Thermal Effect on the Development and Reproduction of an Indigenous

Appl. Entomol. Zool. 45 (2): 313–318 (2010) http://odokon.org/

Thermal effect on the development and reproduction of an indigenous mirid bug, Pilophorus typicus Distant (Heteroptera: Miridae), a potential biological control agent in Japan

Hiroshi NISHIKAWA, Takuji SHIMADA, Kengo NAKAHIRA† and Ryo ARAKAWA* Laboratory of Applied Entomology, Faculty of Agriculture, Kochi University; Kochi 783–8502, Japan (Received 17 July 2009; Accepted 21 January 2010)

Abstract In order to establish the optimal thermal conditions for mass rearing of the predatory mirid bug Pilophorus typicus, we investigated the effect of temperature on the development and fecundity of this bug at 6 constant temperatures (17.5, 20.0, 22.5, 25.0, 27.5, and 30.0°C) under a 16L8D photoperiod. The developmental period of P. typicus from

egg to adult at different temperatures was not affected by sex. The developmental zero (T0) and thermal constant (K) of females from egg to adult were 12.0°C and 357.1 day-degrees, respectively. The corresponding values for males were 12.1°C and 357.1 day-degrees, respectively. The mean generation time (T) of P. typicus decreased with an in-

crease in temperature from 17.5°C to 30.0°C. Among the temperatures investigated, the net reproductive rate (R0) was highest at 25.0°C, whereas the highest intrinsic rate of natural increase (rm) occurred at 27.5°C. These results indicate that the optimal temperature for the mass rearing of P. typicus is between 25.0°C and 27.5°C.

Key words: IPM; indigenous natural enemy; mass rearing; developmental zero; intrinsic rate of natural increase

against B. tabaci in these programs. INTRODUCTION A number of predacious bugs belonging to the In Japan, the application of integrated pest man- family Miridae play important roles in biological agement (IPM) programs has now extended to control programs (Hagen et al., 1999). Macrolo- greenhouse vegetable cultivation. These programs phus caliginosus Wagner (Heteroptera: Miridae), reduce the frequency of use and quantity of chemi- for example, is currently used commercially in Eu- cal pesticides and are non-detrimental to indige- rope to control whiteﬂies (including B. tabaci) in nous natural enemies. One of these natural enemies tomato greenhouses. Other mirid bugs (Het- is the mirid bug, Pilophorus typicus (Distant) (Het- eroptera: Miridae)—Dicyphus hesperus Knight in eroptera: Miridae). In 2005, in sweet pepper and Canada (McGregor et al., 1999, 2000), D. hyalin- eggplant greenhouses of Kochi Prefecture, Japan, ipennis Burmeister in Hungary (Ceglarska, 1999), where IPM programs have been implemented, P. D. cerastii Wagner in Portugal (Carvalho and typicus was found as a predator of the serious pest Mexia, 2000), D. tamaninii Wagner in Spain (Alo- Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodi- mar and Albajes, 1996), Deraeocoris brevis dae) (Nishikawa, unpublished). B. tabaci is one of (Uhler) in United States of America (Kim and the most signiﬁcant pests in IPM greenhouse pro- Riedl, 2005), Nesidiocoris tenuis (Reuter) in the grams in Japan because of its resistance to chemi- Canary Islands and Philippines (Torreno, 1994; cal controls (Nouen et al., 2002; Horowitz et al., Carnero et al., 2000), N. tenuis and D. errans Wolff 2003; Ueda and Brown, 2006). Thus, P. typicus is in Italy (Quaglia et al., 1993; Tavella et al., 1997), an alternative control method to chemical control and Macrolophus pygmaeus (Rambur) in Greece

* To whom correspondence should be addressed at: E-mail: [email protected] † Present address: Tropical Agriculture Research Front, Japan International Research Center for Agricultural Science, Ishigaki, Okinawa 907–0002, Japan. DOI: 10.1303/aez.2010.313

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(Perdikis et al., 1999; Perdikis and Lykouressis, 27.5, and 30.0°C) under a photoperiod of 16L8D. 2000)—are recognized as potential biological con- The P. typicus eggs laid on each leaf were counted trol agents of vegetable pests in their respective under a binocular microscope after 24 h, and the countries. P. typicus is considered to be a potential leaves were transferred into a new plastic cup at the biological control agent of B. tabaci in Japan. same temperature. Hatchings from each leaf were However, in order for P. typicus to become a recorded every 24 h. Newly hatched first instars commercially viable biological control agent, it were individually reared at the same temperature in will first be necessary to establish an efficient a glass vial (diameter, 1.5 cm; length, 5.5 cm) con- mass-rearing technique for this species. The eggs taining a new leaf of Christmas cheer and approxi- of Mediterranean flour moth, Ephestia kuehniella mately 15 mg defrosted E. kuehniella eggs. The Zeller (Lepidoptera: Pyralidae), are useful for rear- leaf and E. kuehniella eggs were replaced with a ing polyphagous mirids such as M. caliginosus fresh leaf when the leaf had partly faded at the (Hart et al., 2002). In this study, in order to clarify record of the adult emergence. Adult emergence the optimal thermal conditions required for mass was recorded every 24 h in order to determine the rearing with the moth egg, the development, sur- developmental period and survival rate at each vival, longevity, and fecundity of P. typicus were temperature. investigated at 6 different constant temperatures. Adult females and males newly emerging within 24 h at each temperature were reared as a pair in a glass vial (diameter, 1.5 cm; length, 5.5 cm). For MATERIALS AND METHODS the different temperatures investigated, between Culture. P. typicus nymphs and adults were col- 5 to 32 females were paired. These adults were lected from eggplants infested with B. tabaci at the reared on approximately 100 mg defrosted E. Monobe Campus of Kochi University, Nankoku kuehniella eggs and a leaf of Christmas cheer. The City, Kochi Prefecture, Japan. Six nymphs and two eggs inserted by females into Christmas cheer were adults, collected from eggplant, were reared in counted daily under a binocular microscope. The plastic containers (length, 25 cm; width, 20 cm; survival of females and males was monitored daily. height, 10 cm) with defrosted eggs of E. kuehniella, Rearing from eggs to adults was conducted under a and a leafed branch of the succulent plant Kalan- photoperiod of 16L8D. Every 3 days until adult choe blossfeldiana Poelln (Saxifragales: Crassu- death, the remaining moth eggs were replaced with laceae). Every 3 days, the remaining moth eggs fresh moth eggs. The Christmas cheer was also were removed from the containers, and were replaced every 3 days. replaced with fresh eggs (approximately 100 mg). Data analysis. Differences in the developmental The Kalanchoe branch was also changed every 3 period, fecundity, and longevity of P. typicus at dif- days. Adult females of P. typicus partly insert their ferent temperatures were analyzed at the pϭ0.05 eggs into the stems or leaves of Kalanchoe. The level of significance using Tukey’s HSD test (http:// removed Kalanchoe branches were maintained in www.R-project.org.). Differences in the develop- separate containers in order to rear a new genera- mental period of males and females at each tem- tion of P. typicus. From the next generation, eggs, perature were analyzed at pϭ0.05 using Welch’s nymphs, and adults of P. typicus were separately t-test (http://www.R-project.org.). The effect of reared in containers with the same foods and temperature on the survival rate of P. typicus was plants. This rearing was continued over 15 genera- analyzed at pϭ0.05 using the chi-square test after tions under 16L8D and at 25 Ϯ1°C. arcsine transformation (Zar, 1999). If significant Experiment. Twenty females of P. typicus from differences were indicated in the chi-square test, the laboratory culture were transferred into a plas- the differences in survival rates at different temper- tic cup (diameter, 8 cm; height, 4 cm) containing 10 atures were analyzed using a Tukey-type multiple leaves of Christmas cheer Sedum rubrotinctum comparison test (Zar, 1999).

Clausen (Saxifragales: Crassulaceae) and approxi- The developmental zero (T0) and thermal con- mately 100 mg defrosted E. kuehniella eggs. The stant (K) of females and males from egg to adult cups were placed in cages maintained for 24 h at 1 were estimated from a regression equation of the of 6 constant temperatures (17.5, 20.0, 22.5, 25.0, velocity of development (1/D) against rearing tem-

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perature (t). Mean generation time (T), net repro- (Nishikawa et al., unpublished). In this study, the

ductive rate (R0), and the intrinsic rate of natural developmental period from egg to adult was unaf- increase (rm) were calculated from the survival rate fected by the difference in sex at each temperature (lx) of immature and adult stages and the age- (Table 1). A similar developmental period for specific fertility schedule (mx) (Birch, 1948). The females and males has been reported in M. caligi- increase rate for 30 days was calculated by exp (30 nosus (Hart et al., 2002). The survival rates of the ϫ rm). In this study, the female-to-male ratio was eggs and nymphs, and from eggs to adults, of assumed to be 0.5, since this is the sex ratio gener- P. typicus were significantly affected by tempera- ally exhibited by insects belonging to the Miridae ture (Table 1). The survival rates of eggs to adults (Yasunaga, 2001). at 20.0°C to 25.0°C were significantly higher than at the other three temperatures investigated (Table 1). The lowest survival rate from egg to adult was RESULTS AND DISCUSSION observed at 30.0°C (Table 1). A similar low sur- The developmental periods of eggs and nymphs, vival rate at high temperature has been reported in and from eggs to adults, in males and females of P. M. caliginosus (Hart et al., 2002). The survival rate typicus decreased significantly as the temperature of P. typicus at 25.0°C was also similar to that of increased (Table 1). At 25.0°C, the developmental P. typicus reared with B. tabaci nymph (Nishikawa period from egg to adult was 28.4 d for females et al., unpublished). Regression equation relation- and 28.6 d for males (Table 1); these results are ships between the velocity of development and similar to the developmental period of the commer- rearing temperature for females and males from cial biological control agent M. caliginosus at 25°C egg to adult were 1/Dϭ–0.0337ϩ0.0028T (r2ϭ (Fauvel et al., 1987; Hart et al., 2002) and P. typi- 0.9953) and 1/Dϭ–0.0340ϩ0.0028T (r2ϭ0.9854),

cus reared with B. tabaci nymph at 25.0°C respectively. The developmental zero (T0) and ther-

Table 1. Developmental period (meanϮSD) and survival rate of P. typicus at different temperatures under 16L8D

Developmental period (days)a Temperature Age-speciﬁc Stage (°C) survival rate (%)a Femaleb Maleb

Egg 17.5 31.3 Ϯ 1.4 (8) a 32.3 Ϯ 2.3 (3) a 87.5 (32) a 20.0 20.5 Ϯ 0.7 (31) b 20.6 Ϯ 0.7 (35) b 84.5 (97) ab 22.5 14.7 Ϯ 0.9 (34) c 14.7 Ϯ 0.8 (32) c 84.3 (83) ab 25.0 11.9 Ϯ 0.9 (57) d 12.1 Ϯ 0.9 (32) d 80.5 (149) ab 27.5 9.7 Ϯ 0.7 (32) e 9.8 Ϯ 0.7 (42) e 69.4 (206) b 30.0 8.5 Ϯ 0.7 (44) f 8.5 Ϯ 0.7 (50) f 70.1 (318) ab

Nymph 17.5 40.8 Ϯ 3.3 (8) a 40.7 Ϯ 3.1 (3) a 39.3 (28) c 20.0 24.8 Ϯ 1.4 (31) b 25.5 Ϯ 1.4 (35) b 80.5 (82) b 22.5 18.8 Ϯ 1.2 (34) c 19.4 Ϯ 1.2 (32) c 94.3 (70) a 25.0 16.5 Ϯ 1.1 (57) d 16.5 Ϯ 1.1 (32) d 74.2 (120) b 27.5 13.4 Ϯ 1.2 (32) e 13.3 Ϯ 1.0 (42) e 51.7 (143) c 30.0 12.1 Ϯ 0.9 (44) f 12.2 Ϯ 1.0 (50) f 42.2 (223) c

Egg to adult 17.5 72.0 Ϯ 4.5 (8) a 73.0 Ϯ 2.0 (3) a 34.4 (32) c 20.0 45.9 Ϯ 1.8 (31) b 46.1 Ϯ 1.6 (35) b 68.0 (97) ba 22.5 33.5 Ϯ 1.7 (34) c 34.1 Ϯ 1.7 (32) c 79.5 (83) a 25.0 28.4 Ϯ 1.5 (57) d 28.6 Ϯ 1.1 (32) d 59.7 (149) b 27.5 23.1 Ϯ 1.6 (32) e 23.1 Ϯ 1.3 (42) e 35.9 (206) c 30.0 20.7 Ϯ 1.1 (44) f 20.8 Ϯ 1.1 (50) f 29.6 (318) c

a Number of samples that completely developed from egg to adult is shown in parentheses. Developmental periods and survival rates followed by a different letter in the same developmental stage are signiﬁcantly different among the temperatures (pϽ0.05). b Developmental periods of females and males were not signiﬁcantly different (pϾ0.05).

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Table 2. Fecundity, longevity and related parameters (meanϮSD) of P. typicus females at different temperatures under 16L8D

Preoviposition Oviposition Fecundity per Temperature (°C) Na Longevity (days)b period (days)b period (days)b femaleb

17.5 5 55.2 Ϯ 23.2 a 29.8 Ϯ 25.7 a 16.6 Ϯ 14.3 bc 12.0 Ϯ 7.8 c 20.0 26 45.7 Ϯ 20.5 a 12.5 Ϯ 4.6 b 26.6 Ϯ 19.1 b 23.7 Ϯ 25.9 c 22.5 32 46.9 Ϯ 18.4 a 6.0 Ϯ 2.5 c 36.0 Ϯ 16.6 ab 87.4 Ϯ 62.9 ab 25.0 20 48.8 Ϯ 18.9 a 5.1 Ϯ 1.0 c 40.5 Ϯ 17.9 a 121.2 Ϯ 52.1 a 27.5 21 29.6 Ϯ 6.4 b 4.3 Ϯ 1.1 c 24.1 Ϯ 15.7 bc 91.8 Ϯ 51.0 ab 30.0 24 18.0 Ϯ 8.5 b 4.6 Ϯ 1.3 c 12.3 Ϯ 8.4 c 50.4 Ϯ 42.3 bc

a N indicates the number of pairs. b Means within a column followed by different letters are signiﬁcantly different at the 6 temperatures (pϽ0.05).

Fig. 1. Mean survival curve (thick line) and oviposition curve (thin line) of P. typicus females at different temperatures under 16L8D.

mal constant (K) of females from egg to adult were from egg to adult in P. typicus are higher than for 12.0°C and 357.1 day-degrees, respectively. The M. caliginosus (8.4°C, Hart et al., 2002) and M. corresponding values for males were 12.1°C and pygmaeus (8.6–8.7°C, Perdikis and Lykouressis,

357.1 day-degrees, respectively. The T0 values 2002).

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Table 3. Population growth parameters of P. typicus at different temperatures under 16L8D

Mean generation Net reproductive Intrinsic rate of natural Increase rate Temperature (°C) time (T) (days) rate (R0) increase/day (rm) for 30 days

17.5 101.9 1.8 0.0060 1.2 20.0 67.4 6.5 0.0283 2.3 22.5 54.2 29.1 0.0667 7.4 25.0 50.1 30.0 0.0747 9.4 27.5 35.7 12.7 0.0752 9.6 30.0 30.2 5.3 0.0566 5.5

P. typicus that did not lay eggs were observed in nosus at 22°C, (Hansen et al., 1999). this study, but the rates were low at each tempera- M. caliginosus is not an indigenous natural ture. For this reason, the data of females that did enemy in Japan. This mirid bug cannot easily be not lay eggs were excluded from the calculations of imported from Europe to Japan because its release all parameters in this study. The longevity of P. typ- would risk predation on non-target insects due to icus at temperatures lower than 25.0°C was signifi- its polyphagous habit. In Japan, we have estab- cantly greater than above 27.5°C (Table 2 and Fig. lished that the augmentative release of P. typicus is 1). The preoviposition period at temperatures lower effective in suppressing B. tabaci populations on than 20.0°C was significantly longer than above sweet pepper and eggplant in greenhouses (unpub- 22.5°C (Table 2 and Fig. 1). The oviposition period lished); however, an efficient mass-rearing tech- at 20.0°C to 25.0°C was significantly longer than at nique for P. typicus will be necessary if this species 30.0°C (Table 2 and Fig. 1). The fecundity per is to be used commercially for biological control in female at 22.5°C to 27.5°C was significantly higher Japan. than at 17.5°C and 20.0°C (Table 2 and Fig. 1). Parameters related to the population growth of The mean generation time (T) of P. typicus P. typicus are useful for predicting the conditions decreased with an increase in temperature from necessary for mass rearing. Nevertheless, alterna- 17.5°C to 30.0°C. Among the temperatures investi- tive food and plant sources will be needed to estab-

gated, the net reproductive rate (R0) of P. typicus lish efﬁcient mass rearing, since some authors was highest at 25.0°C, whereas the intrinsic rate of have pointed out that commercially available E.

natural increase (rm) of P. typicus was highest at kuehniella eggs are too expensive for rearing cer- 27.5°C. As the difference in the rm values for tain mirid predators (Castane et al., 2006). Accord- 25.0°C and 27.5°C is small (Table 3), we assume ingly, we should seek alternative food and plant that, of the temperatures investigated, the optimal sources for the mass rearing of P. typicus. temperature for the mass rearing of P. typicus is ACKNOWLEDGMENTS 25.0°C and 27.5°C. M. caliginosus, a polyphagous predator of small We wish to thank Mr. Y. Sugata and Mr. A. Tamada at insects, is currently used commercially in Europe Kochi University, and eggplant and sweet pepper farmers in for the control of whiteﬂies. The preoviposition pe- Kochi Prefecture, Japan, for their support and assistance. riod of P. typicus at 22.5°C was similar to that of REFERENCES M. caliginosus at 22°C, but longevity and the Alomar, O. and R. Albajes (1996) Greenhouse whiteﬂy (Ho- oviposition period of P. typicus at 22.5°C were moptera: Aleyrodidae) predation and tomato fruit injury largely longer than that of M. caliginosus at 22°C, by the zoophytophagous predator D. tamaninii (Het- and fecundity per female of P. typicus at 22.5°C eroptera: Miridae). In Zoophytophagous Heteroptera: was greater than that of M. caliginosus at 22°C Implications for Life History and Integrated Pest (Hansen et al., 1999). For the reproductive capac- Management (O. Alomar and R. N. Wiedenmann, eds.). Thomas Say Publications in Entomology, Entomological ity, the T value of P. typicus at 22.5°C was similar Society of America, Maryland, pp. 155–177. to that of M. caliginosus at 22°C (Hansen et al., Birch, L. C. (1948) The intrinsic rate of natural increase in 1999), whereas the R0 and rm values of P. typicus at an insect population. J. Anim. Ecol. 17: 15–26. 22.5°C were still larger than those of M. caligi- Carnero, A., S. Diaz, S. Amador, M. Hernandez and E. Her-

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