Cost-effectiveness evaluation of mass-rearing Cadra cautella (Lepidoptera: Pyralidae) based on harvest theory for sustainable alternative prey production.

Cadra cautella (Walker) (Lepidoptera: Pyralidae) is a pest in barn, and its eggs are often utilized as an alternative prey or as hosts for mass production of insect predators and parasitoids. To aid in developing a mass-rearing system for C. castella, the suitability of using an artificial diet based on brown rice flour and whole brown rice was compared using the age-stage, 2-sex life table. Compared with those reared on brown rice, the insects reared on an artificial diet had a shorter preadult period (32.08 vs 37.38 d), higher fecundity (468.14 vs 356.20 eggs/female), greater intrinsic rate of increase (0.1509 vs 0.1145 d-1), and higher net reproductive rate (199.28 vs 103.52 offspring). Small populations were required to rear the moth on an artificial diet to achieve the same daily production of C. cautella. Still, the food expense was only 60.2% of that of C. cautella reared on brown rice. Approximately 99.44% of the eggs in each rearing procedure could be supplied as alternative prey for predators, with the remainder served to maintain the colonies for subsequent batches. Only eggs laid within 6 d would be utilized to ensure the high quality of alternative prey for the mass production of predacious bugs. Additionally, a multifunctional device was designed for moth rearing and egg collection, reducing labor input and minimizing health risks for workers coping with inhaled scales. To encourage the production of natural enemies, a cost-effective diet for maintaining a sustainable colony, and a system for daily egg-harvesting of alternative prey were proposed.

Seasonal Dynamics of Flight Phenology of the Euwallacea fornicatus Species Complex and an Associated Parasitoid Wasp in Avocado Groves in Taiwan.

The Euwallacea fornicatus species complex (Coleoptera: Curculionidae: Scolytinae: Xyleborini) is a group of four cryptic ambrosia beetle species. Native to Asia, several members of the complex have invaded other continents, where they cause significant economic losses to agricultural crops (e.g., avocado) and natural ecosystems. We were primarily interested in developing management strategies by focusing on the flight behavior of the beetles. Thus, seasonal differences in flight activity were assessed using panel traps baited with a commercial quercivorol lure, placed in infested avocado orchards in Danei, Tainan, Taiwan. Same traps were used to investigate the flight activity of a natural enemy, an undescribed species of the Braconid genus Eucosmophorus sp. Shothole borer species were identified using a DNA-based, high resolution melting assay. Trap data were compared to the predictions of a simple degree-day model, incorporating developmental data and several environmental parameters known to influence flight. Such as the time period representing most of flight activity in a day and temperature-dependent flight propensity. In stark contrast to the degree-day model which predicted the highest emergence, and by extension flight, of shothole borers during spring and summer (May to November), flight activity was actually lowest during these months, and instead, peaked during the winter (October to March). Abundance of the parasitoid wasp closely mirrored flight activity of the shothole borers. The mismatch of trapping and modeling data can have many causes, heavy precipitation and possibly cooperative brood care may suppress the dispersal behavior of the shothole borers during the summer.

Demographic Characteristics and Population Simulation of Newly Invasive Fall Armyworm on Arachis hypogaea (Fabales: Fabaceae) and Dominant Green Manure Plant in Taiwan.

Spodoptera frugiperda (J.E. Smith) is a severe and fast-spreading pest of numerous agro-economic crops, including miscellaneous, vegetables, and green manure crops. Understanding pest ecology represents a core component in integrated pest management decision-making. In Taiwan, peanut (Arachis hypogaea L.) is an important miscellaneous crop, whereas sesbania (Sesbania roxburghii Merr.) is the most frequently used green manure crop. To improve the S. frugiperda management in Taiwan, the demographic characteristics and population simulation of this pest reared on peanut and sesbania leaves were analyzed using the age-stage, two-sex life table theory. The intrinsic rate of increase, finite rate of increase, and net reproductive rate of S. frugiperda were higher when reared on peanut (0.1625 d-1, 1.1764 d-1, 264.9 offspring) than on sesbania (0.0951 d-1, 1.0997 d-1, and 30.3 offspring). Population projection of S. frugiperda on peanut demonstrated that this crop is a more suitable host plant than sesbania. Yet, this suboptimal host still assures an increasing trend of more than 357-fold individuals in 75 d, from the initial cohort of 10 eggs. Our data suggest that green manure plants in fallowing fields may support the pest's survival all year round, and may be responsible for a successful establishment and unexpected outbreaks of this invasive pest on the neighboring crops in Taiwan. Our study thus highlights the importance of assessing the population dynamics and areawide pest management of an invasive polyphagous pest on a noneconomic crop to mitigate the potential risk of reinfestation and thus outbreaks.

The Attractiveness of α-Copaene to Members of the Euwallacea fornicatus (Coleoptera: Curculionidae) Species Complex in California and Taiwan.

Species belonging to the Euwallacea fornicatus Eichhoff (Coleoptera: Scolytinae) species complex have invaded the continental U.S. since at least 2003. Three species of this complex are known to have established, two in California (E. fornicatus; and Euwallacea kuroshio), and a third in Florida (Euwallacea perbrevis). Their native ranges are spread across southern and southeast Asia. In Taiwan, all three species occur in sympatry. They attack healthy trees of widely varied species and cause severe damage and death to the trees. The attractant quercivorol is commonly used to promote their detection by passive trapping. Recent studies in Florida have shown that trapping of E. perbrevis can be further improved by adding a synergist, α-copaene, alongside the quercivorol lure. Thus, we were interested in testing the effectiveness of α-copaene for trapping the other invasive members of the complex in California and in an area of Taiwan where all three species co-occur. We found that α-copaene marginally enhanced the trapping of E. perbrevis in Taiwan, but had no effect on the trapping of E. fornicatus or E. kuroshio in either California or Taiwan. We conclude that any enhancing effect of α-copaene is specific to E. perbrevis. This highlights the economic importance of accurate species identification in developing and implementing an efficient, and yet cost-effective, monitoring program for the management of E. fornicatus and E. kuroshio in California and elsewhere.

Comparison of Artificial Diets and Natural Prey for Mass Rearing of Orius strigicollis (Hemiptera: Anthocoridae) Using Demographic Characteristics to Optimize Cost-Efficiency.

Orius strigicollis (Poppius) has been commonly released to control minute pests due to its remarkable foraging and predation ability. Despite decades long history of mass-rearing using eggs of Cadra cautella Walker (Lepidoptera: Pyralidae) as food, the cost of this food impeded the predator's marketing potential. Finding cost-effective artificial diets for mass rearing programs is, therefore, the key to promote the use of this generalist predator in practice. The aim of this study was to explore suitability of alternative diets for mass rearing of this predator, using the age-stage, two-sex life table. Eight recipes of artificial diets were initially screened, and the candidate diets were subsequently evaluated using the population parameters of O. strigicollis. The highest intrinsic rate of increase was found in the O. strigicollis fed on the meridic combined Diet 1, where nymphs and adults were fed different diets. However, the intensive period of oviposition by females reared on oligidic Diet O3 contributed to the shorter rearing period (42 d) and lower rearing cost than that on combined Diet 1 (60 d). Besides, with the harvest rate of 0.919, the minimal population size of 10,774 individuals with a stable age-stage distribution was needed for daily harvesting 1,000 third instars of O. strigicollis reared on Diet O3 at the rearing cost of 0.295 NTD (new Taiwanese dollar) per nymph. Thus, Diet O3 was determined to be the most cost-effective recipe for the mass-rearing of O. strigicollis among those used in this study.

Direct and Knock-on Effects of Water Stress on the Nutrient Contents of Triticum aestivum (Poales: Poaceae) and Population Growth of Rhopalosiphum padi (Hemiptera: Aphididae).

To ascertain the direct effects of water stress upon wheat plants (Triticum aestivum L.) and how these effects, in turn, influence the population growth of the bird cherry-oat aphid (Rhopalosiphum padi L.), we conducted a physiological analysis of wheat seedlings grown under three different watering regimes and subsequently determined the population parameters of the aphid using the age-stage, two-sex life table. A significantly higher content of free amino acids and soluble sugars were observed in wheat seedlings exposed to drought stress compared to seedlings that were well-watered and those that were grown under waterlogged conditions. Extended phloem salivation and stylet penetration with shorter duration of sustained ingestion from phloem was observed in an electrical penetration graph (EPG) of R. padi on drought-stressed wheat seedlings. This suggested that the aphid's feeding activity, as well as nutrient intake, were impeded. The significantly higher percentage of essential amino acids found in wheat seedlings grown under waterlogged conditions promoted significantly higher fecundity and intrinsic rate of increase in R. padi populations compared to aphids fed on drought-treated or well-watered wheat seedlings. Our findings suggest that wheat seedling responses to water stress involve changes in sap composition that are responsible for altering the aphids' nutrient intake and consequently affect their population growth. From a grower's perspective, extending wheat cultivation in a rice-wheat rotation paddy field during the winter season may not be economically profitable if the fields are chronically waterlogged, since this may potentially lead to a higher infestation of cereal aphids.

Draft Whole-Genome Sequences of Xylella fastidiosa subsp. fastidiosa Strains TPD3 and TPD4, Isolated from Grapevines in Hou-li, Taiwan.

We report the draft assemblies of TPD3 and TPD4, two Xylella fastidiosa subsp. fastidiosa isolates infecting grapevines in Hou-li, Taiwan. TPD3 and TPD4 showed similar characteristics regarding genome size (2,483,503 bp and 2,491,539 bp, respectively), GC content (51.49% and 51.47%, respectively), and number of protein-coding sequences (2,394 and 2,413, respectively).

Economic Injury Level and Demography-Based Control Timing Projection of Spodoptera litura (Lepidoptera: Noctuidae) at Different Growth Stages of Arachis hypogaea.

Spodoptera litura (F.), one of the most devastating pests in many Asian countries, is normally controlled by relying on chemical insecticides. To encourage an integrated pest management approach, we determined the economic injury level (EIL) for S. litura on peanut, Arachis hypogaea L., by larval infestation with late instars at different crop growth stages. The cumulative consumption rate of the fifth- and sixth-instars was used as the relative unit for the "Spodoptera injury equivalent" (SIE). The yield of marketable pods significantly decreased from 6.19 to 1.63 g.plant-1 as larval infestation intensity increased throughout the entire cropping season. When supplemented with timely applications of the insecticide, indoxacarb, an oxadiazine insecticide, the EIL values obtained in the larval infestation trial ranged from 3.26 to 13.47 SIE per 20 plants depending on the timing of initial infestation. The economic threshold (ET) for late instars, i.e., multiplying the EIL by 0.75, could not be utilized as a control timing index for the outbreak of injurious larvae population because of the time-lag. When the occurrence of natural mortality in the egg to pupal stage was considered, the ETs were adjusted to reflect the average survivorship. ETs of 27.3, 55.9, 51.3, and 112.6 eggs.m-2 were recommended at the early vegetative growth, blooming/pegging, pod-setting, and pod-filling stages, respectively, for initiating control measures. By simulating the pest population with the program, Timing-MSChart, we integrated the stage-specific EILs and ETs with the life-table data of S. litura on peanut and then proposed a demography-based control timing.

Treating Prey With Glyphosate Does Not Alter the Demographic Parameters and Predation of the Harmonia axyridis (Coleoptera: Coccinellidae).

Glyphosate is an herbicide that is used worldwide with potential environmental risks to nontarget organisms. We applied an age-stage, two-sex life table approach to assess the sublethal effects of short-term oral exposure to a glyphosate-based herbicide on the life table parameters and biocontrol potential of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Aphids (Metopolophium dirhodum (Walker) (Sternorrhyncha: Aphididae)) treated with herbicide (an isopropylamine-salt of glyphosate) at low recommended, maximum recommended, and double the maximum recommended concentration for agricultural situations, and untreated controls were offered to the fourth instar of H. axyridis for 24 h. Development, consumption, and fecundity were measured daily until death. We detected minor differences in the hatching rate and mean generation time, whereas the longevity, fecundity, net reproductive rate, intrinsic rate of increase, finite rate of increase, and consumption were unaffected across treatments. We conclude that biocontrol potential of H. axyridis was not affected by acute oral intoxication by a glyphosate-based herbicide during the larval stage for 24 h under the study design.

Treatment by glyphosate-based herbicide alters life history parameters of the rose-grain aphid Metopolophium dirhodum.

Glyphosate is the number one herbicide in the world. We investigated the sub-lethal effects of this herbicide on the aphid Metopolophium dirhodum (Walker), using an age-stage, two-sex life table approach. Three concentrations of the herbicide (low - 33.5, medium - 66.9 and high - 133.8 mmol dm(-3) of active ingredient) and distilled water as the control were used. The LC50 of the IPA salt of glyphosate on M. dirhodum was equivalent to 174.9 mmol dm(-3) of the active ingredient (CI95: 153.0, 199.0). The population parameters were significantly negatively affected by herbicide application, and this negative effect was progressive with the increasing concentration of the herbicide. A difference of two orders of magnitude existed in the predicted population development of M. dirhodum between the high concentration of the herbicide and the control. This is the first study that comprehensively documents such a negative effect on the population of an herbivorous insect.

Comparison of Demographic Parameters and Predation Rates of Orius strigicollis (Hemiptera: Anthocoridae) Fed on Eggs of Tetranychus urticae (Acari: Tetranychidae) and Cadra cautella (Lepidoptera: Pyralidae).

Orius strigicollis (Poppius) is an anthocorid bug with high foraging ability on thrips as well as on mites, and the bug has been considered as a potential biological control agent in Taiwan. Life table and predation studies of O. strigicollis fed on Cadra cautella (Walker) and Tetranychus urticae (Koch) eggs were conducted at 25 ± 1°C. Data were analyzed and compared using TWOSEX-MSChart and CONSUME-MSChart software. O. strigicollis fed on eggs of C. cautella, a substitute prey, showed significantly higher survival rate and developmental rate than individuals fed on their natural prey, T. urticae eggs. The fecundity of O. strigicollis fed on C. cautella eggs was, on average, 13.2 times higher than that of those fed on T. urticae eggs, despite of the fact that during the entire nymphal stage, the consumption rate of O. strigicollis on T. urticae eggs was ca. 9 times higher than on almond moth eggs The conversion rate (i.e., number of prey eggs needed to produce one predator egg) for this predatory bug reared on T. urticae eggs and almond moth eggs were 604.6 and 6.0, respectively, indicating that almond moth eggs served as an effective alternative prey for ensuring the predator's reproduction. This is the first study pertaining to the population parameters and predation rates of O. strigicollis using the age-stage two-sex approach to describe differences between O. strigicollis populations reared on natural and alternative preys. This information may be useful in mass rearing programs and field application involving this biological control agent.

Xylella fastidiosa Transmission and Life History of Two Cicadellinae Sharpshooters, Kolla paulula and Bothrogonia ferruginea (Hemiptera: Cicadellidae), in Taiwan.

Xylella fastidiosa causes Pierce's disease (PD) and is transmitted by xylem-sap-feeding insects. While X. fastidiosa -infected grapevines have been detected, the transmission vectors reported have never been recorded in Taiwan. Previous studies have suggested that Kolla paulula (Walker) and Bothrogonia ferruginea (F.) are candidate vectors in Taiwan. Here, we explored the life history of these two leafhoppers, evaluated the transmission efficiency of X. fastidiosa by the vectors, and investigated the genetic identity of three collected X. fastidiosa strains, namely, GMb, BQa, and BQ7f from the grapevine cultivars Golden Muscat (GM) and Black Queen (BQ), and one previously extracted strain GV148 from Kyoho (GV) showing PD symptoms in local vineyards. The results showed that all four strains were 100% identical to X. fastidiosa isolate Temecula1 from a naturally infected grapevine in the United States based on sequence analyses of 16S rRNA and 16S-23S ITS. The acquisition rates by K. paulula and B. ferruginea from the symptomatic cultivar Golden Muscat were 83.3 and 70.0% per individual, and the transmission rates to healthy grapevines were 13.3 and 6.7%, respectively. The acquisition rates by the groups of three K. paulula from the symptomatic cultivars Golden Muscat and Black Queen were 54.7 and 49.6%, respectively. Additionally, the transmission rates by K. paulula from and to each of these two grapevine cultivars were not significantly different. In view of their acquisition from infected grapevines and the effective transmission of X. fastidiosa to healthy grapevines, these two sharpshooter species are vectors of X. fastidiosa in Taiwan.

Survival and Reproductive Strategies in Two-Spotted Spider Mites: Demographic Analysis of Arrhenotokous Parthenogenesis of Tetranychus urticae (Acari: Tetranychidae).

Tetranychus urticae Koch is a cosmopolitan pest whose rapid developmental rate enables it to produce colonies of thousands of individuals within a short time period. When a solitary virgin female colonizes a new host plant, it is capable of producing male offspring through the arrhenotokous parthenogenesis; once her sons mature, oedipal mating occurs and the female will produce bisexual offspring. To analyze the effect of arrhenotokous reproduction on population growth, we devised and compared separate life tables for arrhenotokous and bisexual populations of T. urticae using the age-stage, two-sex life table theory. For the cohort with bisexual reproduction, the intrinsic rate of increase (r), finite rate (λ), net reproductive rate (R0), and mean generation time (T) were 0.2736 d(−1), 1.3146 d(−1), 44.66 offspring, and 13.89 d, respectively. Because only male eggs were produced during the first 8 d of the oviposition period and the cohort would soon begin bisexual reproduction, it would be theoretically wrong to calculate the population parameters using the survival rate and fecundity of an arrhenotokous cohort. We demonstrated that the effect of arrhenotokous reproduction could be accurately described and evaluated using the age-stage, two-sex life table. We also used population projection based on life table data, quantitatively showing the effect that arrhenotokous reproduction has on the growth potential and management of T. urticae.

Demography and Consumption of Spodoptera litura (Lepidoptera: Noctuidae) Reared on Cabbage and Taro.

Spodoptera litura (F.) causes considerable economic damage to multiple agro-crops annually in many countries. In this study, the demography of S. litura reared on cabbage and taro was investigated using the age-stage, two-sex life table at 25±1°C, 60±10% relative humidity, and a photoperiod of 12: 12 (L:D) h. Our results showed that the net reproductive rate, intrinsic rate, and finite rate of population increase on cabbage (1893.1 offspring, 0.2374 d(−1), and 1.2679 d(−1)) were all not significantly different from those on taro (1361.0 offspring, 0.2298 d(−1), and 1.2584 d(−1)). The net consumption rate on cabbage (439.1 cm2) was, however, three times higher than that on taro (141.7 cm2). According to the population parameters, both cabbage and taro are suitable host plants for S. litura. When both the population growth rate and the consumption rate were taken into consideration, the finite consumption rate on cabbage (ω=3.8054) was significantly higher than that on taro (ω=1.3184). In Taiwan, taro and cabbage are commonly planted in adjacent farm plots, with taro being grown from March to November and cabbage from October to April. Because of the overlapping growth periods of the two crops, S. litura can easily propagate throughout the year by switching between the adjacent crops during the overlap periods. Pest management strategies for controlling S. litura must be thoroughly reevaluated based on ecological characteristics, including its life table and consumption rate on its major host plants.

Linking Life Table and Predation Rate for Biological Control: A Comparative Study of Eocanthecona furcellata (Hemiptera: Pentatomidae) Fed on Spodoptera litura (Lepidoptera: Noctuidae) and Plutella xylostella (Lepidoptera: Plutellidae).

To better understand the predator-prey relationship and to compare predation rates, we studied the life table and predation rate of the predator Eocanthecona furcellata Wolff (Hemiptera: Pentatomidae) when reared on two major crucifer pests, Spodoptera litura (F.) (Lepidoptera: Noctuidae) and Plutella xylostella L. (Lepidoptera: Plutellidae). The net reproductive rate, intrinsic rate of increase, finite rate, and net predation rates of E. furcellata reared on P. xylostella were 292.4 offspring, 0.1389 d(-1), 1.1490 d(-1), and 644.1 third instars of P. xylostella, respectively. These values are significantly higher than those reared on S. litura, i.e., 272.3 offspring, 0.1220 d(-1), 1.1298 d(-1), and 863.1 third instars of S. litura. To evaluate the predation potential of E. furcellata fed on P. xylostella and S. litura, we combined both the growth rate and predation rate to calculate the finite predation rate (ω); our results showed that E. furcellata is an effective predator of both S. litura (ω = 1.6029) and P. xylostella (ω = 1.4277).

Growth Performance and Biometric Characteristics of Spodoptera litura (Lepidoptera: Noctuidae) Reared on Different Host Plants.

Spodoptera litura (F.), an important polyphagous insect pest, attacks ca. 300 economic crops in dozens of countries. Investigations into its growth and development performance on different host plants can provide an understanding of the potential for increase of S. litura population in the field. We measured the development time, body weight, and head capsule width of S. litura larvae reared on cabbage, taro, peanut, and sesbania, a green manure. Larvae reared on cabbage ingested a significantly higher amount of protein and completed the immature stages in a shorter period than those reared on the other three plants. The relationship between head capsule width and larval instars on these four crops fitted well with Dyar's rule, and the Dyar's ratios ranged from 1.4554 to 1.6786, although a few supernumerary instar individuals on sesbania, peanut, and taro showed lower ratios (1.0103 to 1.1330). The head capsule width among cohorts fed on different host plants varied significantly and overlapped between late instars, which could lead to a misjudgment of instar stage in the field. The growth index of S. litura on cabbage was significantly higher than on the other host plants. Larvae fed on sesbania showed the highest feeding index and a better growth index than on taro and peanut. We therefore suggest that the area-wide pest management against S. litura should take into consideration its occurrence on sesbania in intercropping seasons. Additionally, the effective management of this pest during cropping windows between all these four plants should not be ignored.

Life table and consumption capacity of corn earworm, Helicoverpa armigera, fed asparagus, Asparagus officinalis.

The life table and consumption rate of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) reared on asparagus, Asparagus officinalis L. (Asparagales: Asparagaceae) were studied under laboratory conditions to assess their interaction. Development, survival, fecundity, and consumption data were analyzed by the age-stage, twosex life table. This study indicated that asparagus is a natural host of H. armigera. However, the poor nutritional content in asparagus foliage and the poor fitness of H. armigera that fed on asparagus indicated that asparagus is a suboptimal host in comparison to hybrid sweet corn. The uncertainty associated with life table parameters was estimated by using jackknife and bootstrap techniques, and the results were compared for statistical inference. The intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and mean generation time (T) were estimated by the jackknife technique to be 0.0780 day(-1), 1.0811 day(-1), 67.4 offspring, and 54.8 days, respectively, while those estimated by the bootstrap technique were 0.0752 day(-1), 1.0781 day(-1), 68.0 offspring, and 55.3 days, respectively. The net consumption rate of H. armigera, as estimated by the jackknife and bootstrap technique, was 1183.02 and 1132.9 mg per individual, respectively. The frequency distribution of sample means obtained by the jackknife technique failed the normality test, while the bootstrap results fit the normal distribution well. By contrast, the relationship between the mean fecundity and the net reproductive rate, as estimated by the bootstrap technique, was slightly inconsistent with the relationship found by mathematical proof. The application of the jackknife and bootstrap techniques in estimating population parameters requires further examination.

Effects of green manure cover crops on Spodoptera litura (Lepidoptera: Noctuidae) populations.

Spodoptera litura (F.) is an important pest of numerous agro-economic crops, including green manure cover crops. In Taiwan, sesbania (Sesbanin roxburghii Merr.), sunn hemp (Crotalaria juncea L.), and rapeseed (Brassicae campestris L. variety chinensis) are the most popular green manure crops; sesbania and sunn hemp are commonly planted in warm seasons, whereas rapeseed is grown in the winter. In this study, life-table data for S. litura reared on these three green manures were collected to evaluate their roles as refuges of this pest. The net reproductive rate, intrinsic rate of increase, and finite rate of increase of S. litura were the highest when reared on sesbania (1428.1 offspring, 0.2327 d(-1), 1.2621 d(-1)), followed by sunn hemp (778.4 offspring, 0.2070 d(-1), 1.2300 d(-1)) and rapeseed (737.6 offspring, 0.2040 d(-1), 1.2263 d(-1)). The high growth rates on these green manure crops show that they can serve as potential breeding sites for S. litura. Population projection demonstrated the rapid growth of S. litura on sesbania, sunn hemp, and rapeseed as well. Because most growers have traditionally ignored pest management in green manure fields, the mass emergence of S. litura in these fields may cause unexpected infestations in nearby vegetable, corn, and peanut crops. This study shows that the use of green manures as sources of nutrients should be critically reassessed and an area-wide pest management program should be instituted by taking the population of S. litura in green manure fields into consideration.

Population and damage projection of Spodoptera litura (F.) on peanuts (Arachis hypogaea L.) under different conditions using the age-stage, two-sex life table.

BACKGROUND: The common cutworm, Spodoptera litura (Fabricus), is the most serious pest of peanuts in Taiwan. In order to devise an ecology-based and cost-effective control program, we collected life table data and consumption rates from larvae reared indoors at a constant temperature of 25°C, or outdoors at ambient temperatures during the spring and fall of 2010. A computer simulation was then used to project the population growth and damage potential of S. litura on peanuts. RESULTS: Laboratory-reared S. litura individuals produced 3548 eggs/female, whereas those reared outdoors produced 3452 and 3072 eggs/female in the spring and fall, respectively. The intrinsic rate of increase was 0.1828, 0.1308 and 0.1545 day(-1), and the net consumption rate was 194.0, 132.2 and 166.6 cm(2) larva(-1) at 25°C, in spring and fall, respectively. Population projection showed a faster growth and higher damage potential of S. litura in the fall. CONCLUSION: Population projections based on life tables and stage-specific consumption rates can reveal the stage structure and damage potential of the pest population. Our results showed that monitoring data obtained by using pheromone traps were not in concordance with the damage potential of the pest population. This approach offers a promising tool for pest management.