Interactions between Beauveria bassiana and Trichogramma pretiosum under laboratory conditions

Abstract

Knowledge about interactions among biological control agents, used in sequence or simultaneously, may help to increase their efficiency, or in the case of conservation biological control, to avoid the impairment of efficiency. The aim of this study was to evaluate the interaction between two isolates of Beauveria bassiana (Bals.) Vuill. (Hypocreales) (Unioeste 47 and Unioeste 57) and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), varying the timing of sprays of the fungus. Isolates were sprayed at 109 conidia ml−1 upon cards (1 × 5 cm; i.e., 2 × 105 conidia mm−2) with eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) and the control group was sprayed with sterile distilled water with Tween® 80 (0.01%). First, the percentage of parasitized eggs was assessed in a choice test: females of T. pretiosum were confined with two cards, one of them treated with either of the fungus isolates, the other a water‐treated control. Second, parasitism was compared on cards sprayed at various time intervals pre‐ vs. post‐parasitism: the number of parasitized eggs was assessed, as well as the parasitoid's emergence percentage, egg‐adult period, offspring sex ratio, and the longevity of parasitizing females. Trichogramma pretiosum preferred to parasitize control eggs (65 and 72%) and parasitization of the treated eggs did not differ between fungus isolates: 35% (Unioeste 47) vs. 28% (Unioeste 57). Spraying before or after parasitizing did not affect the number of parasitized eggs, nor offspring sex ratio; however, both treatments affected the percentage of emerged adults, egg‐adult period, and longevity. These findings suggested that isolates did not interfere in the longevity of parasitizing females. When the fungus was sprayed on the various development stages of the parasitoid within the host egg, or when it was offered to the parasitoid at different times after spraying, differences in adults' longevity, parasitism, emergency period from egg to adult, and sex ratio were observed. Beauveria bassiana may be used in conjunction with this parasitoid in a program of pest control.

Is Isaria fumosorosea selective to Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)?

“…Potrich et al (2009) also report that the sex ratio of T. pretiosum emerging from A. kuehniella eggs sprayed with M. anisopliae and B. bassiana both before and after being parasitized does no differ from that recorded for the control, which is similar to that recorded in the present study. Using B. bassiana, spraying before or after parasitism, also did not affect the sex ratio of the offspring (Potrich et al, 2015).…”

“…Dalvi et al (2007) also do not report a statistical difference in the longevity of T. atopovirilia females that come in contact with L. lecanii and those in the control. Simi- larly, Potrich et al (2009) and Potrich et al (2015), report that the longevity of T. pretiosum females that come into contact with isolates of the fungi B. bassiana and M. anisopliae when parasitizing eggs of A. kuehniella is not affected.…”

“…The biological parameters evaluated in both bioassays were the number of blackened eggs of A. kuehniella eggs (parasitism signal) (Cônsoli et al, 1999), percentage of eggs from which adult parasitoids emerged, longevity of emerged adults, duration of the egg-adult period and sex ratio, as recorded by Hassan (1997) and using the equations proposed by Potrich et al (2015). The longevities of the females of T. pretiosum that parasitized the eggs were recorded and, after death they were placed in a humid chamber to confi rm they were killed by the fungus.…”

“…Of the fungus suspensions (1.0 × 10 9 conidia.mL -1 ) 0.2 mL was sprayed on one of the cards and sterile distilled water containing Tween ® 80 (0.01%) was sprayed on the other card, this volume was suffi cient to cover the eggs on each card. The procedures followed were those used by Potrich et al (2015).…”

Integration of Entomopathogenic Fungi into IPM Programs: Studies Involving Weevils (Coleoptera: Curculionoidea) Affecting Horticultural Crops

“…Several studies have focused on the direct effect of EPF on predators of A. signatus (e.g., the generalist predatory bug Anthocoris nemorum [ 303 ]), C. sordidus and R. ferrugineus (e.g., the predatory earwig Euborellia annulipes [ 304 ]), D. abbreviatus (e.g., Asian lady beetle Harmonia axyridis and the generalist predatory lady beetle Olla v-nigrum [ 305 , 306 , 307 ]) and parasitoids of H. hampei (e.g., the bethylid ectoparasitoid Prorops nasuta [ 308 ], egg parasitoid Trichogramma pretiosum [ 309 , 310 , 311 ], eulophid endoparasitoid Phymastichus coffea [ 312 ] and bethylid ectoparasitoid Cephalonomia stephanoderis [ 313 ]). These studies indicate that the integration of EPF with predators and parasitoids should be feasible, but EPF should be applied at different times relative to any supplementary releases of beneficial insect species.…”