Impact of Biotic and Abiotic Factors on the Population Dynamics of Bemisia tabaci (Genn.) and Tetranychus urticae (Koch) Infested Tomato Plant Lycopersicon esculentum L. at kafr El sheikh Governorate

Egyptian Academic Journal of Biological Sciences is the official English language journal of the Egyptian Society for Biological Sciences, Department of Entomology, Faculty of Sciences Ain Shams University. Entomology Journal publishes original research papers and reviews from any entomological discipline or from directly allied fields in ecology, behavioral biology, physiology, biochemistry, development, genetics, systematics, morphology, evolution, control of insects, arachnids, and general entomology. www.eajbs.eg.net Provided for non-commercial research and education use. Not for reproduction, distribution or commercial use.


INTRODUCTION
Tomato Solanum lycopersicum Milles is the 3 rd most economically important vegetable crop after potato and onion.FAO classified Egypt as the 5 th country around the world (China, USA, India, Turkey and Egypt, respectively) (FAO, 2008) and the second around the Mediterranean countries in production and exportation of tomato.Tomato is a dietary source of vitamins especially A and C, minerals and fibres, which are important for human nutrition and health.Also, tomatoes are the richest source of lycopene, a phytochemical that protects cell from oxidants that have been linked to human cancer (Giovannuci, 1999 andMutanen et al., 2011).).Tomatoes are hosts of wide varieties of pests, between 100 and 200 species are reported to attack tomatoes worldwide (Lange and Bronson, 1981) such as Leafminer pests; Tuta absoluta (Meyrick) Phthotimaea operculella (Zeller) and Liriomyza Trifolii (Burgess), sap sucking pests; Bemsia tabaci Genn., Aphis gossypii Glov., Myzus persicae (Sulzer) Pseudococcus solenopsis Tinsley, Tetranychus urticae Koch and Aculops lycopersici Massee and army worms; Helicovepra zea (Bod), Agrotis ipsilon (Haf) and spodoptera littoralis (Biosd).All these pests attack all tomato plant parts causing directly reduction in growth or death feeding or indirectly by transmission of many vectoring diseases Shaheen (1977) Gravena (1984) Kirk et al. (1993) Obopile et al. (2008) Harizanova et al (2009) Erler et al. (2010) Pokle and Abhishek (2016).
The level of infestation depends on the temperature and weather, and thus varies from year to year.It also depends on the plant species and cultivar in question (Kielkiewicz and Tomczyk, 1987;Labanowska, 1992 andSkorupska, 2004).
This study aimed to evaluate the population fluctuation of certain pests infesting tomato plant Lycopersicon esculentum L. and the combined effects of principle abiotic & biotic factors on the population dynamics of these pests.

MATERIALS AND METHODS
Experiments were carried out on tomato plants at Mahalet Abo-Ali village, Desok, Kafr El-sheikh governorate during two successive years of plantations (2016 and 2017) of tomato plants.Alissa variety (genotype) was cultivated in spring plantation.Inspection was started 15 days after plantation of tomato seedlings.Sample content 10 leaves from three levels of plants (lower, mid and upper) (50 leaflets/replicate); four replicates were found.Samples were taken early in morning between 8 and 10 a.m. and transferred to the laboratory in plastic bags, the upper and lower surface of the leaflets were extremely examined by the aid of stereomicroscope in the same day for examination and identify the collected pests and natural enemies.
To study the effect of abiotic factor (Maximum temperature, Minimum temp.and Mean relative humidity) and biotic factors (natural enemies) on population dynamics of these pests, the simple correlation (r) and the partial regression (b) were calculated between each of the above mentioned factors (Xs) and the weekly mean numbers of these pests.

Population Fluctuations of Certain Pests Infesting Tomato Plant Lycopersicon Esculentum L. : Spring Plantation of 2016&2017 Season: 1. Bemisia tabaci (Genn.):
The infestation of tomato plants with B. tabaci was expressed as the number of eggs laid, number of nymphs and pupae/leaf, recorded at weekly intervals, applying the plant sample counting technique.Population density in the first season 2016 was higher than that recorded in the second season 2017 with general mean numbers 15.78 and 9.39/ leaf, respectively.Tables (1&2) Eggs: The data in Table 1 showed mean number of B. tabaci eggs on tomato plants during the first season was higher than that was recorded during the second season with mean numbers 4.71 and 3.11 eggs /leaf for the first and second season, respectively (2016&2017).

st season 2016:
Table 1 revealed that the population density of B. tabaci eggs was appeared with fewer mean number on 3 rd week of March after that fluctuated to increase gradually and recorded two peaks on 2 nd and 4 th week of May with mean numbers of population density 11.4 and 20.1 eggs / leaf, respectively.Data in Table , (5) showed insignificant positive effects to maximum & minimum temperature, C. undecimpunctata, S. corollae, Amblyseius swirskii and N. tenuis on the seasonal fluctuations of B. tabaci eggs whereas, "r" values were 0.43, 0.47, 0.36, 0.27, 0.36 and 0.43, respectively.The mean percentage of relative humidity had significant negative effect whereas, "r" value was -0.63.The combined effect of these factors as a group (E.V.) showed responsible of 62% on the population dynamics of B. tabaci eggs.

nd season 2017:
Table 2 showed that the population density of B. tabaci eggs started to appear in few mean numbers during first four inspections at end of March then increased gradually to record two peaks on 2 nd and 4 th week of May with mean numbers of population density 9 and 12.2 eggs/ leaf for the two peaks, respectively.Data in Table , (5) showed insignificant positive effects to max.& min.temp., R. H. and S. corollae whereas, "r" values were 0.54, 0.50, 0.44 and 0.39, respectively.The mean of C. undecimpunctata had significant positive effect whereas; "r" value was 0.60.The mean of Amblyseius swirskii and N. tenuis had significant negative effect on the seasonal fluctuations of B. tabaci eggs whereas, "r" values were -0.75 and -0.69, respectively.The combined effect of these factors as a group (E.V.) showed responsible of 86% on the population dynamics of B. tabaci eggs.

Nymphs:
Data in Table , 1&2 showed that the mean number of B. tabaci nymphs on tomato plants during the first season was higher than that was recorded during the second season with general mean numbers 6.95 and 4.11 nymphs / leaf for the first and second season, respectively.1 st season 2016: The population density of B. tabaci nymph was absent in first five inspections during March and appeared with fewer mean number in the 1 st week of April then fluctuated to increase gradually and recorded a higher number on 1 st week of June with mean number 20.3 nymph / leaf.Data in Table , (5) showed significant positive effects to maximum & minimum temperature, C. undecimpunctata, N. tenuis and C. carnea on the seasonal fluctuations of B. tabaci nymphs whereas, "r" values were 0.79, 0.74, 0.60, 0.62 and 0.69, respectively.The mean percentage of relative humidity had significant negative effect, whereas "r" value was -0.62.Partial regression analysis illustrated insignificant positive relation between S. corollae and Amblyseius swirskii B. tabaci nymphs whereas, "r" values were 0.24 and 0.36, respectively.The combined effect of these factors as a group (E.V.) showed responsible of 94% on the population dynamics of B. tabaci nymphs.

nd season 2017:
The population density of B. tabaci nymphs absent during first seven inspections then increased gradually to recorded highest peak on 1 st week June with mean numbers of population density 14.8 nymph/ leaf for the two peaks, respectively.Data in Table , (5) the partial regression analysis demonstrated insignificant positive effect of weather factors (max. & min. temp. and R. H.). C. undecimpunctata, whereas "r" value were 0.24, 0.47, 0.48 and 0.31, respectively and insignificant negative effect of S. corollae and Amblyseius swirskii whereas, "r" value -0.01 and -0.54, respectively.The results showed that N. tenuis and C. carnea had significant negative effect (r = -0.64 and -0.60, respectively) on the B. tabaci nymphs.The combined effect of these factors as a group (E.V.) showed responsible of 77% on the population dynamics of B. tabaci nymphs.
Also the results close to the results of Ahmed (1990) who reported that, the initial occurrence of B. tabaci took place on July 12 th on H. sabdariffa during 1986-1987, population increases gradually reaching a light peak on September 6 th .Insect population still low until the end of September, then increased rapidly to reach its peak on October 18 th .Afterward the population declined gradually until the end of the season on December.The accordance with results of Lin et al. (2002) also indicated the population of Bemisia tabaci increased continually and up to a peak at around August, then gradually decreased.Also these results are in agreement with those obtained by EI-Sayed et al. (1991) who indicated that bean leaves showed high rate of infestation with B. tabaci immature stages in all plantations (early summer, summer and winter).They also mentioned that periods of high infestation rates were in August and September for summer plantation, October and November for winter plantation and July and August for the early summer plantation.Meena, et al. (2013) revealed that the whitefly, Bemisia tabaci (Genn.)appeared in the third week of July and continue up to fourth week of November.The population increased gradually and touched its peak with mean population of 6.9 whiteflies / 3leaves /plant in first week of September during 2006-07 while, the population of whitefly touched its peak with 6.7 whiteflies 3 leaves /plant in the second week of September during 2007-08.Thereafter, the population decline gradually and reached up to 1.1 and 1.2 whiteflies/3 leaves /plant.The findings confirmed with the results obtained by Shanab and Awad-Allah (1982) who reported that the whitefly on tomato appeared in May and reached to its peak during July to October.He also reported that the higher temperature declined the pest incidence, whereas scattered rain and high relative humidity favoured the population build up.However Farman et al. (2004) observed that the whitefly infestation started on brinjal in mid of May and reached to its peak in July.While, Bharadia and Patel (2005) reported maximum population of whitefly in the 4 th week of October.This might be due to variable climatic conditions of that particular region and time of cultivation that particular crop.Lal and Pillai (1982) mentioned that, the correlation between B. tabaci population and max.temp.was positive and significant correlation, it increased with the increase of max.temp Tetranychus urticae Koch.

2.Tetranychus urticae Koch.
The infestation of tomato plants with T. urticae was expressed as the number of eggs laid and movable stage (immature and adult)/leaf recorded at weekly intervals.The result showed that, the seasonal general mean number of T. urticae on tomato plants during the first season 2016 higher than the second season 2017 season 2.28 and 1.88, respectively and with mean numbers of 0.67 eggs &1.61 movable stage / leaf and 0.59 eggs &1.3 movable stage / leaf for season 2016&2017, respectively.

Table (3&4) Eggs: 1 st season 2016:
Data in Table , (3) indicated that, the mean number of T. urticae eggs was absent in the first seven inspections.It increased above to record 0.3 eggs / plant on 3 rd week of April.Then, the mean increased gradually by the time at the end of the season to record two peaks on 2 nd week of May and1 st week of June with mean numbers of population density 2 and 2.2 / leaf, respectively.Data in Table, (6) cleared that max.& min temp., C. undecimpunctata and Amblyseius swirskii had highly significant positive effects on seasonal fluctuation of T. Urticae eggs whereas, "r" values were 0.75, 0.85, 0.89 and 0.77, respectively.The mean percentage of R.H. had significant negative effect whereas, "r" value was -0.77.The percentage of explained variances (E.V.) for the three selected ecological factors and C. undecimpunctata & Amblyseius swirskii was 84 % effect on the dynamics of T. urticae eggs.The 2 nd season 2017: Table (4) indicated that, the individuals of T. urticae eggs not appeared in six inspections.The mean numbers of T. urticae began to appear 2 nd week of April and recorded two peaks on 2 nd week of May and 1 st week of June with mean numbers of population density 1.2 and 2.5 / leaf, respectively.Data in Table, (6) cleared that the mean percentage of Min.Temp., RH and C. undecimpunctata had significant negative effect whereas, "r" values were -0.63, -0.75 and -0.60, respectively, but A. californicus had significant positive effect (r = 0.75).The results showed that the max.temp.had insignificant positive effect whereas, "r" value was (-0.50).The combined effect (E.V.) of these factors on T. urticae eggs showed that these factors were responsible as a group for 77% effect.

Movable stages:
The population densities of T. urticae movable stages were higher abundance but not much in the first season 2016 than that recorded in the second season 2017 with general mean1.61and 1.3/ leaf, respectively.Data in Table, (3&4) indicated that, the individuals of T. urticae movable stages not appeared in six inspections in both season 2016&2017.In the season 2016 & 2017, the population had two peaks in the 2 nd week of May and 1 st week of June, respectively with mean number 4.8& 6.7 and 2.8&5.1/leaf, respectively.1 st season 2016: Data in Table ( 6) indicated that significant negative effect for R.H. on the seasonal fluctuations of T. urticae movable stages whereas, "r" value was -0.68.The results showed highly significant positive effects for max.& min.temp., C. undecimpunctata and A. californicus on the seasonal fluctuations of T. urticae movable stages, whereas "r" values were 0.85, 0.86, 0.89 and 0.68, respectively.The combined effect (E.V.) of these factors on T. urticae movable stages showed that these factors were responsible as a group for 84% effects on the population dynamics of T. urticae .The results revealed that max.& min.temp., R.H. and C. undecimpunctata had significant negative effects on seasonal fluctuation of movable stages of T. urticae whereas "r" values were -0.85, -0.64, -0.61 and -0.60, respectively.The partial regression analysis demonstrated a highly significant positive effect of A. californicus on T. urticae population (r.= 0.94).The E.V. percentage recorded 98%.Table , (6) The effectiveness of weather factors and the predators on the population density of sucking pests on different crops have been studied by several researchers (Ali and Rizk, 1980;Liu, 1993;Koleva et al., 1996;Abou-Elhagag and Abdel-Hafez, 1998).In addition, Dent (1991) reported that environmental conditions at any location influence the seasonal phenology of pest numbers, the number of generations and the level of pest abundance.
These regard was in agreement with Hollingsworth and Berry (1982) mentioned that, population of T. urticae Koch declined abruptly on peppermint after reaching a peak density during late June.Yasin (1997) added that there were many different factors effect on the population density of phytophagous mites other than, (predaceous mites and environmental conditions) factors.Ghallab (2001) found that the population of T. urticae was a significant increase between April and June.Shereef et al. (1980) recorded that temperature but not humidity was positively and significantly correlated with pest mite numbers.Results not agreement Atef and Wael (2013) recorded that the percentage of explained variance of abiotic factors (minimum-maximum temperatures and relative humidity) and biotic factors (predators and parasitism percentages) altogether in the population densities of B. tabaci and T. urticae in the second season were the greater percentage values as 63.2%, and 68.3%, respectively, compared to the first season (45.5% and 69.8% respectively), but the disagreement from , date of plantation which different from governorate to others and different position so differences climatic factors.

Table ( 1
): Weekly mean numbers of Bemisia tabaci during spring plantation / leaf, its associated natural enemies and ecological factors at kafr El sheikh governorate in 2016 season

Table ( 2
): Weekly mean numbers of Bemisia tabaci during spring plantation / leaf, its associated natural enemies and ecological factors at kafr El sheikh governorate in 2017 season

Table ( 3
): Weekly mean numbers of Tetranychus urticae during spring plantation / leaf, its associated natural enemies and some ecological factors at kafr El sheikh governorate in 2016 season

Table ( 4
): Weekly mean numbers of Tetranychus urticae during spring plantation / leaf, its associated natural enemies and some ecological factors at kafr El sheikh governorate in 2017 season Mean

Table ( 5
): Simple correlation and partial regression values of the three main weather factors and biotic factors on B. tabaci and corresponding percentage of explained variance on tomato spring plantation at kafr El sheikh governorate during 2016 and 2017 seasons.

Table ( 6
): Simple correlation and partial regression values of the three main weather factors and biotic factors on T.urticae and corresponding percentage of explained variance on tomato spring plantation at kafr El sheikh governorate during 2016 and 2017 seasons.