An Analysis of Predatory Bugs ( Orius spp., Hemiptera: Anthocoridae) and Pest Insects on Some Crop Plants: Their Distributions, Abundance and Population Developments

The seasonal distributions of predatory bugs, specifically species of Orius (Hemiptera: Anthocoridae), and the population dynamics of some sucking pests including aphids, leafhoppers, and thrips in crops plants (i


Introduction
To maintain the population of harmful insects/mites at a rate below the economic damage threshold in plant production and increase yields, insecticides/acaricides have been widely used due to their biological effectiveness and rapid suppression of pests (De Waard et al. 1993).Pesticides were first introduced in the 1940s and, while their use has increased, as have their negative effects, the widespread commercial use of pesticides initially did not raise concerns about residue problems.Harmful organisms such as insects and mites have developed resistance to pesticides over time, potentially rendering them less effective in the future (Bass et al. 2015;Gould et al. 2018).The indiscriminate and intensive use of pesticides in modern agriculture has adverse effects on human and environmental health.It leads to pesticide resistance, a reduction in beneficial organisms, decreased biodiversity in agricultural ecosystems and crop residue problems (Carson 1962;Brammall & Higgins 1988;Dreistadt et al. 1994;Rosell et al. 2008;Pereira et al. 2016;Silva et al. 2019;Alengebawy et al. 2021).As an alternative to chemical control, there have been efforts to adopt more economical and environmentally friendly methods that promote the health of living organisms and minimise the unnecessary use of pesticides.Studies on biological control methods have been conducted for this purpose (Clausen 1958;Howarth 1991;Bueno et al. 2006).Some predatory insect species, which belong to the Anthocoridae (Hemiptera) family, are commercially reared and used primarily to control harmful thrips in greenhouses (Riudavets & Castena 1994;Topakçi & Keçeci 2017;Van Lenteren et al. 2020).The genus Orius in the family Anthocoridae is common in nature, particularly in areas with high biodiversity, and six species of this genus have been recorded in Turkey (Önder 1982).Both nymphs and adults of the Orius species exhibit zoophagous behaviour, feeding on various insects and mites that are detrimental to plants, including whiteflies, aphids, spider mites, psyllids, Lepidoptera and Coleoptera, with a particular focus on species of thrips (order Thysanoptera) (Riudavets and Castane 1994;Önder 1982;Lodos 1986;Lattin 1999;Pehlivan & Atakan 2020).O. laevigatus, Orius insidiosus (Say), and Orius tristicolor (White) have been commercially used for controlling Frankliniella occidentalis (Pergande) in protected crops since 1990 (Chambers et al. 1993;Ferragut & Zamora 1994;Disselvet et al. 1995;Pozzebon et al. 2015).Orius niger (Wolff) has been found together with F. occidentalis on weeds in the Adana and Mersin Provinces, located in the Eastern Mediterranean region of Turkey (Atakan & Tunç 2010).In the Adana Province, O. niger was the most common species in fields where broad beans, clovers and strawberries were cultivated (Atakan &Tunç 2004;Atakan 2010a;Atakan 2011).
While polyphagous Orius species are generally associated with thrips, understanding their interactions with different types of prey in various crop plants throughout the season can provide valuable ecological information about their role in suppressing crop pests.This study aimed to examine the composition of predatory Orius species and the distribution of common pests, such as aphids, thrips and leafhoppers, in various agricultural crop plants products within a designated polyculture ecosystem.Additionally, it investigated the population changes and interactions among these pest insects.The results obtained about the importance of the Orius species as biological control agents of crop pests will be discussed.Overall, the study provides valuable insights into the seasonal dynamics of the Orius species and pest insects across various plant groups in different ecological areas, enhancing our understanding of their interactions and population fluctuations in agricultural areas.

Definition of sampling area
The location Balcalı is a neighbourhood located in Adana Province, Turkey.It houses the Çukurova University, Faculty of Agriculture Research and Application Farm, situated approximately seven kilometers away from the main campus.This research area spans around 700 hectares where citrus, stone fruits, subtropical fruits and both cool and warm climate cereals are cultivated.In addition, wheat is grown in an area of approximately 400 hectares that is not irrigated.Flood irrigation is the predominant method used in irrigable sections.It is worth mentioning that the region also serves as a nature reserve, ensuring the protection of wildlife.The location Balcalı experiences a typical Mediterranean climate, characterised by warm and dry summers, mild and wet winters and overall moderate temperatures throughout the year.

Sampling of insects
Seasonal abundance and distribution of the Orius species, and its relationships with different types of prey (thrips, aphids and leafhoppers) were investigated in Balcalı at the Çukurova University Farm, in 2019-2020.Three ecological areas have been identified where different plant species are grown for both production and research.For this purpose, winter and summer vegetables and citrus were sampled in the Research and Implementation Area of the Plant Protection Department to check for numbers of pest insects such as aphids, leafhoppers and thrips, as well as predatory bugs.In the Field Crops Research and Implementation Area, various field crops, including cotton, soybean, sesame, peanuts, and temperate climate fruit trees such as apple, nectarine, and loquat, were sampled as part of the research conducted in Research and Implementation Area of the Horticulture Department.The sampling sites are about two or three kilometers apart from each other.Insect pests have been recorded on all these plants.Species-level distinctions were not done for the pest groups: Aphids, thrips and leafhoppers.Common species were found in vegetables and field crops.These included the cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae), western flower thrips, Frankliniella occidentalis (Pergande), cotton thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae) and cotton leafhopper, Empoasca decipiens Paoli (Hemiptera: Cicadellidae).
For winter vegetable plants, plots were created in four territorial units using a randomised block trial design.The plants included spinach (Spinacia oleracea L.), lettuce (Lactuca sativa L.), cauliflower (Brassica oleracea var.botrytis L.), red cabbage (Brassica oleracea var.appitate f. rubra L.), cabbage (Brassica oleracea L.), rocket (Eruca vesicaria L.), peppergrass (Lepidium sativum L.), radishes (Raphanus sativus L.) and broad beans (Vicia faba L.).Each plot consisted of four rows, with fifteen plants in each row.A free space of 1.5 meters was left between plots, and there were five meters between the blocks.A similar trial model was created for the following summer vegetable plant species: cucumber (Cucumis sativus L.), squash (Cucurbita moschata L.), beans (Phaseolus vulgaris L.), peppers (Capsicum annuum L.), tomatoes (Solanum lycopersicum L.), potatoes (Solanum tuberosum L.) and eggplants (Solanum melongena L.).To investigate the population density of thrips and predatory insects in some field crops, plots containing cotton (Gossypium hirsutum L.), sesame (Sesamum indicum L.) and soybean plants (Glycine max L.) were established according to the randomised block design with four replicates.The plot size for each plant species was designed as 96 square meters with a row length of ten meters, consisting of ten rows, with a distance of 0.80 meter between rows.A free space of two meters was left between the plots and five meters between the blocks.Nectarines (Pyrus persicae L.) and pomegranates (Punica granatum L.) were planted with 3 x 5 spacing, apples (Malus domestica L.) with 1 x 4 spacing, pears (Pyrus communis L.) with 4 x 6 spacing, plums (Prunus persica L.) lemons (Citrus lemon L.) and almonds (Prunus dulcis Mill.D. A. Webb) with 5 x 5 spacing and loquats [(Eriobotrya japonica (Thunb.)Lindl.)] with 7 x 7 spacing.Ten rows of each fruit tree species were planted, with twenty trees in each row.There was a 20-meter gap between the large plots representing each fruit species, and they were lined up next to each other.Each tree species planted was nearly fifteen years old.In the samplings, 20 plants from annual herbaceous crops (vegetable species and field crops) and 30 cm-long flowering or fruitbearing shoots were randomly selected from each of the 20 fruit trees, positioned in the four cardinal directions.In general, the plants with flowers were taken into consideration in the samplings, which started with the beginning of the flowering period of the different plant groups.This decision was made because Orius and their primary prey, thrips, are found mostly on flowers, as these predatory species feed on the nectars and pollens in the flowers when there is no prey (Riudavets & Castane 1994;Hansen et al. 2003;Funderburk et al. 2000;Funderburk et al. 2018).Flowering or fruiting shoots measuring 30 cm-long in four different directions on the trees were randomly selected for sampling.In herbaceous plants, the upper halves of the plants were considered in the sample.In the surveyed areas, shoots or plants were shaken for 5-10 seconds into a white container measuring 34 × 23 × 7 centimeters, and the Orius species and herbivorous insects that fell into the container were lifted out by a suction tube and/or fine brush and placed in Eppendorf tubes containing 70% ethyl alcohol.Insect samples collected from each plant species on each sampling date were placed in a tube.The information about the samplings of insects in various plant groups is summarised in Table 1.Sampling was carried out in three different ecological areas on the same day between 08:00 and 12:00.Insect samples (Orius and herbivorous pest insects) were brought to the laboratory and placed in Petri dishes to be counted under a stereo binocular microscope, to classify them as thrips, aphids or leafhoppers without making any distinction between species.While making the diagnosis, nymphs of Orius and larvae of thrips were sampled from the most common broad bean plants but were not evaluated because they were found only in very small numbers.Orius adults were separated according to genital organ and morphological characteristics, after which they were identified.

Identification of Orius
The samples collected in the survey were first placed into Eppendorf tubes containing ethyl alcohol and their setae in the pronotum were examined under a stereo binocular microscope.Then the tips of the abdomens were cut off and transferred to glass containers containing 10% potassium hydroxide (KOH) solution and left at room temperature for one day.At the end of a day, it was put into clove oil for about five minutes, after which, using a needle, it was transferred to a slide prepared with Hoyer's medium and covered with a coverslip.In addition, nail polish was applied around the slide to prevent air from getting in.The preparation was dried in an oven heated to 45°C, where it remained for fifteen days (Silveira et al. 2003), after which the mating tubes of the females and the genital organs of the males of the Orius species were examined under a light microscope and a diagnosis was made according to the key identifications published by Péricart (1972) and Önder (1982).

Statistical analysis
The seasonal distributions of harmful insects and Orius species in various cultivated plants were calculated separately following the method of Karman (1971).The distributions, representing the ratios of total adult individuals, were calculated using the Microsoft Excel spreadsheet program.To analyse the seasonal averages of both Orius spp.and prey pests in the plant groups within the same ecological area, one-way analysis of variance (ANOVA) and the Tukey test were applied with a significance level of P<0.05 (SPSS 2016).The comparison of averages considered the same sampling dates for each plant group, including both winter and summer vegetables, fruit trees and field crops.To evaluate the population fluctuations of the predator and pest groups, as indicated in the methods section because the number of predatory and pest individuals in certain plant species within the plant group was very low or could not be found on some sampling dates.We calculated the average number of individuals collected from these plant species on each sampling date by adding up the counts and dividing by the number of samples.The combined data were then presented as total mean values for summer/winter vegetables, fruit trees and field crops.Since the cultivated plants sampled from different plant groups were grown in different ecological areas and had varying growing periods, the seasonal averages of beneficial insects (Orius spp.) and harmful insects on crop plants were not statistically compared.The prey/predator ratios were determined based on the number of harmful insects and Orius obtained from the plant groups.The total values obtained from 20 plants in each plant category (vegetables, field crops and fruit trees) were entered into the Excel program, according to the respective sampling dates.To assess the correlations between the mean numbers of predators (Orius spp.) and the numbers of pest insects (aphids, leafhoppers and thrips) within each plant group, a simple correlation analysis (Pearson correlation) was conducted at a significance level of P<0.05 (SPSS 2016).Specifically, we considered 21 sampling dates for winter vegetables, 19 for summer vegetables, 20 for field crops and 31 for fruit trees.The study's statistical analysis and tables provide information about the seasonal dynamics and interactions between Orius species and pest insects across different plant groups and ecological areas.

Distribution of Orius species and harmful insects on the crop plants
The survey, conducted in the Balcalı region, yielded a total of 134 Orius species collected from winter vegetables (Figure 1a).Among these, O. laevigatus was dominant, with 105 individuals, making up 78.36% of the total adult population.Regarding pest insects, the survey revealed that, in winter vegetables, 735 individuals of thrips were collected, constituting 50.94% of the total number of adult pest individuals (Figure 1b).The second most common pest taxon was leafhoppers, with a rate of 43.73% and a total of 631 individuals collected (Figure 1b).A total of 77 aphid individuals were recorded, accounting for 5.93% of the total pest population.Thrips was most frequently found in association with Orius species, which aligns with previous studies indicating that Orius primarily prefer thrips as their prey and some Orius species are important predators of thrips.On fruit trees, O. laevigatus, O. niger and O. vicinus individuals were detected, with an incidence of 77.27%, 18.18%, and 4.55%, respectively (Figure 1c).However, O. albidipennis species was not found in the survey.On fruit trees, thrips were the most common insects, with 620 individuals, accounting for 94.06% of the total pest population (Figure 1d).Aphids and leafhoppers were collected in very low numbers, with three and thirteen individuals, respectively, accounting for 1.02% and 4.92% of the total number of individuals (Figure 1d).In summer vegetables, O. niger was the most common species, with 17 adults, representing 56.67% of the total adults (Figure 1e).Orius laevigatus was the second most common species, with 20 individuals, comprising 40% of the total individuals (Figure 1e).Individuals of aphids were observed in lower numbers in summer vegetables, constituting 3.95% of the total prey population species (Figure 1f).In field crops, O. laevigatus dominated the Orius populations (Figure 1g).Individuals of thrips (mainly F. occidentalis) were the most common pests, with 239 individuals collected, constituting 68.68% of the total adult herbivorous insect population (Figure 1h).These survey findings provide valuable insights into the population dynamics and interactions between Orius species and pest insects in different plant groups within the location Balcalı contributing to our understanding of natural pest control mechanisms.

Population dynamics of Orius and harmful insects on the crop plants
The population dynamics of Orius in relation to pest species on various winter and summer vegetables, fruit trees and field crops are illustrated in Figure 2. In winter vegetables (Figure 2a), the number of thrips and aphids increased steadily since the first sampling date and, accordingly, Orius species were recorded.However, the densities of Orius remained lower than those of the prey insects.From 15 th January to 15 th March 2020, Orius populations showed fluctuations, likely influenced by the densities of both thrips and leafhoppers.In winter vegetable species, considering the average population densities of predatory and herbivorous insects, statistically significant and positive relationships were found only between Orius and thrips populations (Orius-Thrips: R= 0.55, P= 0.009; Orius-aphids: R= 0.20, P= 0.398; Orius-leafhoppers: R= 0.39, P= 0.443).On fruit trees (Figure 2b), Orius individuals were recorded alongside thrips and leafhoppers during the first sampling week.Relatively high thrips densities were detected in fruit trees on 22 nd January and 29 th April 2020, and the numbers of.Orius fluctuated in response to the thrips populations.In fruit trees, the Orius population showed a strong dependence on the thrips populations, and significant positive relationships were detected (Orius-thrips: R = 0.65, P = 0.0001; Orius-aphids: R = 0.22, P = 0.226; Orius-leafhoppers: R = 0.21, 0.316).In summer vegetables (Figure 2c), thrips and leafhoppers increased during the October-December period in 2019 and, correspondingly, the Orius population increased as well.In 2020, thrips and Orius exhibited similar population patterns until the last sampling date; the densities of Orius appeared to be lower than the thrips densities.However, statistically significant positive relationships were observed among the Orius and both thrips and aphid populations (Orius-thrips: R = 0.58, P = 0.009; Orius-aphids: R = 0.54, P = 0.007; Orius-leafhoppers: R = 0.43, 0.062).In field crops (Figure 2d), there was a short-term increase in the thrips population on 28th September 2020 and, during this period, the Orius density also increased temporarily, although it remained at a lower level than that of the thrips populations.At the last sampling date, although the aphid population increased on the leaves, Orius individuals were not found.A significantly strong and positive relationship was found only between the Orius and thrips populations (Orius-thrips: R = 0.73, P = 0.006; Oriusaphids: R = 0.14, P = 0.655; Orius-leafhoppers: R = 0.22, 0.488).Overall, the population dynamics of Orius seemed to be closely associated with the fluctuations in thrips populations in the different plant environments.

Discussion
Although the numbers of thrips were higher in winter vegetables than in other crop plants, except for broad beans, the reason that Orius individuals were found in very low numbers may be related to the absence of flowers during this period.It is worth noting that broad bean plants showed lower numbers of thrips than leafhoppers.The high number of Orius in broad bean plants could be attributed to the plants' morphological structure and chemical content such as the presence of extrafloral nectars for them to feed on, rather than relying solely on prey such as thrips.In the Çukurova region, broad bean plants remain in bloom from December to early March, providing large covered flowers that may serve as protection, shelter and even sites for mating and egg laying for predatory species like Orius.Moreover, broad bean plants are known to be richer in extrafloral nectars, attracting many beneficial insects (Nuessly et al. 2004).Notably, O. niger and O. laevigatus species were detected in both winter and summer vegetables in the Çukurova region (Zeren & Düzgüneş 1983).To summarise, the presence of flowers and extrafloral nectars in broad bean plants may have contributed to the higher number of Orius individuals, while their low presence in other winter vegetables could be attributed to the absence of these essential resources during that season.
Frankliniella occidentalis and T. tabaci were widely found in summer vegetables in this region.Frankliniella occidentalis was abundant in eggplant and pepper flowers, but its presence was minimal in tomato flowers (Atakan 2010b).According to Bahşi (2011), the most common Orius species in Antalya was O. laevigatus (66%), followed by O. niger (33%).Additionally, O. limbatus (Wagner), O. majusculus (Reuter), O. minutus (L.) and O. vicinus were also recorded in this region.Thrips were the most prevalent pest group in various plant samples, often found alongside Orius species.While O. laevigatus was most common in winter vegetables (mainly broad beans), O. niger dominated in summer vegetables (mainly beans; Table 5).Orius populations were relatively low in fruit trees, indicating a preference for herbaceous habitats regardless of prey species and their densities.In Adana, O. niger played a crucial role in controlling pest thrips like Frankliniella flower thrips in unsprayed cotton fields (Atakan and Özgür 2001).A study conducted in a clover field in the same region revealed that F. occidentalis was the most harmful thrips species, with O. niger and O. laevigatus frequently found together with these pest thrips throughout the year (Atakan & Tunç 2004).
Although the number of thrips in pepper plant flowers was higher compared to other summer crops like tomatoes, eggplants and beans, only a few Orius specimens were detected (Table 5).In Florida, O. tristicolor effectively suppressed Frankliniella flower thrips in field-grown peppers (Funderburk et al. 2000).Researchers (Dissevelt et al. 1995) reported that eggplants and, more particularly, peppers due to their abundant pollen were more attractive to Orius species.The lack of Orius in tomato plants may be attributed to reduced mobility of nymphs or adults due to the plants' secretions negatively affecting Orius' searching ability and, thus, their predation on pest insects (Coll & Ridgeway 1995).Orius species densities were lower in field crops like cotton when compared to previous studies in the same ecological area (Table 7).Previous research in a pesticide-free cotton field in the region recorded a significant number of Orius adults preying on flower thrips in cotton flowers (Atakan 2006).Orius niger closely followed the populations of Frankliniella flower thrips, indicating that this predatory bug could effectively suppress pest thrips in unsprayed cotton fields (Atakan 2006;Atakan 2010a).
The distribution and population of Orius in different plant groups varied primarily due to thrips populations, which appeared to be their main prey.Studies on the field peppers (Funderburk et al. 2000;Hansen et al. 2003;Funderburk et al. 2018) and cotton (Atakan and Özgür 2001;Atakan 2006) confirmed that Orius plays an essential role in controlling Frankliniella flower thrips, leading to reduced thrips populations in the absence of pesticide application.Thrips and leafhoppers, along with Orius, were recorded on summer vegetables and newly planted broad beans in autumn.In spring, the insects found on fruit trees were mainly thrips and limited numbers of Orius individuals.After the flowering period of the sampled trees, thrips and Orius shifted together to summer vegetables, indicating similar distribution patterns and population dynamics throughout the year, according to the flowering cycle of cultivated plants.
Thrips and Orius were collected primarily from the flowers of the sampled cultivated plants, except for broad beans, where few predators were found during the winter months, likely due to the lack of blooming.Orius nymphs and adults were observed gathering in the same flowers infested by thrips, depending on thrips density (Ramachandran et al. 2001;Reitz et al. 2003).The scarcity of thrips larvae in the sampled plants may be because the predators prefer thrips larvae, as they are less mobile and easier to prey on than adult thrips (Funderburk et al. 2000;Baez et al. 2004).Despite low Orius numbers in the sampled plants compared to previous studies in the area, the prey/predator ratios were low in many plants, suggesting that thrips, in particular, were at risk of being preyed upon.For instance, in field conditions in Florida, 40 thrips per predator were sufficient to keep the thrips population in control (Funderburk et al. 2000;Reitz et al. 2003).

Conclusions
The study reveals that O. laevigatus has been observed in both cold interior and warm regions of Turkey.The population dynamics of Orius and thrips were found to be influenced by the flowering patterns of the sampled crop plants.Orius populations showed fluctuations in response to changes in thrips populations.Notably, in regions where pesticide use is limited, Orius emerged as a significant biological factor in controlling thrips density, particularly in plants belonging to the Fabaceae family, such as broad beans.This indicates the potential of Orius as an important natural predator for managing thrips populations in agricultural settings without heavy reliance on pesticides.

Figure 1 -
Figure 1-Distributions of Orius species and prey groups (aphids, thrips and leafhoppers) on different arable crops, a, b: winter vegetable, c, d: fruit tree, e, f: summer vegetable, g, h: field crop

Figure 2 -
Figure 2-Seasonal densities of Orius spp.and different prey groups on different cultured plant groups; a: winter vegetables, b: fruit trees, c: summer vegetables and d: field crops.

Table 4 -Total average number of Orius spp. and pest insects (mean ± SE/20 plants) in winter vegetables in Balcalı in 2019-2020
a When the columns are examined, means with the same letter are statistically insignificant according to the Tukey HSD test (P>0.05).b Values in parentheses indicate the total number of individuals

Table 5 -Total average number of Orius spp. and pest insects (mean ± SE/20 plants) in summer vegetables in Balcalı in 2019- 2020
a When the columns are examined, means with the same letter are statistically insignificant according to the Tukey HSD test (P>0.05).b Values in parentheses indicate the total number of individuals

Table 6 -Total average number of Orius spp. and pest insects in fruits trees (mean ± SE /20 plants) in Balcalı in 2019-2020
When the columns are examined means with the same letter are statistically insignificant according to the Tukey HSD test (P>0.05).b: Values in parentheses indicate the total number of individuals.
a :

Table 7 -Total average number of Orius spp. and pest insects ((mean ± SE/20 plants) in field crops in Balcalı in 2019-2020
a When the columns are examined means with the same letter are statistically insignificant according to the Tukey HSD test (P>0.05).b Values in parentheses indicate the total number of individuals.