Functional response of Wolbachia-infected and uninfected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) to Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae) eggs

Accepted Manuscript Functional response of Wolbachia-infected and uninfected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) to Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae) eggs

Hui Dong, Quanquan Liu, Lina Xie, Bin Cong, Huan Wang PII: DOI: Reference:

S1226-8615(16)30483-6 doi: 10.1016/j.aspen.2017.05.001 ASPEN 983

To appear in:

Journal of Asia-Pacific Entomology

Received date: Revised date: Accepted date:

25 October 2016 4 May 2017 9 May 2017

Please cite this article as: Hui Dong, Quanquan Liu, Lina Xie, Bin Cong, Huan Wang , Functional response of Wolbachia-infected and uninfected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) to Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae) eggs, Journal of Asia-Pacific Entomology (2016), doi: 10.1016/j.aspen.2017.05.001

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ACCEPTED MANUSCRIPT Functional response of Wolbachia-infected and uninfected Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) to Asian corn borer , Ostrinia furnacalis Guenée

† These authors contributed equally to this work. *Corresponding author

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Hui Dong†, Quanquan Liu†, Lina Xie†, Bin Cong, Huan Wang*

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(Lepidoptera: Pyralidae) eggs

Huan Wang: Shenyang Agricultural University, Shenyang, Liaoning, 110866, China.

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Tel: 86-24-88487148 E-mail: [email protected]

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ACCEPTED MANUSCRIPT ABSTRACT Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) are haplo-diploid egg parasitoid wasps widely used as biological control agents against the Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae). Two reproductive modes have been found in this species. Typically, female wasps produce haploid male offspring from unfertilized eggs and diploid female

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offspring from fertilized eggs (bisexual). However, they can also produce only diploid

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females when they are infected with Wolbachia, though the eggs are unfertilized (thelytokokous). To investigate the potential of a thelytokous Wolbachia-infected and a bisexual uninfected T. dendrolimi strain as inundative biocontrol agents, the functional

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responses of both strains toward their natural enemy (Asian corn borer) were evaluated at three constant temperatures (20, 25 and 30°C). The results revealed two types of

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functional response for both strains: type II and III. Thelytokous strain displayed type II at 30°C (high temperature) and III at 20°C (low temperature) and 25°C, while bisexual

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strain displayed type II at 20°C and III at 25°C and 30°C. The comparison of functional response between two strains indicated TdW+ and Td strain had no significant difference

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at 20 °C. However, the estimated host handling time of the TdW+ strain was

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significantly shorter than that of the Td strain at 25 °C, and TdW+ strain had significantly higher instantaneous search rate and shorter handling time than Td strain at

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30 °C. Shorter host handling time and higher instantaneous search rate in thelytokous Wolbachia-infected T. dendrolimi showed that this strain might be more effective for controlling Asian corn borer.

Key words: Biological control, Functional response, Thelytokous, Bisexual, Predatorprey interactions, Wolbachia

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Introduction

Corn (Zea mays L., Poaceae) plays an extraordinary important role in grain production and ranks first in planting area in China (Editoral Board of China Agriculture Yearbook, 2009). The Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae) is

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considered the most destructive insect pest of corn that occurs in most corn-growing

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areas in China for its strong adaptability and tolerance to unfavourable environmental conditions (Wang et al., 2014). It is estimated that average annual losses due to this insect were 6 to 9 million tons (He et al., 2003; Wang et al., 2014). In recent years, with corn planting area expanded, planting density increased, climate warming and

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cultivation system reformed, the cardinal number and generation of Asian corn borer

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have significantly increased.

A variety of techniques have been used to control the borer. Insecticides are used in many countries, but they are not totally reliable to control Asian corn borer.

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Augmentative release of egg parasitoids is widely used in China and has been tested

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elsewhere, and it is ecological friendly (Nafus & Schreiner, 1991). Among these egg parasitoids, the Trichogramma genus has been proved to be effective inundative

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biological control agents against Asian corn borer (Haile et al., 2002; Yu et al., 2009).

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Nearly 700,000 ha of Chinese corn fields were treated with Trichogramma totally from the 1960s to 1970s (Guo, 1986). T. dendrolimi Matsumura has been identified as a promising egg parasitioid of the genus Trichogramma and widely used as natural enemies in China because these parasitioid wasps can be mass produced by Antheraea pernyi eggs and artificial eggs (Li, 1994). In North-east China, there is nearly 4,000,000 ha of corn released with T. dendrolimi annually (Wang et al., 2014). From 1990 to 2002, T. dendrolimi was mass released on 4,000,000 million ha of corn totally in Jilin province with good biological 3

ACCEPTED MANUSCRIPT control efficacy: the parasitism of Asian corn borer eggs by T. dendrolimi ranged from 73.4% to 87.8% and stalk damage was decreased by 92.5% (Liu et al., 2000). Trichogramma are haplo-diploid hymenopterous insects which typically produce female offspring from fertilized eggs and male offspring from unfertilized eggs (bisexual). However, certain strains of Trichogramma can reproduce only female

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offspring from unfertilized eggs (thelytokous). Thelytokous forms are often associated

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with the presence of endosymbiotic Wolbachia bacteria (Stouthamer et al., 1993). Compared to bisexual forms, the potential advantages of thelytokous parasitoid wasps are: a) their higher population growth rate and more excellent parasitic ability due to all

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offspring consisted of female; b) their easier establishment at low wasp population densities because they do not require to waste time in finding mates; c) their less costs

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of a mass rearing program as no males produced which can not kill the host insect (Stouthamer, 1993; Silva et al., 1999).

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Besides manipulating reproduction, the endosymbiotic Wolbachia bacteria can also affect other important biological control traits. Silva et al. (2000) evaluated the effects

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of Wolbachia on dispersion, fecundity and parasitic ability of T. cordubensis and T.

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deion under laboratory and greenhouse conditions, demonstrated that despite Wolbachia negatively affected fecundity, the dispersion and parasitic ability were improved, in

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consequence thelytokous strains showed a higher potential for biological control than their bisexual conspecifics. Van Hezewijk et al. (2000) reported that the searching and walking speeds of thelytokous females T. minutum were significantly higher than bisexual conspecifics. Hohmann et al. (2000) showed that the fecundity and egg development of Wolbachia-infected T. kaykai were lower and slower than the Wolbachia-uninfected strain, but longevity was obviously longer. De Almeida (2004) indicated that Wolbachia had no effect on creep speed, oviposition and host egg stab of

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ACCEPTED MANUSCRIPT T. atopovirilia. Although Wolbachia can function as a parasite to reduce host fitness, it also might serve as a mutualist to benefit the host (Dedeine et al., 2001; Foster et al., 2005) Whether a biological control program is successful can also be evaluated by understanding predator-prey interactions. It is most commonly done through the

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analysis of functional response (Huffaker & Messenger, 1976; Walde & Murdoch,

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1988). A functional response refers to the change in the parasitization rate of the parasitoid over a range of host densities (Solomon, 1949; Holling, 1968). Holling (1959, 1966) proposed three types of functional response：type I, II and III. Among

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the three types of functional response, type II and III have received the most attention. The parasitism efficiency in a type II functional response decreases as the total handling

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time increases with host egg density, whereas type III is generally related to an increase in searching activity when host densities increase at low, but not at high, host densities

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(Hassell, 1978).

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Moreover the differences in functional response among species and strains may also be caused by genetic and/or phenotypic differences (Farrokhi, 2010). The release of

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Trichgramma for controlling Asian corn borer has become one of the key techniques of IPM for corn. Currently there is little information on predator-prey interactions between

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T. dendrolimi and O. furnacalis on dates. So, it is particularly important to find the best species or strains of Trichgramma for controlling insect pests. In the present study, we evaluated functional responses of a thelytokous Wolbachia-infected strain and a bisexual uninfected T. dendrolimi strain towards O. furnacalis at different constant temperatures. Our investigation was aimed at establishing the potential of thelytokous Wolbachia-infected T. dendrolimi strain for managing Asian corn borer.

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ACCEPTED MANUSCRIPT Materials and Methods

Parasitoid and host cultures Bisexual uninfected Trichogramma dendrolimi strain was provided by Plant Protecting Station of Xiuyan in Liaoning Province. Thelytokous Wolbachia-infected

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pure strain, which has been stable parthenogenesis for more than 500 generations, was obtained from Pest Biological Control Laboratory, Shenyang Agricultural University. Both strains were reared on eggs (<3d old) of the factitious host, rice moth Corcyra cephalonica. The parasitoid wasps were reared at 25±1 °C, 75 ± 5% RH and L16: D8

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photoperiod. Bisexual uninfected T. dendrolimi strain and thelytokous Wolbachiainfected strain were designated as Td and TdW+, respectively. Asian corn borer, O.

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furnacalis, was collected from the corn field near Changchun, Jilin province in 2011, and reared in artificial climatic chamber at 25± 1 °C, 75 ± 5% RH and L16: D8

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photoperiod. The pupae were placed in 35 cm× 20 cm× 15 cm gauze cage. The moths

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were feed with 50% honey solution. A large piece of wax paper was hung in this cage for egg-laying, and the wax paper with newly-laid eggs was removed periodically for

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the experiments. Before starting our experiment, two separate isofemale Wolbachiainfected and uninfected strains were established on rice moth eggs (more than 30

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generations) and all samples used in this study were from these two isofemale strains. The presence of Wolbachia was detected and determined by following protocols: the DNA of Specimens with highly female biased sex ratio were extracted using TIANamp Marine Animals DNA Kit (Tiangen, Beijing, China) according to the manufacture’s protocol. Each DNA sample was checked for the presence of Wolbachia by PCR with specific primers (81F: 5’-TGGTCCAATAAGTGATGAAGAAAC-3’ and 691R: 5’AAAAATTAAACGCTACTCCA-3’) for the wsp gene (Braig et al., 1998).

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ACCEPTED MANUSCRIPT Functional response experiments To determine the functional response of the strains, five densities (10, 20, 40, 60 and 80 eggs per adult parasitoid) of O. furnacalis egg were used. One-day-old mated Td and TdW+ strain female wasps were confined individually in glass tubes (10×45 mm), and provided with an egg card of defined density and 30% honey/water as food. All

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prepared tubes were respectively kept at 20, 25 and 30 °C, 70 ± 5% RH, and L16: D8 photoperiod condition. Ten replications of each density were set up, simultaneously. After 24 hours the female parasitoids were removed and host eggs were maintained under 25 ± 1 °C and 70± 5% RH condition. The blackened eggs were counted and

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recorded by strain and density.

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Calculation and data analysis

The two-step approach for analysis of functional response was suggested by

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Juliano (2001). In the first step, the curve shape (type) of functional response was

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determined by logistic regression of the proportion of parasitized hosts (Na) vs. the initial number of hosts (N0) which is the most effective way of determining this

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(Allahyari et al., 2004; Farrokhi, 2010). The polynomial function was fitted as follows

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(Juliano, 2001):

2 3 Na exp(P0  PN 1 0  P2 N0  P3 N0 )  2 3 N0 1  exp(P0  PN 1 0  P2 N0  P3 N0 )

(1)

Where P0, P1, P2 and P3 are the intercept, linear, quadratic and cubic coefficients, respectively. These parameters were estimated using the method of maximum likelihood by CATMOD procedure in SAS software (Juliano, 2001). The sign of P1 and P2 can be used to distinguish the shape of the curves. A positive linear parameter (P1)

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ACCEPTED MANUSCRIPT and a negative quadratic parameter (P2) indicate that functional response is type ΙΙΙ, whereas the functional response is type ΙΙ when both parameters are negative. Once the type of functional response is determined, it must be described by suitable model and the parameters in the model must be estimated (second step). Random attack model (Rogers, 1972) is used widely to describe the functional response.

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However, it is not suited to our study for two reasons. First of all, the random attack

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model assumes that the parasitoids encounter every host with same probability, but a parasitoid wasp is more likely to encounter hosts that are near to its path (Rogers, 1972). Therefore, the parasite search will not be random over short periods of time (like 24

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hours in this study). In addition, prey depletion should be included in a random attack model. However, although the number of suitable eggs decreased with parasitized eggs,

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examination of parasitized eggs still occurred for T. dendrolimi. Hence the prey depletion was not accounted for in this study (Reay-Jones et al., 2006) and the random

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attack model was not considered. Therefore, we used Holling’s disc equation which is also a widely used model to describe the functional response and the parameters of the

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Holling’s disk equation were estimated by using nonlinear least square regression

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(NLIN procedure in SAS). For the type II functional response, the following equation was used (Holling, 1959):

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Na  aTN0 1  aTh N0 

(2)

Where Na is the number of eggs parasitized, N0 is the density of host eggs, a is the instantaneous search rate, T is the total time of host–parasitoid exposition (24 hours in this study) and Th is the handling time. For the type III functional response, the instantaneous search rate a is a function of host density N0 (Hassell et al., 1977):

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ACCEPTED MANUSCRIPT a   d  bN0  1  cN0 

(3)

Where b, c and d are constants. Replacing equation 3 in equation 2 yields the following type III functional response equation:

(4)

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Na  dN0T  bN02 1  cN0  dN0Th  bN02Th 

After estimating the parameters of Holling’s disc equation by nonlinear least square regression, the obtained parameters were compared [Th, and either a (for type II)

equation with indicator variables: b  Db  j  TN0 1 b  Db  j  Th  DTh  j  N02

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Na 

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or b, c, and d (for type III)]. The comparison between two functions was done by an

(5)

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Where j is an indicator variable and in this study value 0 was set for Td strain and

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value 1 for TdW+ strain. Db and DTh are parameters to estimate the differences between the two strains in the value of parameter b and Th, respectively. In other words, Th is the

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handling time for Td strain, and Th + DTh for TdW+ strain. If DTh is significantly different from zero, then the difference between Th and Th + DTh is significant, which

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means that there is a difference between two handling times. Otherwise, the difference between Th and Th + DTh is not significant and the two handling times are not statistically different (Juliano, 2001). The model was implemented in NLIN by Newton’s method (Juliano and Willians, 1987), which is same as the previous model for a single population. Separation of statistically different parameter estimates was made using 95% confidence intervals. Parameter estimates are not significantly different if comparisons produce 95% confidence intervals that included zero (Juliano, 2001).

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ACCEPTED MANUSCRIPT Significant differences among differernt densities and various temperatures of host eggs parasitized by both strains of T. dendrolimi were determined by two-way ANOVA. For type III functional response, results of nonlinear least square regression in our study indicated that parameters c and d were not significantly different from zero (the asymptotic 95% CI included 0, data not shown). So they were eliminated from the

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reduced model. The function, consequently, had an attack constant a = bN0. Besides,

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direct comparison of parameters is difficult for the form of the functional responses (type III vs. type II). Based on Juliano’s (2001) suggestion, a type III response was tried

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to fit for all temperature treatments.

Results

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Determination of functional response type

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The analysis of logistic regression (Table 1) indicated that the functional response types were different for two strains at different temperatures. For TdW+ strain, P1 of the

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logistic regression were positive and the P2 were negative at 20 and 25 °C, suggesting a

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type III functional response. The functional response curves showed the proportion of eggs parasitized (Na) initially increased then decreased as N0 increased (Figure 1). And

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P1 was negative at 30°C, representing a type II functional response where proportion of eggs parasitized (Na) decreased with N0 increasing (Figure 1). In the same way, functional response of Td strain was type II at 20 °C, type III at 25 and 30 °C. The scatter of observed mean proportions of parasitized eggs and the predicted proportions was illustrated in Figure 1.

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ACCEPTED MANUSCRIPT Functional response The coefficients of instantaneous search rate (a) and handling time (Th ) were the parameters used to determine the magnitude of functional response. The values of instantaneous search rate (a) and handling time (Th) of both strains were changed with

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temperature. As shown in Table 2, the instantaneous search rate (a) of TdW+ strain was

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lowest at 20 °C and reached a maximum at 30°C. The longest handling time (Th) was at 20 °C and the shortest was at 30 °C. It suggested that the highest number of eggs consumed at 30°C (12 eggs per day).

For Td strain, the lowest instantaneous search rate (a) was at 30 °C and the highest

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was at 25 °C. The longest handling time (Th) was at 20 °C and shortest at 25 °C. The

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highest number of eggs consumed at 25 °C (4.03 eggs per day) (Table 2). Significant differences were revealed in the means of host eggs parasitized among different initial densities (F4=16.53, p<0.001, for TdW+; F4=6.72, p<0.05, for Td) and various

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temperatures (F3=13.29, p<0.01 for TdW+; F3=9.44, p<0.05 for Td).

Comparison on functional response of two strains

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Equation 5 was used to compare the differences in functional response between

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Wolbachia-infected strain and uninfected strain of T. dendrolimi. The results were summarized in table 4. The asymptotic 95% confidence intervals for both Db and DTh included 0 at 20°C which suggested no significant difference between b and b+Db, Th and Th+DTh , i.e., the instantaneous search rate and handling time between two strains were not significantly different at 20°C, respectively. At 25°C, asymptotic 95% confidence interval for Db included 0 but that of DTh was greater than 0, showing that there was no significant difference in instantaneous search rate but handling time was significantly different between two strains. And at 30 °C, the asymptotic 95% 11

ACCEPTED MANUSCRIPT confidence interval for both Db and DTh were significant values which indicated that the instantaneous search rate and handling time between two strains were significantly different.

Discussion

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Understanding of the functional response of a parasitoid is basic to the description of parasitism (Hassell, 2000). Previous work indicated that both T. dendrolimi strains were suitable for suppression of O. furnacalis (Cong et al., 2014) and our study revealed that the functional response types were different for two strains at different

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temperatures. The functional response of TdW+ strain was type III at 20 °C (low temperature) and 25 °C, and type II at 30 °C (high temperature), while Td strain was

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type II at 20 °C, and type III at 25°C and 30 °C. Studies demonstrated that the functional response of parasitoids might change from one type to another as

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environmental conditions (temperatures mainly) change (Wang & Ferro, 1998;

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Mohaghegh et al., 2001; Moezipour et al., 2008). Such changes may due to effects on the foraging behavior of parasitoids (Guo, 1986). The present study indicated that there

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existed differences between strains when they adapted to different temperatures, which implied that Wolbachia may play an important role in determining how host-parasitoid

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interactions respond to climate change (Jeffs & Lewis, 2013). Trichogramma species typically have type I or II functional response in laboratory studies, such as the functional response of T. pretiosum Riley with Phthorimaea operculella Zeller eggs (type II; Kfir, 1983), T. minutum Riley with Ephestia kuehniella Zeller eggs (type I; Mills & Lacan, 2004), T. chilonis Ischii with Chilo sacchariphagus Bojer eggs (type II; Reay-Jones, 2006), T. brassicae Bezdenko with Ostrinia nubilalis Hübner eggs (type II; Farrokhi et al., 2010). However, type I functional response was

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ACCEPTED MANUSCRIPT not found in this study and type II was observed less often than type III for T. dendrolimi with O. furnacalis eggs. The form of type III functional response curves is generally attributed to an increase in searching activity with increasing host density within a certain range (Hassell, 1977). Hassell (1977) remarked that searching effort decreased at low prey densities can yield a low return by reducing searching effort. The

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authors explained that foraging behavior can be increased by temperature, leading to

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accelerated learning process of the wasp in discriminating between parasitized and unparasitized eggs, thus increased the rate of parasitized eggs, resulting in a type III functional response (Wang & Ferro, 1998; Mohaghegh et al., 2001; Moezipour et al.,

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2008).

However, there is another explanation: superparasitism can occur when excessive

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numbers of parasitoid eggs are laid in a host egg, leading to incomplete parasitoid development (Salt, 1934; van Lenteren, 1981). The failure to reach the pupal stage

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meant that parasitism was not detected in our study (i.e., the eggs did not turn black). Superparasitism was likely to occur at low host densities, and rates of parasitism would

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be low, which gave the functional response a characteristic type III curve. In order to

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confirm whether this phenomenon occurred in our study or not, future studies will be performed by monitoring wasp activity and recording probing behavior and oviposition

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at appropriate periods of the day (Suzuki et al., 1984). However, provided the superparasitism occurred, TdW+ strain showed better adaption to superparasitism than Td strain for higher maximum parasitoids (Table 2, Table 3). The results suggested that the optimum temperature according to the highest value of a (searching ability of parasitoid) and the lowest value of Th (handling time), was 30 °C (type II) with maximum parasitoids (12.32 eggs per day) for TdW+ strain and 25 °C (type III) with maximum parasitoids (4. 03eggs per day) for Td strain. In North-east

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ACCEPTED MANUSCRIPT China, the Asian corn borer generally goes through two generations a year (All China Corn Borer Research Group, 1988; Cong et al., 2000). Although the first generation occurring in whorl stage corn cause more serious direct yield loss, the indirect reduction in yield caused by second generation that occurs in silking or pollen-shedding stage is much greater because the feeding activity of larvae would induce ear and kernel rot

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which result in contamination of corn grains by mycotoxins produced by harmful

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organisms (Zhou & He, 1995; Wang et al., 2005). In that case, additional Trichogramma release is needed when the egg masses of the second generation are observed. Our field investigation and some previous works revealed that the

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temperatures in Liaoning Province, China were usually around 30 °C in early August when the Asian corn borer of second generation firstly occurred (Cong et al., 2000).

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Therefore, the TdW+ strain might be more appropriate to control Asian corn borer not only for the significantly higher searching ability and lower handling time in 30°C (see

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Results) than Td strain but also for the optimum temperature. In some cases, Wolbachia increases some aspects of fitness on egg parasitoids

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under unfavourable conditions (Wu et al., 2016a). Hohmann and Luck (2000) found that

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Wolbachia-infected thelytokous Trichogramma kaykai Pinto and Stouthamer developed faster than bisexual strain under low ambient temperature (15–16 °C). The field

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collected Wolbachia-infected Trichogramma ostriniae entered heat coma at higher temperatures than uninfected wasps (Wu et al., 2016b). The comparison of functional response between two strains in our study indicated that the TdW+ strain had higher instantaneous search rate and shorter handling time than Td strain at 30 °C, which seemed like Wolbachia showed potential fitness effects on TdW+ strain under high temperature (Wu et al., 2016a).

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ACCEPTED MANUSCRIPT A ‘quality’ parasitoid for inundative releases is defined as having high fecundity, emergence, proportion of female offspring, longevity, host preference for the target species, host-searching activity, and tolerance to local weather conditions (Smith, 1996). In field, the efficacy of inundative releases of parasitoids is crucial during the first 24 h (Reay-Jones et al., 2006). Because of shorter handling time and higher

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instantaneous search rate, the TdW+ strain was able to parasitize more host eggs in 24h.

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Apparently, the proportion of females in TdW+ strain (100%) was larger than in the Td strain, which can be an advantage for inundative release (no host eggs ‘wasted’ in males). And our results of comparison of maximum parasitoids, functional response

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parameters between two strains at different temperatures (see above) suggested that TdW+ strain might be more adaptable to different temperature environments. Besides,

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some authors (Stouthamer, 1993; Silva et al., 1999) indicated that thelytokous parasitoid wasps are relatively more economic biological control agents than bisexual strain (see

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Introduction). Given all above, the TdW+ strain might be more effective for controlling O. furnacalis.

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In conclusion, temperature had a significant impact on the magnitude of

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parasitisation capacity and the type of functional response. The endosymbiotic Wolbachia bacteria had a significant impact on the type and parameters of functional

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response. There is a positive effect on the parasitoid efficiency of T. dendrolimi wasps for O. furnacalis egg. The functional response of TdW+ and Td strain changed under different temperature. Wolbachia infection may affect the reproductive fitness and ecological adaptability of T. dendrolimi. The TdW+ strain might be an optimum strain for inundative releases to control the O. furnacalis. Although functional response studies in small laboratory arenas have been criticized (O’Neil, 1989; Wiedenmann & O’Neil, 1991), they can improve the

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ACCEPTED MANUSCRIPT understanding of the T. dendrolimi-O. furnacalis interaction in the laboratory and got some value for evaluating parasitoid potential. However, we have to point out there are some limitations in our study. Firstly, all data were just from lab and it remains unknown whether these data are also applied to practical works. Therefore, field experiments are necessary to better understand the interaction between T. dendrolimi

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and O. furnacalis. Besides, though TdW+ strain showed higher ‘quality’ than uninfected

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strain, it doesn’t mean thelytokous Wolbachia-infected T. dendrolimi is definitely better than uninfected T. dendrolimi in controlling O. furnacalis, because there are still many factors that could influence the parasitic efficiency, such as fecundity, longevity and

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body size (Roitberg, 2001). Our study was just the first step to developing a better strategy for the biological control of O. furnacalis by optimum parasitoid wasp in

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North-east China. Acknowledgments

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The work was supported by the National Key Research and Development Program of

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China (2016YFD0300704); the Special Fund for Agro-scientific Research in the Public

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(2015020768).

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Interest (201303026) and the Natural Science Foundation of Liaoning Province

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ACCEPTED MANUSCRIPT References All China Corn Borer Research Group., 1988. Studies on the identification of the dominant corn borer species in China. Acta Phytophylacica Sinica. 15, 145-152. Allahyari, H., Fard, P.A., Nozari, J., 2004. Effects of host on functional response of offspring in two populations of Trissolcus grandis on the sunn pest. Journal of

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Applied Entomology. 128, 39-43.

Braig HR., Zhou W., Dobson S., O'Neill SL., 1998. Cloning and characterization of a gene encoding the major surface protein of the bacterial endosymbiont Wolbachia. Journal of Bacteriology. 180, 2373-2378

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Cong, B., Zhang, T. S., Hu Z. F et al., 2014. Biological control effect of thelytokous strain Trichogramma dendrolimi. Chinese Journal of Aplied Entomology. 51(5),

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1289−1298

Cong, B., Zhang, Y. J., Wang, L. X., 2000. Factor of affecting the second-generation

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Asian maize borer population fluctuation with path analysis method. Journal of

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Shenyang Agricultural University. 31(5), 448-450. De Almeida, R.P., 2004. Trichogramma and its relationship with Wolbachia:

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identification of Trichogramma species, Phylogeny, Transfer and Costs of Wolbachia Symbionts. Wageningen University, Netherlands.

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Dedeine, F., Vavre, F., Fleury, F., Loppin, B., Hochberg, M.E., Boulétreau, M., 2001. Removing symbiotic Wolbachia bacteria specifically inhibits oogenesis in a parasitic wasp. Proceedings of the National Academy of Sciences of the USA. 98, 6247-6252. Editoral Board of China Agriculture Yearbook., 2009. China Agriculture Yearbook. China Agriculture Press, Beijing.

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ACCEPTED MANUSCRIPT Farrokhi, S., 2010 . Evoluation of Wolbachia impact on biological characteristics of thelytokous Trichogramma brassicae.University of Tehran, Iran. Farrokhi, S., Ashouri, A., Shirazi, J., Allahvari, H., Huigens, M. E., 2010. A comparative study on the functional response of Wolbachia-infected and uninfected forms of the parasitoid wasp Trichogramma brassicae. Journal of insect science.

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10(167), 1-11.

SC RI P

Floate, K.D., Kyei-Poku, G.K., Coghlin, P.C., 2006. Overview and relevance of Wolbachia bacteria in biocontrol research. Biocontrol Science and Technology. 16(8), 767-788.

NU

Foster, J., Ganatra, M., Kamal, I., Ware, J., Makarova, K., Ivanova, N., 2005. The Wolbachia genome of Brugia malayi: endosymbionts evolution within a human

MA

pathogenic nematode. Public Library of Science. 3, 121. Guo, X., 1986 . Bionomics of Trichogramma ostriniae Pang et Chen. Chinese Journal

ED

of Biological Control. 2, 148-152.

Haile, A.T., Hassan, S.A., Sithanantham, S., Baumgärtner, J., 2002 . Comparative life

PT

table analysis of Trichogramma bournieri Pintureau and Babault and Trichogramma

CE

sp. nr. mwanzai Schulten and Feijen (Hym., Trichogrammatidae) from Kenya. Journal of Applied Entomology. 126(6), 287-292.

AC

Hassell, M.P., 1978. The Dynamics of Arthropod Predatory-Prey Systems. Princeton University Press. Hassell, M.P., 2000 . The spatial and temporal dynamics of host-parasitoid interactions. Oxford Series in Ecology and Evolution. Oxford University, London. Hassell, M.P., Lawton, J.H., Beddington, J.R., 1977. Sigmoid functional responses by invertebrate predators and parasitoids. J. Anim. Ecol. 46, 249-262.

18

ACCEPTED MANUSCRIPT He, K.L., Wang, Z.Y., Zhou, D.R., Wen, L.P., Song, Y.Y., Yao, Z.Y., 2003. Evaluation of transgenic Bt corn for resistance to the Asian corn borer (Lepidoptera:Pyralidae). J. Econ. Entomol. 96, 935-940. Hohmann, C.L., Luck, R.F., 2000. Effect of temperature on the development and thermal requirements of Wolbachia-infected and antibiotically cured Trichogramma

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kaykai Pinto and Stouthamer (Hymenoptera: Trichogrammatidae). An. Soc.

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Entomol. Bras. 29, 497–506

Hohmann, C.L., Luck, R.F., Stouthamer, R., 2001. Effect of Wolbachia on survival and reproduction of Trichogramma kaykai Pinto and Stouthamer (Hymenoptera:

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Trichogrammatidae). Neotropical Entomology. 30(4), 607-612.

Can. Entomol. 91(7), 385-398.

MA

Holling, C.S., 1959. Some characteristics of simple types of predation and parasitism.

Holling, C.S., 1966. The functional response of invertebrate predators to prey density.

ED

Mem. Entomol. Soc. Can. 48, 1-86.

Holling, C.S., 1968. The tactics of a predator. In: Southwood, T.R.E. (Ed.), Insect

PT

Abundance. Symposia Royal Entomological Society, London, pp. 47–58.

CE

Huffaker, C.B., Messenger, P.S., 1976. Theory and practice of biological control. Academic Press, New York.

AC

Jeffs, C. T., Lewis, O. T., 2013. Effects of climate warming on host–parasitoid interactions. Ecological Entomology. 38(3), 209-218. Juliano, S.A., 2001. Nonlinear curve fitting: predation and functional response curves. In: Scheiner SM, Gurevitch J eds. Design and Analysis of Ecological Experiments. 2nd edn. Oxford University, New York, pp.178-196. Juliano, S.A., Williams, F.M., 1985. On the evolution of handling time. Evolution. 39, 212-215.

19

ACCEPTED MANUSCRIPT Kalyebi, A., Overholt, W.A., Schulthess, F., Mueke, J.M., Hassan, S.A., Sithanantham, S., 2005. Functional response of six indigenous trichogrammatid egg parasitoids (Hymenoptera: Trichogrammatidae) in Kenya: influence of temperature and relative humidity. Biological Control. 32, 164-171. Kfir, R., 1983. Functional response to host density by the egg parasite Trichogramma

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pretiosum. BioControl. 28(4), 345-353.

SC RI P

Li, Y.L., 1994. Worldwide use of Trichogramma for biological control on different crops: a survey. In: Wajnberg E, Hassan SA, editors. Biological control with egg parasitoids. CAB International.

NU

Liu, Z.C., Liu, J.F., Zhang, F., Li, D.S., Feng, X.X., 2000. Production and Field Application Techniques of Trichogramma. Golden Shield Press, Beijing.

MA

Mills, N. J., Lacan, I., 2004. Ratio dependence in the functional response of insect parasitoids: evidence from Trichogramma minutum foraging for eggs in small host

ED

patches. Ecological Entomology. 29(2), 208-216. Moezipour, M., Kafil, M., Allahyari, H., 2008. Functional response of Trichogramma

CE

62(2), 245-250.

PT

brassicae at different temperatures and relative humidities. Bulletin of Insectology.

Mohaghegh, J., De Clercq, P., Tirry, L., 2001. Functional response of the predators

AC

Podisus maculiventris (Say) and Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) to the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae): effect of temperature. J.Appl.Ent. 125, 131-134. Nafusa, D.M., Schreiner, I.H., 1991. Review of the biology and control of the Asian corn borer, Ostrinia furnacalis (Lep: Pyralidae). Tropical Pest Management. 37(1), 41-56.

20

ACCEPTED MANUSCRIPT O’Neil, R.J., 1989. Comparison of laboratory and field measurements of the functional response of Podisus maculiventris (Heteroptera: Pentatomidae). J. Kansas Entomol. Soc. 62, 148-155. Reay-Jones, F.P.F., Rochat, J., Goebel, R., Tabone, E., 2006. Functional response of

Entomologia Experimentalis et Applicata1.18, 229-236.

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Trichogramma chilonis to Galleria mellonella and Chilo sacchariphagus eggs.

SC RI P

Rogers, D., 1972. Random search and inscet population models. J.Anim. Ecol. 41, 369383.

Roitberg, B. D., Boivin, G., Lem, V., 2001. Fitness, parasitoids, and biological control:

NU

an opinion. Canadian Entomologist. 133(3), 429-438.

Salt, G., 1934. Experimental studies in insect parasitism II. Superparasitism.

MA

Proceedings of the Royal Society Series B. 144, 455-476. Silva, I.M.M.S., 1999. Identification and evaluation of Trichogramma parasitoids for

ED

biological pest control. Wageningen University. Silva, I.M.M.S., Roskam, M.M., Hoogenboom, A., Gort, G., Stouthamer, R., Van Meer,

PT

M.M.M., 2000. Biological control potential of Wolbachia-infected versus uninfected

CE

wasps: Laboratory and greenhouse evaluation of Trichogramma cordubensis and T.deion and strains. Biocontrol Sci. Technol. 10, 223-228.

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Smith, S.M., 1996. Biological control with Trichogramma: advances, successes, and their potential use. Annual Review of Entomology. 41, 375-406. Solomon, M.E., 1949. The natural control of animal populations. J. Anim. Ecol. 18, 135. Stouthamer, R., 1993. The use of unisexual versus asexual wasps in biological control. Entomophaga. 38, 3-6.

21

ACCEPTED MANUSCRIPT Stouthamer, R., Breeuwer, J.A.J., Luck, R.F. Werren, J.H., 1993. Molecular identification of microorganisms associated with parthenogenesis. Nature. 361, 6668. Suzuki, Y., Tsuji, H., Sasakawa, M., 1984. Sex allocation and effects of superparasitism on secondary sex ratios in the gregarious parasitoid, Trichogramma

T

chilonis (Hymenoptera: Trichogrammatidae). Animal Behavior 32: 478–484.

SC RI P

Van Lenteren, J.C., 1981. Host discrimination by parasitoids. Semiochemicals. Their Role in Pest Control. ed. by Nordlund, D.A., Jones, R.L., Lewis, W.J., pp. 153-179. Van Hezewijk, B.H., Bourchier, R.S., Smith, S.M., 2000. Searching speed of

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Trichogramma minutum and its potential as a measure of parasitoid quality. Biological Control. 17, 139-46.

Rev. Entomol. 33, 441-446.

MA

Walde, S.J., Murdoch, W.W., 1988. Spatial density dependence in parasitoids. Ann.

ED

Wang, B., Ferro, D.N., 1998. Functional response of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) to Ostrinia nubilalis (Lepidoptera: Pyralidae)

PT

under laboratory and field conditions. Environmental Entomology. 27, 752-758.

CE

Wang, Z., He, K., Yan, S., 2005. Large-scale augmentative biological control of Asian corn borer using Trichogramma in China: A success story. In Proceedings of the

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Second International Symposium on Biological Control of Arthropods. Davos, Switzerland (Vol. 12). Wang, Z.Y., He, K.L., Zhang, F., Lu, X., Babendreier, D., 2014. Mass rearing and release of Trichogramma for biological control of insect pests of corn in China. Biological Control. 68, 136-144.

22

ACCEPTED MANUSCRIPT Wiedenmann, R.N., O’Neil, R.J.,1991. Laboratory measurement of the functional response of Podisus maculiventris (Say) (Heteroptera: Pentatomidae). Environ. Entomol. 20, 610-614. Wu, L. H., Hoffmann, A. A., Thomson, L. J., 2016a. Potential impact of climate change on parasitism efficiency of egg parasitoids: A meta-analysis of Trichogramma under

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variable climate conditions. Agriculture, Ecosystems & Environment. 231, 143-155.

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Wu, L.H., Hoffmann, A.A., Thomson, L.J., 2016b. Trichogramma parasitoids for control of Lepidopteran borers in Taiwan: species, life-history traits and Wolbachia infections. J. Appl. Entomol. 140, 353–363.

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Yang, C.C., Wang, C.S., Zheng, Y.N., Fu, B., Na, C.Y., Su, X.M., 2011. Sustained effects of Trichogramma dendrolimi on Ostrinia furnacalis. J. Maize Sci. 19, 139-

MA

142.

Yu, J.Y., Zhou, Y.F., YU, Q.L., Qi, H.X., He, Z.D., 2009. Population dynamic of

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Ostrinia furnacalis and biological control on the pests by releasing Trichogramma dendrolimi in the corn fields. Chinese Agricultural Science Bulletin. 25(24), 344-

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351.

CE

Zhou, D. R., He, K. L., Wang, Z. Y., Ye, Z. H., Wen, L. P., Gao, Y. X., Song, Y., 1995.

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Asian corn borer and its integrated management. Golden Shield, Beijing.

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ACCEPTED MANUSCRIPT Figure legends Fig.1 The proportion (Na/N0) of eggs parastized by Wolbachia-infected Trichogramma dendrolimi strain (TdW+) and uninfected strain (Td) to different egg densities of Ostrinia furnacalis at different constant temperatures (symbols: observed; line:

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predicticted by model)

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ACCEPTED MANUSCRIPT Table 1. Estimates and standard errors of linear and quadratic coefficients for the proportion of eggs parasitized by two strains of Trichogramma dendrolimi TdW+ Temperature(℃)

Td

Parameters Estimate

SE

χ2

P value

Estimate

SE

χ2

P value

P0

-3.083

0.9352

10.87

0.001

0.0496

1.1352

0

0.9651

P1

0.185

0.082

5.09

0.0241

-0.2026

0.1117

3.29

0.0697

P2

-0.00546

0.00201

7.34

0.0068

-0.00362

0.00276

1.72

0.1892

P3

0.00004

0.000014

7.87

0.005

0.00002

0.000019

1

0.3179

P0

-2.3221

0.7501

9.58

0.002

-3.7965

1.041

13.3

0.0003

P1

0.1297

0.0635

4.18

0.041

0.2367

0.0911

6.76

0.0093

P2

-0.00277

0.00154

3.24

0.0717

-0.00668

0.00224

8.85

0.0029

P3

0.00013

0.000011

1.34

0.2478

0.000048

0.000016

8.98

0.0027

P0

0.7546

0.6564

1.32

0.2503

-0.9278

1.8595

24.9

<0.0001

P1

-0.0993

0.057

3.04

0.0812

0.618

0.1463

17.83

<0.0001

P2

-0.00181

0.00136

1.76

0.1845

-0.0146

0.00343

18.17

<0.0001

P3

0.00001

9.52E-06

1.63

0.2016

0.000098

0.000024

16.97

<0.0001

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Note: P0: Intercept coefficient; P1: Linear coefficient; P2: Quadratic coefficient; P3 : Cubic coefficients ; TdW+ : Thelytokous Wolbachia-infected T. dendrolimi

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strain; Td: Bisexual Wolbachia-uninfected T. dendrolimi strain.

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Table 2 Estimates of the functional response type and parameters for thelytokous strain (TdW+) of Trichogramma dendrolimi to different egg densities of Ostrinia furnacalis at different constant temperatures Asymptotic

Asymptotic

95% CI

95% CI

Functional Temperature response

a ±SE

T P

C S U

b±SE

Th±SE

(℃) type

Lower

upper

Lower

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Ⅲ

-

0.0020±0.0039

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Ⅲ

-

0.0032±0.0043

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Ⅱ

0.0488±0.0713

0.0987

0.1963

D E

0.0036±0.0056*

upper

N A

0.0060

I R

Asymptotic 95% CI

Namax

Lower

upper

0.0100

5.1195±1.6410

1.7248

8.5143

4.69

0.0056

0.0120

2.8875±0.6531

1.5366

4.2385

8.31

0.0079

0.0152

2.2321±0.5926 *

1.0062

3.4581

10.75 *

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Note: Data in the table are mean±SE. a: Instantaneous seach rate; b: In the best fit of the type Ⅲ model, Instantaneous seach rate (a) increased linearly with

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prey density (a = bN ) , and b is constants; Th: Handling time; r: Coefficient; Namax: Maximum number of eggs laid per day; * : The functional response

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parameters of type Ⅱ estimated by type Ⅲ equation.

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Table 3 Estimates of the functional response type and parameters for bisexual strain (Td) of Trichogramma dendrolimi to different egg densities of Ostrinia furnacalis at different constant temperatures Asymptotic Temperature

Functional

(℃)

response type

a±SE

95% CI Lower

upper

0.0063

0.0149

T P

Asymptotic

Asymptotic

95% CI

b±SE

Lower

upper

0.0010±0.0019 *

4.5986

19.3640 0.0076

20

Ⅱ

0.00428±0.0051

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Ⅲ

-

0.0017±0.0028

0.0042

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Ⅲ

-

0.0007±0.0013

0.0020

I R

Th±SE

N A

Namax

Lower

upper

11.9813±3.5689 *

4.5986

19.3460

2*

5.9557±1.698

2.4418

9.4696

4.03

6.5963±2.5815

1.2562

11.9364

3.64

C S U

0.0034)

95% CI

Note: Data in the table are mean±SE. a: Instantaneous seach rate; b : In the best fit of the type Ⅲ model, Instantaneous seach rate (a) increased linearly with

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prey density (a = bN ) , and b is constants; Th: Handling time; r: Coefficient; Namax: Maximum number of eggs laid per day; * : The functional response parameters of type Ⅱ estimated by type Ⅲ equation

D E

T P E

C C

A

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Table 4 The comparative on functional response parameters of Wolbachia-uninfected and infected Trichogramma dendrolimi at different constant temperatures Asymptotic 95% CI Parameter

Estimate

SE Lower

Upper

Db

0.0045

0.0385

-0.0564

0.0986

DTh

-2.5291

11.0270

-24.7252

19.6671

Db

0.0144

0.0355

-0.3580

0.0570

DTh

-3.3437

2.1324

T

Temperature

7.6361

Db

0.0380

0.0602

0.0832

0.1591

DTh

-4.5689

4.1943

3.8738

13.0117

20

0.9486

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Note: Db denotes the difference in instantaneous search rate between two strains in Type II and

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Type Ⅲ functional response, and DTh denotes the difference in handling time between two strains. If zero is included in 95% CI, it indicates no significant difference between two

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strains.

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Fig.1

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Graphical abstract

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Highlights ●The

thelytokous Wolbachia-infected stain is more effective for control of Asian

corn borer.

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functional response was affected by Wolbachia significantly.

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●The

strains display either a type Ⅱor Ⅲ functional response at different temperature.

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●Both

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