Journal Of Crop Protection
Volume:5 Issue: 3, Sep 2016

Insect stress effects have been the subject of many reviews including heat, cold, and population stress. Production of winged aphids in unfavorable conditions or migrant phase of locust and armyworms, are reactions to crowding. Various crowding levels stress and treatment with low to high sub-lethal doses of insecticides at first had no effect but reduced Dysdercus fasciatus Sign. reproduction at higher levels. Stressors such as, crowding, toxins of sub-lethal doses of pesticides, host plant chemicals and environmental pollutants may produce comparable effects on insects.Stress may cause dispersion, migration, and insect pest outbreak.Locusts, aphids, armyworms and D. fasciatus react via plasticity to stressors including crowding stress by production of polymorphic phase. Neurohormones generally regulate the hormonal production of corpora alata, corpora cardiac and affect insect metabolism. This review relates the stress of crowding and insect phase to insect–plant relationships and the route to pest outbreak.

Tomato leaf miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is one of the most destructive pests of tomato in many parts of the world including Iran. Field studies were conducted to determine the short and long term effects of Bacillus thuringiensis var Kurstaki (Bt), azadirachtin (AZ), a mix of AZ Bt, and indoxacarb, as a current chemical insecticide, on T. absoluta larvae. Also, effects of the insecticides were studied on the coexisting generalist predators, Coccinella septempunctata L., Chrysoperla carnea Stephens and Syritta sp. Sampling of T. absoluta and its coexisting generalist predators were performed 1 day before treatment (DBT) and one, 5, 8, 14 and 19 days after treatment (DAT). The results indicated significant short term effect of indoxacarb on the pest larvae. Indoxacarb reduced T. absoluta density and damages. Bt, AZ and mixture of them significantly suppressed the larval density at 19 DAT and caused significant reduction in leaf, stem and fruit damage. The highest long term effect on the pest abundance and damage were observed in Az Bt caused 100% reduction in fruit and foliage damage compared to the control. The highest and lowest adverse effects on C. carnea, C. septempunctat and Serrita sp. were observed in indoxacarb and Bt treatments, respectively. Findings of this study imply that the mixture of Az Bt has the highest selective toxicity on the pest and the lowest effect on its coexisting generalist predators.

Field experiment was conducted in 2010 and 2011, in order to study the effects of NPK fertilizers on the incidence of Verticillium wilt of a commercial variety 'Agria' in deficient soil at Eghlid Agriculture Research Station in the north of Fars province, Iran. Experimental design was randomized complete blocks and each treatment replicated three times. Treatments were the amounts of recommended NPK rate (180N, 125P, 100K), 20% and 40 % less and more than the rate based on the soil tests. Soil at planting sites was inoculated with 5 ml of microsclerotia suspension (70 ms/ml). Tubers weight, plant height and disease scores were recorded. Two-year combined analysis indicated that there were significant differences at 1% level between the treatments. The results showed a marked decrease in Verticillium wilt incidence and increase in yield when NPK was used at the recommended rate. Lowest disease score and highest yield even more than the cultivar potential were obtained in the plots when N was used 40 % more than the recommended level of the soil test (252 N), combined with K at the level of the soil test (100 K). P was essential for plant growth but had no effect on the disease.

Blue mold disease caused by Penicillium expansum is a major post-harvest disease of apples. In this research, the biochemical basis of apple resistance to this pathogen was studied in two relatively resistant and susceptible cultivars, Granny smith and Mashhad, respectively. The activities of catalase (CAT), peroxidase (POX), superoxide dismutase (SOD) and polyphenol oxidase (PPO) enzymes and polyphenol content were compared at different time intervals of 0 to 7 days. Based on the results, fruit polyphenol content of Granny smith was higher than that of Mashhad PPO, SOD and CAT activity was higher in Granny smith than Mashhad but CAT activity decreased three days post-treatment. No detectable difference was found in POX activities in the two cultivars. It is concluded that polyphenols contribute in apple resistance to blue mold. Activation of PPO and SOD, lack of POX activity and decrease of CAT activity, all together, could lead to a toxic environment around the blue mold fungus.

Fusarium proliferatum, as a toxigenic fungus, is one of the important agents of onion basal rot (FBR). Among the control methods of the disease, biological control is considered as one of the best options. In this study, Trichoderma harzianum strain T100 at the rate of 1 × 106 cfu/g was mixed with pot soil artificially infested with F. proliferatum. Also Glomus mosseae was applied to each pot at the rate of three grams of soil containing 80 chlamydospores/ml. Combination of T100 and G. mosseae was used as well. Onion seeds were disinfected & planted in pots, arranged in completely randomized design in 4 replicates under greenhouse condition and finally, the individual or combined effects of these bioagents were assessed on FBR control and also root colonization by Glomus 23, 30 and 36 days after sowing. Inoculation of Arbuscular mycorrhizae improved onion growth effectively, but its biocontrol effect was not considerable. Trichoderma amended soil decreased disease incidence by 25% but its usefulness as biocontrol agent was reduced in the course of time. AM root colonization was decreased in plants in presence of Trichoderma. Nevertheless, the disease control in combination of Trichoderma and Glomus treatment was better than the treatments by each one of the agents singly. The disease control achieved by fungicide seed treatment was inferior to that of Trichoderma and Glomus in combination.

In this study, the efficiency of essential oils from asafoetida, Ferula assa foetida L.,geranium, Pelargonium hortorum L.H. Bailey and walnut leaves, Juglans regia F. was investigated on nutritional indices of Rhyzopertha dominica (F.) adults. Wheat grains were treated with different concentrations of the oils. The nutritional indices: relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI) and feeding deterrence index (FDI) were measured at 28 ± 2 °C, 65 ± 5% R. H. in continuous darkness. RGR, RCR and ECI deceased as the concentration level was increased. While, FDI percent increased significantly as the concentration level increased. Asafoetida oil had the most efficiency on nutritional indices and 28.61 ppm of the oil was enough to decrease RGR, RCR and ECI% to 0.032 mg/mg/day, 0.444 mg/mg/day and 6.994%, respectively. FDI percent of adults exposed to 6.5 ppm of asafoetida oil was 13.31% which increased upto 64.62% at the concentration of 28.61 ppm. In the second experiment, the effect of tested essential oils was evaluated on F1 progeny reduction of R. dominica. Walnut and asafoetida leaves essential oils significantly suppressed progeny production by (59.92%) and (53.2%) respectively.

The fungal genus Paecilomyces comprises numerous pathogenic and saprobic species, which are regularly isolated from insects, nematodes, soil, air, food, paper and many other materials. Some of the Paecilomyces species have been known to exhibit capabilities for curing human diseases. Here, bioactivities of metabolites from some soil inhabitant and invertebrate pathogenic Paecilomyces species were explored against a panel of target prokaryotic and eukaryotic microorganisms. First, Petri plate assays indicated that all tested Paecilomyces species were capable of producing diffusible metabolites and volatile compounds with antifungal activities against Pyricularia oryzae and Saccharomyces cerevisiae. Subsequently, the metabolites of the Paecilomyces species were extracted and the growth inhibitory and antimitotic effects of extra-cellular metabolites were shown using the yeast S. cerevisiae as a model. Further research indicated some antibacterial activity of extra-cellular metabolites from Paecilomyces species against human pathogenic bacteria Staphylococcus aureus, Bacillus subtilis, Streptococcus pyogenes (G) and Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi (G-). These findings indicate that the Paecilomyces species, either saprobic or pathogenic, have a strong arsenal of bioactive metabolites which show inhibitory or cytotoxic effects against other microorganisms, with a potential for application in agroforestry and medicine.

Stripe rust cause by Pucciniastriiformis f. sp. tritici is one of the most important diseases of wheat and can cause severe yield loss in many wheat growing regions of the world including Iran. To determine yield loss caused by this disease and evaluate the effect of some chemical components on reduction of yield loss in south of Iran, field experiments were carried out in split plot design with three replications at Ahvaz research station during 2014-2015. Three cultivars; Chamran, Virinak and Boolani, were used and artificial inoculation was performed using an isolate which was collected from south of Iran and designated as Yr27 race variant. Meanwhile the effects of propiconazole and some herbicides on yield loss reduction were studied. In this study, grain yield and area under disease progress curve (AUDPC) were measured. Statistical analysis showed that the level of the yield reduction was significantly different in the three studied cultivars and different treatments. Propiconazole could control the disease significantly. The highest yield loss was observed for cv. Boolani in both with (9%) and without (54%) fungicide treatments. Combined application of propiconazole and herbicides significantly reduced yield loss compared with using them separately. The results of crop loss modeling using integral and multiple point regression models showed that the integral model (L = 0.017AUDPC-17.831) could explain more than 69% of AUDPC variations in relation to crop loss in all cultivars. In multiple point models, disease severity at various dates was considered as independent variable and crop loss percentage as dependent variable. This model with the highest coefficient of determination had the best fitness for crop loss estimation. The results showed that the disease severity at GS39, GS45, GS50 and GS60 stages (Zadok's scale) were more important for crop loss prediction than those in other phenological stages.

This study was undertaken to find out the optimum physicochemical parameters of fermentation, i.e. pH, incubation temperature and incubation time for the cellulase enzyme production of Trichoderma harzianum. The extracellular protein content was estimated by the dye binding method of Bradford. Endo-glucanase (EG), exoglucanase (or Cellobiohydrolase; CBH), β-glucosidase and total cellulase activity were investigated. The molecular weight of cellulase enzymes was studied using SDS-PAGE. To identify the predominant catalytic components in optimum conditions of enzyme production, cellulases were separated by an adapted two-dimensional electrophoresis technique. Estimated optimum conditions for cellulase enzyme were found as: pH 6.5, incubation temperature 28°C and incubation time 72 h. The SDS-PAGE profiles showed several enzyme bonds such as CBHs, EGs and BGLs. The T. harzianumhad both enzyme bonds of Cel7A (CBHI) and Cel7B (EG). Finally, the results of the 2D PAGE analysis showed that the profile of protein in optimium conditions of enzyme production had several enzymes such as CBHs, EGs and the high values of cellulose activity due to synergism that occurred between the CBH and EG.

This is the first report of two ectoparasitoid wasps, Elachertus inunctus (Nees, 1834) in Iran and Elachertus pulcher (Erdös, 1961) (Hym.: Eulophidae) in the world, that parasitize larvae of the tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lep.: Gelechiidae). The specimens were collected from tomato fields and greenhouses in Ahwaz, Khouzestan province (south west of Iran). Both species are new records for fauna of Iran. The knowledge about these parasitoids is still scanty. The potential of these parasitoids for biological control of T. absoluta in tomato fields and greenhouses should be investigated.

While searching for food, predators use herbivore induced plant volatiles (HIPV), host plant volatiles and those related to con/heterospecifics to find their prey. Not only the volatile components vary among plant species, but also the predator perception of these components might differ among species and samples. Here, we compared the olfactory response of two samples (Turkey and University of Tehran) of Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) when received herbivore induced plant volatiles (HIPV) from Tetranychus urticae Koch (Acari: Tetranychidae) infested cucumber and bean leaves, along with testing the effect of rearing experience of Turkey sample on its olfactory response in our laboratory conditions. Our data showed that P. persimilis of both samples significantly moved towards leaf odors (either cucumber or bean) when they received clean air from the alternative arm. For both samples, the predator did not make a preference between clean bean and cucumber leaves. When the predators were offered a choice between T. urticae infested bean and cucumber leaves, they significantly moved towards bean leaves in both samples. Rearing experience did not affect the predator choice of host plant species and P. persimilis from both samples preferred odors related to clean leaves rather than clean air. The number of experienced predatory mites moved towards T. urticae infested bean leaves was significantly higher than that preferred T. urticae infested cucumber leaves in both samples. We discussed whether their similar olfactory responses would be related to their experience of previous rearing conditions.

Lady beetles are the most important predatory species among arthropods, so studying their population parameters gives a clear picture about their life span. The life histories of variegated lady beetle, Hippodamia variegata (Goeze), fed on the English grain aphid, Sitobion avenae Fabricius, on different host plants were studied under laboratory conditions, at 25 ± 1 °C, 65 ± 5% Relative Humidity and a photoperiod of 16:8 (Light: Dark) h. Developmental, survival and fecundity data were analyzed using the age-stage, two-sex life table method. According to the age-stage, two-sex life table, the net reproductive rates (R0) of ladybird fed on S. avenae reared on Triticum aestivum var. tajan, Hordeum vulgare var. Dasht, Zea mays var. single cross 704 and Sorghum durra var. Speed feed were estimated to be 235.38 ± 36.15, 190.74 ± 33.37, 293.54 ± 46.66 and 137.46 ± 23.66 female offspring / female, respectively. Based on the results, the intrinsic rate of increase as an index of population increase of H. variegata, was 0.181 ± 0.006, 0.179 ± 0.006, 0.163 ± 0.006 and 0.162 ± 0.006 h-1 preyed on host reared on T. aestivum var. tajan Z. mays var. single cross 704 S. durra var. Speed feed and H. vulgare var. Dasht, respectively. Our findings demonstrate that by using the age-stage, two-sex life table we can accurately describe the growth, survival and development of the predator. Our finding may provide basic information for developing aphid biological control programs.

In the present study, seven indigenous, widely distributed plants of Meghalaya, namely, Pinus kesiya Royle (Pinaceae), Lantana camara Linn. (Verbenaceae), Litsea cubeba Lour. (Lauraceae), Gaultheria fragrantissima Wall. (Ericaceae), Mikania micrantha Kunth.(Asteraceae), Ambrosia artemisiifolia Linn.(Asteraceae) and Eupatorium riparium Regel (Asteraceae) were screened for their larvicidal and antifeedant activity against fourth instar larvae of the cotton bollworm, Helicoverpa armigera (Hübner) under laboratory conditions. The crude extracts of all the seven plants demonstrated a dose dependent increase in bioactivity. However the bioactivity of four plants namely, L. camara, G. fragrantissima, L. cubeba and P. kesiya was significantly higher (p ≤ 0.05) than the negative (solvent) control and extracts of A. artemisiifolia, E. riparium and M. micarantha. Methanol extract of L. camara caused highest oral toxicity with larval mortality ranging between 27.77% and 53.33% across the test concentration (0.25%, 0.5% and 1% w/v) while extract of G. fragrantissima demonstrated the highest feeding deterrence with reduction in larval feeding by50.92% and 70.61% at 0.1% and 0.5% respectively. Crude extract of L. cubeba leaves demonstrated high oral toxicity and feeding deterrence while extract of the needles of P. kesiya showed moderate level of oral toxicity as well as feeding deterrence at the highest tested concentration. Phytochemical analysis of the extracts of these four plants, revealed the presence of five different classes of phytocompounds each of which is known to have deleterious effect on insect pests.Thus it may be concluded that four out of the seven plants possess insecticidal property and can be further investigated for the development of a potent botanical insecticide.