Effect of natural and chemical insecticides on Hyalopterus pruni and Armeniaca vulgaris

Experiments were carried out to evaluate the effect of water extracts of Fagonia arabica, Salix alba and Anthmis pseudocotula and their mixtures with chemical insecticide (Malathion) on growth of Hyalopterus pruni and characters of Armeniaca vulgaris plants and their soils. The data revealed that F. arabica extract at 20% concentration was the most effective followed by S. alba which recorded 62.66 and 56.16% reduction in H. pruni population density, respectively. While the mixture of Malathion with F. arabica or S. alba or A. pseudocotula extracts (each one at half concentration) results in 57.88, 57.42 and 60.86% reduction in aphid population, respectively. The plant extracts treatment resulted in significant increase in chlorophyll pigments and total carbohydrates in A. vulgaris whereas carotenoids and total protein content decreased (except S. alba extract treatment which increased total protein content). Soil cations; Ca, Na, Mg, K and anions; SO4 , HCO3 , Cl increased with all plant extracts treatment with exception of A. pseudocotula extract treatment that decreased HCO3 concentrations. This study recommended that natural insecticides were more effective and safe than chemical ones in pest control.


INTRODUCTION
Fruits are considered strategic crops and have obtained special attention all over the world.Aphids are considered the main pests which threaten the quantity and quality of the yield of these crops.The recent widespread application of pesticides for controlling the pests has a serious effect on the natural balance of the ecosystem.Several investigators in different parts of the world have initiated large-scale screening efforts to find plants which have interesting physiological effects on pests (Ghamry 1986, Venkaietan et al., 1987and Bandara et al., 1990).Previous studies have not recorded the use of natural extracts of Fagonia arabica, Salix alba and Anthmis pseudocotula and their mixtures with chemical insecticide (Malathion).*Corresponding author.E-mail: akram692000@yahoo.com.Tel: 00966557554020.Fax: 00966 1 4675833.Therefore our investigations were carried out to evaluate these plant extracts to minimize the growth of Hyalopterus pruni populations on apricot trees (Armeniaca vulgaris) and their effects on the tree and their supporting soils.

Preparation of extracts
The plants F. arabica, S. alba and A. pseudocotula were immersed in warm water for 48 h and filtered to get the plant extract for each plant.

Preparation of concentrations
Crude solution of plant extracts used at rate of 750 ml from each plant extract was diluted with 3 liter water to reach 20% final concentration.The recommended concentration of Malathion (57% EC) is 250 ml/100 liter water.Each plant extract-Malathion mixture was prepared by using the half of the preceding rates.

Application against H. pruni on apricot trees
To study the initial and residual toxicity of the tested plant extracts against H. pruni individuals, the experimental area with 24 apricot trees, were divided into 8 treatments; each one included three trees (3 replicates for each treatment).Spraying was carried out by using a knapsack motor sprayer.Samples from each treatment were collected randomly by taking 20 leaf/tree from three canopy positions (upper, middle, lower) of the tree in plastic bags just before the insecticidal application.This include pretreatment samples and treatment collection after 2, 3, 5, 7, and 9 days post treatment.The samples were examined directly by the aid of stereoscope microscope in the laboratory, where the individuals of H pruni were counted pre-and post-treatment.The reduction percentages of aphid population were calculated according to Handerson and Tilton (1955) formula.

Soil analysis
The soil profiles supporting apricot trees were sampled and collected in plastic bags for chemical analysis.The soil samples were taken at depth 20 cm after one week of application; the samples were air dried, sieved through 2 mm meshes and analysis was carried out.Seven hundreds ml of distilled water were added to 140 g of air-dried soil and were shaken for two hours.The heavier particles were allowed to settle and the supernatant liquid was decanted into Pastur Chamber land filter.After repeated filtration, clear soil solution was obtained then determination of anions and cations were carried out according to Jackson (1967).

Pigment analysis
The photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) were determined spectrophotometrically according to Metzner et al. (1965).A known fresh weight of leaves was homogenized in 85% aqueous acetone for 5 min.The homogenate was centrifuged and the supernatant was made up to known volume with 85% acetone and measured against a blank of pure 85% aqueous acetone at 3 wavelengths of 452.5, 644 and 663 nm.Taking into consideration the dilution made, it was possible to determine the concentrations of the pigment fractions (chlorophyll a, chlorophyll b and carotenoids) as g / ml using the following equations:

Estimation of carbohydrates
Dry sample (0.05 g) was hydrolyzed with 20 ml HCl (6 N) in carbohydrates tube for 6 h in boiling water bath and then filtrated using whatman 1. 20 ml NaOH (6 N) was added to the filtrate and made up to 100 ml with distilled water.Five ml from the filtrate was taken in test tube and 2 ml of 3,5 dinitrosalicylic acid was added.The mixture was shaken and heated for 10 min in boiling water bath, and immediately cooled in ice.The optical density was measured at 550 nm using spectrophotometer.The concentrations were obtained from standard curve (mg/g).

Estimation of protein
Nitrogen percentage was measured by taking 0.2 ml from the digested sample in 25 ml flask, then distilled water was added to reach half of the flask. 1 ml of Nesler's solution was then added.
Reading was made at 420 nm using.Then total protein percentage determined according to the following equation:

Statistical analysis
The data obtained were subjected to statistical analysis by ANOVA using SPSS version 11.Duncan's multiple range tests was used to determine the significant of the difference between mean values of the treatments.

Effect of extracts on H. pruni
Data in Table 1 summarized the efficiency of the plant extracts and its mixtures with Malathion as well as Malathion alone against H. pruni populations.Initial reduction percentages of aphid population measured after 48 h post treatment ranged between a minimum of 27.82% for A. pseudocotula extract to a maximum of 39.71% for S. alba extract comparing with Malathion which recorded 71.82% as initial effect.The residual reduction percentages mean of aphids measured at days (3, 5, 7 and 9 post treatment) ranged between a minimum of 52.48% for A. pseudocotula extract to a maximum of 62.66% for F. arabica extract comparing with Malathion that recorded 71.78%.These results were in agreement with Ghamry (1986) who tested the efficacy of five plant extracts against aphids on citrus trees, Venkaietan et al. (1987) when investigating various plant extracts on Aphis gossypii (Glov.)populations and Hala (2000) who reported that aqueous extracts of some plants causing high reduction percentages of aphids population.

Photosynthetic pigments
We can infer from the combined data of the two weeks that the variations in the content of chlorophyll a and b and carotenoids in the leaves of apricot trees as affected by plant extracts and malathion treatments (Table 4).
There was no significant increase in chlorophyll a and b content at 7 and 14 day after application of all treatments.It is evident that there were remarkable decreases in the content of carotenoids in the leaves of apricot trees treated with the same materials.There was high significance between all treatments compared with control in chlorophyll a, b and carotenoids content.These results agree with El-Quesni and Radwan (1993) who found that the treatment with Topogard (terbuthylazine + terbutryn) on faba bean increased chlorophyll a, b and chlorophyll a+b content but decreased carotenoids in the leaves.Chlorophyll pigments, considered the most important chemical components that convert photoenergy to chemical energy, play an active role in photosynthesis and carotenoid pigments protect chlorophyll against pho-tooxidation and transfer of energy to chlorophyll.

Total carbohydrates and proteins
It is evident in Table 5 that there were significant increases in the mean total carbohydrates in the treated leaves of apricot trees with plant extracts; 29, 27.33 and 29% for F. arabica, A. pseudocofula and S. alba extract, respectively.The control has 27% carbohydrates but in case of Malathion the percentage decreased to 25.33%.It was also clear that there was no significant increase in percentage of total protein in S. alba extract and Malathion treated palnts when compared to control, while there was significant decrease of total proteins in F. arabica and A. pseudocotula extracts treated plants (Table 5).In harmony with the above results, Woda (1994) reported that spraying potato plants with metribuzin reduced reducing sugars, non reducing sugars and starch in leaves of potato and influenced on protein metabolism.Carbohydrates and proteins are organic compounds used in tissue synthesis and organs synthesis.

Table 1 .
Effect of plant extracts and malathion and their mixtures on the number of Hyalopterus pruni under field conditions.

Table 2 .
Effect of some plant extracts and malathion on cations of the soil supporting apricot trees.

Table 3 .
Effect of some plant extracts and malathion on anions of the soil supporting apricot trees.

Table 4 .
Effect of some plant extracts and malathion on photosynthetic pigments of apricot leaves trees.

Table 5 .
Effect of some plant extracts and malathion on mean total carbohydrates and total proteins of apricot leaves trees.