Research Article

The Efficiency of Predatory Beetle Cybocephalus rufifrons Reitt. (Coleoptera: Cybocephalidae) on Date Palm Scale Parlatoria blanchardi (Targioni-Tozzetti) (Hemiptera: Diaspididae)

Mustafa Abbas Al-Jbouri1* and Feryal Bahjat Hermize2

1Department of Plant Protection, College of Agriculture Engineering Science, University of Baghdad, Baghdad, Iraq; 2Department of Entomology, College of Agriculture Engineering Science, University of Baghdad, Baghdad, Iraq.

Received | February 05, 2025; Accepted | April 08, 2025; Published | June 17, 2025

*Correspondence | Mustafa Abbas Al-Jbouri, Department of Plant Protection, College of Agriculture Engineering Science, University of Baghdad, Baghdad, Iraq; Email: [email protected]

Citation | Al-Jbouri, M.A. and F.B. Hermize. 2025. The efficiency of predatory beetle Cybocephalus rufifrons Reitt. (Coleoptera: Cybocephalidae) on date palm scale Parlatoria blanchardi (Targioni-Tozzetti) (Hemiptera: Diaspididae). Sarhad Journal of Agriculture, 41(2): 875-880.

DOI | https://dx.doi.org/10.17582/journal.sja/2025/41.2.875.880

Keywords | Biological control, Date palm scale, Predatory beetle, Cybocephalus rufifrons, Parlatoria blanchardi, Prey consumption rate, Predatory efficiency

Copyright: 2025 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

White or armored scale insect Parlatoria blanchardi Targ. (Homoptera-Diaspididae) is a highly destructive and widespread pest of date palm and other ornamental palms. Although it is native to the West Asian region, it has spread to several other mediterranean and West Asian countries including Iraq. Both nymphs and adults of this pest infest all parts of date palm including leaf-sheaths, leaflets, offshoots, tender shoots, twigs and fruits. Due to intensive desaping, the infested plant parts lose their vigour and become wilted and ultimately fruit quality declines (Awadalla et al., 2023). Moreover, photosynthetic disruption due to the sooty mould growth on the sugary secretions produced by these scale insect pests is also a major indirect damage inflicted to the infested date palm tree (Kosztarab and Kozár, 2012; Moghaddam et al., 2021).

Date palm scale insect P. blanchardi has been a major challenge for date palm growers in all palm growing areas. Farmers can deploy a variety of cultural, mechanical and chemical control methods to manage the infestation of P. blanchardi. Particularly they rely exclusively on the application of synthetic chemicals which not only give unsatisfactory control due to the presence of a water impermeable cushion around these scale insects’ body (Raupp et al., 2001; Belkhiri et al., 2011), but these chemicals applications also cause many ecological consequences including environment contamination and health hazards. Hence, there is a need to look for biorational pest management approach such as biological control against P. blanchardi (Assari et al., 2023; Awadalla et al., 2023).

Biological control is one of the modern and promising strategies being used in different integrated pest management programs against various insect pests (Giles et al., 2017; Jeffers and Chong, 2021). It is considered as an eco-friendly approach as it does not conflict with other control methods (Baker et al., 2020). Apart from abiotic weather factors, the population dynamics of each insect pest species is being naturally regulated by different biotic factors, particularly by a wide array of natural enemies including predators, parasitoids and pathogens (Fischbein and Corley, 2022; Bhagarathi and Maharaj, 2023).

Predatory beetles belonging to Coccinellidae and Cybocephalidae are major natural enemies of P. blanchardi (Smith, 2022; Ben Chaaban et al., 2025). The predatory beetle Cybocephalus rufifrons Reitt. (Coleoptera: Cybocephalidae) is an important biological control agent registered for control of P. blanchardi in the countries of the Mediterranean Basin. As there is a lack study regarding the quantitative estimation of biocontrol efficiency of predatory fauna and the determination of the extent to which the population of target pests is being affected, this study aimed to evaluate the predatory efficiency of different life stages and by different larval instars against the nymphs of white scales of date palm and to determine its importance as biological control agent in reducing the population density of the P. blanchardi.

Materials and Methods

Date palm offshoots infested with the white scale insects (P. blanchardi) were obtained from the Fadk Palm Farm which is a date-filled oasis central to Islam’s origins and is a 500-hectare farm operated by the Imam Hussein Shrine in the nearby holy city of Karbala. After species confirmation, these nymphs and adults of P. blanchardi were reared in the laboratory at a temperature of 25±2 °C and at 8:16 h (light: dark) photoperiod. Their colonies were maintained continuously for the purpose of taking samples for experiments. Adult C. rufifrons beetles were fed on the laboratory reared nymphs of P. blanchardi which were initially collected from the Fadk Palm Farm, Karbala, Iraq, and after confirming its diagnosis from the Natural History Museum, these were placed in 17 × 17 × 8 cm plastic rearing cages, closed from the top with a piece of cotton cloth and were fixed with a rubber band and were provided with palm wickers infested with the scale insect P. blanchardi as food for the predator (Al-Jbouri and Hermize, 2023).

The food was replaced daily and the rearing cages were provided by adequate moisture by placing small Petri plates with a cotton swab moistened with water (Grafton and Gu, 2003) The laid eggs were isolated and each egg was placed in 10 × 1.5 cm a plastic tube that was closed with a piece of muslin cloth and a rubber band. It was monitored daily until the eggs hatched and the larvae emerged, which were fed daily with the nymphs of the scale insect P. blanchardi until it matures. The culture was carried out in incubators at a temperature of 25°C ±2 and a relative humidity of 70–60% and at a photoperiod of 8:16 h light: dark (Al-Jbouri and Hermize, 2023). Predatory efficacy of different life stages and different larval instars of C. rufifrons were evaluated by feeding them on the nymphs of P. blanchardi. Ten newly hatched C. rufifrons were offered to experimental treatments by placing a wicker sheet containing 25, 50, 100 and 200 prey nymphs per treatment. Data regarding the number of prey nymphs consumed were recorded for each treatment on each day.

For the predatory Study of C. rufifrons by feeding on date palm scale nymphs, 5 pairs (male and female) of newly emerged adult predators were selected as 5 replicates (each of them was placed inside 10 × 1.5 cm plastic tubes and were provided with 200 scale insect nymphs and a small piece of cotton moistened with water was placed in the tubes and these tubes were kept in an incubator at a temperature of 25°C ± 2 and a relative humidity of 70 - 60% and were checked daily to calculate the number of nymphs consumed by females and males for five consecutive days.

The completely randomized design (CRD) was used in the experiment and the differences between treatments and prey-consumption rates were compared with ANOVA and student’s t-test at standard level of significance (P ≤ 0.05). The results were analyzed by the program GenStat (Payne et al., 2009).

Results and Discussion

Decision-making regarding the incorporation of any biological control agent such as predatory insect species in integrated pest management programs requires necessary information about the efficiency and effectiveness of predators. This is possible by analysing the specific components of the attack rate as well as the effect achieved by the predation process to the response of the population density of each species, prey and predator. This laboratory study evaluated the predatory potential of different life-stages and larval instars of the predatory beetle C. rufifrons against nymphs of date palm scale insects (P. blanchardi).

Study results regarding the predatory efficiency of C. rufifrons beetles on scale insect P. blanchardi nymphs are shown in Table 1. It is evident from these results that the predatory efficiency of larval instars of C. rufifrons increased along with the age of the P. blanchardi, mainly due to their larger size and increased nutritional requirements. The rate of prey consumption varied between the first, second and third instar larvae with the fourth instar consuming the highest number of P. blanchardi nymphs. A total of 1296 nymphs were consumed by the predator during the bioassay (Table 1).

The study also found significant differences in the consumption rates between larval and adult phases of the predatory beetles. For adults, the average daily consumption of female beetles was about 128.5 nymphs per day, while the daily consumption rate of male beetles was about 107 nymphs per day (Table 1). Results also revealed a significant difference in the consumption rates between the larval and adult roles in both genders. These findings highlight the importance of understanding the role of larval instars in maintaining their nutritional requirements as demonstrated by previous studies (Al-Shami and Qureshi, 2022; Ramzan and Khursheed, 2023).

Findings of this laboratory study advocate the fact that C. rufifrons is an efficient natural enemy and an important potential biological control agent which would play a significant role in preying the date palm scale insect P. blanchardi and in reducing its population density out in the field (Assari et al., 2023). Results of this study regarding the differential prey consumption by male and female beetles are in accordance with those of Yang et al. (1997) who studied the predatory efficacy of male and female predatory beetle Chilocorus kuwanae (Coleoptera: Coccinellidae) against oriental scale insect Unaspis yanonensis

 

Table 1: The predatory efficiency of different life phases and larval instars of predatory beetle Cybocephalus rufifrons on the nymphs of the date palm scale insect Parlatoria blanchardi.

	Predation rates of predator roles		Larval instar predation rates
Predator phase	Daily average ± SE	Total average ± SE	Larval instar	Daily average ± SE	Total average ± SE
Larva	264.87 ± 15.81	1296.58 ± 35.60	1st instar	24.78 ± 2.33	96.12 ± 8.30
Adult (female)	128.50 ± 3.60	-	2nd instar	35.28 ± 2.76	172.41 ± 10.23
Adult (male)	107.21 ± 4.24	-	3rd instar	66.61 ± 8.99	329.06 ± 15.40
			4th/last instar	141.20 ± 21.90	702.10 ± 23.74
CV	19.33			7.65	16.29

Treatments were compared using factorial ANOVA followed by least significant difference (LSD) post-hoc test at standard level of significance (α ≤ 0.05).

 

(Homoptera: Diaspididae) on citrus, and demonstrated that the average consumption of female beetles was 42.7 nymphs per day as compared to the male beetles which consumed an average of 22.3 nymphs per day, and this supports our current study that the female C. rufifrons beetles in terms of their consumption more than that of the male beetles. It differs quantitatively due to different type of predator and prey relationship. Our results are in accordance with the findings of Ponsonby and Copland (2000) as well demonstrating the more food requirement and intake of nymphs of scale insect Abgrallaspis cyanophylli by the female larval instars of predatory beetle Chilocorus nigritus as compared to males.

Results of the study are in line with the findings of many previous studies. For instance, Al-Rawy et al. (2012) showed high efficiency of the predator Chrysoperla carnea to attack and consume the nymphal instars and adults of cabbage aphid, Brevicoryne brassicae. Zarghami et al. (2016) tested the predatory efficiency of the larval and adult phases of an indigenous predator Nephus jaderiensis (Coleoptera: Coccinellidae) against citrus mealybug Planococcus citri (Hemiptera: Pseudococcidae). The results showed that the predator had a high predatory efficiency in consuming the immature stages of the studied citrus mealybug.

Similarly, Kamel et al. (2016) studied some life-history aspects and the predatory efficiency of the predatory beetle Chilocorus bipustulatus (Coleoptera: Coccinellidae) on the date palm scale insect P. blanchardi (Homoptera: Diaspididae) under laboratory setup. They reported that the predator had very high consumption efficiency on scale insect nymphs, and this predation was increased as the larvae grown from first instar to onwards (Ponsonby and Copland, 2000; Al-Hamwandi and Abdel-Khalek, 2011; Al-Shami and Qureshi, 2022; Ramzan and Khursheed, 2023).

Conclusions and Recommendations

Overall study results have demonstrated the predatory potential of beetle C. rufifrons, of both adults and larvae, against the nymphs of date palm scale insect P. blanchardi. The larval predation efficiency has been found significantly higher than that of adult beetles, and the prey consumption rate also increased along with the larval age or instar. These results in general advocate the potential consideration and implication of this predatory beetle (C. rufifrons) in future integrated management programs combating date palm scale insect pests, particularly against P. blanchardi.

Acknowledgements

The authors are grateful to Fadk Farm, Karbala, Iraq for the provision of date palm material and to the College of Agriculture and Engineering Science, University of Baghdad, Iraq for facilitating the successful conduction of this research work.

Novelty Statement

This study is the first to evaluate the predatory efficiency of Cybocephalus rufifrons against Parlatoria blanchardi on date palms under field conditions. The results provide new insights into the potential use of this beetle as a biological control agent in integrated pest management programs. This novel research encourages the use of natural enemies and contributes to reducing the harmful effects of chemical pesticides.

Author’s Contribution

MAA and FBH conceived of the research idea. MAA performed experiment and recorded and analyzed the data. FBH wrote the first draft. MAA provided resources and supervised the project. FBH revised the draft and technically proofread the manuscript. All authors contributed equally.

Conflict of interest

The authors have declared no conflict of interest regarding the submission and publication of this research work.

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