The silverleaf whitefly (Bemisia tabaci) is one of the most harmful insects attacking several economic plant crops worldwide, and it has developed a resistance toward several conventional insecticides. This study was conducted to estimate the impact of potassium phosphite (PK), effective microorganisms (EMs), and salicylic acid (SA) as plant inducers, and imidacloprid (IMI) as a synthetic insecticide on the systemic acquired resistance of sweet pepper (Capsicum annuum var. annuum) crop, whitefly population, and crop yield under greenhouse conditions. The treatment plots were sprayed with IMI, PK, EMs, SA, and water (control) on the 27th day after planting, and dinotefuran was applied when the whitefly-infestation ratio reached 3.00%. The enzymes responsible for the internal defence system, whitefly population, and crop yield were determined. Our results confirmed the idea that the PK, EMs, and SA may induce the synthesis of plant enzymes responsible for the internal defence system. The IMI, PK, EMs, and SA significantly suppressed the whitefly population compared with the control. Moreover, the reduction percentages of the whitefly population were significantly higher when using IMI and PK than EMs and SA. The IMI, PK, EMs, and SA improved the crop yield. It could be concluded that PK, EMs, and SA enhanced the systemic acquired resistance in sweet pepper crop causing high defence against the population of whitefly and might be a potent alternative to conventional insecticides and compatible with an integrated pest management program.
The rice weevil, Sitophilus oryzae (L.), is the most destructive insect pest of stored cereals worldwide. The current study was conducted to determine the lethal, reproductive, and histological effects of gamma irradiation on S. oryzae adults. In addition, the impact on germination, chlorophyll, and proline content in wheat seedlings from treated grains was determined. Wheat grains were infested with rice weevil adults and then irradiated by gamma rays. Gamma radiation was applied at a dosage of 0.10, 0.25, 0.50, and 1.00 kGy. Mortality percentage and LD50 were recorded after 48, 72, 96, and 120 h of treatment. The dosage of 1.00 kGy caused 100% mortality after 96 h of irradiation. The required dosage of gamma radiation to kill 50% (LD50) of adults after 48 h was 1.51 kGy. All tested doses caused complete sterility to 24 h old adults. A histological alteration was noticed at a dosage of 1.00 kGy, which showed cytoplasmic vacuolization, tissues exhibiting signs of putrefaction, and necrosis of cells; furthermore, gamma irradiation affected chlorophyll a and b. The highest amounts were detected in wheat seedlings from grains irradiated at 0.10 kGy. There was a significant increase in plant proline content at the higher doses (0.50 and 1.00 kGy) compared with seedlings from nonirradiated grains. It could be concluded that gamma radiation can be used as an eco-friendly trend to control stored-product pests without any residual effects.
This study was conducted to estimate the impact of contact and fumigation toxicity of garlic (Allium sativum L.) and mandarin (Citrus reticulata L.) essential oils against two of stored product insects Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.) for 1, 2 and 3 days after exposure under laboratory conditions. Results showed that garlic was more effective than mandarin, where contact LC50 after 3d was 0.336 mg/mL compared to 5.49 mg/mL for mandarin on T. castaneum (Herbst) and 0.343 mg/mL, 4.130 mg/mL on R. dominica (F.) at the same investigation period. The same trend was observed for fumigation where LC50 of garlic were 0.789, 0.386 µL /L air against T. castaneum (Herbst) and R. dominica (F.) respectively and 7.778, 6.305 µL/L air of mandarin against T. castaneum (Herbst) and R. dominica (F.) after 3days respectively. Gas chromatography-mass spectrometry (GC-MS) analysis showed that the major compounds of garlic essential oil were diallyl sulfide (9.5%), diallyl disulfide (27.9%),dimethyl tetrasulfide (2.9%), allyl methyl trisulfide (17.7%), and diallyl trisulfide (16.8%). In mandarin the main components were tricarbonyl [methyl 6-vinylidenehepta 2,4-dien-1-oate]iron (52.8 %), dimethyl hexane ( 15.28%), p-cymene (5.45 %), limonene (3.88 %) and Ɣ terpinene (9.47 %). The results elucidated that, essential oils may be a promising safe alternatives to synthetic chemical insecticides for control stored product insects either by contact or fumigation treatment and compatible with integrated pest management.
The present study was carried out to evaluate the relative biological activity of six treatments. Four nanoparticles (chitosan, Hydroxyapatite, chitosan hydroxyapatite and silver hydroxyapatite), one bio-agent effective microorganisms (EMs) compared to one synthetic acricide (bifenzata) were tested against the female adults and eggs of Tetranychus urticae and its predatory mite Amblyseius gossipi using standardized method of bioassay under laboratory conditions. Effect of the tested agents on the activity of carbohydrates enzymes, total lipid and total protein content were determined. The results revealed that chitosan (NPs) showed significantly adulticidal activity against T. urticae. Furthermore, EMs was the most effective treatment on the eggs of T. urticae followed by bifenzata under laboratory conditions. Therefore, nanoparticles and EMs appeared to be highly safe and selective against Amblyseius gossipi. This study suggests the possible use of nanoparticles as safe alternatives to conventional acaricides and compatible with integrated pest management practices. They might be contribute to future applications in pest control for sustainable agriculture.
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