Economic damage thresholds of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) on cotton in Egypt

A simple but effective method is presented of assessing damage caused by the cotton leafworm, Spodoptera littoralis, on cotton. A minimum economic damage threshold of 10 000 egg masses/ha was found to be a practical level for most years in Fayoum, Egypt.     

High level of metaflumizone resistance and multiple insecticide resistance in field populations of Spodoptera exigua (Lepidoptera: Noctuidae) in Guangdong Province,China

Spodoptera exigua is a phytophagous pest that causes critical economic losses in vegetable crops, and insecticides are commonly used against it in vegetable growing areas. However, excessive and frequent applications of insecticides cause resistance in S. exigua. The current resistance in field populations of S. exigua collected from Huizhou, Guangdong Province, China to 12 insecticides was investigated. S. exiguahad developed very high resistance to lambda cyhalothrin (2925- to 3449-fold), chlorpyrifos (>1786-fold), emamectin benzoate (174- to 867-fold), and metaflumizone (60.3- to 942-fold). High resistance to tebufenozide (51.5- to 75.4-fold) and chlorfluazuron (60.4- to 63.0-fold) was also found. Synergism assays revealed that the resistance to metaflumizone and lambda cyhalothrin was associated with esterase and microsomal oxidases, respectively. The resistance to emamectin benzoate was not affected by detoxification enzymes inhibitors and might be conferred by other mechanisms. The selection of the field population by metaflumizone for 10generations in the laboratory resulted in a 6.1-fold increase in metaflumizone resistance but did not lead to increases in resistance to other insecticides. After metaflumizone selection, susceptibilities to spinosad and endosulfan did not change, and the susceptibilities to indoxacarb, methomyl, pyridalyl, tebufenozide, chlorfluazuron, emamectin benzoate and lambda cyhalothrin decreased slightly. However, no statistically significant differences in the resistance levels were observed among the selected population, its starting strain and the unselected strain. The resistance to chlorantraniliprole noticeably decreased in unselected strain and the strain subjected to selection for 10 generations compared with their starting strains. Lack of cross-resistance to tested insecticides suggested the involvement of multiple mechanisms of resistance and the need for wise application of these insecticides for the management of S. exigua.     

Monitoring of insecticide resistance in Spodoptera litura (Lepidoptera: Noctuidae) from four districts of Punjab,Pakistan to conventional and new chemistry insecticides

Studies were carried out to evaluate the resistance of Pakistani populations of the beet armyworm, Spodoptera litura (F) to several commonly used insecticides. Different field populations of S. litura from four districts of the Punjab were monitored from 2009 to 2011 for resistance to insecticides using a standard leaf dip bioassay method. For organophosphates and pyrethroids, resistance ratios compared with a susceptible Lab-Pk population were in the range of 8–109 fold for deltamethrin, 11–139 fold for cypermethrin, 19–143 fold for chlorpyrifos and 39–162 fold for profenofos. For new chemistry insecticides, resistance levels were 2–74 fold for spinosad, 4–216 fold for abamectin, 7–87 fold for indoxacarb, 2–77 fold for emamectin benzoate, 1.9–58 fold for lufenuron and 4–43 fold for methoxyfenozide. Pairwise correlation coefficients of LC₅₀ values showed a positive correlation with cross-resistance among deltamethrin, cypermethrin and chlorpyrifos, while resistance to profenofos showed correlations with resistances to other insecticides except chlorpyrifos. New chemistry insecticides showed no correlations between any of the tested insecticides. There were high to very high levels of resistance to organophosphates in most of the population, which suggested that the use of these should be avoided against this pest. Selective use of pyrethroids in several areas, including Bahawalpur and Lodhran, where the pest showed a low level of resistance, would appear to be acceptable, the new chemistry insecticides, lufenuron, methoxyfenozide, emamectin and indoxacarb had no, very low, low and moderate resistance levels against populations, respectively. These are considered to be safe to the environment and safer to natural enemies.     

Effect of temperature on development,survival and reproduction of the mealybug,Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) on cotton

The effect of temperature on life cycle of the solenopsis mealybug, Phenacoccus solenopsis Tinsley, on cotton (Gossypium hirsutum L.) was assessed under laboratory conditions at ten constant temperatures (18–40 °C). The development duration of female and male nymphal instars linearly decreased with the increase in temperature from 18 to 32 °C. Cumulative developmental time of females ranged from 43.9 d (18 °C) to 15.0 d (32 °C). Survival of crawlers to adulthood was lowest (<53%) at 20 and 36 °C and highest (80%) at 32 °C. The solenopsis mealybug exhibited obligate sexual ovoviviparous reproduction and the pre-oviposition period in mated females showed a significant decreasing trend between 20 °C (23.0 d) and 30 °C (9.5 d). The oviposition period of 10.2–11.5 d at ≥25 °C was nearly half the duration than at 20 °C and the highest fecundity (245 eggs + crawlers) was observed at 30 °C. Longevity of mated females was significantly prolonged at 20 °C (46.0 d) compared to 30 °C (21.4 d). Proportion of females was highest (97.5%) at 25 °C. Males required higher degree-days (363.6) for their cumulative development compared to females (317.5). Lower temperature thresholds estimated from the linear model for cumulative female and male development were 11.7 and 10.1 °C, respectively. The estimated optimum temperature thresholds for nymphal instars (32–33.4 °C) from β type distribution function were closer to the observed maximum developmental rate compared to Lactin-2 model. The population trend index using survival, fecundity, and sex ratio of P. solenopsis with an initial population of 100 crawlers in the Morris-Watt life table model indicated a potential population increase of 170.3 and 97.6 times at 30 and 35 °C, respectively, in the next generation. The usefulness of the information on the temperature-dependent life cycle of P. solenopsis in understanding its field abundance and distribution on cotton and implications for management is discussed.     

Toxical effect of Peganum harmala L. leaves on the cotton leaf worm, Spodoptera littoralis Boisd and its parasitoids Microplitis rufiventris Kok

The leaf extract and its fractions of Peganum harmala L. have shown pronounced mortal effect, decreased percent pupation and adult emergence of the cotton leaf worm, Spodoptera littoralis Boisd. The third instar larvae fed for two days on treated leaves were more susceptible to plant extract and its ethyl acetate and chloroform fractions. The active lowest concentration (5%) of the leaf fractions of P. harmala showed significant effect on the percentage of emerged adult parasitoids, Microplitis rufiventris Kok. GC/MS analysis showed the major constituent in ethyl acetate fraction was (23S) ethylcholest-5-en-3 beta-ol (28.04%) while those of chloroform fraction were hydroxyfuranocoumarin (Bergaptol) (15.68%), piperidinone (12.08%), thymol (11.82%), phosphoric acid, tributyl ester (9.80%) and trimethyl-nonenol (9.66%). The medicinal plant P. harmala could be carefully applied in integrated pest management due to its strong effect on cotton leaf worm pest.     

Low susceptibility of Spodoptera cosmioides,Spodoptera eridania and Spodoptera frugiperda (Lepidoptera: Noctuidae) to genetically-modified soybean expressing Cry1Ac protein

Spodoptera cosmioides (Walker), Spodoptera eridania (Stoll) and Spodoptera frugiperda (J. E. Smith) have caused significant damage on soybean Glycine max (L.) Merrill in Brazil. Genetically-modified MON 87701 × MON 89788 soybean that expresses the Cry1Ac protein is potentially an alternative tool for the management of these species. Purified protein bioassays were done to evaluate the susceptibility of S. cosmioides, S. eridania and S. frugiperda to Cry1Ac protein. The level of efficacy of the Bt soybean plants in controlling these species was measured through laboratory and greenhouse trials under high artificial insect infestations. The biology of these insects was evaluated over their development cycles to understand their life history when fed on Bt soybean. Purified Cry1Ac protein at the maximum concentration tested (100 μg Cry1Ac mL⁻¹ diet) resulted in low mortality of S. cosmioides and S. eridania (<13%) and intermediate mortality of S. frugiperda (50%). No significant effects of the Bt soybean plants were observed in the life table parameters of S. cosmioides and S. eridania. However, S. frugiperda fed on Bt soybean plants had a prolonged larval stage (by 5 days), reduced larvae viability, increased mean generation time (by 8 days) and reduced intrinsic rate of increase. In general, the Bt soybean plants showed poor control of Spodoptera species when evaluated by leaf-disc bioassay and greenhouse trials. Consequently, other control tactics must be used in combination with MON 87701 × MON 89788 soybean in the field for the efficient management of S. cosmioides, S. eridania and S. frugiperda.     

Effect of photoperiod on development and reproduction of Megacopta cribraria(Hemiptera:Plataspidae)

Megacopta cribraria (Hemiptera: Plataspidae) continually outbreaks due to suitable photoperiod in recent years. Effect of photoperiod on growth, development and reproduction of M. cribraria were assessed in this study. Results indicated that developmental duration, nutrient accumulation efficiency, and adult fecundity of M. cribraria were significantly different under 6 photoperiodical conditions. Developmental duration of nymph stage gradually tended to be shorter as day time increase. Body weights of 5th instar nymphs for 16 h and 4 h day time photoperiods were 5.2 mg and 4.6 mg, respectively. Moreover, longevity of adults tended to be longer as day time increase. However, for the short day photoperiod (4 L:20 D and 8 L:16 D), population showed no reproductive behaviors. Index of population trend increased with photoperiod extension and adults showed stronger reproductive capacity and longer longevity. This research identified the favorable photoperiodical conditions before outbreak. It may provided reference for ecological adaptability of M. cribraria, and contribute to the scientific basis for forecasting and controlling of M. cribraria.     

Effect of different host plants on the fitness of diamond-back moth, Plutella xylostella (Lepidoptera: Plutellidae)

The diamond-back moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a destructive cosmopolitan pest of cruciferous crops. The pest is present wherever its host plants exist and is considered to be one of the most widely distributed of all the Lepidoptera. We investigated the effect of various host plants on the fitness of P. xylostella and tested the hypothesis by studying development time, growth, fecundity and survival on cabbage (Brassica oleracea capitata), cauliflower (Brassica oleracea botrytis), radish (Raphanus sativus), turnip (Brassica rapa), mustard (Brassica compestris) and canola (Brassica napus var. canola). The developmental time from eggs to adult eclosion was the shortest (10 days) on canola and the longest (13 days) on turnip. Fecundity was greatest on canola (350) followed by cauliflower (268 eggs) by females eclosed from the pupae reared on canola and cauliflower, respectively, while the minimum numbers of eggs (184) were observed on cabbage. The number of eggs hatched was the highest (80%) when larvae fed on cauliflower. Survival to the adult stage was the highest (94%) on mustard followed by cauliflower and lowest (64%) on turnip. The net replacement rate was lowest for populations reared on cabbage (32.3), which was also reflected by the lowest intrinsic rate of population increase (0.20). The correlation between the intrinsic rate of population increase (r_m) and the mean relative growth rate was significant (t = 20.02 d.f. = 4, P < 0.05). Canola and mustard proved to be the most suitable hosts for P. xylostella because of shorter developmental period, higher percentage of survival and higher number of eggs. The data point to the role of host plants in increasing local P. xylostella populations.     

Effect of six synthetic pyrethroids on two populations of potato tuber moth,Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), in Peru

The toxicity of six synthetic pyrethroids, permethrin, cypermethrin, flucythrinate, fenvalerate, cyfluthrin and deltamethrin, were evaluated on two populations of potato tuber moth (PTM) Phthorimea operculella (Zeller) in Peru. Deltamethrin was most toxic with an LC₅₀ of 120 μg/ml for male PTM from La Molina and 137 μg/ml for female PTM from San Ramon. Fenvalerate was least toxic and the other four insecticides were intermediate in toxicity. At field recommended concentrations (0·05-0·04%) none of the six synthetic pyrethroids were effective on the two populations tested.     

Selection,mechanism, cross resistance and stability of spinosad resistance in Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

Spodoptera litura is one of the most destructive pests in Pakistan and in many other regions of the world. A field collected population of S. litura was selected with spinosad for eleven generations under controlled laboratory conditions to study the cross resistance, mechanism and stability of spinosad resistance in S. litura. The resistance to spinosad in S. litura increased 3921-fold (after eleven generations of selection with spinosad) as compared to a susceptible population of S. litura. No cross resistance between spinosad and emamectin benzoate, methoxyfenozide, fipronil, indoxacarb, profenofos, lufenuron or deltamethrin was found in the spinosad-selected population of S. litura. To find the possible mechanism of spinosad resistance in S. litura two synergists, Piperonyl butoxide (PBO), S, S, S-tributyl phosphorotrithioate (DEF) were tested on the susceptible and resistant strains and on the un-selected field population. The values of the synergism ratios of PBO and DEF were 2.33 and 1.06 for the spinosad-selected strain, 1.36 and 1.06 for the un-selected field population and 1.14 and 1.00 for the susceptible strain, respectively. As high PBO ratio indicates the role of microsomal O-demethylase in causing spinosad resistance in S. litura. The spinosad-resistant and field populations of S. litura were reared without any selection pressure from the 12th to the 16th generation (G₁₂–G₁₆). The spinosad resistance decreased from 3921 to 678-fold in the spinosad-resistant population and from 31.1 to 15.1-fold in the un-selected population of S. litura as compared to the susceptible strain. Spinosad resistance in S. litura has a high reversion rate (−0.15) which indicates that spinosad resistance in S. litura is unstable and can be easily managed by switching off the selection pressure for a few generations or alternating with insecticides having different modes of action.     

Effect of host plant resistance and insecticide on brown planthopper Nilaparvata lugens (Stål) and predator population development in the Mekong Delta, Vietnam

Crop yield and populations of brown planthopper Nilaparvata lugens (Stål), whitebacked planthopper Sogatella furcifera (Horvath) (Homoptera: Delphacidae), green leafhopper Nephotettix spp. (Homoptera: Cicadellidae), and hemipteran and spider predators were monitored on rice varieties susceptible, moderately resistant, and highly resistant to N. lugens, under insecticide-treated and insecticide-free conditions. Nilaparvata lugens outbreaks and hopperburned plants were observed only in plots of the insecticide-treated susceptible varieties. In insecticide-free plots, the yield of the susceptible variety was lower than those of resistant varieties in only one of four seasons. In plots of a moderately resistant and a highly resistant variety, populations of N. lugens, S. furcifera, Nephotettix spp., and predators were generally similar, and yields did not differ, under both insecticide-treated and insecticide-free conditions. In insecticide-free plots, predator-N. lugens ratios were generally higher on resistant varieties than susceptible varieties. Two conclusions can'be drawn from our results relevant to the question of what levels of N. lugens host plant resistance are appropriate for farmers who do not overuse insecticides. First, susceptible varieties will not necessarily be damaged by N. lugens, even when N. lugens outbreaks occur in adjacent plots. Second, moderate and high levels of N. lugens resistance do not appear to be incompatible with biological control of N. lugens or other homopteran pests.     

Plants used in controlling the potato tuber moth, Phthorimaea operculella (Zeller)

A survey of literature (published from 1915 to 1993) on the plants used for the control of the potato tuber moth, Phthorimaea operculella (Zeller) has revealed that the preparations from 35 plant species are effective against the pest either in the storage (non-refrigerated) or in the laboratory. In some studies chopped and dried leaves were used, while in others leaf/seed extracts, fruit peel, bulb, root and rhizome were used. Plant preparations are effective in reducing the pest damage or killing at different stages of the pest.     

Effect of feeding crude Red Palm Oil (Elaeis guineensis) and grain Amaranth (Amaranthus paniculatus) to hens on total lipids,cholesterol, PUFA levels and acceptability of eggs

Eggs, though a very nutritious food, also have high amounts of cholesterol and hence are not recommended to be consumed regularly by persons having hypercholesterolemia and associated cardiovascular diseases (CVD). In this context, an attempt was made in this study to reduce the cholesterol content of eggs by diet manipulation, using two naturally available and already proved hypocholesteromic agents [Red Palm Oil (RPO) and Grain Amaranth]. Thirteen experimental rations using raw and popped grain Amaranth and RPO were fed to 24 weeks old hens for a period of 6 weeks, singularly and in combinations. Total lipids, cholesterol and PUFA contents were analyzed in the experimental and control eggs. The results showed that RPO and RPO + Popped Amaranth feeding resulted in a maximum reduction in total lipids and cholesterol contents. Significant increase was observed in linoleic acid content in RPO + popped Amaranth; raw Amaranth and RPO fed groups. Acceptability studies showed that the products made from lower cholesterol eggs were well accepted.     

Elucidation of the sex pheromone system of the potato tuberworm moth,Phthorimaea operculella (Zeller) (Lepidoptera,Gelechiidae): a short review

Summary Recent research, reviewed here, of the pheromone system of the potato tuberworm moth has led to the isolation, identification, and synthesis of its components.trans-4,cis-7-tridecadien-l-ol acetate (PTM 1) andtrans-4,cis-7,cis-10-tridecatrien-l-ol acetate (PTM 2), mixtures of which are much more attractive in the field than 2 virgin female moths or each compound on its own.     

Some aspects on the feeding of Gerres oblongus (Cuvier, 1830) dwelling from the Jaffna lagoon

A total of 179 fishes of Gerres oblongus (Cuvier, 1830) ranging in standard length 40 to 169 mm were collected in the morning from four collection sites in the Jaffna lagoon. The stomach contents were assessed qualitatively and quantitatively. The fishes were placed in 19 mm size class intervals and the food analysis were done both by qualitatively and quantitatively. Variation of food with respect to month was also determined. The analysis of gut contents of G. oblongus showed that it is an omnivore and the preference to animal diet is higher than the vegetable matter. The presence of molluscs, soil particles and polychaetes indicated that it is a substratum feeder or feed largely on attached surfaces. Feeding intensity was high during February which has been reflected by the satiation index (8.3) in the same period. At the same time coefficient of condition has been fluctuated in between 2.2-3.7 except in May (4.4) indicated that it has slow growth rate. The mean relative gut length showed a positive increase with the body length. The value for the relationship between the mean relative gut length to body length further confirms that it is omnivorous in feeding habit.     

Transcriptome Analysis of Detoxification-Related Genes in Spodoptera frugiperda (Lepidoptera: Noctuidae)

Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is an important pest on maize, and it can cause large yield losses. As S. frugiperda has invaded many developing countries in Africa and Asia in recent years, it could impact food security. Pesticides remain the main method to control S. frugiperda in the field, and this pest has developed resistance to some pesticides. In this study, we used second-generation sequencing technology to detect the gene expression change of S. frugiperda after treatment by LC₂₀ of three pesticides, lufenuron, spinetoram, and tetrachloroamide, which have different modes of actions. The sequence data were first assembled into a 60,236 unigenes database, and then the differential expression unigenes (DEUs) after pesticide treatment were identified. The DEU numbers, Gene Ontology catalog, and Kyoto Encyclopedia of Genes and Genomes pathway catalog were analyzed. Finally, 11 types of unigenes related to detoxification and DEUs after pesticide treatment were listed, and Cytochrome P450, Glutathione S-transferase, and ATP-binding cassette transporter were analyzed. This study provides a foundation for molecular research on S. frugiperda pesticide detoxification.     

茶细蛾幼虫空间分布型研究

茶细蛾幼虫主要分布在芽下一、二叶上(占76.06%～93.46%).本文应用多种聚集度指标测定结果表明,该虫幼虫在一切密度下都呈聚集分布,分布的基本成份为个体群,且聚集程度随种群密度升高而增加.聚集原因由成虫选择嫩叶产卵、幼虫的习性和茶园环境中任一因子引起的.应用Iwao的抽样模型建立了茶细蛾幼虫的田间理论抽样数公式:N=1/D2(1.7958/m+0.3107),给出了不同密度下、不同误差要求的最适抽样数.     

取食藜和龙葵对甜菜夜蛾生长发育及杀虫剂敏感性的影响

在室内分别用人工饲料、藜(Chenopodium album L.)或龙葵(Solanum nigrum L.)饲喂甜菜夜蛾(Spodoptera exigua)初孵幼虫,研究饲喂上述2种杂草对甜菜夜蛾存活率、发育历期、化蛹率、羽化率和繁殖力的影响,同时采用室内毒力生物测定的方法,比较取食不同寄主的甜菜夜蛾3龄幼虫对甲...