الفهرس 
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Abstract
Biochemical aspects in different instar larvae of The Amarican bollworm, Helicoverpa armigera:
1. Hydrolases:
Activity of the tested hydrolyzing enzymes i.e., acetylcholinesterase, α- and β-esterases, alkaline and acid phosphatases as well as were estimated during various instars of both a field colony collected from Menoufia Governorate and a laboratory strain of H. armigera. Determination of enzymes activity in laboratory strain and in field colony might throw light on inductive effect insecticides on the insect.
1.1. Acetylcholinesterase (AChE) activity:
Organophosphorus and carbamate insecticides are known to be acetylcholinesterase inhibitors. AChE is playing an important function in central nervous systems. So the inhibition of AChE due to paralysis and death of the insects.
The obtained data showed marked differences between field colony and laboratory strain at respective instars of the insect. Moreover, marked differences were recorded for AChE between different instars of the insect within the field colony as well as within the laboratory strain. Comparison between the enzymatic activity per gram body weight for the insect insars for both the field colony as well as the baseline laboratory strains, it was the highest in the 6th instar larvae, followed by the 5th instar larvae. The lowest enzymatic activity levels were recorded for the 3rd instar larvae of both field colony and the laboratory srain.
The AChE activity ratio values (i.e., field colony: laboratory strain) were ranged between 1.851 and 3.284. This finding showed clearly the inductive effect of toxic chemicals in the insect environment, including organophosphates and carbamate insecticides on the enzyme activity in insect body.
1.2. Alpha and beta nonspecific esterase’s activity:
Non-specific esterase or esterases hydrolyzing α and β-naphthyl acetate were classified as Cholinesterase, carboxyl esterase and aryl esterase according to their reaction with organophosphates and serine This type of enzymes plays a vital role in the mechanism of resistance. Comparison of non-specific esterase activity in the whole homogenates of various instars of the American bollworm, Helicoverpa armigera revealed that some physiological differences existed between the field colony and the laboratory strain. The results recorded that the levels of α and β- esterase’s activity were much higher in all field instar larvae compared with that of the respective laboratory strain. It is obvious that the levels of α-esterase’s activity in the larval instars were much higher than that of the respective β-esterase’s activity.
1.3. Alkaline and acid phosphatases activity:
The results indicated that the alkaline phosphatase activity in the different larval instars homogenates of H. armigera field colony as well as the laboratory strains are remarkable higher than the respective acid phosphatase activity. The enzymatic activity increased steadily from the 3rd larval instar to the 6th instar larvae. This was the general trend of results either for field colony or laboratory strain insect instars. The enzymatic activity in the field colony larval instars was remarkable much higher than that of those in the corresponding in the laboratory strain. The enzymatic ratio of the alkaline phosphatase activity ranged between 2.325 and 4.018 in comparable with activity ratio ranged between 1.321 and 2.296 for the acid phosphatase activity relative to the baseline laboratory strain.
1.4. Glutathion S- transferases Activity:
The results indicated that the different instar larvae of the field colony showed much higher levels of glutathione S- transferases than the corresponding levels of the laboratory stain. Based on the levels of glutathione S- transferases activity, the instar larvae could be divided into three categories. The first one included the 3rd and 4th instar larvae which have the lowest levels of glutathione S- transferases activity. The second category included the 6th instar larvae that recorded the highest levels of the enzymatic activity. The third one included the 5th instar larvae that occupied the middle situation among the two categories that mentioned previously.
1.5. Mixed function oxidases:
The obtained results indicated that the enzymatic activity in the different instar larvae of the field colony strains recorded remarkable higher than the corresponding enzymatic activity of the laboratory strain. The highest enzymatic activity levels were noticed in the 6th instar larvae of both the field colony and laboratory strains. The activity ratios in the different instar larvae that mentioned previously were 1.948&1.806, 2.229&2.122, 2.317&2.287 and 2.66&2.647 per individual and per g.b.wt.; respectively.
1.6. Total protein contents:
The obtained results showed much higher amount of the total soluble protein contents in the different instar larvae of the field colony than the corresponding instar larvae of the laboratory strain. The highest amount of the total protein amount was noticed in the 6th instar larvae of both field colony and laboratory strains. The lowest amount of total sluble protein was attained in the 3rd instar larvae. The amount protein ratios were ranged between 1.806 and 2.647 per g. tissue; repectively.
2. Efficacy of different insecticides against the 2nd and 4th instar larvae of the American bollworm, Helicoverpa armigera:
In this study, the used insecticides are biomagic and bio-power (entomopathogenic fungi), dipel DF(entomopathogenic bacteria), spentor (biocide), tafaban (organophosphate) and proclaim (newnoctinoid). The tested materials were evaluated against both the 2nd and 4th instar larvae of the laboratory strain of H. armigera. The evaluation of the insecticidal efficiency was compared as follows:
2.1. Comparison on basis of LC50, LC90, LC99 and toxicity ratio values:
The obtained data indicated that the trend of the insecticides toxicity against the 2nd and 4th instar larvae was similar at both LC50 and LC90 levels. It was obvious that the 2nd instar larvae were more susceptible to the tested insecticides than the 4th instar larvae. The entomopathogenic bacteria, dipel DFwas the most pronounced material against both instar larvae. On the other hand, the entomopaphogenic fungus, bio-power was the least toxic compound against the two instar larvae.
2.2. Comparison on basis of toxicity index values:
The toxicity index values at LC50 level of bio-magic, bio-power, spentor, tafaban and proclaim against the 2nd instar larvae of H. armigera laboratory strain were 11.59, 3.24, 58.85, 16.40 and 50.13% as toxic as the toxicity of dipel DF; respectively. Concerning the 4th instar larvae of H. armigera laboratory strain, the toxicity index of bio-magic, bio-power, spentor, tafaban and proclaim at the LC50 level were 24.80, 6.76, 85.08, 22.47 and 77.47% as toxic as the toxicity of dipel DF; respectively.
2.3. Comparison on basis of slope of values, LC90/LC50 ratio and relative potency levels:
The tested products seemed to have three trends of slopes, the steepest being that of bio-power followed by the second trend included tafaban, dipel DFand bio-magic the third one included proclaim in case of treating the 2nd instar larvae. Also, the tested toxicants applied against the 4th instar larvae showed three trends, the steepest one was bio-power and dipel DF, the second trend included bio-magic, tafaban and proclaim, the third one included spentor. An increase in the slope value is parallel to decrease in LC90/LC50 ratios.
On the light of relative potency levels, the toxicity of the tested materials bio-magic, dipel DF, spentor, tafaban and proclaim at LC50 values against the 2nd instar larvae recorded 3.54, 31.08, 18.29, 5.05 and 15.41 as toxic as the toxicity of bio-power; respectively. The efficiency of the aforementioned compounds against the 4th instar larvae at LC50 exhibited 3.67, 14.80, 12.59, 3.32 and 11.48 folds as effective as the toxicity of bio-power, respectively.
2.4. Evaluating the latent effect of the tested products on basis of quantal scoring and inhibition of the adult emergence:
It is clear that the EC50 of the quantal scoring as well as IC50 values of the inhibition of the adult emergence very clearly illustrate the superiority of treating the 2nd instar larvae to the biological activity of the tested toxicants on the pupae and adults of H. armigera. Based on the EC50 values resulted from treating the 2nd instar larvae, could be descendingly arranged in order as follows: dipel DF, spentor, proclaim, tafaban, bio-magic and bio-power. In case of the 4th instar larvae, the efficacy of the tested materials on the basis of EC50 could be decsendingly arranged in order as follows: dipel DF, proclaim, spentor, bio-magic, tafaban and bio-power.
Based on the IC50 associated to the inhibition of the adult emergence resulted from testing the 2nd instar larvae, the efficiency of the tested products could be descendingly arranged in order as follows: dipel DF, spentor, proclaim, tafaban bio-magic and bio-power. Concerning the effectiveness of the tested toxicants on the inhibition of the adult emergence produced from treating the 4th instar larvae could be descendingly arranged in order as follows: proclaim, dipel DF, spentor, bio-magic, tafaban and bio-power.
2.5. Monitoring insecticidal resistance in the 4th instar larvae of the field colony strain treated with different toxicants by using discriminating technique:
Discriminating concentration of the tested products was used for rapid monitoring the insecticidal resistance in the field populations. The discriminating concentration (LC99) of the baseline laboratory strain caused 52, 76, 88, 92, 81 and 84% mortality in the field strains 4th instar larvae treated with the different toxicants; tafaban, proclaim and spentor (insecticidal products), bio-magic and bio-power (entomopathogenic fungi) and dipel DF(entomopathogenic bacteria); respectively. The corresponding resistance levels were 47.47, 23.23, 11.11, 7.07, 18.18 and 3.13%; respectively. It was obvious that the organophosphorus insecticide exhibited the highest level of resistance in the pest.
3. Potency of different control methods on male moths caught in pheromone baited traps and tomato infestation percentages with the larvae of Helicoverpa armigera:
The male moth’s populations as well as larval infestation of H. armigera in both T. evanescens released either supported with a belt of the same parasitoid or combined with mass- trapping of the male moths were always lower than the other control methods. The lowest reduction rates in the number of the trapped male moths and the larval infestation of the insect treated with different control methods were noticed in the entomopathogenic agents. The highest reduction rate in number of the caught male moths as well larval infestation were attained in T. evanscens plot supported with additional belt of the same egg parasitoid. Mean reduction rates in the numbers of the captured male moths and the larval infestation of the pest under the study were noticed in fields received T. evanescens release alone and that fields of the insecticides plots occupied the middle situation among the previous two plots.
3.1. Toxicity effect of different control methods on some predators inhabiting treated tomato plants:
Predators as one of the integrated pest management factors having a great important role in reducing the H. armigera larvae infesting tomato fruits. The continuous use of chemical insecticides against tomato fruit worm, the picture of predators could differ greatly due to the adverse effect of the chemical insecticides.It was obvious the populations of the predators were always lower in the different control methods than the untreated plot. The highest total numbers of the predators in the different control methods were recorded in T.evanescens release plot; whereas the lowest predator number was determined in the insecticides plot. The predator, C. undecimpunctata recorded the highest general total numbers in the untreated plot as well the three control methods plots compared with the other predators . True spider predator exhibited the lowest general total numbers in afore going plots. The total numbers of chrysoperla carnea and P. alfierii in the treated plots are occupied the middle situation among the two predators that mentioned previously.