Oviposition Preferences of Oriental Fruit Moth Grapholita Molesta (Lepidoptera: Tortricidae) To Pear HIPVs

Herbivore-induced plant volatiles (HIPVs) are regarded as an indirect plant defense against herbivores, since they attract natural enemies to the infested plant. On the other hand, HIPVs also affect behavioral responses of herbivores. In a previous study, Lytopylus rufipes, a parasitoid of the oriental fruit moth (Grapholita molesta), showed positive responses to pear HIPVs, but the influence of pear HIPVs on G. molesta is still unclear. To better understand these responses, we first tested oviposition preferences of G. molesta to uninfested and infested pear shoots (US and IS, respectively) and uninfested mature leaves (ML) in dual-choice bioassays with a cylindrical tube. Then, preferences to volatile components were also assessed. Results show that G. molesta females preferred US-, IS-, and ML-treated areas compared to the control area (no leaves), respectively. Subsequently, G. molesta females preferred IS over US, and US more than ML when comparing pear tissues. Furthermore, G. molesta females didn’t show any significant preference to individual volatile components, but more eggs were laid in the area treated with a synthetic pear HIPV blend, compared to the hexane-treated area (control). These results indicate that G. molesta females do not avoid infested pear shoots nor HIPVs. Moreover, HIPVs may recruit not only natural enemies, but herbivores to the release point of HIPVs. Thus, it is important to examine the responses of G. molesta females to HIPVs in the field before employing them for pest management.

Influence of wild, local and cultivated tobacco varieties on the oviposition preference and offspring performance of Spodoptera litura

The influences of different plants on herbivores have recently attracted research interest; however, little is known regarding the effects of wild, local and cultivated varieties of the same plant from the same origin on herbivores. This study aimed to examine the effects of different tobacco varieties from the same origin on the oviposition preference and offspring performance of Spodoptera litura. We selected two wild (‘Bishan wild tobacco’ and ‘Badan wild tobacco’), two local (‘Liangqiao sun-cured tobacco’ and ‘Shuangguan sun-cured tobacco’) and two cultivated (‘Xiangyan No. 5’ and ‘Cunsanpi’) tobacco varieties from Hunan Province, China. We found that female S. litura varied in oviposition preferences across the tobacco varieties. They preferred to lay eggs on the cultivated varieties, followed by the local varieties, with the wild varieties being the least preferred. Furthermore, different tobacco varieties significantly influenced the life history parameters of S. litura. Survival rate, pupal weight, emergence rate and adult dry weight decreased in the following order: cultivated varieties > local varieties > wild varieties. Conversely, the pupal stage and development period decreased in the following order: wild varieties > local varieties > cultivated varieties. Therefore, we conclude that wild tobacco varieties have higher resistance to S. litura than cultivated and local varieties, reflecting the evolutionary advantages of wild tobacco varieties.

Fitness Consequences of Oviposition Choice by an Herbivorous Insect on a Host Plant Colonized by an Endophytic Entomopathogenic Fungus

Entomopathogenic fungi (EPF), often considered as a bioinsecticide, are also able to colonize and establish a symbiotic relationship with plants as an endophyte. Recent studies demonstrated that endophytic EPF can enhance plant growth and are antagonistic to fungal pathogens. These newly emerging, but not yet fully understood, ecological roles suggest the possibility that EPF may further mediate oviposition preferences and offspring performance of an herbivorous insect. However, such EPF-mediated effects and underlying mechanisms are largely unexplored. Here, we examined the hypothesis that the endophytic EPF Beauveria bassiana can modulate oviposition behavior of the Asian corn borer Ostrinia furnacalis. We observed that O. furnacalis females preferred to lay eggs on B. bassiana inoculated maize plants. This is likely attributed to the net effects of plant volatile profiles induced by B. bassiana, with an increase in emitted amount of insect-attractive compounds 2-ethyl-1-hexanol and 3-hexen-1-ol and a decrease in insect-repellent compounds β-caryophyllene, naphthalene, and α-pinene. This finding provides an example of EPF-induced plant volatile-mediated interaction between plants and insects. However, fewer O. furnacalis larvae, pupae, and adults survived on the oviposition-preferred maize possibly due to lower plant nitrogen content. These results indicated that oviposition selection by O. furnacalis did not reflect the maximization of offspring fitness following B. bassiana inoculation. We suggest that fitness consequences of oviposition preferences should be considered when incorporating EPF as a biopesticide and as a potential biofertilizer within an integrated pest management programs.

Up and to the light: intra- and interspecific variability of photo- and geo-tactic oviposition preferences in genus Trichogramma

Trichogramma are parasitic microwasps much used as biological control agents. The genus is known to harbor tremendous diversity, both inter- and intra-specific. The successful selection of appropriate strains rests on a careful evaluation of this diversity at the phenotypic level, especially regarding oviposition performance and behavior. Oviposition preferences in relation to environmental cues such as light and gravity, although suspected to play an important role in microhabitat selection and oviposition patterns, have received little attention so far in this group, either alone or in combination. The extent of their variability is thus virtually unknown. Here we use a novel experimental approach relying on automatic image analysis to characterize the oviposition preferences in relation to light, gravity, and their interaction, in 25 populations of Trichogramma from five species. We show that most Trichogramma populations and species harbour preferences for light and preferences for elevated parts. However, the two trait harbor significant inter and intraspecific variation. The effects of light and gravity on oviposition patterns were found to be almost perfectly additive overall, with two exceptions. Oviposition preference patterns were not static but very plastic in time: preferences tended to relax over consecutive days, and the strongest preferences relaxed the fastest, presumably because of the density-dependent effect of resource depletion. A correlation of oviposition patterns with the vegetation stratum at which populations were sampled suggests that different species/populations may be associated with different strata with corresponding differentiation in light- and gravity-related oviposition preferences.

Preference Provides a Plethora of Problems (Don't Panic)

This review was solicited as an autobiography. The “problems” in my title have two meanings. First, they were professional difficulties caused by my decision to study oviposition preferences of butterflies that were not susceptible to traditional preference-testing designs. Until I provided video, my claim that the butterflies duplicate natural post-alighting host-assessment behavior when placed on hosts by hand was not credible, and the preference-testing technique that I had developed elicited skepticism, anger, and derision. The second meaning of “problems” is scientific. Insect preference comes with complex dimensionality that interacts with host acceptability. Part Two of this review describes how my group's work in this area has revealed unexpected axes of variation in plant–insect interactions—axes capable of frustrating attempts to derive unequivocal conclusions from apparently sensible experimental designs. The possibility that these complexities are lurking should be kept in mind as preference and performance experiments are devised.

Asian corn borer (Ostrinia furnacalis Guenee) oviposition preferences on maize (Zea mays Linn), king grass (Panicum maximum Jacq.), and cogon grass (Imperata cylindrica (L.)

<p>Insects’ oviposition behavior on alternate host plants is very helpful to understand the interaction between host plants and insects, the dynamics of insect populations, and the effectiveness of alternate host plants as refugia in managing insect resistance. The oviposition preference of <em>Ostrinia furnacalis</em> on maize (<em>Zea mays</em> L), king grass (<em>Panicum maximum</em> Jacq.), and cogon grass (<em>Imperata cylindrica</em> (L.) was studied through no-choice test, two-choice test, and three-choice test. The oviposition preferences hierarchy of <em>O. furnacalis</em> on maize, king grass, and cogon grass wass sequentially maize &gt; king grass &gt; cogon grass when the tested plants were at 21 DAP (days after planting). However, the hierarchy pattern may change depending on host plants phenology. The 35-day-old king grass was more preferred by <em>O. furnacalis</em> (proportion of eggs = 0.692; OPI = 37.57) than maize (proportion of eggs = 0.301; OPI = -38.780) and cogon grass (proportion of eggs = 0.174; OPI = -65.183) for oviposition. These findings indicated that king grass was a potential alternate host for <em>O. furnacalis </em>to survive and could serve as refugia in IRM strategy. However, it needs further research in the field to ensure the potential of king grass as refugia for <em>O. furnacalis.</em></p>