الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
1. Survey of pests and its associated predators occurred on strawberry plants:
1.1. The recorded pests
The survey of insect and mite pests recorded on strawberry plants revealed to two classes and five orders about seven insect pest species; (Myzus persicae, Bemisia tabaci, Empoasca decipiens, Franklienilla occidentalis, Thrips tabaci, Spodoptera littoralis, Pentodon bispinosus, belong to six insect families and one mite species (Tetranychus urticae) belong to Tetranychidae during two successive seasons 2018 and 2019 in the nursery and production land at Giza governorate.
1.2. The associated predators
The survey of associated predators abundant strawberry plant revealed that, eight species; (Orius spp., Scolothrips sexmaculatus, Crysoperla carnea, Stethorus punctilllum, Coccinellaundecim punctata, Phytoseiulus persimilis, Neoseiulus californicus, Neoseiulus cucumeris) belong to five families of five orders during two successive seasons 2018 and 2019 in the nursery and production land at Giza governorate.
2. Effect of some ecological factors and its associated predators on population dynamics of pest infesting Festival cultivar of strawberry plants.
2.1. Frankliniella occidentalis
2.1.1. Population dynamics of Frankliniella occidentalis infesting Festival cultivar of strawberry plants
There were no significant difference between population densities of F. occidentalis during two seasons 2018 & 2019 (106 and 102 thrips/10 leaves, respectively), whereas t value equal 0.04.
In the first season 2018, the population of F. occidentalis gave two peaks on the 2nd week of July and 2nd week of August with total number 76 and 9 thrips/10leaves. While in the second season 2019, the population recorded three peaks, on the 1st week of July, 3rd week of July and 2nd week of August with total numbers 30, 52 and 10 thrips/10leaves, respectively.
2.1.2. Effect of some ecological factors on population dynamics of Frankliniella occidentalis infesting strawberry var. Festival plants
The results revealed that Maximum temperature, Minimum temperature, Dew of point and Relative humidity had insignificant negative effects on the population density of F. occidentalis whereas ”r” values were -0.18, -0.33, -0.55 and -0.34, respectively, during the first season 2018.
In the second season 2019, the results revealed Maximum temperature, Minimum temperature and Relative humidity had insignificant positive effects on the population density of F. occidentalis whereas ”r” values were 0.28, 0.24 and 0.14, respectively, while Dew of point had insignificant negative effects on the population density of F. occidentalis whereas ”r” value was -0.04.
Simultaneous effect of four selected ecological factors (E.V.) during two seasons were 49% and 57% effects on the population density of movable individual of F. occidentalis throughout two successive seasons, respectively.
2.2. Tetranychus urticae
2.2.1. Population dynamics of Tetranychus urticae infesting Festival cultivar of strawberry plants
The mean number of T. urticae on strawberry var. Festival during third season 2020 was higher than that was recorded during 1st and 2nd season with mean 360.2, 93.7 and 44.6 movable individual/10 leaves, respectively. F value= 5.9 sig. at 0.01.
In the first season 2018, the population of Tetranychus urticae recorded one peak on the 1st week of March with mean number 304 movable individual/10leaves. While in the second season 2019, the population recorded one peaks, on the 2nd week of March, with mean numbers 112 movable individual/10leaves. In the third season 2020, the population recorded two peaks, on the 1st week of February and 3rd week of March, with mean numbers 350 and 905 movable individual/10leaves, respectively.
2.2.2. Effect of some ecological factors and its associated predators on population dynamics of Tetranychus urticae infesting strawberry var. Festival plants
The results revealed that Maximum temperature, Minimum temperature, Dew point and Relative humidity had insignificant positive effects on the population density of T. urticae whereas ”r” values were 0.22, 014, 0.45 and 0.37 respectively, while predators had significant positive effect on the population density of T. urticae whereas ”r” values was 0.88 & b= 0.08 during the first season 2018 (Wardan).
In the second season 2019 (Wardan), the results revealed Maximum temperature and Dew point had insignificant positive effects on the population density of T. urticae whereas ”r” values were 0.25 and 0.15, respectively. Minimum temperature and predators had insignificant negative effects on the population density of T. urticae whereas ”r” values were -0.03 and -0.37, respectively. Relative humidity had significant positive effect on the population density of T. urticae, whereas ”r” value was 0.85 & b= 0.72.
In the third season 2020 (Elktta), the results revealed Maximum temperature, Minimum temperature, Dew point and Relative humidity had insignificant positive effects on the population density of T. uritcae whereas ”r” values were 0.43, 0.45, 0.42 and 0.38, respectively. The predators were absent in third season (Elktta, 2020), so the number of T. uritcae was highly than the previous seasons.
The percentages of explained variances (E.V.) for the four selected ecological factors and predators during three seasons were 81%, 76% and 21% effects on the population density of movable individual of Tetranychus urticae, throughout three successive seasons, respectively.
3. Interaction between agricultural ecosystems on the rate of infestation with Tetranychus urticae
Statistical analysis revealed significant differences between three types of soil, whereas F value equal 191 sig. at 0.001 and L.S.D. equal 0.77 movable individual. Three ecosystems could be arranged to the abundance of T. urticae into three groups: 1st Shbin Elkanater, 2nd Behos Elbasateen (Elkanater Elkhairia) and 3rd Wardan, with mean number of 11, 34 and 88 movable individuals/10 leaves, respectively.
Results indicated that, the high infestation rate was observed in Giza Governorate with mean number 88.3 movable individual/10leaves. While the least infestation rate was observed in, Qualiobya Governorate with mean number 21.5 movable individual/10leaves, and there was insignificant difference between them.
4. Susceptibility of certain strawberry cultivars to the infestation degree by strawberry pests (Frankliniella occidentalis and Tetranychus urticae)
4.1. In the nursery (Frankliniella occidentalis)
4.1.1. `Field study
A significant differences in numbers of F. occidentalis on the strawberry cultivars in both 2018 and 2019 seasons were occurred, (ANOVA, F=318, and 228.1 sig. at 0.001, respectively). For the 2018 season, ten strawberry cultivars could be divided into three groups based on mean infestation throughout the season. The susceptible cultivars were; Fortuna, Sahary, Festival and Forintaris (9.2, 8.9, 8.5 and 7.9 thrips per ten leaves, respectively). The second group (moderate) included Red Merlin, Winter Star, Winter Dawn, and Eliana cultivars (6.7, 5.8, 5.4, 5.3 thrips per ten leaves, respectively). The resistant cultivars were Montary and Florida (3.9 and 3.3 thrips per ten leaves, respectively).
During the second season, five cultivars were tested. Cultivars could also be divided into three groups based on infestation by Frankliniella occidentalis. The first group was the susceptible and again contained the Fortuna and Festival cultivars (12.4 and 11.7 mean thrips per ten leaves, respectively). The second group, intermediate in susceptibility, contained Eliana with a mean of 8.9 thrips per ten leaves. As in 2108, the most resistant cultivars were Montary and Florida (2.4 and 1.9 mean thrips per ten leaves). Even though the overall numbers of F. occidentalis were higher than in 2018, the mean number of thrips on both Montary and Florida cultivars was lower than in the previous year.
4.1.2. Determination of susceptibility of strawberry cultivars to infestation by Frankliniella occidentalis
Cultivars varied significantly in nitrogen (N), phosphorus (P), potassium (K), and total phenols (ANOVA, F= 189.3, 179.7, 86.5, 27.1 and 424, sig. at 0.001, respectively). The amount of nitrogen was higher (3.2 mg/g) in Montary cultivar, while Forintaris had the lowest amount (1.1 mg/g). The phosphorus content was lowest significant difference in Montary and Florida resistant cultivars as compare to other cultivars (0.17 & 0.13 mg/g, respectively). The highest amount of potassium were found in Montary and Florida resistance cultivars 2.8 mg/g for both cultivars, whereas Fortuna susceptible cultivar contains on lowest amount 2.1 mg/g. The highest amount of total phenol was found in the resistant cultivars against F. occidentalis, the obtained values were 36.7, 32.3 and 34.2 mg/g for Eliana, Montary and Florida, respectively.
There was no significant relationship between nitrogen and the mean number of F. occidentalis on each cultivar. There was a significant positive relationship between infestation and Phosphorus content (r= 0.64*, b=0.02 mg/g; sig. at 0.05). There were a significant negative relationship between the number of Frankliniella occidentalis and the amount of potassium & total phenol content of the leaves of the ten cultivars (r=-0.66* & -0.88 ***, b=-0.08 µEq/g & -3.3 µgGA/g, respectively).
The combined effect of these factors (E.V.%) on population of F. occidentalis were responsible as a group for 88% during 2018 season. Multiple linear correlation ”R” was 0.94, while multiple determined coefficients ”R2” was 0.88.
4.1.3. Effect of physical features of strawberry leaves on the population density of Frankliniella occidentalis
Statistical analysis indicated that, there were highly significant difference between density of non glandular trichome on leaflets of 10 cultivars and number of F. occidentalis. These cultivars could be divided into 6 groups. 1stgroup include Montary & 6th group contains Fortuna and the others cultivars come between them. On the other hand, statistical analysis indicated that, a significant negative correlation between number of F. occidentalis and density of non-glandular trichomes, whereas ”r” value=-0.85 & ”b” = -0.17 insect.
According to length of non-glandular trichomes, the statistical analysis indicated that, there was insignificant difference between cultivars.
Montary and Florida resistance cultivars contain on the highest number from glandular trichomes 4 & 5 /cm2, respectively. While in other eight cultivars, there were no any trichomes on these cultivars.
Statistical analysis indicated that, there were highly significant differences between thickness of leaflet and number of F. occidentalis, whereas, F value=13.6 sig. at 0.001& L.S.D.=16.7 µm. The cultivars divided into five groups. 1st group include Florida and 5th group contains Fortuna cultivar. Also, there were significant negative between thickness of leaflet and number of F. occidentalis whereas, ”r” value was -0.75 & ”b”= -0.075 insect. Florida cultivar the least infested had the greatest leaf thickness.
The simultaneous effect of previous independent factors on population density of Frankliniella occdidentalis (E.V.%) was 89% in 2018. Multiple linear correlation ”R” was 0.94, while multiple determined coefficients ”R2” was 0.89.
4.2. Production land (Tetranychus urticae)
There were a significant differences in the numbers of T. urticae on the strawberry cultivars in both 2018 and 2019 seasons, whereas, F. values =1158 & 1374.8 sig. at 0.001 and L.S.D. were 8.4 & 3.1 movable individuals, respectively. The susceptible cultivar was Fortuna with 340.2 and 155.6 movable individual/10 leaves in two seasons 2018 and 2019, respectively). The resistant cultivar was Winter Star with 93.4 and 45 movable individual/10 leaves in two seasons 2018 and 2019, respectively)
5. Loss assessment and estimation of economic levels of infestation
5.1. The infestation –yield relationships
Results of statistical analysis indicated that the relationship between population density of T. urticae and crop yield of strawberry was negative highly significant whereas ”r” values were -0.96*** and -0.97***, while ”b” values were -0.117 kg and -0.04 kg for two successive seasons 2019 and 2020, respectively. Coefficient of determination ”r2” was 0.92 and 0.94 throughout two successive seasons 2019 and 2020, respectively.
5.2. The unit effect of infestation with single pest on the crop yield of strawberry:
The results showed that a single individual of T. urticae caused reduction percentages of 1.8% and 0.7% in crop yield of strawberry in 2019 and 2020 seasons, respectively i.e. about 1.25% in total yield/sample in average.
5.3. The approximate damage threshold:
5.3.1. In the first season 2019
Estimation of economic levels of infestation showed that, when population density of Tetranychus urticae less than 21.8 movable individuals/10 leaves could be regarded as (General Equilibrium Position), when population arrived to 27.6 movables individual/10 leaves, the chi-square χ2 value for the yield (10.7) was significant DROP in the yield was occurred. Therefore, 27.6 movables individual/10 leaves could be regarded as [E.T.L.], no need for control measures, but must be ready if population density increases above that level. Afterwards, population density increased upwards from 27.6 to 40 movables individual/10 leaves, the yield loss decreased to 1.8 kg the obtain χ2 value (7) was significant. This level of infestation could be regarded as [E.I.L.], at this level of infestation control measures must be applied. Then, population density increased upwards from 40 to 56 movables individual/10 leaves, the yield loss decreased to one kg, the obtain χ2 value (66.6) was highly significant. This level of infestation could be regarded as [E.D.L.].
5.3.2. In the second season 2020
Estimation of economic levels of infestation showed that, when population density of T. urticae less than 16.4 movables individuals /10 leaves could be regarded as (General Equilibrium Position), when population arrived to 22.2 movables individual/10 leaves, the chi-square χ2 value for the yield (11.8) was significant DROP in the yield was occurred. Therefore, 22.2 movables individual/10 leaves could be regarded as [E.T.L.], no need for control measures, but must be ready if population density increases above that level. Afterwards, population density increased upwards from 22.2 to 34.4 movables individual/10 leaves, the yield loss decreased to 0.6 kg the obtain χ2 value (6.29) was significant. This level of infestation could be regarded as [E.I.L.], at this level of infestation control measures must be applied. Then, population density increased upwards from 34.4 to 53.6 movables individual/10 leaves, the yield loss decreased to 0.4 kg, the obtain χ2 value (32.6) was highly significant. This level of infestation could be regarded as [E.D.L.].
In general, when population density of Tetranychus urticae less than 16.4 to 21.8 movables individual/10 leaves could be regarded as General Equilibrium Position (in average 1.9 pest/leaf). When population ranged between 22.2 to 27.6 movables individual/ 10 leaves could be regarded as Economic Threshold Level (in average 2.5 pest/leaf). When population density ranged between 34.4 to 40 movables individual/10 leaves could be regarded as Economic Injury Level (in average 3.7 pest/leaf). When population density ranged between 53.6 to 56 movables individual/10 leaves could be regarded as Economic Damage Level (in average 5.5 pest/leaf).
6. Effectiveness of some pesticides in the control of Frankliniella occidentalis and Tetranychus urticae on strawberry plants
6.1. The effectiveness of the tested compounds on Frankliniella occidentalis in the nursery
Effectiveness of different chemical compounds included Spinetoram 12% SC, Naphthyl acetic acid – Chitosan, Glyceryl stearate 32% and Chitosan 0.1% in reducing the population densities of F. occidentalis on strawberry plants were assayed received one spray of each compound during the experimental period.
According to general mean percentage of reduction in population of F. occidentalis, there were significant differences among the four compounds whereas χ2=29.5 sig. at 0.01. These compounds could be divided to three groups. The first group contained on Spinetoram 12% SC showing high mortality (63.5%). The second group contained on Naphthyl acetic acid – Chitosan and Chitosan 0.1% showing moderate effect (46.44% & 34.3%), respectively. The third group contained on Glyceryl stearate 32% showing least effect (28.36%).from these results; it’s clear that the chemical compound Spinetoram 12% SC was the most effective while the natural compound Glyceryl stearate 32% was the lowest in controlling Frankliniella occidentalis under these experimental conditions.
6.2. Effectiveness of the tested compounds on Tetranychus urticae in the production land
Effectiveness of different chemical compounds included Spirodiclofen 24% SC, Bifenazate 24% SC, Chlorfenapyr + Emamectin benzoate 12% SC, Emamectin benzoate 1.9%EC, Abamectin + Imidacloprid 15% CS, Abamectin 5%EC, and Chitosan 0.1% in reducing the population densities of T. urticae on strawberry plants were assayed after receiving one spray of each compound during the experimental period.
According to general mean percentage of reduction in population of Tetranychus urticae, there were insignificant differences between the seven compounds whereas χ2= 3.75 insig. So, the cheaper compound was the best choice. The mortality percentages were 85.94 %, 82.18%, 81.4%, 79.36%, 78.14%, 77.94% and 75.9%, for compounds; Bifenazate, Chlorfenapyr + Emamectin benzoate, Spirodiclofen, Emamectin benzoate, Chitosan, Abamectin and Abamectin + Imidacloprid, respectively. from these results; it’s clear that Bifenazate compound was the most effective compound and Abamectin + Imidacloprid was the lowest one. The other compounds ranged between them in controlling T. urticae under the experimental conditions.
7. Residue of selected pesticides on strawberry fruits
7.1. Bifenazate
The initial residue deposits, which remained on strawberry fruits one hour after treatment (zero day) was 37.7 p.p.m which degrades to 18.5, 10.6, 4.9 p.p.m at 1, 3, 7 days, respectively, which was still above the MRL. At 14 and 21 days it was 1.94 and 0.95 p.p.m which was blew the MRL=2 p.p.m set by FAO-WHO Codex Alimentarius Commission Recommended. Determined residues of Bifenazate in strawberry fruits were at level below the maximum residue limits (MRL), 2 mg/kg (Codex 2010), so that the strawberry fruits could be used safely after 15 days from the spray by Bifenazate. The half-life value of Bifenazate in strawberry fruits was 0.99days.
7.2. Spirodiclofen
The initial residue deposits, which remained on strawberry fruits one hour after treatment (zero day) was 15.3 p.p.m which degrades to 5.34 p.p.m with loss 65.1% while at 3 day was 1.3 p.p.m with loss 19.5% which was below the MRL=2 p.p.m set by FAO-WHO. At 7, 14, 21 days, the residues were non-detectable.
Determined residues of Spirodiclofen in strawberry fruits were at level below the maximum residue limits (MRL), 2 mg/kg (Codex 2010), so that the strawberry fruits could be used safely after 3 days from the spray by Spirodiclofen. The half-life value of Spirodiclofen in strawberry fruits was 0.86 days.
7.3. Abamectin
The initial residue deposits, which remained on strawberry fruits one hour after treatment (zero day) was 4.1 p.p.m which degrades to 3.24, 2.87, 1.65, 0.47, 0.38 p.p.m after 1, 3, 7, 14, 21 days of application, respectively. The concentration of Abamectin after 21 days doesn’t reach to MRL (0.15 mg/kg) according to Codex Alimentarius Commission Recommended. The half-life value of Abamectin in strawberry fruits was 5.7 days.