J. Appl. Entomol. ORIGINAL CONTRIBUTION Cryptolaemus montrouzieri as a predator of the striped mealybug, Ferrisia virgata, reared on two hosts H. Wu1,2, Y. Zhang1, P. Liu1, J. Xie1,Y.He1, C. Deng1, P. De Clercq2 & H. Pang1 1 State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, China 2 Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium Keywords Abstract biological control, cotton, Cryptolaemus montrouzieri, Ferrisia virgata, Planococcus The striped mealybug, Ferrisia virgata (Cockerell) (Hemiptera: Pseudococ- citri, prey suitability cidae), is a cosmopolitan pest of a variety of agricultural crops including cotton. To investigate the biological control potential of the predatory Correspondence ladybird Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) Hong Pang (corresponding author), State Key against this pest, we evaluated its developmental and reproductive fitness Laboratory of Biological Control, School of when feeding on F. virgata reared on pumpkin fruits or on cotton leaves Life Sciences, Sun Yat-sen University, No.135 Xingang Road West, Guangzhou 510275, and compared this to a diet of Planococcus citri Risso (Hemiptera: Pseudo- China. E-mail: [email protected] and coccidae) reared on pumpkin fruits. F. virgata and P. citri reared on pump- Patrick De Clercq (corresponding author), kins were equally suitable prey for the pre-imaginal stages of Department of Crop Protection, Faculty of C. montrouzieri. Duration of total immature development was 1 day longer Bioscience Engineering, Ghent University, in C. montrouzieri offered F. virgata reared on cotton as compared with Coupure Links 653, Ghent 9000, Belgium. F. virgata or P. citri reared on pumpkin, whereas no significant difference E-mail: [email protected] was observed in survival rates. Diet significantly influenced the reproduc- Received: January 4, 2014; accepted: February tive fitness of C. montrouzieri. Females offered P. citri reared on pumpkin 20, 2014 had significantly shorter pre-oviposition periods and higher fecundity and fertility than those given F. virgata reared on pumpkin or cotton leaves. doi: 10.1111/jen.12127 F. virgata grown on cotton leaves supported the reproduction of C. mont- rouzieri better than F. virgata reared on pumpkin. Our study established that C. montrouzieri can successfully complete its development and repro- duction when fed exclusively on F. virgata and indicates its potential as a biological control agent of this emerging cotton pest. may fail to open, and plant senescence can be Introduction induced. Feeding mealybugs also excrete a sugary The striped mealybug, Ferrisia virgata (Cockerell) solution called honeydew, which contributes to the (Hemiptera: Pseudococcidae), is a polyphagous pest development of black sooty mould (Nagrare et al. on a variety of crops, such as cotton, sweet potato, 2011). In addition, mealybugs can also be vectors of cassava, coffee, cocoa, citrus, tomato, papaya and egg- plant pathogens and cause chlorosis, stunting, defor- plant (Schreiner 2000; Ben-Dov et al. 2005). mation and death of plants (Bhat et al. 2003; Recently, it was reported to infest coloured fibre cot- Ben-Dov et al. 2005). Chemical control of the mealy- ton, and it is emerging as a serious pest in north-east bugs in cotton with conventional insecticides has often Brazil (Silva-Torres et al. 2013). In cotton, F. virgata been unsuccessful because the pest is covered with a infestation occurs in patches, feeding on all plant wax-type material that prevents toxic chemicals from parts, particularly the growing tips of leaves, petioles, being absorbed into the system (Joshi et al. 2010). leaf veins, squares and bolls (Hanchinal et al. 2011; Therefore, biological control using natural enemies is Nagrare et al. 2011; Silva-Torres et al. 2013). Mealy- an effective alternative method to manage this pest. bug infestations can be detrimental to host plants in a The ladybird Cryptolaemus montrouzieri Mulsant number of ways: they can reduce plant vigour, bolls (Coleoptera: Coccinellidae) is a highly efficient © 2014 Blackwell Verlag GmbH 1 C. montrouzieri as a predator of F. virgata H. Wu et al. natural enemy of mealybugs and plays an important Materials and Methods role in the integrated management of mealybug pests in various cropping systems. This ladybird has been Insects and plants reported to feed on about 21 mealybug species (Jiang et al. 2009) and has been widely used as a biological All insects (C. montrouzieri, P. citri and F. virgata) were control agent in areas where mealybugs such as Pla- originally obtained from the State Key Laboratory of nococcus citri (Risso), Maconellicoccus hirsutus Green, Biocontrol, Sun Yat-sen University, Guangzhou in Phenacoccus solenopsis Tinsley and F. virgata outbreaks China. The stock colony of C. montrouzieri was reared occur (Mani and Krishnamoorthy 2008; Afifi et al. on P. citri produced on pumpkins [Cucurbita moschata 2010; Hanchinal et al. 2010; Kaur and Virk 2012; (Duch.ex Lam.) Duch. ex Poiretand] in metal frame Khan et al. 2012). Although C. montrouzieri appears cages (45 9 36 9 33 cm) covered with fine-mesh to be an opportunistic generalist predator of mealy- nylon gauze. Both the P. citri and F. virgata colonies bugs, it is plausible that only a subset of mealybug were maintained on plastic trays (40 9 30 cm) con- species serve as essential foods capable of supporting taining pumpkins as food. All colonies were main- immature growth and adult reproduction of C. mont- tained under controlled conditions [26 Æ 2°C, rouzieri. Indeed, nutrients or antinutrients present in 50 Æ 10% RH, and a 14:10 h (L:D) photoperiod]. different prey species may affect life attributes of Non-transgenic cotton plants (Gossypium hirsutum ladybirds differently (Evans et al. 1999). These influ- L., cv. Zhongmiansuo 23) were planted individually ences may vary from more serious deleterious effects in plastic pots (16 9 13 cm) with soil. Cotton plants such as mortality caused by the toxicity of prey, to were cultivated from seed in an insecticide-free minor effects such as changes in developmental and greenhouse under ambient environmental condi- survival rates or in reproductive capacity (Hauge tions. Plants used in the experiments were in the et al. 1998; Srivastava 2003; Cabral et al. 2006; 6–8 true leaf stage, which developed 7 weeks after Mignault et al. 2006). Therefore, investigating prey sowing. suitability is one of the most important steps in eval- uating the potential use of a predator in biological Egg incubation control programmes (Dixon 2000; Zhang et al. 2007, 2012). Three plastic boxes (12.0 9 5.0 9 4.0 cm, covered Cryptolaemus montrouzieri is mass reared mostly with fine-mesh nylon gauze for ventilation) contain- according to a tritrophic system using live mealybugs, ing C. montrouzieri eggs (100, 100 and 60/box) laid by such as P. citri on potato sprouts or pumpkin fruits. 40 pairs of adults within a 12 h period were collected Pumpkin has also shown to be a feasible host for mass from the stock colony and maintained in a climate rearing the striped mealybug, F. virgata (Oliveira chamber [25 Æ 1°C, 75 Æ 5% RH, and a 14:10 h et al. 2014). F. virgata is a widely spread mealybug (L:D) photoperiod]. The eggs were observed carefully and is reported in more than 100 countries around every 12 h, and numbers of larvae that hatched were the world, including the USA, Argentina, Canada, recorded. India, China, Brazil and Pakistan (Ben-Dov et al. 2005), where cotton is widely cultivated. However, Development, survival and weight studies on the development and reproduction of C. montrouzieri when feeding on F. virgata are lacking. Eggs of C. montrouzieri were randomly assigned to Further, the predator has been widely released to three groups, which were fed on three different control various mealybugs in different cropping sys- diets. In all treatments, newly hatched first instars of tems, but it has not been used in cotton against the predator were placed in individual plastic Petri F. virgata. dishes (9.0 9 1.5 cm). The first group was fed on To improve our understanding of the feeding ecol- P. citri reared on pumpkin fruits: newly hatched first ogy of C. montrouzieri and its potential role as a biolog- instars from 100 eggs (93 larvae) were supplied ad ical control agent of F. virgata, we evaluated the libitum with mixed aged P. citri collected from a col- developmental and reproductive fitness of the preda- ony reared on pumpkins. Mealybug prey were tor when feeding on this mealybug reared on pump- replaced every 24 h. In a second group, newly kin fruits or cotton leaves. The predator’s hatched first instars from 100 eggs (91 larvae) were performance on F. virgata was compared with that on offered mixed aged F. virgata reared on pumpkins. its commonly used prey in laboratory cultures, the cit- Fresh mealybugs were again provided to the preda- rus mealybug P. citri. tor larvae every 24 h. A third group was fed on 2 © 2014 Blackwell Verlag GmbH H. Wu et al. C. montrouzieri as a predator of F. virgata F. virgata reared on cotton leaves. The mealybug Statistical analysis prey in this group had been maintained on cotton for at least a single generation. Here, the newly All data were subjected to statistical analysis (Ver. 20; hatched first instars from 60 eggs (54 larvae) of the IBM SPSS Statistics, SPSS Inc., Chicago, IL, USA) to predator were individually transferred to 9-cm Petri determine the significance of the treatment effects. dishes, which had a small hole drilled into the side The Kolmogorov–Smirnov and Levene test were used for allowing a cotton leaf to be inserted. A single leaf to test the normality and homogeneity of variances of (still attached to the plant) infested with F.