Infochemicals in a tritrophic system : interactions between Brassica, Pieris and Cotesia

In this thesis the isolation and identification of infochemicals which are involved in Cotesia-Pieris-Brassica relationships with the prospect of their eventual use in cabbage crop protection, are described. The study focuses on two topics: regulation of Pieris oviposition behaviour and host selection behaviour of parasitoids of Pieris larvae.A general introduction about relationships between plants/insects and insects/insects, and more specifically the relationship between Crucifers and their associated insect herbivores as well as phytochemical information about Cruciferae is given in chapter 1.In chapter 2 the isolation and identification of the oviposition stimulant for the large cabbage white butterfly, present in the leaf surface of Brussels sprout plants, is described. The oviposition stimulant could be identified as glucobrassicin (3-indolyl-methyl-glucosinolate), a secondary plant compound belonging to the glucosinolates which are characteristic for the genus Brassica.The identification of oviposition deterrents from the eggs of the large cabbage white is described in chapter 3. Three compounds, responsible for the oviposition deterring activity of an egg wash when sprayed onto a cabbage leaf, were isolated and identified as trans -2-[3-(3,4,5-trihydroxy- phenylpropenoyl)-amino]-3,5-dihydroxy-benzoic acid (miriamide), trans -2-[3-(3,4-dihydroxyphenylpropenoyl)amino]-3,5-dihydroxybenzoic acid and trans -2-[3-(3,4-dihydroxy-5-β- glucopyranose-phenylpropenoyl)amino]-3,5-dihydroxybenzoic acid. The synthesis of the first two compounds is also described. The three previously unknown avenanthramide alkaloids (amides of derivatives of anthranilic and cinnamic acid) form a group of compounds that have not been reported from the animal kingdom before.The structure-activity relationship of the isolated avenanthramide alkaloids (described in chapter 3) and eight related synthesized compounds, as oviposition deterrents for P.brassicae L., is studied in chapter 4. For ten of the tested compounds, the effective dosis at which an oviposition deterring index of 50 % (ED 50 ) occurred, has been calculated. At least three groups with different activity levels were found. Changes in the way both ring systems were connected had no influence on the deterrent activity, while modifications of groups linked to the anthranilic part of the molecule led to a reduction of activity compared to miriamide. Mono- and dihydroxy substituted cinnamic parts of the molecule increased its effectiveness. trans -(4-Hydroxyphenylpropenoyl)amino]-3,5-dihydroxybenzoic acid was found to be significantly more active than miriamide.In chapter 5, the question whether ovipositing female butterflies, after landing on the upper surface of a cabbage leaf, can perceive the host marking pheromone (HMP) present on the eggs deposited on the lower side of the leaf is studied. The strongly oviposition deterring avenanthramide alkaloids could not be detected in leaf surface extracts from leaves from which egg batches had been removed. Thus the isolated avenanthramide alkaloids are not directly responsible for the HMP effect. Evidence is obtained that cabbage leaves themselves produce oviposition deterrents in response to oviposited egg batches, thus making the use of the terni HMP disputable. Fractions containing potent oviposition deterrents were isolated from surface extract of leaves from which previously laid egg batches had been removed.In chapter 6 headspace analysis of intact cabbage plants and cabbage plants infested with larvae of the small cabbage white and the large cabbage white is described. The volatile production of intact cabbage plants shows a seasonal fluctuation with the highest production rate in the summer period.Major differences in the headspace profile of intact and caterpillar damaged plants were revealed for hexyl acetate, cis -3-hexenyl acetate, myrcene, sabinene and 1,8-cineole. No significant quantitative differences were found between the headspace of cabbage plants infested by one or the other caterpillar species. In a windtunnel bioassay (dual-choice), it was found that the solitary parasitoid of the small cabbage white and a gregarious parasitoid of the large cabbage white distinguish between intact cabbage plants and cabbage plants infested with their preferred hosts

Jasmonic Acid-Induced Changes in Brassica oleracea Affect Oviposition Preference of Two Specialist Herbivores

Jasmonic acid (JA) is a key hormone involved in plant defense responses. The effect of JA treatment of cabbage plants on their acceptability for oviposition by two species of cabbage white butterflies, Pieris rapae and P. brassicae, was investigated. Both butterfly species laid fewer eggs on leaves of JA-treated plants compared to control plants. We show that this is due to processes in the plant after JA treatment rather than an effect of JA itself. The oviposition preference for control plants is adaptive, as development time from larval hatch until pupation of P. rapae caterpillars was longer on JA-treated plants. Total glucosinolate content in leaf surface extracts was similar for control and treated plants; however, two of the five glucosinolates were present in lower amounts in leaf surface extracts of JA-treated plants. When the butterflies were offered a choice between the purified glucosinolate fraction isolated from leaf surface extracts of JA-treated plants and that from control plants, they did not discriminate. Changes in leaf surface glucosinolate profile, therefore, do not seem to explain the change in oviposition preference of the butterflies after JA treatment, suggesting that as yet unknown infochemicals are involved

Novel N-acyl-anthranilic acid compounds, and use of N- acyl-anthranilic acid compounds in insect control

The invention relates to the use of an N-acyl-anthranilic acid compound of the formula 1, where: R1 to R9 inclusive represent a hydrogen atom, halogen atom, alkyl group, phenyl group, hydroxyl group, alkoxy group, acyloxy group or a sugar radical, with the option of two adjacent groups out of R1 to R9 inclusive alternatively representing an alkylenedioxy group; X represents a direct bond or an alkylene, alkenylene or alkynylene group which may substituted with one or more alkyl groups or hydroxyl groups; Y represents a hydrogen atom or an alkyl group; and Z represents a hydrogen atom, methyl group, hydroxyl group, alkoxy group, mercapto group, alkylthio group, amino group or mono- or dialkylamino group, or a salt thereof, in insect control, in particular relating to insects of the order Lepidoptera, more particularly the family Pieridae, more particularly the genus Pieris. Also described are novel active substances and crop protection agent