JOURNAL OF CROP PROTECTION
Year:2018 | Volume:7 | Issue:3 |Papers Count:8

Demographic parameters such as intrinsic rate of increase estimates are of main interest in a wide range of ecological researches. Two widely used uncertainty estimate techniques are bootstrap and jackknife methods.Bootstrap estimates are time-consuming processes that are impossible to use without a computer program. Unfortunately few programs, if any, have been developed for this task. In this study a guideline was offered to prepare a program in Microsoft Excel environment to carry out time-consuming calculations of reproductive life table data in a minute or two by repeatedly pressing a shortcut key.

SorghumSorghum bicolor L. releasing allelochemicals in the soil through their root exudation that functional their associated soil microorganisms and can help in building disease control strategy for increasing sustainability. The obtained results of sorghum rhizospheric exudates exhibited markedly effect on bacterial count in rhizosphere soil. The extract of root exudates profile was tested by two prepared concentrations; 500 ppm and 1000 ppm against theBipolaris sorokiniana compared to untreated control. The reduction percentages were calculated after four and seven days of fungus growth, the results represented that the reduction over control were 17.53, 45.63% after four days, however after seven days the reductions over control were 17.28, 36.40%. For sorghum root parts, the reduction increase with increasing concentration ranged from 49.71 to 71.67%, the highest reduction was afforded by conc.1600 ppm while the lowest reduction by 200 ppm. The analysis to identify sorghum allelochemicals was conducted by LCMS/ MS and FTIR afforded; proline, coumaric acid, cinnamic acid, hydroxycoumarin, benzoxazolone, ferulic acid and sorgoleone. While, sorghum root parts extract compounds were; coumaric acid, cinnamic acid, vanillic acid, luteolin3-Hydroxycoumarin, gallic acid, ferulic acid and sorgoleone. It could be used sorghum root exudates and root parts extract in disease bio-control due the effect of secreted biochemical molecules as step toward sustainable agriculture.

Laboratory experiments were carried out to evaluate the susceptibility of six improved cowpea varieties to seed beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae) attack at a temperature of 29 ± 2oC and a relative humidity of 65 ± 3%. Fifty grams of each variety were weighed in Kilner jars (250ml) and infested with three females and two males of C. maculatusthat were 1-2 days old. Data recorded were the physical characteristics of the cowpea varieties, number of eggs laid, percentage egg survival, number of emerged adults, duration of emergence (DE), mean developmental period (MDP), percentage seed weight loss, percentage seed damage and susceptibility index. The experiment was a completely randomised design with three replications. Results showed that significant differences (p<0.05) existed in DE and MDP among the cowpea varieties studied. IT90K-76, IT98K-131, IT11D-15-21 and IT07K-299-6 performed significantly better in duration of emergence than IT10K-866-1 and TVx 3236.IT98K-131-1 performed significantly better in median developmental period (26.67 days) than other varieties except for IT90K-76 (22.67 days). Results showed that IT90K-76, IT10K-866-1 and IT98K-131-1 were moderately resistant while IT07K-299-6, IT11D-15-21 and TVx 3236 were susceptible.This study recommends IT90K-76 because it performed appreciably better in these parameters than the other cowpea varieties when infested with C. maculatusin storage.

Habrobracon hebetorSay (Hymenoptera: Braconidae) is one of the major parasitoids which is used against various lepidopteran larvae in Iran. Due to extensive application of chemical pesticides in farms, study of their side effects on natural enemies is necessary. Therefore, in this study, side-effects of two prevalent insecticides, NeemAzal and Takumi (at dosage 2000 mg/l and 437.5mg/l, respectively), on functional response of H. hebetor to different densities of 5th instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were evaluated in laboratory conditions. Host densities of 2, 4, 8, 16, 32 and 64 were randomly exposed to selected treated females of H. hebetor in 8 cm Petri dishes. Ten replications were conducted for each host density. The control was treated with water. The data were analyzed using logistic regression to find functional response type and non-linear regression to estimate functional response parameters. The results revealed a type ΙΙ response for all treatments.This study showed that H. hebetor had the shortest (0.269 h) and longest (1.822 h) handling times in Takumi and NeemAzal treatments, respectively. Also, the highest and lowest searching efficiency of H. hebetor were recorded for the Takumi (0.188 h–1) and NeemAzal (0.0396 h–1) treatments, respectively.According to the results of the study, Takumi may be more compatible with biological control agent in IPM programs.

The essential oils of plants are composed of several volatile compounds, which may have different concentrations and may be determinant for their toxicity. Thus, in this work, sublethal and lethal effects of the compounds, geraniol and citronellal on the biochemical and reproductive parameters of Spodoptera frugiperda were investigated. For the geraniol compound the LD30 of 9.42 mg/g and LD50 of 13.65 mg/g was used, while for the citronellal LD30 of 0.06 mg/g and LD50 of 0.08 mg/g. Pure acetone was used in the control. Third instar caterpillars were treated topically in the prothoracic region by applying 1 ml of the respective compounds with a HamiltonTM 50 ml syringe. After 48 h the caterpillars were macerated in sodium phosphate buffer at a ratio of 4 caterpillars / 5 ml of the buffer, the levels of total protein, total sugar, lipid and glycogen were measured. The daily posture was evaluated in order to determine the periods of preoviposition, oviposition, post-oviposition and egg quantity. The results showed a reduction in the concentration of proteins and sugars for both compounds and concentrations studied. There was no change in lipid concentration. Citronellal increased the concentration of glycogen for both concentrations. The oviposition period and the number of eggs were reduced. However, there was no difference for the pre-oviposition and post-oviposition periods. Thus, it is inferred that geraniol and citronellal compounds cause alterations in the biochemical parameters that reflect in the reproduction of S. frugiperda.

Small walnut aphid (SWA) Chromaphis juglandicola is an economic pest of walnut trees. Population fluctuation of SWA was studied in Mamaghan walnut orchards (East Azarbaijan Province, Iran).Three factors affecting population density of SWA, including vertical divisions of canopy (upper and lower half), geographical orientations of canopy (at four levels) and elongation of branch (basal and distal ends), were investigated. Sampling unit was a cluster of five leaves. Totally 128 samples were taken weekly from all strata upon eight chosen trees, repeating 30 times during the season. Natural enemies also were counted. The first SWA individuals were observed early May, consisting of first instar larvae and alate females. A sudden population increase occurred in mid-May. Maximum 40 aphids/leaf were observed in early June with first and second instars dominant, followed by a sudden decline in late June. A small peak was observed at early October. A partial tendency was observed toward north of canopy, at basal half of downward branches. Positive linear correlation between natural enemies' and SWA populations suggests density dependence. Moreover 2-4 week delay was present between them.Trioxys pallidus (Holliday) was dominant natural enemy in the region. Contrary to previous works, overwintering stages of the SWA in the region were predominantly developed stages (third and fourth instars as well as pre-reproductive winged females).

The egg parasitoids of the genusTrichogramma have become one of the most important economic insects, for they are widely used in biological control of Lepidopteran key pests. For that reason, all aspects of their mass production including diapause have been considered over the last few years. In this study, the effect of host quality on the diapause induction of sexual and asexualT. brassicae Bezdenko (Hym: Trichogrammatidae) have been investigated at two temperatures. Maternal generation developed at two distinct temperatures (14 and 20oC) and they oviposited on four different qualities of Ephestia kuehniellaZeller (Lep: Pyralidae) eggs including fresh eggs, frozen eggs, host eggs with developing embryo and low quality eggs. Data analysis revealed significant influence of temperature and host quality on diapause induction in both sexual and asexual strains. Maximum diapause happened in host eggs with developing embryo even though they were in fetal development.A higher level of diapause was observed inT. brassicae whose maternal generation had developed at 20oC. The diapause induction in asexual T. brassicaewas less than sexual wasps. The results imply that Wolbachia causes a disturbance in the diapause process. The outcomes of this study, which are new, indicate the complexity of diapause and the importance of factors such as host quality which have received less attention in diapause induction.

Environmental risks associated with the use of synthetic fungicides have resulted in an emergent trend in plant disease control with focus on the use of botanicals. In this work, the peels of ripe sweet orange fruits were removed, air dried, powdered and extracted with 95% ethanol.The agar diffusion method was used to test the crude extract against the mould, Lasiodiplodia sp. IMI 50324 Which was originally isolated from rotten orange fruits. The extract inhibited mycelial growth of the fungus. The ethanolic extract was subsequently purified by column chromatography and the fractions separately tested for antifungal action. Total phenol contents of fractions and crude extract were both determined. Active fractions were pooled together and analyzed by gas chromatography-mass spectrometry (GC-MS) for structural elucidation. GC-MS revealed that the peel extract contained the flavonoid 5, 6, 7, 8, 3', 4' -hexamethoxyflavone which is commonly called nobiletin. The presence of 5, 6, 7, 8, 3', 4' hexamethoxyflavone in the peel together with the high total phenol content probably account for inhibition of the test fungus.