Physical and chemical plant characters inhibiting the searching behaviour of Trichogramma chilonis

Abstract

Several plant characters are known to affect the searching behaviour and parasitization efficiency of Trichogramma spp. (Hymenoptera: Trichogrammatidae). In this study, plant characters contributing to the low Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) egg parasitism levels on pigeonpea (Cajanus cajan (L.) Millspaugh) were investigated. The efficiency of T. chilonis on pigeonpea was dependent on the plant structure on which the host eggs were found. In a cage experiment, more than 55% of eggs placed on leaves were parasitized, while 1% of eggs on calyxes and no eggs on pods were parasitized. In a filter paper bioassay, parasitoids were deterred by acetone and hexane surface extracts from pigeonpea pods but showed no response to water extract. The searching behaviour of the parasitoids was not affected by different solvent extracts from the surface of pigeonpea leaves. In a four-armed airflow olfactometer, T. chilonis was repelled by volatiles from pigeonpea pods but showed no response to volatiles derived from hexane extract of pod surfaces. Volatile infochemicals and hexane surface extracts from pods of two wild Cajanus species, C. scarabaeoides (L.) Thours and C. platycarpus (Bentham) van der Maesen, were similarly deterrent to T. chilonis. The movement of the parasitoids on pigeonpea pods and calyxes was inhibited by long trichomes and wasps were trapped by sticky trichome exudates. Parasitoids walked significantly faster on leaves than on pods. The walking speed on both pods and leaves increased significantly after washing with hexane. The results presented in this paper show that the plant growth stage and the plant structures preferred by H. armigera for oviposition are the least suitable for T. chilonis, contributing to the low parasitoid efficiency on pigeonpea.

Effect of pigeon pea intercropping or shading with leucaena plants on the occurrence of the coffee leaf miner and on its predation by wasps in organic coffee plantings

“…In addition to leaf nutritional condition, the headspace volatiles in the planting may affect CLM dynamics because coffee volatiles can influence CLM mating behavior (FONSECA et al, 2013). Pigeon pea probably affected CLM behavior as well; this plant has been reported to have insectrepellent proprieties (ROMEIS et al, 1998, OBICO & RAGRARIO, 2014. Additional studies must be conducted to confirm CLM repellence by pigeon pea plants compared with coffee plants.…”

Estudios biológicos de Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae), parasitoide de huevos de Tuta absoluta Meyrick (Lepidoptera: Gelechiidae)

“…Los parámetros poblacionales de T. bactrae sobre S. cerealella en el tejido foliar y la cartulina (S/C vs S/T) no difi rieron estadísticamente (prueba t, P > 0.05) (Tabla 2). Contrariamente, algunos autores han encontrado que la densidad y tipo de tricomas puede afectar a los microhimenópteros en su capacidad de búsqueda y parasitismo (Romeis et al 1998, Olson & Andow 2006 ha visto que como Lycopersicon esculentum no posee pelos glandulares, el desempeño de los parasitoides se ve afectado sólo cuando hay una elevada densidad de tricomas, lo que se observa principalmente en las hojas más nuevas y los brotes (Mulatu et al 2005, Arantes Faria 2008.…”

“…Si bien los tricogramátidos pueden tener un relativamente amplio rango de huéspedes, se acepta que tienen gran especifi cidad por el hábitat, por lo que el cultivo debe jugar un papel importante en el desempeño del parasitoide, tanto por su estructura individual y la del canopeo, como por las características físico químicas del tejido vegetal (Smith 1996, Vinson 1997, Romeis et al 1998, Hunter 2003 y en particular, la densidad y tipo de tricomas (Kauffman & Kennedy 1989, Gonçalvez-Gervásio et al 2000, Mulatu et al 2005, Simmons & Gurr 2006, Arantes 2008. El sistema L. esculentum-T. absoluta-T. bactrae es una relación nueva, ya que este parasitoide ha sido hallado en la naturaleza parasitando otras especies de lepidópteros que además no son plaga del tomate.…”

Associative learning and discrimination of 10 plant species by the egg-larval parasitoid, Ascogaster reticulata Watanabe (Hymenoptera: Braconidae)

“…Trichomes or secretions from glandular trichomes on the plant surface sometimes interfere with insect behavior. Parasitic wasps have also been shown to be affected by hairy structures or repelled by glandular trichome volatiles (van Lenteren et al, 1995;Sutterlin and van Lenteren, 1997;Romeis et al, 1998;Al-wahaibi and Walker, 2000;Lovinger et al, 2000). Trichomes and similar plant structures are likely to have negative impacts on host-searching behavior of A. reticulata, and so can be expected to affect the preference for and discrimination of plant species.…”