PLANT PEST RESEARCH
Year:2013 | Volume:3 | Issue:4|Papers Count:6

Habrobracon hebetor (Hym.: Braconidae), as a cosmopolite ectoparasitoid and one of the most important biocontrol agents, is widely used against different lepidopteran pests. Adult wasps feed on sugar resources to obtain energy. In the present study, the effects of two factors, i.e. different concentrations of a sugar solution (0, 10, 30, 50 and 70%) and different feeding frequencies (no feeding, water-feeding once a day, one-time sugar-feeding on the first day of experiment, sugarfeeding once a day, sugar-feeding once every two days, sugar-feeding once every three days, sugarfeeding once every four days) on longevity and progeny production of adult wasps were examined.Sugar solution was a mixture of 1: 1: 1 glucose, fructose and sucrose. In the absence of larvae of the Mediterranean flour moth as host, the highest longevities were observed at 30, 50 and 70% concentrations, as 31.8, 35.9 and 27.5 days for males, and 39.5, 43.3 and 39.9±4.6 days for females, respectively (with no significant difference). In the absence of host larvae, the highest longevity of adults was obtained when wasps fed sugar once per day as 31.6 and 39.5 days, for males and females respectively. Also in the presence of host larvae, the highest longevity of females was observed when the wasps fed sugar once per day. Females fed from 30, 50 and 70% concentrations had the highest progeny productions of 93.4, 104.2 and 77.8 adult individuals/female, respectively. Finally, female feeding on sugar once a day produced the highest progeny (94.7 adult individuals/ female; with significant difference to other treatmants). These results indicated the importance of sugar in diet of adult parasitoid wasp of H. hebetor and its significant effects on their longevity and reproduction, this in turn can improve the diets used for mass rearing.

The Cotton whitefly, Bemisia tabaci is an important pest of cotton which by transmitting plant pathogenic viruses cause damage and reduce lint quality. The attractiveness and oviposition preference ofB. tabaci for seven cotton cultivars (Okra, Red Okra, khordad, Sahel, Mehr, Varamin and Termus 14) of two species of cotton (Gossypium hirsutum L.) and (Gossypium barbadence L. were studied in a choice test in greenhouse and laboratory conditions 24±2oC, 65±5% relative humidity and photoperiod 16: 8h (L: D). Results showed that, the number of whitefly at different time intervals (48 to 72 h) in the greenhouse and laboratory conditions on Termus 14 cultivar was significantly higher than other cultivars (P<0.01). In the choice test the highest mean number of egg deposited on the leaves 72 h after the infestation was observed on Termus 14 and it was significantly higher than other cultivars (P<0.01). According to these results, B. tabaci was highly attracted by the whitefly and oviposition preference on Termus 14 representing the susceptibility of this cultivar to activity of B. tabacirather than the others. The results obtained here can be used in integrated management programs of this whitefly in cotton field.

Variation in host plant quality in response to nitrogen fertilization could influence on performance and population of insect herbivores. Current greenhouse study was conducted to determine the effect of four nitrogen fertilization levels including 0, 75, 150 and 225 kg. ha-1 in canola (Brassica napus L.) on performance and population growth rate of mustard aphid (Lipaphis erysimi Kalt.). The results showed that increasing nitrogen levels had significantly affected the nitrogen content and carbon/nitrogen of canola plants. The maximum percent of leaf-N (3.05±0.09) and minimum ratio of C/N (16.00±0.70) were observed in plants fertilized with the highest nitrogen level. Increasing nitrogen fertilization significantly enhanced aphid performance. The shortest nymphal developmental period (5.76±0.08 days) and the maximum fecundity (95.38±5.03) were observed at the level of 225 kg N.ha-1. Regression analysis showed a positive significant relationship between the intrinsic rate of increase (rm) and nitrogen treatment. The aphids’ rm increased 20.64 % with increasing nitrogen levels from 0 to 225 kg. ha-1. Moreover, the population of mustard aphid significantly was affected by nitrogen treatment and sampling date. The maximum population was observed in 3rd sampling date and in the highest nitrogen fertilization. In all sampling dates, the maximum population growth rate was calculated in the highest nitrogen level. The population growth rate showed a decreasing trend with increasing sampling date.

The flour moth, Ephestia kuehniella, is one of the important pests of stored products that cause annually severe damages. In the current study, changes of detoxifying enzymes, some enzymes involved in intermediary metabolism and some non-enzymatic compounds were determined in the larvae of E. kuehniella treated with different concentrations of hexaflumuron. Larvae were treated by 100, 300 and 700 mg/ml of hexaflumuron and aceton (as control) at different time intervals of 24 and 48 hours. Larvae treated by 300 mg/ml of hexaflumuron demonstrated the highest activity of general esterases in both time intervals whena-naphtyl acetate was used as substrate. By using b-maphtyl acetate as substrate, the highest activity was observed in the larvae treated by 100 mg/ml of hexaflumuron. Similar results were observed in case of glutathioneS- tranferase thatimply presence of some isoforms of these enzymes. After 24h, activity of alanine aminotransferase was elevated along with increase of hexaflumuron concentration but adverse results were observed after 48 h. In case of aspartate aminitranferase, the highest activity was observed in the larvae treated with 700 mg/ml concentration. Increasing of hexaflumuron concentration causes higher activity of lactate dehydrogenase in both time intervals. After 24h, the highest activity of phenoloxidase was observed in the larvae treated with 300 mg/ml but no statistical differences was observed after 48 hours. There were no significant differences for protein and triglyceride concentrations after 24 hours but their highest amounts were observed in the larvae treated with 300 mg/ml. Increasing of hexaflumuron concentration decreased amount of glycogen in the treated larvae. These results revealed that haxaflumuron could intervene in intermediary metabolism of E. kuehniella in addition to disruption in growth and development.

The safflower fly, Acanthiophilus helianthi is one of the most important pests of safflower in the world that every year causes sever damage to the crop. In order to study population density of the safflower fly in 2012, seven safflower cultivars including Goldasht, Padideh, Zarghan, Varamin, PI, Acataria, Mec163 were cultivated under Completely Randomized Block Design with four replicates in research field of Shahed University (Southern Tehran). Once adult were captured, sampling was started from safflower bolls on weekly basis from late June to late of August. The number of larvae and pupae in each boll were counted separately for each cultivar and recorded in tables. Cultivar PI (10.81) had the highest density of larvae than other varieties. Cultivars Mec163 and Goldasht with rank mean of 60.45 and 62.83 had the lowest larval density than other varieties, respectively. Padideh and Zarghan cultivars with rank mean of 75.83 and 75.40 had the highest density of pupae than other varieties, respectively. Mec163 cultivar with a rank mean of 63.10 comparisons with other varieties had the lowest density of pupae. Varamin cultivar in comparison with other cultivars with rank mean rank of 77.9 had the highest safflower fly developmental stages, and then PI and Padideh cultivars with rank mean of 76.5 and 76.2 had the highest density of total developmental stages, respectively.Mec163 cultivar among varieties, with a rank average of 58.50 and Goldasht with the rank mean of 59.28 had the lowest density of all developmental stages. In general it can be concluded that mean density of different developmental stages of pest on some cultivar was low because of premature and early emergence and spiny bolls.

The dubas bug, Ommatissus lybicus Bergevin, is one of the most important pests of date palm, Phoenix dactylifera L. in several countries in the Middle East such as Iran and North Africa. In this study, the effect of climatic and crop management factors were investigated on the density of dubas bug in north of Hormozgan and south of Fars Provinces during 2010-2011. Correlation and factor analysis were used to determine the relationship between dubas bug density and management factors.Correlation analysis between pest density and management variables showed that in most studied regions, there were positive correlations with variables such as age and height of date palms, mixed cultivation with citrus, application of fertilizers, yellow wasp (Vespidae) population, intensity of weeds and number of date palm leaves, and negative correlations with variables such as irrigation period, application of pesticides, mites and scale population and distance between date palm stands.According to the results of factor analysis, seven factors explained 74.68 percent of total variance. To evaluate the impact of these factors on the population density of dubas bug, the multivariate regression was used. The results showed that the factor which included variables such as wall around the palm orchards, yellow wasp population and distance between date palms had the most contribution to prediction of dubas bug density. The second and third most contributing factors in prediction of pest density were factors which included variables such as collecting the pruned leaves and intensity of weeds, and variables such as irrigation period, age and height of date palm, number of leaves and intercropping with citrus, respectively. The highest nymphal density of the pest on date palm leaflet was observed in Farashband followed by Forg, Hagiabad and Jahrom regions, respectively. Among the weather factors, hourly solar radiation and relative humidity had negative and positive association with dubas bug density, respectively.