Effect of Different Temperatures on the Life Table Parameters of Rhyzobius Lophanthae Blaisdell (Coleoptera: Coccinellidae)

The purple scale predator, Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) is known as coccidophagous ladybird predator, and effective against scales’ insects. The present study aimed to evaluate the optimum temperature for the species to be more ecient. In this study, the life table parameters of R. lophanthae were determined on different temperatures at 4, 16, 18, 20, 22, 24, 26, 28, 30 and 32 °C and 60% RH, by calculations using RmStat-3 software according to Euler-Lotka equation. The results showed that the intrinsic rates of increase (r m ) were 0.016, 0.022, 0.030, 0.052, 0.056, 0.068, 0.120, 0.142, 0.132, 0.021 females/females/day, respectively, while the net reproductive rates (R 0 ) were 7.082, 9.514, 11.960, 50.906, 54.150, 49.525, 56.883, 80.944, 31.149, 1.882 females/females/generation, respectively. The mean generation times (T 0 ) were 125.966, 104.602, 84.009, 75.742, 71.511, 57.568, 33.801, 30.866, 25.978, 30.759 days, respectively. Total productivity rates (GRR) were 34.865, 39.210, 48.216, 201.990, 209.469, 166.207, 177.779, 303.751, 105.751, 12.622 egg/female, respectively. The study concluded that 26-30 °C was the optimum temperature range for the ecient role of R. lophanthae under laboratory conditions. From the results, it is still needed to do more studies on the interactions of pests, predators with environmental conditions.


Introduction
Citrus trees production in Turkey has been affected by different insect pests including scale insects that have been increased recently. For controlling such pests, the intensive use of chemical pesticides has led to decrease the role of natural enemies; caused pesticides residues in the agricultural productions, environmental pollution and negative effects on human health. Producers of citrus have preferred to use various methods and reduce pest populations. Biological control is one of these methods and can be a promise way to control pests (Uygun & Karaca, 1998). The purple scale predator, Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) is known as an important coccidophagous ladybird predator and very effective against soft scales insects and is frequently observed in citrus and other fruit orchards where scale insects are present (Branco et al., 2017). R. lophanthae is native to Australia and has distributed too many regions of the world as a biological control agent (Hodek & Honek, 1996). The predator has been reported on many countries, except Turkey as an important biocontrol agent of scale insects (Stathas et al., 2002;Mellado, 2011). As reported in many studies the development and e cacy of many predator and parasitoid insects are affected by temperature (Luhring et

Culture of Aspidiotus nerii Bouché
Aspidiotus nerii was used as a prey in the present study. The culture of soft scale insect was obtained from the mass production at the laboratory from Biological Control Research and Application Center, Faculty of Agriculture, Isparta University of Applied Sciences, Turkey. The A. nerii was continued reproductive in weekly periods of the study. A. nerii was reared on potato tubers (Solanum tuberosum L.). Infested potato tubers with A. nerii were placed on the clean potatoes for increasing the population culture of the pest to be used in experiments.

Culture of Rhyzobius lophanthae
Rhyzobius lophanthae samples were collected from citrus orchards in Adana Province located in Turkey. The predators were collected, using shaking method of the infested citrus branches. A laboratory colony of R. lophanthae was raised under incubator chamber at 25±1°C, 65±5% RH with 16L: 8D light conditions at the Department of Plant Protection, Isparta University of Applied Sciences, Turkey. The predator individuals were used as a stock culture for experiments.

Experimental design
This study was carried out in incubators that set up on 10 different temperatures degrees (14,16,18,20,22, 24, 26, 28, 30 and 32°C), and 60% RH with a light period of (16L: 8D). Fresh 40 R. lophanthae adults (20 male, 20 female) newly emerged from pupae were collected. Then, all adults were placed on the potato tubers infested with A. nerii and left in a plastic container (9x9x5 cm dimensions). After rearing 20 pairs of the predator for 15 days on potatoes under the laboratory conditions, the eggs laid by the predator on potato tubers were collected by using a soft sable brush to avoid damaging the eggs. Each egg was placed on an infested potato tuber using a soft brush. Then, the larvae of R. lophanthae, were exposed to different temperatures until the adult stage. The experiment was continued with the pairs formed after the emergence of adult individuals from the pupae. For this purpose, female and male individuals were left on each potato infested with A. nerii depending on the temperature. After this process, daily checks of the replicates were made. Daily number of eggs deposited by female individuals was determined and the trials continued until the last predator died. Life tables' parameters of R. lophanthae at each temperature were recorded based on the data obtained. Replicates were examined daily under a stereomicroscope (Leica S6D) to record the predator life table parameters. Data obtained from the experiments were recorded to determine the development of age-related life tables for each temperature that used.

Statistical analyzes
Life table parameters of the predator were calculated by using RmStat-3 software (Özgökçe & Karaca, 2010) according to Euler-Lotka equation (Birch, 1948) and were evaluated separately. Tukey multiple comparison test was used for comparison of the periods with SPSS (ver. 17) at the signi cant difference p<0.05 level. To calculate the parameters, several equations were used which were:

Results
Daily and total numbers of eggs of the predator R. lophanthae at different temperatures were signi cantly different according to Tukey multiple comparison tests, which were (F DNE = 73.62; DF= 9; P≤ 0.001; F TNE = 18.75; DF= 9; P≤ 0.001). Daily numbers of eggs increased with increasing the temperature degree until 28°C, afterwards, the numbers of eggs decreased. The lowest daily number of eggs was 0.70±0.14 eggs, calculated at 14°C. While the highest daily number of eggs (11.17±0.65 eggs) was recorded at 28°C. In other words, the lowest total numbers of eggs were 64.2±12.1 and 30.9±3.72 eggs, respectively, were determined at 14 and 32°C; while the highest total numbers of eggs (479.7±54.6 eggs) were found at 28°C. Both of daily and total egg numbers were obtained at 28°C and were found statistically different from the number of eggs that recorded at other temperature degrees (Fig. 1  dictiyospermi and A. aurantii at 26°C and the values were 0.120, 0.061 and 0.041 females/female/day, respectively. When the data obtained are examined, it is seen that the intrinsic rate of increase values obtained were close. It is thought that this is due to the fact that these studies were carried out at similar temperature values.