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Abstract
SUMMARY
Field experiments were carried out in a private farm , at Botores village, Abo-Hommos district, El-Behiera Governorate ,Egypt, during two successive growing cotton seasons of 2005 and 2006.
In both season of 2005 and 2006, the experimental area was one feddan that cultivated with cotton variety ” Giza 70”. The normal agricultural practices were followed during both seasons. The experimental area was divided to plots each of an area of 0.25 feddan. The completely randomized design was utilized in the initiated experimental traits with three replicates for each treatment as well as untreated check..
In the growing cotton season of 2005 and 2006, two bioinsecticides (Dipel-2x®WP & Agerin®WP) (both of them contain Bacillus thuringiensis) and one Insect Growth Inhibitors (IGIs) Chlorfluazuron (Atabron ®) were used in the study. These compounds were applied alone in both seasons during the cotton vegetative growth to study their effect on the cotton leafworm.
Moreover, during the cotton boll growth and ripening, the effect of Dipel-2x® alone (T1), parasitoid release of Trichogramma evanescens alone (T2) and Dipel-2x®+ Trichogramma evanescens (T3) was evaluated against both the pink and spiny bollworms compared with the control (untreated check).
The relationship between prevailing weather conditions and the population of the spiny and pink bollworms in both seasons expressed as number of catched male-moths of each of both bollworms was studied by using specified delta traps baited with the characteristic synthetic pheromone of each species and determine the population throughout in the cotton boll growth period during. Filed application of Dipel-2x® alone, release of Trichogramma evanescens alone and Dipel-2x®+ Trichogramma evanescens was done to evaluate the side effect of the different treatmental application on the biological agents beside their effect on yield loss.
The obtained results can be summarized as follows:
5.1. The effect of field application of certain B.t formulations and chlorfluazuron against Spodoptera littaralis during the growing season of 2005&2006.
5.1.1. The growing season of 2005:
The detected number of S. littaralis larvae before the application of tested compounds was ranging between 65.67-68.20 larvae / 15 cotton plants. Overall 14 days post-treatment. The number of larvae in those plants treated with chlorfluazuron (Atabron®) was sharply decreased to 5.26 larvae / 15 plants, while Dipel-2x® gave 5.60 larvae /15 plants. The least ef fective compound was Agerin® (Bt) which gave 12.66 larvae /15 plants compared with control (untreated check) (51 larvae /15 plants) after 14days post-treatment.
5.2.1. The growing season of 2006:
It is noticed that as chlorfluazuron (Atabron ®) was the most effective compound since it reduced the number of the larvae to 1.80 larvae /15 plants giving the higher percentage of larval reduction which calculated by 77.00% as general mean during a fortnight inspection compared with the other tested compounds and control (untreated check) followed by Dipel-2x® (4.53 larvae /15 plants), while Agerin® (Bt) was the least effective compound which gave 7.86 larvae /15 plants compared with control (untreated check) ( 55.53 larvae /15 plants).
5.2. The effect of filed application of the tested B.t formulations and the release Trichogramma evanescens on cotton bollworms infestation during the growing season of 2005 & 2006.
5.2.1. The growing season of 2005:
In this experiment, Dipel-2x® (a commercial product of Bacillus thuringiensis) (T1) (first treatment), parasitoid release of Trichogramma evanescens alone (T2) (second treatment) and parasitoid release with Dipel-2x ® (T3) both were applied alternatively as a weekly sequence till the end of the season. It was found that third treatment (Dipel-2x®+ Trichogramma evanescens ) (T3) was the most effective treatment which decreased the inspected number of the pink bollworm larvae to one larvae/100 bolls and the number of the spiny bollworm larvae to 0.33 larvae/100 bolls followed by T. evanescens alone which gave 2.33 larvae/100 bolls (pink bollworm) and one larvae/100 bolls (spiny bollworm). The least effective treatment was Dipel-2x® alone which gave 4.33 larvae/100 bolls (pink bollworm) and 2 larvae/100 bolls (spiny bollworm) compared with control (untreated check). By the end of the experimental period , the total number of both pink and spiny bollworm larvae were 6.33, 3.33, 1.33 and 11.99 larvae /100bolls inspected in T1, T2, T3 and control, respectively.
5.2.2. The growing season of 2006:
It could be seen that the bollworms infestation during the cotton growing season of 2006 was low compared with that of 2005 because the seeds of cotton were sown at earlier date in the season of 2006. Also, the parasitoid was released earlier in the season before cotton bolls formation. Third treatment (Dipel-2x®+ Trichogramma evanescens ) (T3) was the most effective treatment which decreased the inspected number of larvae to 0.66 larvae /100bolls (pink bollworm) and there was no infestation by the spiny bollworm compared with control (untreated check). By the end of the experimental period , the total number of both pink and spiny bollworm larvae were 5.66, 3.66, 0.66 and 12.33 larvae /100bolls inspected in T1, T2, T3 and control, respectively.
5.3. The rate of captured male-moths of the pink and spiny bollworms during the course of adopted treatmental applications in both cotton growing seasons of 2005 and 2006.
The number of catched male-moths of the pink and/or spiny bollworms during the course of the performed applications of each of the evaluated treatments (Dipel-2x®, the release of the parasitoid and the alternative consequential use of both of them) throughout the ripening stage of the formed bolls till full growth in both seasons of 2005 and 2006 was estimated by setting up specified traps for each of the targeted insects to inspect and count