Research Article

Comparing the Effect of Selected Cabbage Varieties on the Fitness of Diadegma insulare Cresson Parasitizing Plutella xylostella Linnaeus under Controlled Conditions

Riaz Hussain1*, Ata-ul-Mohsin1, M. Farooq Nasir1, Zahid Akram2, Muhammad Sajid Qureshi1 and Abdul Mannan Hamzah1

1Department of Entomology, Faculty of Food and Crop Sciences, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan; 2Department of Plant Breeding and Genetics, Faculty of Food and Crop Sciences, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan.

Received | September 30, 2020; Accepted | February 27, 2023; Published | March 27, 2023

*Correspondence | Riaz Hussain, Department of Entomology, Faculty of Food and Crop Sciences, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan; Email: [email protected]

Citation | Hussain, R., A. Mohsin, M.F. Nasir, Z. Akram, M.S. Qureshi and A.M. Hamza. 2023. Comparing the effect of selected cabbage varieties on the fitness of Diadegma insulare cresson parasitizing Plutella xylostella linnaeus under controlled conditions. Pakistan Journal of Agricultural Research, 36(1): 52-57.

DOI | https://dx.doi.org/10.17582/journal.pjar/2023/36.1.52.57

Keywords | Parasitism, Offspring sex ratio, Diadegma insulare, Plutella xylostella

Copyright: 2023 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Consistent struggles have been made by researchers to increase the productivity of cabbage crop. Practically all methods and strategies for the management of pest have been initiated to control P. xylostella (Glare and Gallagham, 2000). Among those proper selection of suitable varieties and management practices of crop are the important factors that contribute to growing cost-effective crucifers (Zerkoune, 2000). P. xylostella has also been managed by using chemical pesticides however it showed resistant among chemicals but control gone in vain in various parts of USA. To overcome this problem various other control tactics such as biological control, genetic control and cultural control is used (Shelton et al., 1993). Biological control agents such as parasitoids, predators and plenty of diseases are crucially effective for managing P. xylostella (Sarfraz et al., 2005). Among biological control agents, parasitoids are very important and about 135 species of parasitoids have been listed which parasitize on different life forms of P. xylostella (Billqvist and Ekbom, 2001). Parasitoids play a vital role in suppressing P. xylostella populations (Lohr et al., 2007). Most important parasitoids belong to genus Diadegma, Oomyzus, Cotesia and Diadromus of order Hymenoptera, which have also been reported from Pakistan by Qadeem et al. (2015). D. insulare Cresson (Ichneumonidae: Hymenoptera) plays a vital role in managing P. xylostella infestation globally, as its parasitizing efficacy is highest as compared to other biological control agents. Current research has been designed on the importance biological control aspects of Plutella xylostella mainly focusing on D. insulare, as an effective control agent of P. xylostella.

The current study aimed to investigate the impact of selected cabbage varieties on the fitness parameters (developmental duration, percent parasitism and sex ratio) of D. insulare when P. xylostella completes its life cycle on selected cabbage varieties.

Materials and Methods

Culture of cabbage varieties

Two cabbage varieties (viz. Golden Acre and Asha) were used during current experimental studies. Each variety was grown in four seedling trays (i.e., 16×8 holes/ tray) separately in glass house of Entomology Department, PMAS, Arid Agriculture University, Rawalpindi. After thirty-five days of sowing, seedlings were transplanted into plastic pots filled with a mixture of compost and soil at 2:1 ratio. Transplanted cabbage plants from each variety (5-7 leaf stage) were utilized for further studies.

Culture of P. xylostella

P. xylostella in all life stages (e.g., egg, larval, pupal and adult) were collected from farmers’ field of cabbage crop located at Chak Shehzad, Islamabad. Larvae were collected in plastic jars covered with muslin cloth, provided with fresh leaves and honey solution-soaked cotton plugs. Collected population was brought into Bio-control laboratory of Entomology Department, Pir Mehr Ali Shah- Arid Agriculture University, Rawalpindi (PMAS-AAUR). The larvae were then transferred into rearing cages (45×30×35 cm) made up of transparent plastic sheet and ventilated through openings covered with muslin cloth. In rearing cages, potted cabbage varieties were placed singly for maintaining insect culture of P. xylostella. Culture was developed under controlled conditions at 23±2ºC, 60±5% RH and 16L: 8D photoperiod.

Culture of D. insulare

Pupae of P. xylostella were collected from farmers field of cabbage crop located at Chak Shehzad, Islamabad. Larvae were collected in glass jars singly covered with muslin cloth and provided with honey solution (20%) soaked cotton plugs and placed. After adult emergence, D. insulare were released in separate rearing cages for seventy-two hours, provided with honey solution (20%) soaked cotton plugs for mating (2:1). Whereas, emerged adults of P. xylostella in numbers were released on each cabbage variety separately for oviposition and culture development for 24 hours. Five mated female D. insulare adults were released in rearing cages having larval population of P. xylostella on each cabbage variety separately for parasitization. After 24 hours, adult D. insulare were removed from the rearing cages and placed in other cages for further parasitization.

Assessment of D. insulare fitness associated with P. xylostella on selected cabbage varieties

To assess the fitness of D. insulare on two cabbage varieties (viz. Golden Acre and Asha), second and third instar larvae of P. xylostella were utilized for the experimental studies. Twenty potted plants from each variety of cabbage were placed singly in rearing cages. One pair of three days old mated D. insulare were released for 24 hours on ten plants of each variety whereas other ten plants received insect pest only (control). Rearing cages were kept under controlled conditions i.e., 23±2ºC, 60±5% RH and 16L:8D. Insects were observed after every 48 hours and the number of surviving larvae of P. xylostella were noted until pupation. Pupae were collected in labeled glass vessels and placed under above mentioned controlled conditions.

Duration of development

To investigate developmental time taken by D. insulare, eight parasitized second and third instars larvae were isolated and kept in ventilated plastic jars containing leaves of cabbage varieties. For maintaining sanitize environment, the leaves were replaced on daily basis. Experiments were carried out for both second and third instars.

Parasitism percentages of D. insulare

Eight exposed larvae from each separate study were kept and reared in separate plastic jars in the laboratory until the emergence of D. insulare or P. xylostella adults. Number of emerged parasitoids were counted and recorded on daily basis. Number of adult P. xylostella in both cases and control were recorded as well as the dead ones. Natural mortality of P. xylostella larvae and pupae in the experiment were standardized.

Sex ratio of D. insulare

For this purpose, eight second and third instars larvae of P. xylostella were kept in separate closed container and mated female were released for parasitization. Sex ratio of D. insulare was expressed from the progeny adults that emerged from eight exposed larvae of P. xylostella. To measure the sex ratio of D. insulare, emerged males and females were counted separately. Females were simply identified with the presence of ovipositor at the end of abdomen.

Statistical analysis

Analysis of the collected data was performed using Statistics 8.1 statistical software. Completely randomized design (CRD) was followed for analysis of variance and means of significant treatments were compared using Tukey’s HSD test at 5% level of significance. Graphical demonstrations were made using Microsoft Excel 2013 and statistical program Microcal Origin Graphic Package.

Results and Discussion

Assessment of D. insulare fitness associated with P. xylostella on selected cabbage varieties

Experimental studies were performed to assess the fitness of D. insulare on two cabbage varieties (Asha and Golden acre) in associated with P. xylostella when second and third larval instars were used. Parameters of percent parasitism and sex ratio of emerged parasitoids as well as developmental time of parasitized 2nd and 3rd instars larvae were observed and the findings are given below.

Duration of development

Development of D. insulare was significantly different on host larvae reared on selected cabbage varieties. The findings revealed that developmental time taken to reach larvae and then to pupae was shortest on Asha and longest on Golden acre. Similarly, the time taken by pupa to reach adult stage was shortest on Asha and longest on Golden acre (Table 1). Total developmental period from second instars to adult was shortest for parasitoid on Asha (12.11±0.34 days) and significantly different from Golden acre (14.3±1.13 days). While total developmental duration from third instars to adult was longest on Golden acre (8.68±0.54 days) and shortest on Asha (10.9±0.13 days) (Table 2).

Parasitism (%) by D. insulare on two larval instars of P. xylostella

Eight second and third instars larvae were released on both varieties (Golden Acre and Asha). Furthermore, larval parasitoids were released in a container containing immature of P. xylostella. Figure 1 showed that maximum parasitism level (53.53%) was assessed on Asha while minimum parasitism level

 

Table 1: Developmental period (days) of parasitized P. xylostella reared on two cabbage varieties under laboratory conditions.

Host varieties	Larval period (days)			Pupal Period (days)	Developmental time (days) from 2nd instars to Adult
	2nd instar	3rd instar	4th instar
Asha	2.8±0.13a	2.9±0.15a	2.8±0.26c	3.61±0.13b	12.11±0.34b
Golden Acre	2.75±0.31a	3.32±0.35b	3.6±0.2d	4.68±0.8a	14.35±1.13a

Means sharing common letters in each column are not significantly different from each other.

 

Table 2: Developmental period (days) of parasitized P. xylostella reared on two cabbage varieties under laboratory conditions.

Host varieties	Larval period (days)		Pupal period (days)	Developmental time (days) from 3rd instars to Adult
	3rd instar	4th instar
Asha	2.87±0.26a	3.2±0.18c	3.21±0.24ab	8.68±0.54b
Golden acre	3.16±0.28b	3.6±0.2d	4.68±0.15cd	10.9±0.13a

Means sharing common letters in each column are not significantly different from each other.

 

(44.95 %) was observed on Golden acre when D. insulare were reared on second instars larvae of P. xylostella. Figure 2 showed that maximum parasitism level (61.36 %) was assessed on Asha while minimum parasitism level (50.35 %) was observed on Golden acre when D. insulare were reared on third instars larvae of P. xylostella. The experiment was performed under controlled conditions. ANOVA table is also attached.

 

 

Sex ratio of F1 progeny of D. insulare parasitizing two larval instars of P. xylostella

Figure 3 showed number of males to female ratio when second instars larvae were parasitized by larval parasitoid reared on two cabbage varieties (Asha and Golden acre). Figure 4 represents that number of males to female offspring ratio when third instars larvae were parasitized reared on two cabbage varieties.

 

 

Host plants greatly affect insect pests which have positive impacts on biological control agents (Price, 1997). As parasitoid is an important natural enemies against insect herbivores in many cropping systems (Hawkins et al., 1999), majority of studies have revealed that varieties reduce immature consumption rate and maximize their developmental period which is ideal for parasitoid than those one which reduces pest survival rate (Verkerk et al., 1998). Moreover, phases of larval instars that is parasitized by parasitoids effect on sex ratio. When second instars are parasitized more male formed and when third and fourth were parasitized more female are formed (Monnerat et al., 2002). During current study, the findings showed that maximum male offspring emerged when second instars larvae were parasitized while more female offspring were emerged when third instars larvae were parasitized by larval parasitoid reared on both varieties. While maximum female emerged when third instars larvae were parasitized reared on both varieties. The influence of selected varieties on fitness of the parasitoid is as important as parasitism rates to biological control. In this study when second instars larvae were used for parasitization against D. insulare on selected cabbage varieties, maximum parasitization (53.53 %) was assessed on Asha variety while minimum (44.95%) was observed on Golden acre. D. insulare were reared on third instar larvae of P. xylostella on two cabbage varieties. Maximum parasitization (61.17 %) was assessed on Asha while minimum (50.1 %) was observed on golden acre. Further it is concluded that parasitism level depends upon larval instars as our outcomes revealed that third instars were parasitized more as compared to second one.

 

Acknowledgements

Authors are highly thankful to Dr Shakeel Ahmad Dr Muhammad Asghar Hassan, Dr Shehzad Sami and Hafiz Safdar, Department of Entomology, Pir Mehr Ali Shah Arid Agriculture University Rawalpindi for maintaining culture during vacation.

Novelty Statement

It is concluded that Asha variety is considered as best for cultivation as the parasitism level of D. insulare on Asha is maximum and developmental period of parasitized P. xylostella is minimum on Asha. So Asha variety is recommended to farmers for securing and enhancing the yield.

Author’s Contribution

Riaz Hussain: Conducted research trials Data collection and overall management of the article.

Ata-ul-Mohsin: Conceived the idea and technical input at every step.

M. Farooq Nasir and Zahid Akram: Technical input during the study.

Muhammad Sajid Qureshi: Defined the methodology, SPSS analysis and reviewed the article.

Abdul Mannan Hamzah: Laboratory inputs and managed references.

Conflict of interest

The authors have declared no conflict of interest.

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