Biological control of Thrips tabaci ( lind . ) and Aphis gossypii ( Glover ) using different predatory Phytoseiid mites and the biocide vertimec on Eggplant at Behaira Governorate

Three predatory mite species, Phytoseiulus persimilis (Athias-Henriot), Neoseiulus cucumeris (Oudemans) and Neoseiulus californicus (McGregor) and biocide denatol were evaluated as potential biological control agents for Thrips tabaci (lind.) and Aphis gossypii (Glover) on two eggplant cultivars in open field at Behaira Governorate. Field releases of different numbers of mites per plant during 2008 season showed that Neoseiulus cucumeris reduced the number of thrips and aphid in two cultivares of eggplant. We found that earlier releases (averages from 2025 individuals / leaf) resulted in reducing thrips and aphids numbers and lowering their damage. We coclude that inoculative release of Neoseiulus cucumeris one of a potentially useful thrips and aphids management strategy, but needs improvements in release timing and strategy will be required to provide commercially acceptable control.


INTRODUCTION
The importance of cultivating vegetables has extensively increased year after year; due to their economic value.However, most of these agricultural crops are subjected to attack by many piercing sucking insect pests such as aphids, whiteflies and thrips (El-Khawas, 2005).The cotton aphid, (Aphis gossypii Glov.) is one of the most widespread species of aphids, and displays a large range of host-plants, covering very different families.This impressive behavior made it a major pest of numerous crops (Fuchsberg et al., 2007).
The eggplant (Solanum melongena) is a tropical and subtropical plant growing in high temperatures which can produce up to 15 kg of fruit/plant (Filgueira, 2000).Among pests of this crop, the aphids, Aphis gossypii (Glover) (Homoptera: Aphididae) and the thrips, Thrips tabaci Lind.(Thysanoptera: Thripidae) (Etienne et al., 1990;Hosoda et al., 1993 andKajita et al., 1996) are very important.Eggplants when severely attacked by thrips present leaves with small size and silver appearance and deformed fruits (Kawai, 1986;Sakimura et al., 1986 andGallo et al., 2002).Aphid attack causes severe damage to eggplant by feeding on sap, rolling leaves, and secreting honeydew (Hosoda et al., 1993 andGallo et al., 2002).In different crops, T. tabaci and A. gossypii have been controlled primarily with insecticides (Hosoda et al., 1993 andKajita et al., 1996), but the extensive use of these pesticides can promote negative impacts on human health and on ecosystems, besides reducing the number of species and density of natural enemies, developing resistance and increasing production costs (Etienne et al., 1990;Nagai, 1990;Hosoda et al., 1993 andKajita et al., 1996).To reduce these problems, it is necessary to minimize the chemical control by replacement pesticides by using biocides and releasing predatory mites (El-Saiedy, 2003;El-Saiedy and Romeih, 2007).So this work aimed to evaluate the efficiency of three predatory mite species Phytoseiulus persimilis Athias-Henriot, Neoseiulus cucumeris Oudemans and Neoseiulus californicus McGregor and biocide vertimec in controlling Thrips tabaci (lind.)and Aphis gossypii (Glover) on two eggplant cultivars in open field at Behaira Governorate.Also to get quality and quantity of crop yields and get food without residual of pesticides.

Experimental design:
Four experimental treatments were conducted.Each treatment was replicated three times.The replicate consisted of four lines area for each 0.5 meters.width x 10 meters.long.The experimental design was complete randomized blocks.Two cultivars of eggplant were chosen in this work, Baladi and black baity.The experiment were carried out at Behaira Governorate from May to August 2008.Sampling Procedure: Samples were taken weekly for the four treatments on the two cultivars.Twenty leaves were randomly collected, kept into polyethylene bags, tightly closed with rubber bands, then kept in an ice box and transferred to laboratory for examination using a stereomicroscope.Adults of Thrips tabaci , Aphis gossypii and predatory mites were counted and recorded.

Control studies:
To study the effect of different types of biocontrol agents, four treatments were Carried out on two cultivars of eggplant using three predacious mites P. persimilis, N. cucumeris, N. Californicus and biocide Denatol.These forementioned experiments compared with control

Rearing of Tetranychus urticae:
Rearing of Tetranychus urticae was carried on potted beans phaseolus vulgaris L. in an isolated compartment 1.5 x 2.0 m. in experimental glasshouse.The strain of T. urticae was originated from infested leaves of Castor oil collected at Gizza Governorate .

Rearing of the predatory mites:
The predatory mites P. Persimilis, N. cucumeris and N. Californicus were reared using methods modified from ( McMurtry and Scriven 1965), large plastic boxes 26 x 15 x10 cm. were used , cotton pad were placed in the middle of each box, leaving a space provided with water as a barrier to prevent predatory mites from escaping .Excised bean leaves highly infested with T. urticae were Provided every day as food source for mites and plastic boxes were kept in an incubator at 25 C 2 and 70 10 % R.H.

Mass rearing of the predatory mites
For mass rearing of the predatory mites, Phaseolus.vulgaris was served as host plant which reared in a small glasshouse divided into three isolated parts (a) Clean bean Plants, (b) Clean plants at stage of 12 leaves infested with T. urticae (c) bean plants infested of five gravid females of the predatory mites for every plant (El-Saiedy, 2003 andEl-Saiedy andRomeih, 2007).Temperature in the glasshouse ranged from 18 to 25 C and relative humidity from 50 -60% R.H.

Releasing of the Predatory mites
Mites releasing started as the population density of Thrips tabaci and Aphis gossypii build upon eggplant i.e at the beginning of invasion.Samples averages from 20-25 individuals / leaf.The ratio between predator and prey ranged between 1: 7 to 1:5, respectively.The required population size of the predatory mite individuals were calculated according to the following formula.
Released number = Total number of Thrips and Aphis /experimental area Proposed predator /prey percentage Bean leaves with predator mites were transferred in ice -box (10 3 c) to eggplant fields.Distribution was carried out on infested eggplant plants.Repetition of releasing samples were taken weekly, Thrips tabaci and Aphis gossypii stages were calculated as well as the predatory mites .

Statistical analysis
The obtained data of mite numbers and yield quantity were subjected to the analysis of variance test (ANOVA) with mean separation at 5% level of significance according to the method o (Snedecor and Cocharn, 1967).Percentage reduction of the mite population were calculated according to the equation of (Henderson and Tilton, 1955) and ( Fleming and Retnakaran, 1985) Reduction = 100 after control x before Treatmernt before control x after Treatment 1 x

RESULTS AND DISCUSSION
Data presented in tables 1 and 2 show that the release of three predatory mites Phytoseiulus persimilis, Neoseiulus cucumeris and Neoseiulus californicus and spraying of vertimec on two eggplant cultivars on the 14 th may when the main plant sucking insects Thrips tabaci number ranged from 45.14 to 46.40 and 29.98 to 31.0 individual / leaf (Table 1) on Black baity and Baldi eggplant cultivars, respectively.While none Aphis gossypii individual / leaf (Table 2) on the two eggplant cultivars, Black baity and Baldi, respectively.
From obtained results obtained, it is generally noticed that T2 (Neoseiulus cucumeris) obviously redcued the population density of T. tabaci and A. gossypii on both eggplant cultivars and the total average of T. tabaci and A. gossypii / leaf were 5.15 & 4.57 and 0.78 & 1.02, respectively, (Tables 1 and 2 ) on Black baity and Baldi cultivars, respectively, followed by T4 ( vertimec) where the total average of T. tabaci and A. gossypii / leaf were 6.85 & 4.61 and 1.60 & 1.93, respectively, (Tables 1 and  2 ) on Black baity and Baldi cultivars, respectively.Statistical analysis showed that there was no significant differences between treatments, but there are significant between treatment and control.Also data presented in Tables 3 and 4 show percentage reduction as a result of releasing the three predatory mites and spraying biocide vertimec.T2 (Neoseiulus cucumeris) gave the highest percentage reduction of T. tabaci (86.80 and 90.65) on the two cultivars, Black baity and Baldi, respectively, followed by T4 (vertimec), T3 (Neoseiulus californicus and T1 (Phytoseiulus persimilis) on Black baity Cultivar as well as Baldi cultivar, where percentages reduction were (82.22, 65.89 and 56. 35) and (88.54, 58.14 and 56.70), respectively, Table 3.Here again with respect to the Aphis gossypii Glover, as the same T2= Neoseiulus cucumeris gave the highest percentage reduction (95.09 and 97.64) on the two cultivars, Black baity and Baldi, respectively, followed by T4 Vertimec , (93.83 & 87.66 ), T1= Phytoseiulus persimilis (47.67 & 56.73) and T3 = Neoseiulus californicus (40.04 & 49.17), respectively, Table 4.These results agree with those of Gillespie (1989); Hansen (1989); Ader (1990); Castagnoli et al. (1990); Jarosik and Pliva (1995); Courcy -Williams ( 2001) and Sengonca et al. (2004).T1= Phytoseiulus persimilis; T2= Neoseiulus cucumeris; T3 = Neoseiulus californicus and T4 = Vertimec.There is no significant between the same letters.Regarding weekly mean number of three predatory mites after their release in the field, Table 5 showed that the total average numbers of the three released predators on Black baity cultivar were 1.80, 2.29 and 2.19 individulas / leaf for Phytoseiulus persimilis, Neoseiulus cucumeris and Neoseiulus californicus, respectively.On the other hand, Baldi cultivar, reached the highest number at the 3 rd .and 4 th .weeks after release the three predatory mites.Three weeks after release the P. persimilis and N. californicus gave the highest recorded (4.13 & 8.33 individuals / leaf for two above mentioned predators, receptivity, the over all mean of Phytoseiulus persimilis , Neoseiulus cucumeris and Neoseiulus were 1.21, 2.26 and 1.70 individual / leaf, respectively.
In these experiments Neoseiulus cucumeris has proved to be a promising candidate for biological control of Thrips tabaci and Aphis gossypii compared with of Phytoseiulus persimilis and Neoseiulus californicus

Biological control of T. tabaci and A. gossypii using different predatory Phytoseiid mites 17Table ( 2
): Number of Aphis gossypii / leaf on two cultivars of eggplant affected by releasing three predatory mites and sprying with vertimec at Behaira Governorate during 2008 season

Table ( 3
): percentage reduction of Thrips tabaci Lind / leaf on two cultivars of eggplant affected by releasing three predacious mites species spraying with vetimec at Behaira Governorate during

Biological control of T. tabaci and A. gossypii using different predatory Phytoseiid mites 19Table ( 4
): percentage reduction of Aphis gossypii Glover / leaf on two cultivars of eggplant affected by releasing three predacious mites species sprying with vertimec at Behaira Governorate during 2008 season.

Table ( 5
): Weekly mean number of three predatory mites; Phytoseiulus persimilis; Neoseiulus cucumeris and Neoseiulus californicus after their release on two eggplant cultivers in open field at Behaira Governoreate during 2008 season