INTRODUCTION

           Common bean (Phaseolus vulgaris L.) is an annual leguminous plant that belongs to the family Leguminoaceae, with pinnately compound trifoliate large leaves. Common bean has high protein content and is a good source of energy and provides folic acid, dietary fiber and complex carbohydrates Filella, and Penuelas, (1994). Common beans (P. vulgaris L.) contribute up to 57% of recommended dietary protein and 23% of energy to the nutrition of African people (Shellie and Hosfield, 1991). In African fields, numerous insect pests attack all parts of common bean during all stages of growth, from seedling to stored product (Abate, 1984; Abate, 1993; Singh and Emden, 1979).

          In Egypt Common bean usually receives different insect pests that cause considerable damage in both quantity and quality of pods, viz, aphids, leaf miner, leafhoppers, thirps and red spider mite which causes serious damage to plant and subsequently yield (Schuster and Everett, 1983; Parrella et al., 1985; Abd El-Gawwad, 2008 and Saleh, 2011, askar, et. al, 2013, Amaar et al., 2014). The red spider mite (Acari: Tetranychidae), Tetrunychus cinnabarinus, is widely distributed in Africa. Although yield-loss data are not available, this pest is considered a major pest of common bean (Giga, 1989). Of the aphids (Homoptera: Aphididae), the black bean aphid, Aphis fabae, is the principal aphid pest directly damaging beans in Africa (Remaudiere  et. al., 1985 ). Yield loss due to aphid is estimated to 37%, (Munyasa, 2013). It is widely distributed in bean-producing regions. Although it is considered a minor pest in many countries (Bate, 1988; Giga, 1989), it has recently achieved major pest status in some countries. For example, it is the most important bean pest in Sudan, where its damage causes yield losses of 14-86%, depending on the season (Salifu, 1986). The onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is the most damaging Thysanoptera species, insect is an extremely polyphagous species and a serious pest of a wide range of economically important crops including soybean in many parts of the world (Duchovskiene, 2006; Trdan et al., 2007, Amin, et. al., 2010).  This study aimed to evaluate the seasonal abundance and the population fluctuation of certain pests infesting green bean (Phaseolus vulgaris)., number of pests on the plant, the combined effects of principle climatic and plant varietiy factors on the pest density under the field conditions.

MATERIALS AND METHODS

               The present study was carried out at El Delengat district, El-Beheira Governorate, Egypt, in summer and winter seasons (plantations) of common bean plants replicated in two successive years of 2018 and 2019. A general survey was conducted in the common bean plants at El Delengat district during the two growing seasons of 2018 and 2019 (summer and winter plantation). Investigations were made on leaves, stems and pods for insects and mites. Insects’ samples were identified in the field and the laboratory using a hand lens and a microscope. The insects and mites were recorded as main and minor pests according to their severity.

1-    Population fluctuation of the major pests infesting common bean plants:

Field study was carried out at a private farm at El Delengat district, El-Beheira Governorate, Egypt during two successive seasons, of 2018 and 2019. The experimental area was one feddan cultivated with four different cultivars in mid-February and mid- September for both seasons. All recommended agricultural practices were followed during the growing season without insecticide applications. Sampling procedures were started two weeks ago after sowing and continued at weekly intervals until the harvest time. The plants were visually examined in the field with counting the insect pests. Samples collection started after about two weeks from planting and continued until the harvesting time. At weekly intervals, ten leaves from each replicate were picked out and each put in a paper bag early in the morning from three different heights of the plant. Bags were transferred to the laboratory for examination on the same day using a stereomicroscope. The insect stages were the nymphs of Bemisia tabaci, nymphs and adults of Empoasca dispiens, Aphis gossypii and Thrips tabaci larvae of Lyriomyza spp, and all stages of the red mites, Tetranychus urticae were counted and recorded.

2-    Susceptibility of common bean varieties to infestation with the sucking insect pests:

An area of about 3200 m2 (divided into 16 blocks of about 200 m2 /block) was cultivated with the four common bean varieties (Nebraska, Karnak, Giza 6 and Giza 3). Each block was separated from the other by borders (uncultivated two rows). The seeds were obtained from the Ministry of Agriculture, Egypt, and transplanted in the mid-February as a summer plantation and mid-September as a winter plantation. Four replicates of each variety were transplanted and evaluated in complete randomized design. All regular recommended agricultural practices were followed without any pesticide treatments during the whole period of the experiment. Sampling started 15 days post-planting dates, whereas 10 leaves from each replicate were collected at weekly interval up to the end of the season. The leaves were picked manually, placed in paper bags, and transferred to the laboratory for examination using a stereomicroscope to determine the number of adults, nymphs, larvae tunnels leaf and the number of immature stages/leaf of the tested plants.

Data Analysis.

Data were analyzed using (SAS Institute, 1988) to test standard error between treatments (p < .005) and estimate LSD among treatments.  

RESULTS AND DISCUSSION

1.       Population density of the sucking pests attacked common bean varieties during summer and winter plantation in season 2018.

The cotton thrips, Thrips tabaci:

Common bean varieties were received different numbers of insect and mite pests during the study period. As shown in table (1) T. tabaci (nymphs and adults) are recorded in all varieties with highest population on Npraska variety but in a few numbers for Giza3 and giza6.  In summer plantation in season 2018 and 2019 common bean varieties attacked by T. tabaci with high numbers than winter plantation. The average number of T. tabaci was ranged between 20 – 60 individuals / 10 leaves. In addition, average number of insects increased on common bean in winter and summer plantation 2019 than the population in year 2018. described that dry weather with abstemiously high temperature can be the increasing factor for thrips population while wet season with moderately high relative humidity affect the thrips population. Duchovskiene (2006) evaluate two leek varieties against onion thrips, T. tabaci infestation. Also, he reported that, onion thrips infested both the varieties but 100% infestation was found in the next following year. He observed the population of thrips throughout the season with peak in the month of July and reaches 3.4 thrips per plant at the end of growing season.

Table 1. Population density of Thrips tabaci. on common bean varieties during season 2018 and 2019

as summer and winter plantation

The potato leafhopper, Empoasca dispiens

Seasonal average of E. dispiens insect density was counted and recorded on four varieties of common bean in years 2018 and 2019 (table2).   In summer plantation common bean varieties attack by high number of insects compared with winter plantation. E. dispiens density not increased above 60 individual insect/ leaf and not decreased than three insects on one leaf spatial in winter plantation. On the other hand, E. dispiens preferred Npraska variety and activation its population in summer plantation while the lowest numbers were recorded on Giza3 variety in summer plantation. The winter plantation of all varieties recorded a fewer numbers (8 insects/10 leaves) under field conditions. The common bean, P. vulgaris (L.) can be affected on E. dispiens insect density so our data was nearly agreement with Naseri et al. (2009) how determined the population density and spatial distribution pattern of Empoasca decipiens Paoli were in Tehran area, Iran, during 2004-2005 on four species of common bean Phaseolus vulgaris (L.) var. Talash, lima bean P. lunatus (L.) Savi ex Hassk. var. Sadaf, rice bean P. calcaratus Roxb. var. Goli and cowpea Vigna sinensis (L.) var. Parastoo. The highest and lower mean population densities of E. decipiens per leaf were observed on Parastoo cowpea (18.85 in 2004 and 29.94 in 2005) and Talash common bean (1.08 in 2004 and 0.37 in 2005), respectively in summer plantation.

Table. 2. Population density of Empoasca dispiens. On common bean varieties during season 2018 and 2019 as summer and winter plantation

The cotton whitefly, Bemisia tabaci

                      As shown in table (3), Bemisia tabaci attacked the common bean varieties during the season 2018 and 2019 in summer and winter plantation, forever Npraska varity received the highest numbers while Giza3 attacked by the lowest number of insects. Data also reflected that B. tabaci was activated more in winter compared with the other insects. On summer plantation B. tabaci numbers ranged between 120- 260 individuals / 10 leaves during the study period. Jha and Varkkey (2018) reviewing a paper to assess the effect of different environmental factor on the population of whitefly B. tabaci and found that different environmental factors affect insect population in different extent even variation was found in same calamitic factors in different location or different time and its distribution.

Table. 3. Population density of Bemisia tabaci. On common bean varieties during season 2018 and 2019 as summer and winter plantation

The cotton aphid, Aphis gossypii.

The data in table (4), showes that, A. gossypii was more active on Krnak variety than all common bean varieties and increased its density till recorded 23 and 24 insects/ 10 leaves in summer and winter 2018 respectably. The density decreased on Giza3 recorded the lowest number in winter 2019. On the other hand in 2018,  A. gossypii recorded with high number in summer plantation of all varieties accepted Krnok variety.

Table. 4. Population density of Aphis gossypii. On common bean varieties during season 2018 and 2019 as summer and winter plantations

Lyriomyza leafminers

                     Numbers of larvae of Lyriomyza spp, was recorded in average numbers on common bean varieties, no significant variation were observed between the different varieties (as shown in table (5). Npraska variety, reflected the performance of Lyriomyza spp naturally occurred and recorded the highs number mor than 16 insect/10 leaves  in summer 2019 but in summer 2018 Lyriomyza spp density decreased recording less than 11 individuals/10 leaves on Giza6 variety. On fact of year 2018 and 2019, Lyriomyza spp recorded active in the summer than in the winter.

Table 5. Population density of Lyriomyza spp. On common bean varieties during season 2018 and 2019 in both summer and winter plantation

The red mite, Tetranychus urticae:

          The means of T. urticae were presented in common bean varieties and recorded with high number (table 6).  The data reflected that, T. urticae preferred that the Npraska variety then giza6 than Krnok and giza3. The average natural occurrence was active in summer 2018 than all seasons and recorded the highest density on Npraska. The lowest occurrence of T. urticae recorded in winter at all time of study period. Abd EI-Gawwad (2004) showed that the population density of T. urticae was the main Tetranychidae mite infesting common bean leaves.

Table 6. Population density of Tetranychus urticae  On common bean varieties during season 2018 and 2019 as summer and winter plantation

2.Susceptibility of common bean varieties caused by sucking insect pest's density and distribution.

              Common bean, Phaseolus vulgaris varieties received several pests as shown in Table (7). The date collected and calculated in average number of all pests on each of plant varieties to estimated the effect on pest density. Giza3 variety was received the lowest number of A. gossypii and Lyriomyza spp. T. tabaci, recorded with the highest number of 31.38 / 10 leaves on giza3 variety. Meanwhile in case of Giza6 variety, the population of all pests was increased gradually than the population of pests on giza3.  B. tabaci was recorded with highest average number of 113.38 individual / 10 leaves but Lyriomyza spp recorded the lowest average number of 7.95 on giza6. All pests recorded with the highest numbers on Npraska the population increased till recorded the highest average number of 197.47 for B. tabaci. On the fact of Krnak variety, Lyriomyza spp was recorded with a few numbers but the number increased in all pests recorded the highest number in B. tabaci. Sedaratian, et al. (2010) studied Population density and distribution of Thrips tabaci Lindeman on seven soybean varieties (Williams, Tellar, Sahar, Dpx, L17, Sari and Zane) and one genotype (Ks3494) in Tehran region, during 2007. They also recorded that, the highest population density of the thrips per leaf was recorded on varieties, Dpx and on Ks3494 (0.81±0.05 and 0.80±0.05, respectively). But the lowest population density was observed on L17 and Tellar (0.62±0.04 and 0.64±0.03, respectively).

Table 7. Average seasonal number of common bean pests attacked different varieties of Common bean, P. vulgaris.

Means followed by the same letter(s) within the same column are nonsignificantly different (P ≤ 0.05)

3.Effect of plantation dates on density of the sucking pests and its distribution.

During the season of 2018 and 2019, data collected in the summer and winter season as shown in table (8). Six species sucking insect pests recorded on common bean varieties at all time of the season. Data in Table (8), showed that, numbers of T. tabaci were significantly variation between the two plantation in each year and recorded the highest number 45.87 in summer 2019 but the lowest number was 32.25 in winter 2018.  Bemisia tabaci recorded with the highest number compared with all pests to record 161.07 individual in summer 2019. The cotton aphid, A. gossypii recorded the lowest numbers in summer and winter season of 2018 and 2019 (Table 2). In addition, E. dispiens recorded the lowest number in winter plantation of season 2019 but in summer 2019 it recorded the highest numbers with 41.42 individual insects. In the fact of Lyriomyza spp, the pest recorded with highest numbers (12.97) during the 2019. On the other way of insect, the red mites, Tetranychus urticae was recorded at all time with significant deferent average numbers between 10.63 and 36.76 individual mite. In the general Bemisia tabaci, recorded with the highest average number of 161.07 in summer 2019 but E. dispiens recorded with the lowest number of 3.69 in winter 2019. Data in table (8) reflected that, all pests recorded with high number in the summer compared with winter plantation. The present research the observations of Nayak et al. (2004) who reported that the minimum temperature was positively correlated with B. tabaci and so in agreement with those obtained by Younes et al. (2001) who detected significant negative correlation between the tested weather factors. Jesus et al. (2009) noted a negative and non-significant linear correlation between average temperatures of whitefly number.

                     Mastoi, et al. (2013) carried out studies on varietal resistance of okra against whitefly (B. tabaci) and fruit borer (Earias spp) at Entomology department, on seeds of six varieties namely, Sabzpari, Super green, Noori-786, Sharmeeli, Pusa sawani, and Ambak which sown on April 19, 2004 in a randomized complete block design (RCBD) with four replications. They also recorded the observations on pest infestation started in the second week of May, 2004 and continued till harvest of the crop.  Observations were recorded at weekly intervals from five plants selected at random per treatment. The results revealed that the population of whitefly varied significantly (P < 0.05) on different dates and varieties. Okra variety Sabzpari harbored the minimum pest (3.17 insects/leaf) population, while Noori-786 harbored the maximum (4.46 insects/leaf) population. El-Saidy et al. (2012) reported that common bean cultivar Hama was more susceptible than Polista cultivar. The authors found significant differences between the two kidney bean cultivars for B. tabaci the susceptibility of the two cultivars to these insect infestations was also varied during the two studied seasons. Therefore, plant breeders must be study characters of this cultivar in more details and transferred the desirable one’s into the other new produced cowpea cultivars. Amal et. al, (2018) The number of white flies infested the three cultivars was statistically significant during 2013 and 2014 summer and winter cropping seasons. In summer 2013 cropping season, the cultivars Copy and Polesta were the most susceptible varieties while, the cultivar Manga was less susceptible one. In winter 2013 cropping season, the cultivars Copy and Manga were more susceptible to whitefly infestation than Polesta cultivar.

Table 8. Average number of common bean pests in summer and winter seasons of the two successive years 2018 and 2019.

Means followed by the same letter(s) within the same column are nonsignificantly different (P ≤ 0.05)