences in the pheromone communication system of three different populations of the corn stalk borer Sesamia nonagrioides (Lef.) in France. Spain. and Greece were carried out. The two main pheromone components (Z)-11-hexadecenyl acetate (Z11-16:Ac) and (Z)-11-hexadecenol (Z11-16:OH), were detected in all analyses with very small differences in the three populations. Among the minor components, analyzed by GC-MS on concentrated gland extracts from French and Greek origin females, (Z)-l1-hexadecenal (Z11-16:Ald) was detected in minor amounts. Wind-tunnel and field studies revealed similar a male response in the three populations to pheromone glands extracts and synthetic pheromone regardless of the female/male origin. The results do not support the assumption of the existence of different pheromone types of the corn stalk borer S. nonagrioides due to geographic isolation.

Alkadienes and alkenes, sex pheromone components of the almond seed wasp Eurytoma amygdali.

Whole body extracts of virgin Eurytoma amygdali females were attractive to males in laboratory bioassays. Extracts of various body parts of the female wasp elicited different responses to males, with the thorax extract being the most active. Preparative fractionation of the crude hydrocarbon extract on a silver nitrate impregnated silica gel column (alkanes, alkenes, and alkadienes) revealed that the highest male response was elicited by alkadienes and the lowest by alkenes, with the alkane fraction being inactive. The identification of alkenes and alkadienes was based on gas chromatographic, mass spectrometric, and gas-phase infrared data. Laboratory bioassays suggested that the two alkadienes, (Z,Z)-6,9-tricosadiene [(Z,Z)-6,9-C23:2], and (Z,Z)-6,9-pentacosadiene [(Z,Z)-6,9-C25:2], and to a lesser extent alkenes, identified in the female extract of E. amygdali were male attractants.