Appropriate functional response to prey or host densities is one of the important criteria for evaluating the efficacy of natural enemies in biological control programs. Cryptolaemus montrouzieri Mulsant is one of the main predators of citrus mealybug,Planococcus citri (Risso). In this research, the functional response of fourth larval instars and the female adults of this ladybird to different densities of second and third instars and female adults of citrus mealybug was studied under laboratory conditions. All experiments were carried out inside incubator with 25±1˚C, 80±5 %RH and photoperiod of 14 L:10 D hours. Individual fourth larval instars and female adults of ladybird were kept separately at densities of 4, 6, 8, 16, 20, 30, 40, 50 and 60 preys for 24 hours. Duration of each experiment was 24 hours and all experiments were carried out in 6 replications. A logistic regression was used to determine the type of functional responses and a nonlinear regression was used to fit Rogers and Holling’s equations to data for estimating searching efficiency (a) and handling time (Th) parameters. The results showed that the functional responses of fourth larval instars to different densities of second and third instars and the female adults of citrus mealybug were type III, III and II respectively, while the functional responses of the female adult ladybird to different densities of second and third instars and the female adults of prey were type II, III and II respectively. The rates of searching efficiency (a) for fourth larval instars of ladybird on second and third instars and the female adults of prey were estimated 0.0126, 0.0165 and 0.002, and the rates of handling time (Th) were obtained 0.701, 1.012 and 2.05, respectively. The rates of searching efficiency of female ladybirds on second and third instars and the female adults of prey were estimated 0.048, 0.013 and 0.098 and the rates of handling time were obtained 0.177, 0.843 and 2.79, respectively.

The coccinellid Cryptolaemus montrouzieri Muls. is an oligophagous predator that is used to control mealy bugs in the orchards and greenhouses. Citrus soft scale, Pulvinaria aurantii, as an active pest on citrus plants in North of Iran is also attacked by this predator. This research was conducted to study biological characteristics of C. montrouzieri on citrus soft scale and mealy bug, Planococcus citri. Initially, Cryptolaemus eggs were collected from colonies of two preys and reared in laboratory (14 L: 10 D, 25±1˚C, and RH 70 ±5%). The incubation period of eggs, 1st, 2nd, 3rd and, 4th larval instars, and total larval, prepupal, and pupal stages were studied on two preys. The developmental stages on two preys were not significantly different, except for the 4th larval instar at 1% and total larval stages at 5%. The sex ratio of male to female on two preys were not significantly different at 1% and was 1:1. Except for pre-oviposition period, other parameters including female longevity, average number of eggs laid per day, average total number of eggs laid per female and percentage of hatching were significantly different at 1% on the two preys. The average feeding of total larval period on eggs of mealy bug and citrus soft scale were 5715 and 7694, respectively that, the difference was significant at 1%. The results showed that some of the biological characteristics of Cryptolaemus on two preys were significantly different. Since the predator feeding on the eggs of citrus soft scale was higher than the mealy bug, it seems that this beneficial insect could be used for biological control of the citrus soft scale.

Orange pulvinaria scale, Pulvinaria aurantii Ckll., is one of the most important pest on citrus in north of Iran. At present, the farmers use chemical control methods to prevent crop losses by the pest. Using effective natural enemies has a special importance in controlling of this pest. The present investigation was conducted to determine the efficacy of coccinelid beetle, Cryptolaemus montrouzieri Muls. (Col.: Coccinellidae), and it's releasing time against orange pulvinaria scale in screen house and citrus orchard. The treatments were conducted in three different experiments with a completely randomized design. The result revealed that the feeding rate of adult coccinelid beetle (each pair) from ovisac of orange pulvinaria scale was 35 in a month. The result indicated that the best treatment in these experiments was twice ladybird beetle releases (one pair in the beginning of oviposition and another in the peak of egg sacs) in controlling the population of this pest.

Acute toxicity of the field recommended concentration of three conventional insecticides (Diazinon, Malathion and Chlorpyrifos) and mineral oil was evaluated on 3rd and 4th instar larvae and adults of Cryptolaemus montrouzieri Mulsant. The mortalities caused by the insecticides and mineral oil were significantly different. Diazinon and Malathion with 100% mortality showed the highest toxicity to the different stages of the ladybird. Chlorpyrifos and mineral oil caused less than 30% mortality, while mineral oil had the lowest harmful effect on this predator. Based on LC50 and LC90 values 24h after treatment, the male and female adults of C. montrouzieri were more susceptible to Diazinon (701 and 635; 1257 and 1194ppm) than to Chlorpyrifos (4238 and 4316, 5683 and 5480 ppm). Based on International Organization of Biological Control (IOBC) classification, Chlorpyrifos and mineral oil were classified as category 1 (harmless) and Diazinon and Malathion were placed in category 4 (harmful).

Mealybug destroyer, Cryptolaemus montrouzieri Mulsant is the most important natural enemies of the citrus mealybug, Planococcus citri (Risso). Life table parameters of C. montrouzieri feeding on citrus mealybug, P. citri was studied at eight temperatures ranging 13 to 35 (±1) °C, 60 ± 10 % RH and a photoperiod of 16:8 (L:D) h. in growth chamber. Development of the coccinellid did not complete or laid eggs were infertile at temperatures 13, 15, 30, 33 and 35 °C. Therefore, life table parameters were estimated only in three temperatures, 20, 25 and 27°C. Construction of the life table and calculation of its parameters was conducted using Carey procedure. According to the results, the maximum and minimum values of the net reproductive rates (Ro) were 208.48 and 77.52 female/female/generation at 20 and 25°C, respectively. The values of finite rate of increase (λ) at the same temperatures were 1.04, 1.14, and 1.08 day-1, respectively. The maximum values of intrinsic rate of increase (rm) were 0.085 female / female / day and shortest mean generation time (T) was 57.37 days, at 27 °C. Estimated values for the doubling time (DT) were 15.56, 8.30 and 8.09 days at temperatures 20, 25 and 27°C, respectively. The results confirmed that temperature has a significant effect on population increase of the predatory coccinelid, C. montrouzieri and 27°C is the optimum temperature for population growth of C. montrouzieri among examined temperatures.

Predator ladybird, Cryptolaemus montrouzieri and the armored-scale ladybeetle, Chilocorus bipustulatus (L.) are important predators of Diaspididae and Eriococcidae families in Iran. Application of mineral oils are among chemical methods to control mealybugs which are more compatible with the environment and relatively quickly are destroyed in the environment and the risk of secondary pest resistance in regards with these compounds is very low. In this study, the effect of Volk oil® on adult and different larval stages of C. montrouzieri and C. bipustulatus was evaluated on citrus leaves in orchard conditions. Ladybeetles were released and then sprayed with Volk oil at the concentrations of 0.5, 1, 1.5 percent and water (control) was carried out and after 24 hours the number of dead and alive insects were determined.. The results showed that there were significant differences between the effects of different concentrations on life stages of both ladybirds at 5% level. The concentration 1.5% had the highest mortality rate, as 92.16±1.11and 96.83±1.24 percent on the 1st larval stage of C. montrouzieri and C. bipustulatus ladybirds, respectively. Based on the results and compared with the evaluation criteria of the International Organization for Biological Control (IOBC), mortality rate caused by 1 and 0.5% concentrations of Volk oil in most age stages for both predators were placed in the second group of side effect ranking (Moderately Harmful).

The citrus mealy bug,  Planococcus citri (Risso) is one of the major pests of citrus and many other orchards crops, as well as ornamental plants in subtropical and tropical regions of the world, including Iran. Due to the harmful effects of chemical pesticides on biological control agents and non-target organisms, along with developing resistance to various pesticides by the pests, there has been an increasing interest in integrating biological control methods in the pest management programs. The predatory ladybird, Cryptolaemus montrouzieri Mulsant is one of the most widely used biological control agents. It is an important natural enemy of many species of mealybugs such as P. citri. Functional response of a predator that refers to the number of prey consumed per predator as a function of a prey density is the important characteristic of predator–prey interactions. Temperature can affects the consumption behaviour of the predators. The aim of the present study is to evaluate the effects of temperature on the functional response of C. montrouzieri to different densities of P. citri. Improving our understanding about predator-prey interactions between C. montrouzieri and P. citri may be helpful to optimize biological control of the mealy bug.

The colony of P. citri was collected from bitter orange in Mehmansara region, Ghaemshahr, Mazandaran province, and was reared on pumpkin, Cucurbita maxima. The laboratory colony of C. montrouzieri was obtained from Baharan Dasht Sahel insectarium in Sari, Mazandaran province, and was reared on P. citri. The functional response experiments were performed with fourth instar larvae and adult females of C. montrouzieri to the adult female of P. citri. The experiments were conducted at the temperatures of 18, 23, 27, 32 and 37±1 °C, 60±10% RH and L16:D8 h. Prey in densities of 3, 5, 7, 10, 15 and 30 was offered to the predators. The predators used for the experiments were < 48 h old and were starved for 24 h before starting the tests. A single bitter orange leaf disc (3 cm2) was centred upside down in each ventilated Petri dish (10 cm diameter). Ten replicates were conducted for each prey density. After 24 h, the predators were removed from the experimental arena and the number of consumed prey was recorded and they were not replaced during the functional response tests. The type of the functional response was determined by logistic regression analysis (SAS/STAT, CATMOD-procedure) of the proportion of prey killed in relation to prey offered. To determine the type of functional response, the sign of the linear coefficient was estimated by the logistic regression. The negative sign is evident to a functional response type II, whereas a positive sign reveals a type III functional response. Parameters of attack rate and handling time were estimated using the PROC NLIN procedure of SAS and compared through the indicator variable method. 

The logistic regression for fourth instar larvae and adult females of C. montrouzieri to P. citri at all temperatures showed a negative linear parameter and the proportion of prey eaten by the predators declined with increasing prey density. This suggested that fourth instar larvae and females of C. montrouzieri exhibited a type II functional response to change in P. citri density at all tested temperatures. The highest attack rate and lowest handling time of fourth instar larvae were estimated at 37 and 27 °C, respectively. Whereas the highest attack rate and lowest handling time of adult females were estimated at 37 and 32 °C, respectively. At the same temperature, the attack rate estimated for the adult female was higher than that of the larval instar of the predator, showing higher predation potential of adult female in compared to the fourth larval instar of the predator. Theoretical maximum attack rates (T/Th) for fourth larval instar of the predator at above-mentioned temperatures were respectively estimated 8.20, 28.81, 43.80, 19.82 and 14.44 and for adult female predator were 9.70, 9.17, 9.10, 18.47 and 17.92, respectively.          

Temperature affected significantly functional response parameters of fourth instar larvae and adult females of C. montrouzieri to P. citri densities. Although the last instar larvae and adult females of C. montrouzieri showed high predation potential at all temperatures, adult females of the predator was more voracious compared to the last instar larvae of the predator especially at higher temperatures.

Type and biochemical properties of the digestive proteases were determined using specific substrates and inhibitors in the larvae and the adults of Cryptolaemus montrouzieri and their activity changes were evaluated when fed on the different preys. Rearing of beetles was done in laboratory conditions and they were fed on citrus mealybug. Dissection was done in NaCl medium and the obtained midgut was homogenized and centrifuged. Then, the activity of digestive proteases determined by using the specific substrates and inhibitors by feeding on three hosts. The results showed that just cysteine proteases and exopeptidases were active in the midgut of adults while both serine and cysteine proteases were engaged in the digestion by the larvae. The highest activity of the serine proteases; trypsin, chymotrypsin and elastase, were found in the pH sets of 8, 8-9 and 9, respectively. The optimal pH of cathepsins B and L were determined in 6 and 5 pH values of the larvae and the adults of C. montrouzieri, respectively. The highest activities of digestive larval amino- and carboxypeptidases were measured at pH 7 while these two enzymes showed the highest activity at pH sets of 7 and 6 in the adults, respectively. The specific inhibitors including cystatin, E-64, TLCK, SBTI, TPCK and AEBSF.HCL significantly decreased the activities of specific proteases in the larvae and the adults of C. montrouzieri. No significant differences were observed in the activities of serine proteases, exopeptidases and cathepsin L in the larvae fed on Planococcus citri, Pseudococcus viburni and Toxoptera aurantii but cysteine proteases and aminopeptidases in the adults fed on tea aphid showed the least activity. The difference in proteolytic profile of the larvae and the adults of C. montrouzieri concur the physiological differences in these two developmental stages with the emphasize on serine proteases in the preservation and control of developmental status of digestive tract. In addition, the higher activity of cysteine proteases in the adults may be related to the nature of utilized prey and presence of different proteinaceous components or even glycoperoteins in the preys.

Biochemical characteristics of α-amylase in the digestive system and head glands of Cryptolaemus montrouzieri, a key predator of citrus mealybug, Planococcus citri (Pseudococcidae), were studied. The major isoform of α-amylase with the same molecular weight was detected in both gut and head glands loaded on polyacrylamide-starch gel electrophoresis. Moreover, a minor band with much lower intensity was observed in zymogram analysis of gut. Results showed that the specific activity of α-amylase from head glands (0.89 ± 0.02 μmol/min/mg protein) was significantly more than that of digestive system (0.76 ± 0.01 μmol/min/mg protein) in common condition (temperature equal to 25 ± 1 oC). The optimal pH and temperature for α-amylases activity were determined to be nearly 4 and 50°C in digestive system and 6 and 60 °C in head glands, respectively. EDTA (Ethylenediamine tetra acetic acid), Mg2+, Na+, Co2+, Fe2+ and Ca2+ inhibited the enzyme activity but Ba2+, Zn2+, Hg+ and K+ enhanced enzyme activity in digestive system. EDTA and all tested metal ions except Ba2+ inhibited the enzyme activity of head glands. Detectable levels of α-amylase activity in the insect reflect adaptation of the coccinellid for using starch granules or sugars (honeydew; sugary excreta of homopterans; and nectar) as a source of food in addition to predatory habits.