فصلنامه تحقیقات آفات گیاهی
سال نهم شماره 2 (تابستان 1398)

IPM is a combination of crop protection practices to keep pests below economic threshold, and one of them is to make the host plants resistant. Various parameters such as the application of fertilizers, irrigation and providing optimum conditions for host plant can benefit its resistance to pests. In order to induce resistance on cucumber (Kish var.), the foliar spray of phosphorus and potassium were incorporated for observing the Tetranychus urticae performance. Therefore, four Fosfalim-k concentrations (i.e. 0, 1, 10 and 30 ml L-1) were sprayed on cucumber (Kish var.) in three time intervals and the life table parameters of T. urticae were studied in the laboratory conditions. The measured plant characteristics included fresh and dry mass, total protein, chlorophyll, carotenoid and the activity of antioxidant enzymes (CAT, APX and GPX). The age-stage, two-sex life table parameters of T. urticae were analyzed using TWOSEX-MSChart software. The 30 ml L-1 concentration caused plant defoliation and was deleted from results. The results showed that CAT and APX enzymes activity and carotenoid concentration were significantly increased while fresh and dry mass and chlorophyll concentration were decreased in response to 10 ml L-1Fosfalim-k. In the studied life table parameters of T. urticae, λ, R0 and r parameters were decreased significantly in this concentration. Hence, spraying cucumber with Fosfalim-k can decrease survival and fecundity of T. urticae and the suggested concentration could be 10 ml L-1.

Coriander, Coriandrum sativum L. abbreviated here as Co, belongs to Apiaceae which is an aromatic herbaceous annual plant. In this study, intercropping coriander with strawberry, Fragaria ananassa Duchesne abbreviated as S, in the two patterns 2S: 2Co and 5S: 2Co (row ratios) were assessed for controlling the two-spotted spider mite, Tetranychus urticae Koch, compared to strawberry. The results indicated that intercropping coriander and strawberry reduced the density of T. urticae eggs compared with strawberry monocropping. Furthermore, the densities of mobile forms of T. urticae were significantly lower in intercropping systems, especially 2S: 2Co compared with strawberry monocropping. Moreover, the land equivalent ratio (LER), which is used to assess the yield benefit in intercropping systems, was greater than 1 in intercrops, especially 2S: 2Co (1.413 in 2017 and 1.430 in 2018). These results indicated that intercropping strawberry with coriander could be beneficial in integrated management of T. urticae by reducing two-spotted spider mite densities and increasing the crop yields.

Biological characteristics of Panonychus citri such as life cycle, abundant progeny and arrhenotoky, have provided the pest a high potential to develop acaricidal resistance. Bromopropylate is recommended by Iranian Plant Protection Organization to control P. citri. In this study, resistance of p. citri to bromopropylate was investigated. Bioassay and synergists tests were performed with a Potter spray tower method. Results showed a resistance of 10.63 fold to bromopropylate in resistant population (RP). Pre-treatment of susceptible population (SP) of P. citri adult with the cytochrome P450 monooxygenase inhibitor, PBO, the esterase inhibitor, TPP, and glutathione-S-transferases inhibitor, DEM, increased bromopropylate toxicity by 5.58, 5.89 and 4.59-fold, respectively, while, these ratios were as 2.44, 2.51 and 2.38-fold, respectively, for RP. The overall lower synergism in RP compared with susceptible population by DEM, PBO and TPP suggests that glutathione-S-transferases, esterases and monooxygenase are not an important factor in resistance. The results of biochemical tests revealed that the activities of monoxygenase, α-naphthyl, β-naphthyl esterases and glutathione-S-transferase in the resistant population was 1.39, 1.70, 1.83, and 1.34- fold higher than that of susceptible population, respectively. Estimation of kinetic parameters showed qualitative changes in esterase and GST. The increased activities of detoxification enzymes may be caused by application of different acaricides which are used for control of this pest in citrus gardens. Therefore, other resistance mechanisms such as reduced penetration and target site insensitivity likely is involved in the resistance. Reduced bromopropylate application as well as application of acaricides with different mode of actions are necessary for avoiding resistance development.

Common bean is cultivated for feeding in the whole world. The two-spotted spider mite, Tetranychus urticae Koch, and the onion thrips, Thrips tabaci Lindemann, are considered as the two important pests of bean and lots of pesticides are being used for their control. One of the most important strategies in integrated pest management programs is the cultural practice. In the present study the effects of cultivars and bean plant density has been taken into consideration to control these pests in a bean field in Boroujerd district, Lorestan province of Iran. This research was performed as per factorial in a completely randomized block design, with three cultivars (Akhtar, Derakhshan and 285) in five plant densities of 20, 30, 40, 50 and 60 plants per m2. Samplings were carried out weekly and in every sampling date, the number of each pest was recorded. Results showed that bean cultivars had significant impact on the number of eggs in spider mite and in total and 1st instar larval populations of onion thrips. The plant density also significantly affected populations of both the pests. Interactions between cultivar and plant density was not significant for both pests. Overall the highest and lowest population densities of the spider mite observed in the cultivar of Derakhshan with 60 plants density in every m2 and then cultivar of 258 with a density of 20 plants per m2 respectively. The lowest and highest total number of thrips was observed in Akhtar cultivar with 60 plants per m2 and then Akhtar cultivar with a density of 20 per m2, respectively. The results of the present study could be recommended in IPM program for bean fields.

Habrobracon hebetor Say is a larval ecto-parasitoid of several moths. In this study, toxicity of Moldavian dragonhead (Dracocephalum moldavica L.)essential oil on Mediterranean flour moth (Anagasta kuehniella Zeller), Indian meal moth (Plodia interpunctella Hubner) and H. hebetor parasitoid waspwere assessed. Essential oil of D. moldavica was extracted by hydrodistillation method using a Clevenger apparatus and its chemical constituents were detected by Gas Chromatography-Mass Spectrometry (GC-MS). Piperitenone Oxide (19.03%), Piperitone Oxide (13.74%) and Citral (9.79%) were identified as the main constituents of the essential oil. It was found that 50% lethal concentration (LC50) values of the essential oil against H. hebetor, A. kuehniella and P. interpunctella adults estimated were 0.995, 9.631 and 10.252 μl/l air, respectively. In order to assess the sub-lethal effects, adult wasps were exposed to LC25 of D. moldavica essential oil and then the demographic parameters of live parasitoids were evaluated. The intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), gross reproductive rate (GRR) and mean generation time (T) were significantly decreased by essential oil. Results of the present study indicated that the essential oil of D. moldavica can be effective in the management of A. kuehniella and P. interpunctella. However, simultaneous application of D. moldavica essential oil and the parasitoid wasp H. hebetor in the management of aforementioned pests, based on toxicity and negative demographic effects of essential oil on this parasitoid wasp is not recommended.

Diamondback moth has a high potential for insecticide resistance. Usage of insecticides with different modes of action as a mixture is one of the strategies of insecticide resistance management. It can reduce the resistance development rate. In this study, hexaflumuron and flubendiamide were tested as alone and their mixture against the third instar larva of diamondback moth. Three concentrations of each insecticide were used in the mixture. The LC50’s values of hexaflumuron and flubendiamide were calculated as 1.48 and 10.27 mg L-1 against the third larvae, respectively. Bioassay of both insecticide mixtures showed that the mixture at the low concentrations had a synergistic effect, whereas it was cumulative effect at the highest concentration mixture. Binary combination of flubendiamide at the lower concentration with hexaflumuron can increase larval mortality. It reduces latent effectiveness of hexaflumuron and causes to decrease crop loss after treatment. Therefore, the use of mixed insecticides in IPM of diamondback moth is possible only with expert advice in the limited concentrations of them.

During 2018- 2019 in a research entitled the identification of arthropods associated with tea, some samples of leaves and branches of tea plant infected by broad mite (Tarsonemidae) were collected. Mites were separated from infected plant parts, cleared in Nesbit’s fluid and mounted on microscopic slides in Hoyer’s medium. Mites were identified by using valid references. Among collected mites, Polyphagotarsonemus latus (Banks, 1904) was identified for the first time from Guilan province on tea plant. The symptoms of damage are diagnosed by deformity, curling, darkening and thickness of leaves and deformation of tip branches and buds. The damage of broad mite is so severe on tip branches and buds of tea plant. This is the first report of yellow broad mite (Polyphagotarsonemus latus) on tea plant in Northern Iran tea gardens.