Journal of Applied Research in Plant Protection
Year:2020 | Volume:9 | Issue:3|Papers Count:8

Application of defense-inducing compounds such as microbial volatiles is a new strategy for suppression of plant diseases based on plant intrinsic genetic potential. In this study, effect of defense inducing compounds including, benzothiazole, methyl salicylate, methyl jasmonate, butanediol, indole and acetoin were investigated on Gaeumannomyces graminis var. tritici mycelial growth in vitro and on suppression of wheat take-all at greenhouse situation as a completely randomized design. Seeds of wheat cultivar Pishgam were surface sterilized and placed in 100 μ M solution of benzothiazole, methyl salicylate, methyl jasmonate, butanediol, indole, acetoin or control (distilled water) for 30 minutes. Seeds were sown in the pots containing pathogen inoculated soil in the greenhouse for 30 days. In vitro experiment showed that indole, butanediol and acetoin as best treatment reduced pathogen mycelial growth only 14. 29, 14. 29 and 8. 27% compared to untreated control. Analysis of plant growth factors showed that defence inducers treatment had no significant effect on root dry weight compared to infected control. In contrast, benzothiazole, acetoin and methyl salicylate significantly increased aerial part dry weight. Moreover, all of the chemical inducers were able to reduce disease severity, significantly. The highest disease suppression were achieved in the case of benzothiazole and acetoin decreasing disease severity by 60. 9 and 57. 4 %, respectively. Exploitation of plant defense inducers seems to be promising strategy in management of wheat take-all disease.

In this research after formulating essential oils of Mentha longifolia, Mentha piperita and Oliveria decumbens, quality of the prepared formulations was studied according to the FAO standards. Then insecticidal efficacy of these compounds was investigated in comparison with Dayabon (Dayabon ® ) and acetamiprid (Mospilan® ) against first instar nymphs and adults of Phenacoccus solenopsis in lab and field conditions. The LC50 values of formulated essential oils of M. longifolia, M. piperita, O. decumbens, Dayabon, Dayabon+ sesame oil and acetamiprid on the adults and the nymphs of P. solenopsis were 164. 55, 171. 41, 195. 92, 6177. 85, 3316. 58, 69. 28 and 49. 77, 55. 13, 65. 32, 4256. 10, 2159. 89 and 16. 45 mg/l, 48h after treatment respectively. Field experiments were also conducted with four replications in a randomized complete block design. The numbers of P. solenopsis (nymph and adult) on branch samples were counted before treatment and 1, 3, 7 and 14 days after treatment. The field bioassay results showed that formulated essential oils had acceptable effects on developmental stages of P. solenopsis. Acetamiprid toxicity was higher than the other treatments but gradually reduced. The total results revealed that formulated essential oils were known as promising compounds in integrated management of this pest.

Integration of different pest control tactics is a principle in modern pest management. Interaction between different tactics and possible antagonism between them then will become important. A common integration is integration of egg parasitoid, Trichogramma spp. and larvicidal microbial agent, Bacillus thuringiensis against some field crop moth-pests, particularly in bollworm-cotton system. Although sequence of application allows avoiding direct antagonism, but indirect effects on the next generation of the parasitoid via treating the target pest’ s larvae is not impossible. Some direct effect via overlapping of different stages of the pest is also possible. Therefore, studying possible maternal effects on parasitoids of the next generation that are developing on B. t.-treated host larvae is required. In this study, response of T. brassicae, was studied on two kinds of hosts; first bollworm, Helicoverpa armigera eggs laid by those females that treated by LC20 of B. thuringiensis in third instar. The second one control (untreated) individuals. Life history parameters were compared between the two groups by two-sided t-test. No significant difference was observed between the two groups. It means that B. t. had no undesirable effect on T. brassicae. The mean value of R0, rm and T were 41. 22 ± 3. 85 female/female/generation, 0. 3545 ± 0. 009 /d and 10. 49 ± 0. 19 d as average of the two treatments. Thus, B. t. is safe for integration with Trichogramma application programs.

Ornamental trees decline is an important disease that threatens many ornamental and forest trees in the world, including ash, acacia, black locust, maple, elm and ornamental palms. In the present research, in order to characterize the fungal agents associated with black locust decline in Ardabil, samples were collected from black locust trees with typical dieback and canker symptoms from green spaces. 150 fungal isolates were isolated and purified using routine plant pathology methods. Identification of species was carried out using morphological and molecular sequence data of the ITS regions or TEF gene. In this study, 10 fungal species including Fusarium oxysporum, F. solani, Acremonium sp., Cytospora chrysosperma, Camarosporidiella elongata, Nigrospora sp., Alternaria alternata, Epicoccum nigrum, Chaetomium sp. and Sordaria macrospora were identified. It seems that Camarosporidiella elongata, Cytospora chrysosperma, Fusarium oxysporum and F. solani are likely involved in the vascular obstruction, dieback and eventually black locust trees decline in green space of Ardabil. This is the first study on the occurrence of black locust decline in Iran. Among the identified isolates, Ca. elongata is reported for the first time in Iran. Acremonium sp. and S. macrospora are new reports on black locust host worldwide.

In this study the effect of washing (soap at the rate of 2/1000) was compared with some acaricides in control of the almond spider mite in the field conditions based on the completely randomized block design during 2009-2010. Treatments included bromopropylate (at the rate of 2/1000), hexythiazox (1/1000), fenazaquin (0. 5/1000), fenpyroximate (0. 5/1000), clofentizin (0. 75/1000) and washing (with soap at the rate of 2/1000). Water spray was used as control. Pest population density was recorded 3, 7, 14 and 21 days after treatments. Results of the first year showed that bromopropylate had the highest mortality, while fenazaquin and clofentizin treatments caused the least mortality in the pest population at different sampling times. Washing, fenpyroximate and hexythiazox treatments ranked the second after bromopropylate. In the second year, bromopropylate and hexythiazox treatments caused the highest and lowest mortality in the mite population, respectively. Washing was not significantly different with fenazaquin, fenpyroximate and clofentizin and ranked after bromopropylate. Comparing mean mortality of the mite (adults and nymphs) in both years of study showed that there was no significant difference between washing of the infested trees and application of acaricides at different sampling times. Using this method, in addition to the pest control, can reduce the production cost, protect the natural enemies and increase the plant photosynthesis.

The functional response is one of the important components of predator-prey interactions. It can be affected by different factors such as host plant quality. In this research, the functional response of the predatory gall midge Aphidoletes aphidimyza larvae to the nymphs of the melon aphid, Aphis gossypii reared on cucumber plants amended with different levels of nitrogen fertilizer (0, 100, 150 and 200 kg/ha) was investigated. The experiments were carried out at 25± 1 ° C, 60± 5 % RH and a photoperiod of 16: 8(L: D). Different densities (2, 4, 6, 8, 12, 16 and 24) of mixed 2-and 3-d old nymphs of the aphid were separately offered to 4-d-old predator larvae. The numbers of killed preys were recorded after 18 h. Logistic and nonlinear regression analyses were used to determine the type of functional response and estimate of attack rate (a) and handling time (Th) parameters, respectively. At all treatments, the predator exhibited a type II functional response to change in A. gossypii density. The attack rate and handling time of the predator were ranged from 0. 0623 to 0. 1512 h-1 and 1. 4646 to 1. 8716 h, respectively. The highest value of attack rate and the lowest value of the handling time of A. aphidimyza were obtained at treatment of 200 kg/ha nitrogen. This study revealed that adding nitrogen to the soil in cucumber cultivation can improve the predatory ability of A. aphidimyza on A. gossypii. However, for understanding further details of the effects of different levels of nitrogen fertilizer on cucumber-A. gossypii-A. aphidimyza interactions, further studies need to be carried out.

Callosobruchus maculatus and Sitophilus granarius are two of the most important pests of stored products and cause heavy damage. Due to economic importance of stored product pests and resistance potential of them to conventional fumigants, it is necessary to replace these insect control agents with novel and safe compounds. Modified atmosphere is a valuable method to control some stored product pests. In this research effect of this method based on the use of carbon dioxide and ammonia was evaluated against adult stages of C. maculatus and S. granarius alone and in combination with each other in glass anaerobic jars. Mortality was recorded after 24 h. The LC50 values of carbon dioxide for C. maculatus and S. granarius were estimated 1322. 53 and 1283. 96 ppm, respectively. The LC50 values of ammonia for these pests were estimated 250. 24 and 366. 79 ppm, respectively. The mixture of carbon dioxide and ammonia (in LC25 values) caused a mortality rate of 86. 67 and 93. 33 % on the adults of C. maculatus and S. granarius respectively. The effects of carbon dioxide and ammonia were also evaluated against germination rate of cowpea and wheat seeds at 2238. 72, 3630. 78 and 426. 58, 549. 55 ppm, respectively. Germination rate was up to 98 percent.

Black or stem rust caused by Puccinia graminis f. sp. tritici is one the most important and destructive fungal disease of wheatworldwide. One of the most virulent stem rust races, having virulence on many stem rust resistance genes, is the race TTKS(Ug99) which was first observed in Uganda in 1998 (Pretorius et al. 2000). Since 1999, 12 different variants of the race TTKSK (Ug99) have been identified worldwide, including TTKSF, TTKST, TTTSK, TTKSP, PTKSK, PTKST, TTKSFTTKTT, TTKTK, TTHSK, PTKTK, and TTHST (Bhavani et al. 2019). Despite the presence of this race in some provincof the country since 2007, none of the variants of the race Ug99 have not yet been reported from Iran. In 2016, in the Shavoodistrict of Khuzestan province, severe stem rust infection was detected on Chamran2 cultivar (harboring the Sr31 gene). Thisevidence raised the possibility for the presence of Ug99 or its variants in the Shavoor region. The infected stem and lea samples were collected from this cultivar and transferred to the cereal rusts greenhouses at Seed and Plant ImprovemeInstitute. Three single-pustule isolates were multiplied on susceptible cultivar McNair 701. A set of 20 North Americadifferential cultivars employed to determine the race. Phenotyping reaction (infection type) was carried out based on the 0 4 scale (Stakman et al. 1962) and the race designation was done based on Jin et al. coding system (Jin et al. 2008). Based on the values determined for each of the North American 20-genotypic differential genotypes, the Shavoor region isolate widentified as TTKTK, which is a variant of the Ug99 race (Figure 1). Previously this race has been reported from UgandEthiopia, and Kenya (Patpour et al. 2016). The reaction of both the Sr31/6*LMPG line carrying the Sr31 resistance gene and the CnsSrTmp line carrying the SrTmp gene and Mv17, Falat, Shiroudi, and Chamran2 cultivars, which were confirmed bmolecular analysis of the Sr31 resistance gene, in all replicates was susceptible to the isolate (3-4). Other races of Pgtincluding TKTTF, TTRTF, and TTTTF, are virulent on the SrTmp resistance gene. It worth mentioning that this race is highvirulent and has very high pathogenicity (infection north American differential line and advances lines of wheat) and previoumolecular studies have shown low frequency of effective resistance genes to Ug99 and its variants in commercial cultivaradvanced and promising wheat lines in Iran (Patpour et al. 2014); hence, this issue is a serious threat to the country's food security. Before the epidemic of this race, appropriate measures must be taken in to account including the introduction effective resistance genes against the TTKSK (Ug99) and its variants in desirable genotypes that are widely cultivated undevarious climatic regions across the country.