Compatibility of entomopathogenic nematodes with insecticides against the cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae)

Background Compatibility of entomopathogenic nematodes (EPNs) with insecticides is a crucial mainstay of integrated pest management (IPM) programs. This study was designed to evaluate the joint action of EPN species and insecticides when employed to deter 3rd and 4th larval instars of cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae) under laboratory conditions. EPNs [Steinernema carpocapsae (All strain), S. feltiae (Filipjev), Heterorhabditis bacteriophora (HP88), and H. bacteriophora (Ar-4)], at concentrations of 50, 100, and 125 IJs/larva, were tested with 3 insecticides (lambda-cyhalothrin, emamectin benzoate, and indoxacarb) at LC25 and LC50 values. Additionally, expression profiles of 2 detoxification genes (CYP6AE120 and PrGSTs1) when the 4th instar larvae were treated by H. bacteriophora (HP88) and lambda-cyhalothrin were examined. Results Data indicated that statistically significant mortality of 2 larval instars of P. rapae was observed in vitro among EPN species and pesticide concentrations. At concentration of 50 IJs/larva, LT50 values were 2.385 and 3.92 days for S. carpocapsae (All strain) and H. bacteriophora(Ar-4), respectively, on 3rd instar larvae; also, these values were 3.506 and 3.107 days for S. feltiae and H. bacteriophora (Ar-4), respectively, on 4th instar larvae Lambda-cyhalothrin was the most toxic insecticide, followed by emamectin benzoate and indoxacarb at LC25 and LC50, respectively. An additive effect was observed between EPN species with LC25 and LC50 of the tested insecticides, except for lambda-cyhalothrin at LC50 with H. bacteriophora (Ar-4), and indoxacarb, with all EPNs showing antagonistic effects on mortality of 3rd instar larvae after 3 days post-treatment. The interaction between the tested pesticides at LC25 and LC50 and EPN species, showed an additive effect, excluding lambda-cyhalothrin at LC25 with S. carpocapsae (All strain) and LC25 of indoxacarb with H. bacteriophora (Ar-4), which showed potentiation effects. The interaction of S. feltiae (Filipjev) with tested insecticides at LC50 exhibited an antagonistic effect on the mortality of 4th instar P. rapae larvae after 3 days post-treatment. The expression of both CYP6AE120 and PrGSTs1 was significantly up-regulated with lambda-cyhalothrin, followed by H. bacteriophora (HP88) compared to control. Conclusions The findings suggested that combining EPNs and the pesticide concentrations can be a practical strategy for managing P. rapae and could pave the way to using new control technologies in protecting organic farm vegetables from lepidopteran pests.

Effectiveness of biological protection of cabbage against pests in the conditions of the Primorsky Territory

The results of the use of entomophages and biological products to regulate the number of cabbage pests (cabbage moth Mamestra brassicae L., cabbage butterfly Pieris brassicae L., turnip butterfly Pieris rapae L., diamondback moth Plutella xylostella L.) are presented. The study was carried out in the Primorsky Territory in 2018-2020. The efficiency of Trichogramma ussuricum Sorokina applications was assessed on cabbage varieties. The effectiveness of the entomophage against the cabbage moth varied from 33.3 to 66.6%, against the turnip butterfly - from 32.6 to 70.2%. In field experiments the effectiveness of biological products Fitoverm EC (0.09 l/ha), Akarin EC (1.6 l/ha), Proclaim WG (0.3 kg/ha), Bitoxibacillin (10 l/ha), Bitoxibacillin P (2 kg/ha), Lepidocid SC (2 l/ha), Lepidocid P (2 kg/ha) against diamondback moth are studied. Cabbage plants were sprayed with the preparations once. Pest counts were carried out before treatment and after treatment on the 5th, 10th and 15th day in accordance with the approved methods. Bioinsecticide Proclaim showed a high efficiency of 93.0-100% on the 5-10th day. The effectiveness of preparations based on aversectin C and avertin N was 65.0-88.6%. Using the biological product Bitoxibacillin and Lepidocid a decrease the number of diamondback moth relative to the control by 61.2-97.5 и 65.0-78.0% was registered.

Simulation of the effects of movement patterns and resource density on the egg distributions of Pieris rapae (Lepidoptera) at multiple spatial scales.

<p>This thesis presents a spatially explicit, agent based simulation, used to explore the ovipositing behaviour of the Small Cabbage White butterfly, Pieris rapae (Lepidoptera). The study concerns the effects of host-plant (Cabbage, Brassica oleracae) density upon P. rapae egg distribution patterns, at multiple scales. A general review of the literature is provided which covers the ecology of animal movement, methods of quantifying movement, models of movement, ecological theory of herbivore responses to plant density (Resource Concentration Hypothesis) and the biology of P.rapae. The construction of the simulation is described in detail and the source code plus an executable version of the software are available as a companion CD. A number of simulation experiments are reported which demonstrate the basic behaviour of the simulation over a simplified resource layout. The framework is then used to explore more complex layouts which are compared to field experiments conducted as part of a separate PhD thesis (Hasenbank, in prep). A Correlated Random Walk simulated a negative relationship between forager egg distributions and resource densities, observed at all scales. Including a diffuse attraction to resources (e.g. olfaction), simulated a negative relationship between egg distributions and resource densities at smaller scales, and a positive relationship at larger scales. This work builds on a large body of previous simulation studies and attempts to produce a useful framework for subsequent researchers to explore the effects of animal movement through the use of random walks. It demonstrates the use of the framework with a specific example concerning the egg distributions of P. rapae and the effect of scale. It provides some useful insights into both the analysis of results from a complex spatial experimental layout, and potential responses which may be observed. It demonstrates that a simple model can, in the case of P rapae be used to obtain relatively realistic egg distributions.</p>

Simulation of the effects of movement patterns and resource density on the egg distributions of Pieris rapae (Lepidoptera) at multiple spatial scales.

<p>This thesis presents a spatially explicit, agent based simulation, used to explore the ovipositing behaviour of the Small Cabbage White butterfly, Pieris rapae (Lepidoptera). The study concerns the effects of host-plant (Cabbage, Brassica oleracae) density upon P. rapae egg distribution patterns, at multiple scales. A general review of the literature is provided which covers the ecology of animal movement, methods of quantifying movement, models of movement, ecological theory of herbivore responses to plant density (Resource Concentration Hypothesis) and the biology of P.rapae. The construction of the simulation is described in detail and the source code plus an executable version of the software are available as a companion CD. A number of simulation experiments are reported which demonstrate the basic behaviour of the simulation over a simplified resource layout. The framework is then used to explore more complex layouts which are compared to field experiments conducted as part of a separate PhD thesis (Hasenbank, in prep). A Correlated Random Walk simulated a negative relationship between forager egg distributions and resource densities, observed at all scales. Including a diffuse attraction to resources (e.g. olfaction), simulated a negative relationship between egg distributions and resource densities at smaller scales, and a positive relationship at larger scales. This work builds on a large body of previous simulation studies and attempts to produce a useful framework for subsequent researchers to explore the effects of animal movement through the use of random walks. It demonstrates the use of the framework with a specific example concerning the egg distributions of P. rapae and the effect of scale. It provides some useful insights into both the analysis of results from a complex spatial experimental layout, and potential responses which may be observed. It demonstrates that a simple model can, in the case of P rapae be used to obtain relatively realistic egg distributions.</p>

The relationship of mean temperature and 9 collected butterfly species’ wingspan as the response of global warming

Background Organism body size is a basic characteristic in ecology; it is related to temperature according to temperature-size rule. Butterflies are affected in various aspects by climate change because they are sensitive to temperature. Therefore, this study was conducted to understand the effect of an increase in temperature due to global warming on the wing of butterflies. Results A total of 671 butterflies belonging to 9 species were collected from 1990 to 2016 in Seoul (336 specimens) and Mokpo (335 specimens). Consequently, as the mean temperature increased, the wing length of the species increased. However, there are exceptions that the Parnassius stubbendorfii, Pieridae canidia, and Pieris rapae wing length of Seoul increased, but the butterfly wing length of Mokpo decreased. Conclusions The positive correlations between the butterfly wing length and mean temperature showed that the change of mean temperature for about 26 years affects the wing length of butterfly species. The exception is deemed to have been influenced by the limited research environment, and further studies are needed. We would expect that it can be provided as basic data for studying effect of climate change.

A Laser Irradiation Method for Controlling Pieris rapae Larvae

At present, chemical pesticides remain the main approach for controlling Pieris rapae (L.) (Lepidoptera: Pieridae). This research proposes a novel laser irradiation method for managing P. rapae larvae as an alternative to chemical control. The effectiveness of controlling larvae and the influencing factors of lasers were studied to estimate optimal parameter combinations. Tests using the antifeedant effect and mortality of the larvae as dependent variables showed that the laser power, irradiation area, laser opening time and irradiation position were positively correlated with the P. rapae controlling effect. The optimal parameters for each factor were the following: laser power, 7.5 W; irradiation area, 6.189 mm2; laser opening time, 1.177 s; and irradiation position, middle of the abdomen. Based on these observations, a validation experiment was performed using the optimal combination of parameters, and the results showed that the antifeedant percentage of P. rapae larvae within 24 h posttreatment was 98.49%, whereas the mortality rate was 100%. The optimal parameter combination identified in the study was suitable for P. rapae larvae from the first- to fifth-instar stages, and a more effective controlling effect was observed with the younger larvae. These results can provide a theoretical basis for future pest control using laser pest-killing robots.

Can Symbiotic Bacteria (Xenorhabdus and Photorhabdus) Be More Efficient than Their Entomopathogenic Nematodes against Pieris rapae and Pentodon algerinus Larvae?

Pieris rapae and Pentodon algerinus are considered a global threat to agricultural crops and food security; hence, their control is a critical issue. Heterorhabditid and Steinernematid nematodes, along with their symbiotic bacteria, can achieve the optimal biocontrol agent criterion. Therefore, this study aimed to evaluate the efficacy of Heterorhabditis bacteriophora, Steinernema riobravis, and their symbiotic bacteria (Xenorhabdus and Photorhabdus) against P. rapae and P. algerinus larvae. The virulence of entomopathogenic nematodes (EPNs) was determined at different infective juvenile concentrations and exposure times, while the symbiotic bacteria were applied at the concentration of 3 × 107 colony-forming units (CFU)/mL at different exposure times. Gas chromatography–mass spectrophotometry (GC-MS) analysis and the cytotoxic effect of Photorhabdus sp. and Xenorhabdus sp. were determined. The results indicated that H. bacteriophora, S. riobravis, and their symbiotic bacteria significantly (p ≤ 0.001) induced mortality in both insect species. However, H. bacteriophora and its symbiont, Photorhabdus sp., were more virulent. Moreover, the data clarified that both symbiotic bacteria outperformed EPNs against P. rapae but the opposite was true for P. algerinus. GC-MS analysis revealed the main active compounds that have insecticidal activity. However, the results revealed that there was no significant cytotoxic effect. In conclusion, H. bacteriophora, S. riobravis, and their symbiotic bacteria can be an optimal option for bio-controlling both insect species. Furthermore, both symbiotic bacteria can be utilized independently on EPNs for the management of both pests, and, hence, they can be safely incorporated into biocontrol programs and tested against other insect pests.

Microevolution of Pieris butterfly genes involved in host-plant adaptation along a host-plant community cline

Herbivorous insects have evolved counteradaptations to overcome the chemical defenses of their host plants. Several of these counteradaptations have been elucidated at the molecular level, in particular for insects specialized on cruciferous host plants. While the importance of these counteradaptations for host plant colonization is well established, little is known about their microevolutionary dynamics in the field. In this study, we examine patterns of host plant use and insect counteradaptation in three Pieris butterfly species across Japan. The larvae of these butterflies express nitrile-specifier protein (NSP) and its paralog major allergen (MA) in their gut to overcome the highly diversified glucosinolate-myrosinase defense system of their cruciferous host plants. Pieris napi and Pieris melete colonize wild Brassicaceae whereas Pieris rapae typically uses cultivated Brassica as a host, regardless of the local composition of wild crucifers. As expected, NSP and MA diversity was independent of the local composition of wild Brassicaceae in P. rapae. In contrast, NSP diversity correlated with local host plant diversity in both species that preferred wild Brassicaceae. P. melete and P. napi both revealed two distinct major NSP alleles, which shaped diversity among local populations, albeit with different evolutionary trajectories. In comparison, MA showed no indication for local adaptation. Altogether, MA appeared to be evolutionary more conserved than NSP, suggesting that both genes play different roles in diverting host plant chemical defense.