Applied Entomology and Phytopathology
Year:2006 | Volume:74 | Issue:1 (81)|Papers Count:12

Crop rotation is one of the most effective methods of reducing the damage of sugar beet cyst nematode (Heterodera schachtii Schmidt, 1871). In this study in a six years period (1992-1997), no-host crops: wheat, clover, cantaloupe, alfalfa, grain maize, cotton and onion were used in a completely randomized block design with five rotation patterns (treatments) and five replications in an infected field in "Jey and Ghohab" area of Isfahan. The eggs and larvae in the cysts per gr. of soil, before planting and after harvest of each crop, percentage of nematode reduction, root and sugar yield per ha. in the final year were measured. The results showed that all the rotation patterns had significantly different data with that of check (six years continuous sugar beet) of 1% level. The rotation of "sugar beet, cotton, wheat, onion, cantaloupe and sugar beet" and also "sugar beet, cantaloupe, wheat, clover, grain maize and sugar beet" reduced the nematode population up to 100% after five years in experimental trials. The yield of sugar beet root at last year was 20.46 and 20.52 and sugar yield was 2.89 and 2.73 ton/ha. for these two groups respectively. The data for check were 16.9 and 2.1 ton/ha. respectively.

To investigate the effects of lambsquarters density and its relative time of emergence on yield and yield components of grain corn a two year experiment was conducted in 2001 and 2002 growing seasons in the research field of Weed Research Department, Plant Pests and Diseases Research Institute, Karaj. Both experiments were conducted using factorial arrangement of treatments in a randomized complete block design with 3 replications. The treatments were the relative time of lambsquarters emergence (1st year: simultaneously, at 2-3 and 4-5 leaves stages of corn; 2nd year: simultaneously, at 2-3 and 5-6 leaves stages of corn) and lambsquarters density (first year: 2, 5, 10 and 15 plant.m-2; second year: 6.6, 13.3 and 20 plant.m-2). A pure plot of corn was also cultivated to evaluate grain yield of corn in weed free conditions. The results indicated that both treatments had significant effects on grain and biological yields, harvest index, grain number/ear row and row number/ear of corn. Thousand-seed weight was not affected by lambsquarters density. The results also showed that the negative effect of interference period on corn was more than that of density. In conclusion, a delay in lambsquarters emergence and a good management against it at the beginning of the growth season can increase the competitive ability of corn against lambsquarters.

Cereal leaf miner is one of the most important insect pests in Southern, Eastern and Southeastern parts of Iran. It cause quantitative and qualitative losses to cereal yield via feeding on leaf tissues. In a two year (2000-2001 and 2003-2004) study, using cards to estimate population density, economic injury level of this insect pest was determined. The results showed that there was a regressive relationship between the number of 1st instar larvae per plant and the grain yield weight at harvest time. The regression equation was constructed as follow: Y=(0.922 - 0.15Ln (X)2 where Ln= natural Logarithm, x= No. of 1st instar larvae per plant at 3-4 leave stage and Y=yield estimate for each plant. Thus based on costs of chemical control, yield reduction estimation and yield price the EIL in dry farming at plant densities of 100, 150 and 170 plants per m2 estimated as 4, 9 and 9 larvae per plant (400, 1350 and 1530 larvae per m2) in 2000-2001 and in 2003-2004 at plant densities of 100, 150 and 170 the EIL, showed to be 4, 8, and 10 larvae per plant (400, 1200 and 1700 larvae per m2) respectively.

Using water yellow traps, population fluctuation of winged aphids, vector of potatoes viral diseases, has studied in four districts of Hamedan province including Hamedan, Kaboodar ahang, Ghahavand and Assadabad during 1998-2000 period. In this connection, four species belonging to family Aphididae and one species of family Drepanosiphidae were collected. Among vector species Therioaphis trifolii forma maculata (Buckton) with 65-91% of total collected population tored other species in all above mentioned district. The other important species, collected in lower number, were Acyrthosiphon pisum (Harris), Myzus persicae (Sulzer), Macrosiphom euphorbiae (Thomas) and Aphis frangullae gossypii (Glover). Kaboodarahang with lowest population of aphid vectors and shortest period of aphid presence in potato fields considered as the most suitable region and Hamedan district owing to high vector population and longest presence of aphids in fields showed to be the most unsuitable site for basic seed potato production the other two districts are evaluated as intermediary to two above-mentioned regions.

In order to determine the critical period of weed control in cotton, an experiment was carried out at Varamin Research Center during years 2000-2001. The experiment was conducted in randomized complete block design with 14 treatments and 4 replications, applied in two series. In the first series, weeds competed with cotton at different phonological stages of cotton (production of I and 5th true leaf stage, I, 3 and 5th reproductive branches and production of brown flower) and during the growing period as check treatment. In the second series, weeds were controlled as above-mentioned stages and during the growing period as check treatment. Results showed that the height of cotton plant, number and length of branches, number of bolls and cotton yield were affected by weed competition. The critical period of weed control began from production of the first reproductive branch and continued up to production of brown flower on cotton plants in the first year of experiment. The critical period began sooner due to drought stress in second year and started when the 5th leaves appeared. Amaranthus retroflexus L., A. viridis L., A. blitoides S.Watson, Portulaca oleracea L., Echinochloa crus-galli (L.) P.Beauv., Cyperus rotundus L., Sorghum halepense (L.) Pers were the most dominant weeds in experimental location.

In this research morphology and some biological and behavioral characteristics of the parasitoid wasp, Telenomus acrobates Giard (Hym.: Scelionidae) as an egg parasitoid of Chrysoperla carnea (Steph.) (Neu.: Chrysopidae) were studied. Experiments were conducted in a growth chamber at constant temperature of 25±0.5°C and 65±5 % relative humidity with a 16:8 h (L:D) photoperiod. The results indicated that mean developmental time of female and male wasps were 11.54±0.054 and 11.41±0.027 days, respectively. The adult longevity of T. acrobates was 26.92±1.59, 16.75±0.69 and 1.04±0.05 days in female and 12.77±1.27, 6.5±0.62 and 1.01±0.04 day in male in three conditions with food, host egg and food, and without host egg and food respectively. In the host preference experiment, it was found that T. acrobates prefers one and two-day old eggs to three-day old ones. The functional response of T. acrobates was of type n. The handling time and searching efficiency estimated 0.059 and 1.675 respectively and the maximum parasitism showed to be 14.33. The seasonal egg parasitism of C. carnea was studied from May to September 2002. The percentage of parasitism and the percentage of female wasp to the whole collected eggs were 52.93 and 64.9 respectively.

In order to determine if Berseem and Persian clovers contained water -and methanolsoluble allelochemicals that affect seed germination of Amaranthus retroflexus, Convolvulus arvensis, Secale cereale and Sinapis arvensis, an experiment was conducted. Aboveground tissues of the clovers was collected and dried. Three concentrations of aqueous and methanolic extracts were used: full-concentration (33.3 g/L), half-concentration (16.7 g/L), and quarter-concentration (8.3 g/L). The weed seeds were placed in petri dishes that contained 8 ml of the legume extracts, or distilled water (control). Percent germination was taken after two weeks. In general, seed germination declined progressively with increasing concentrations of both clover extracts. Wild mustard exhibited the greatest sensitivity to both the extracts. Compared with aqueous extracts, methanolic extracts caused more inhibition in seed germination. Compared with Persian clover, berseem clover was stronger inhibitor of seed germinatiolL Therefore, the contents of allelochemicals in these clovers species seems to be different. It seems that field bindweed had probably more tolerance to these allelochemicals.

Chemical herbicides and fertilizers are two important inputs in cereal production systems. Tank mixing and foliar application of urea fertilizer and selective herbicides could cause reduction of inputs and costs, and increase the fertilizers use efficiency in wheat. For verifying this hypothesis, a three year trail was conducted during 1999 to 2001 at weed research station of Plant Pest and Diseases Research Institute in Karaj. The experiments were carried out in randomized completed block design (RCBD) with four replications in a factorial arrangement of treatments. Treatments included herbicide combination at nine levels and urea application in two methods: foliar application and top dressing. The results of the experiment indicated that foliar application of urea had a significant effect on yield. The urea tank mixing with herbicide had no effect on herbicides use efficiency. Among herbicide and urea combinations, Urea+ Tribenuron-methyl+Clodinafop-propargile were the best combination for controlling weeds and increasing grain and biological wheat yield. This combination could be used as a tool for increasing nitrogen use efficiency and best chemical treatment for weed management in wheat.

In May 2005 on some branches of Pinus eldarica collected in Tehran showed to be infested with Buprestid larvae. The infested branches put in rearing boxes for emergence of adult beetles. The adults emerged on early July proved to be chrysobothris solieri. It is the first record of this species from Iran. Among chrysobothris larvae are observed speciemens parasitized with two following parasitic wasps that identified by J. Macek from Prague museum of Hungary. 1- Liotryphon sp. (Hym.: Ichneumonidae)2- Hockeria sp. (Hym.: Chalcididae)