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APHIDOPHAGOUS INSECTS OF THE MEALY PLUM APHID Hyalopterus pruni (GEOFFROY) IN APRICOT AT SHARKIA GOVERNORATE, EGYPT

The present investigation was carried out at El-Khattara District, Sharkia Governorate, Egypt during 2017 and 2018 seasons to evaluate the population density of the aphidophagous insects of the mealy plum aphid Hyalopterus pruni in apricot. Two parasitoid species belonging to Aphidius colemani Viereck and Aphidius picipes (Nees) and eight predator species, namly: Chrysoperla carnea Steph., Chrysopa septempunctata, Waesmael, Ccoccinella septempunctata, Coccinella undecimpunctata L., Aphidoletes aphidimyza Rond., Syrphus corollae F., Cydonia vicinia nilotica Muls. and Scymnus interruptus Goeze were recorded. C. undecimpunctata came in first rank (16.75 and 17.74%) followed by C. carnea (14.85 and 17.16%) followed by C. septempunctata (12.61 and 14.96%) then Cydonia vicinia nilotica (12.26 and 12.76%), while Ch. septempunctata, S. corollae, Scymnus interruptus and A. aphidimyza were represented by (11.92 and 11.87%), (11.40 and 9.53%), (10.71 and 9.53%), (9.50 and 6.45%), from the total number of aphid predators during 2017 and 2018 seasons, respectively. The highest percentage of parasitism by the two parasitoids were recorded on the first and last week of May (37.20 and 50.00%) during 2017 season, while in the second season (2018) were recorded in the first week of both May and June (43.28 and 62.01%) respectively, with an average percentage of parasitism 27.12 and 35.98% during the two successive seasons, respectively. Statistical analysis showed that temperature and relative humidity were significant with some insects and insignificant with the other. In general, the parasitoid A. colemani and the predator C. undecimpunctata, could be mass reared and released for controlling H. pruni on apricot trees include integrated pest management programs and crop management against H. pruni to save the environment from pollution.


INTRODUCTION
Aphid species are among the most injurious pests attacking fruit trees, damage caused by aphids is mainly due to feeding on the plant-sap causing direct injury to the trees (Ismail et al., 1991;Ibrahim, 1994 Apricot trees are by far one of the most important fruit crops in Egypt. They are widely cultivated in Qalubia Governorate, where their fruit represent one of the most important sources of farmers income. This fruit possesses highly nutritional quality, because of its contents of sugars, proteins and vitamins, especially vitamin "A". Besides, it represents one of the best sources of mineral salts including, Phosphorous, Potassium and Calcium. The apricot fruit trees are liable to attack by the mealy plum aphid H. pruni (El-Kady et al., 1970). In Egypt this aphid has been recognized as a pest of stone fruit trees (Prunus spp.), causing considerable damage by sucking the juice and resulting in loss of the yield (Ibrahim and Afifi, 1994;Abul-Fadi et al. 2005).
Use insecticides in controlling aphids, leads to many problems not only increasing resistant strains of aphids to these chemical substances, but also in induction of pollution to man and beneficial insects (El-Maghraby, 1993 Little information are known on the natural relationship between H. pruni infestation and its natural enemies especially, aphidophagous insects on apricot trees, in the newly reclaimed sandy area. For this reason, this work was conducted to shed light on the population dynamics of aphid H. pruni, surveying the most common natural enemies found associated with the previous aphid species, during the period of aphid existence. Such ecological information will undoubtedly help in planning integrated control programs and apricot management against H. pruni.

Estimation the Role Aphidophagous Insects of Hyalopterus pruni Population in the Field
This work was carried out at El-Khattara district, Sharkia Governorate, Egypt during 2017 and2018 seasons. An area of a faddan (4200m 2 ) was selected. This area received all normal recommended agricultural practices, except absence of any chemical insecticidal treatment. Sampling started in the first week of March. Inspections continued till the 2 nd and 3 rd week of June during 2017 and 2018 seasons. Weekly sampling of 60 infesting leaves (12 leaves from 5 trees) were randomly, respectively for apricot trees. Collected, kept in paper bag and transferred to the laboratory. The numbers of Hyalopterus pruni (nymphs and adults) were recorded for each sample. Meanwhile, the numbers of predators associated with aphid were also recorded. To estimate parasitism rates, mealy plum aphid individuals were fed in the laboratory on their host plant and kept in Petridishes until formation of mummies. The mummies were isolated and kept in small glass tubes until emergence of adult parasitoids. Adult emerged from mummies, were classified, counted and their percentages were also calculated. Emerged parasitoids were mounted and identified at the Biological Control Department, ARC, Giza, Egypt. Percentage of parasitism was calculated as weekly means according to Ferrell and Stufkens (1990 For clearing the effect of certain weather factors such as temperature and atmospheric relative humidity on the population density of the studied aphid and their aphidophagous, the daily records of both maximum, minimum temperature and mean relative humidity throughout the two seasons (2017 and 2018) were provided by the Meteorological Central Laboratory for Agricultural Climate, Agricultural Research center, Dokki, Giza, during the whole period of the study, to show the effect of factors as well as their total effect on insects population density, the values of simple correlation coefficient (r), partial regression coefficient (P) and total explained variance (EV%) were calculated using CoSTAT Software Microcomputer Program (CoSTAT, 2005).

Survey of Aphid Infesting Apricot and Aphidophagous Insects in El-Khattara District
Results presented in Table 1 show that only the mealy plum aphid Hyalopterus pruni Two groups of aphidophagous insects associated with H. pruni on apricot trees were recorded as follows: Predators associated with H. pruni infested apricot trees

Parasitoids of H. pruni on apricot
Results in Table 1 show that two primary parasitoid species, Aphidius colemani (Viereck) and Aphidius picipes (Nees) were recorded, the primary parasitoid A. colemani was the most dominant species with mean relative densities 65.21 and 70.24% followed by Aphidius picipes 34.79 and 29.76% during 2017 and 2018 seasons, respectively.

Population Density of H. pruni on Apricot Trees
Results in Fig. 1 show the population of H. pruni was appeared in the 2 nd week of march by 90 individuals/sample, two peaks of population activity were recorded on the first week of April 1340 individuals/ 60 leaves at mean temp. 19.3°C and 62.0% RH, the second peak of activity 2620 individuals/ sample on the first week of May at mean temp. 22.3°C and 53.9% RH, in the first season 2017. In the second season 2018 (Fig. 3), the infestation started in the 2 nd week of March by 75 individuals/ sample and increased to record two peaks of population activity in the 1 st week of April and May by 1415 and 2715 individuals/ sample at mean 21.8°C and 56.6% RH as well as 24.5°C and 68.3% RH, respectively.
From the aforementioned results, it could be concluded that, the H. pruni was observed with its highest population during April and early May, it appears that, the active period of this aphid species under investigation occurred during the period from March until May. Therefore, this period represents a critical period, for Integrated Pest Management (IPM) programs to protect apricot trees from aphid attacks. El-Kady et al. (1970) showed that, H. pruni is the most injurious aphid species on peach and apricot as well as on reed weed.  Fig. 2 show that C. carnea individuals were appeared in the 3 rd week of March by two individuals/sample, and increased gradually to record two peaks by 14 and 16 individuals/ sample at means (20.3°C and 59.2% RH as well as 21.3°C and 53.9% RH) in the 2 nd week of April and first week of May, respectively and decreased untile the 4 th week of May during the first season 2017. While in the second season were appeared in the 2 nd week of March, 8 individuals / sample, and recorded two peaks by 18 and 14 individuals/sample at means (21.8°C and 56.6% RH as well as 23.5°C and 52.0% RH) in the first and 4 th week of April, respectively (Fig. 4).

Chrysopa septempunctata
The population of activity to this predator recorded two peaks in the 2 nd week of April and in the first week of May during two seasons with (12 and 15 individuals at means 20.3°C and 59.2% RH as well as 21.3°C and 53.9% RH) and (14 and 13 individuals/sample) at means 22.7°C and 57.4% RH as well as 24.5°C and 68.3% RH) during 2017 and 2018 seasons (Figs. 2 and 4), respectively.

Coccinella septempunctata
As seen from Fig. 2, two peaks of activity were recorded on the first week of both April and May by 9 and 14 individuals/sample at means 19.5°C and 62.0% RH as well as 21.3 and 53.9% RH during first season (2017). In the second season (2018), two peaks of population activity were recorded on the same time by 16 and 18 individuals/sample at mean of 21.8°C and 56.6% RH as well as 24.5°C and 68.3% RH, respectively (Fig. 4).

Coccinella undecimpunctata
In the first season (2017) as shown in Fig. 2, two peaks of activity were recorded on the 2 nd week of April and first week of May by 15 and 20 individuals/sample at means 20.3°C and 59.2% RH as well as 21.3°C and 53.9% RH, respectively. In The second season 2018 (Fig. 4) two peaks of population activity were recorded on the first week of both April and May by 19 and 17 individuals/sample at means 21.8°C and 56.6% RH as well as 24.5°C and 68.3% RH, respectively.

Cydonia vicina nilotica
As seen from Fig. 2, two peaks of activity were recorded during 2017 season on the 2 nd week of April and first week of May by 13 and 14 individuals/ sample for each means 20.3°C and 59.2% RH as well as 21.3°C and 53.9% RH, respectively. Also two peaks of activity were recorded in the second season (2018), on the first and the 4 th week of April by 12 and 18 individuals/sample at means 21.8°C and 56.6% RH as well as 23.5°C and 52.0% RH, respectively (Fig. 4).

Scymnus interruptus
In the first season 2017 (Fig. 2) two peaks of activity were recorded by 9 and 12 individuals/ sample, on the 2 nd week of both April and May, at means 20.3°C and 59.2% RH as well as 23.5 and 55.2% R.H., respectively. While in the second season two peaks were recorded on the 2 nd week of April and first week of May by 13 and 10 individuals/ sample at means 22.7°C and 57.4% RH as well as 24.5 and 68.3% RH, respectively (Fig. 4). Fig. 2 show that two peaks of activity were recorded on the first week of both April and May, with values 8 and 13 individuals/ sample at means 19.5°C and 62% as well as RH 21.3°C and 53.9% RH, respectively during 2017 season. In the second season (Fig. 4), two peaks of population activity were observed on the 2 nd week of April and first week of May by 8 and 12 individuals/ sample at means 22.7°C and 57.4% RH as well as 24.5°C and 68.3% RH, respectively.

Syrphus corollae
In the first season (2017) as shown in Fig. 2, two peaks of activity were recorded on the 2 nd week of both April and May by 8 and 15 individuals/sample at means 20.3°C and 59.2% RH as well as 23.5°C and 55.2% RH, respectively. In the second season 2018 (Fig. 4), two peaks of population activity were observed on the first and 4 th week of April by 9 and 16 individuals/ sample at means 21.8°C and 56.6% RH as well as 23.5°C and 52.0% RH, respectively. Fig. 2 show the number of common predators associated with H. pruni on apricot trees. The insect predators belonged to three insect orders: Neuroptera, Coleoptera and Diptera, and four families namly: Chrysopidae, Coccinellidae, Syrphidae and Cecidomyiidae. The total number of insect predators were first appear by two individuals / sample in the second week of March and increased gradually to record two peaks of population density 82 and 114 individuals / sample in the 2 nd week of April and first week of May, respectively. Then, their numbers declined towards the end of the first season. In second season (2018) it appeared by 3 individuals/ sample in the 3 rd week of March and increased to record two peaks of population density (93 and 1020 individuals/ sample) during first week of both April and May, respectively (Fig. 4).

Abul-Fadi et al. (2005) found that most common predators recorded associated with
H. pruni on apricot trees. Several predaceous species belonging to four orders namely: Neuroptera, Coleoptera, Hemiptera and Diptera during the period of study, 2017 and 2018 seasons. Also, Adil and Muhammed (2008), showed that mealy plum aphid, H. pruni was recorded on apricot trees, were associated with 8 species of predators, 5 of them from family Coccinellidae and order Coleoptera, they were:  Table 1 show that two primary parasitoid species Aphidius colemani Vier. and Aphidius picipes (Nees) were recorded, the percentages of parasitism ranged from 8.89% and 50.00% during the first season and from 16.00% and 62.01% during the second season (Table 3). In the first season (2017), the percentage of parasitism started by 8.89% in the second week of March, it increased to record two peaks by 37.20% and 50.0% in the first and 5 th week of May, respectively. In the second season (2018), the percentage of parasitism started by 16.0% in the second season of March, and it increased to record two peaks of 43.28% and 62.01% in the first week of both May and June, respectively.

Rate of parasitization
Total means of parasitism rate of A. colemani and A. picipes together were 27.12% and 35.98% during 2017 and 2018, respectively. The primary parasitoid A. colemani was the most dominant species with mean relative density (68.47% and 67.43%) during the two seasons, respectively. Meanwhile, the mean relative densities of primary parasitoid A. picipes were 24.87% and 26.33% during 2017 and 2018 seasons Table (2 and 3

Combined effects of meterological factors on the mealy plum aphid and associated aphidophagous insects
The effect of maximum temperature, minimum temperature and mean relative humidity on the aphids and their associated aphidophagous insects were estimated by calculating the multiple partial regression analysis. Table 4 Table 5 show the values of the correlation coefficient of relation between predators and the population density of H. pruni during the two successive seasons. The predators Ch. carnea, Ch. septempunctata, C.     NS.: Not significant * Significant ** Highly significant