Response of the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), to residual levels of bifenthrin in field soil

To determine if bifenthrin residues elicit morbidity and surfacing behavior in wireworms, larvae of the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae) were placed in field soil treated with the pyrethroid insecticide bifenthrin ~1 year previous. Morbidity was immediate and lasted as long as wireworms remained in the soil, disappearing quickly after transfer to clean soil. In 2009, field soil treated 336 days previous with bifenthrin at 340 g AI/ha elicited morbidity symptoms similar to that elicited by soil freshly amended with bifenthrin at 100 g AI, and analysis of the field soil confirmed residual levels of bifenthrin exceeding 100 g AI/ha. In 2010, wireworms placed in field soil treated 343 days previous with bifenthrin at 100, 200, and 300 g AI/ha responded as in 2009, with the degree of morbidity increasing with the rate of insecticide, and with wireworms in a non-feeding state more affected than those in a feeding state at each rate. In both 2009 and 2010, moribund wireworms moved to the soil surface within 1 day of placement in the soil containing residual bifenthrin and remained there until reburied, after which they often resurfaced. To confirm that the bifenthrin residues elicited repellency, wireworms were placed in soil window bioassays containing field soil with residual bifenthrin. Wireworms behaved markedly different upon contacting soil containing the residues than when exposed to untreated soil, both in the presence and absence of an attractant, but were less likely to avoid soil containing residual bifenthrin when attracted by wheat seedlings placed inside it.     

Categorization and numerical assessment of wireworm mobility over time following exposure to bifenthrin

We discuss the effect of the pyrethroid insecticide bifenthrin incorporated into soil at 100, 200, and 300 g AI/ha on late-instar larvae of the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), and present a method of assessing wireworm health and mobility over time. Wireworms became moribund within 1 h of placement in soil amended with bifenthrin at all rates. After 2 weeks of morbidity in amended soils, wireworms recovered within 7 days of being placed in clean soil. A considerable proportion (0.13–0.93) of wireworms placed in amended soil moved to the soil surface and remained there for 2 weeks or more in a moribund state; wireworms transferred to clean soil no longer moved to the soil surface. Eight distinct mobility categories were observed and are described, and a new method for assessing wireworm health and mobility over time is discussed.     

Crop protection and mortality of Agriotes obscurus wireworms with blended insecticidal wheat seed treatments

In Canada, as in much of the northern hemisphere, insecticidal seed treatments for cereals that both protect crops from damage by wireworms (Coleoptera: Elateridae) and actually reduce wireworm populations to sub-economic levels are lacking. Thiamethoxam and fipronil applied alone or in combination as wheat seed treatments were evaluated in field studies between 2006 and 2008 in protecting wheat from damage and reducing populations of resident and neonate wireworms. Thiamethoxam alone applied at 5 or 10 g a.i./100 kg seed provided adequate wheat stand and yield protection, but did not significantly reduce Agriotes obscurus wireworm populations. Fipronil alone at 5–50 g a.i./100 kg seed provided adequate wheat stand and yield protection, and also killed significant numbers of both resident and neonate wireworms. Thiamethoxam (10 g a.i.) was initially combined with fipronil at 50, 5, 0.5, 0.05, and 0.005 g a.i./100 kg seed, and subsequently with a delimiting range of fipronil at 50, 5, 1, 0.5, and 0.1 g a.i. Blends of thiamethoxam (10 g a.i.) + fipronil at rates of 50, 5, or 1 g a.i. provided stand and yield as good or better than the former industry standard Vitavax Dual (containing lindane). Combinations of thiamethoxam (10 g a.i.) + fipronil at rates of 50, 5, 1, and 0.5 g a.i. had very low numbers of resident or neonate wireworms relative to the untreated check and were comparable to the Vitavax Dual standard. The benefit of combined thiamethoxam + fipronil seed treatments at these rates, is that crop stand and yield are improved over the individual chemicals applied alone, and resident and neonate wireworm mortality is high. The large reductions in resident and neonate wireworms observed with these combined seed treatments would remove the economic threat of wireworms in fields for 3+ years with rates of insecticides much lower than the formerly used Vitavax Dual.     

IPM thresholds for Agriotes wireworm species in maize in Southern Europe

Currently, integrated pest management (IPM) of wireworms is not widespread in Europe. Therefore, to estimate the densities of three major wireworm species in southern Europe (Agriotes brevis Candeze, A. sordidus Illiger, and A. ustulatus Schäller), bait traps were deployed pre-seeding in maize fields in north-eastern Italy between 1993 and 2011. Research discovered that there was a significant correlation between all three wireworm species caught in the bait traps and damage to maize plants, but damage symptoms varied. Wherever A. ustulatus was the main species caught, there was no significant damage to maize plants, but seeds were damaged. Most of the symptoms caused by A. brevis and A. sordidus were to the central leaf/leaves, which wilted because of feeding on the collar. A. brevis was the most harmful species; when more than one A. brevis wireworm was caught per trap, plant damage sometimes resulted in reduced yield. Five A. ustulatus larvae per trap caused the same damage to maize as one A. brevis. A. sordidus came second (threshold two larvae/trap). These thresholds are reliable for: (1) bare soil in which there are no alternative food sources; (2) average soil temperature 10 cm beneath the surface of above 8 °C for 10 days; (3) soil humidity near to field water capacity, but days of flooding have not been considered. The implementation of the practical method described herein may lead to effective IPM of wireworms in maize and to a significant reduction in the number of fields treated with soil insecticides.     

Varietal susceptibility to the corn wireworm Melanotus communis (Coleoptera: Elateridae) in sugarcane

Wireworms (larval Elateridae) reduce the stand of newly planted sugarcane (complex hybrid of Saccharum spp.) directly by damaging growing points and indirectly by facilitating disease introduction. No research has evaluated resistance or tolerance of sugarcane genotypes grown in Florida to wireworm. Eleven genotypes of sugarcane and a S. spontaneum genotype were subjected to corn wireworm, Melanotus communis (Gyllenhall) (Coleoptera: Elateridae), in greenhouse experiments to evaluate potential host plant resistance. The experiments were designed to measure the effects of wireworms on the first 90 days of growth. Sugarcane stalk sections were planted in trays of soil with and without wireworms in 2010 and 2011. Stand count, dry weight, and percentage of nodes damaged were evaluated. Wireworms reduced stand and dry weight by 40–60 %. Several genotypes were able to produce acceptable stands in wireworm-infested trays by emerging quickly and producing many tillers. CP 88-1762, CP 89-2143, and CP 03-1912 did not suffer statistically significant losses of stand or biomass due to wireworms in either year. Our findings suggest that genotype resistance should be considered as an important component of an integrated program aimed at reducing the use of insecticides to control wireworms in sugarcane.     

Preliminary investigations into the use of trap crops to control Agriotes spp. (Coleoptera: Elateridae) in potato crops

A field trial was conducted to investigate the use of peas (Pisum sativum cv. Valverde), wheat (Triticum aestivum cv. Capo) and oilseed radish (Raphanus sativus var. oleiformis cv. Adagio) as trap crops to control wireworm in potato fields. We investigated the efficacy of trap crops and distance of attraction by counting larvae in both potato and trap crop rows. Wireworms of the genera Agriotes, Adrastus and Hemicrepidius were observed. In the plots planted with peas as a trap crop, significantly more wireworms were observed than in the other treatments, which was clearly due to the influence of the trap crop pea. The potato rows 0.75 m away from the peas showed 2.4 times more larvae than the potato rows 1.5 m away. This may be due to a decrease of the peas’ attractiveness over time (Miles and Petherbridge 1927), with wireworms that were initially attracted to the peas moving back to the nearby potatoes. In the plots planted with wheat, oilseed radish and the control (bare soil instead of a trap crop), there was no significant difference in numbers of larvae between the potato rows. In the control plots, significantly more larvae were found in the potato rows than in the bare soil. We assessed the damage to potato tubers by weighing them and counting the wireworm holes. Our results indicate that peas are more attractive to wireworms than potatoes and might be an effective trap crop if the right timing and spacing relative to the potatoes is found.     

Relative influence of climate and agroenvironmental factors on wireworm damage risk in maize crops

A large-scale survey was carried out in 336 French fields to investigate the influence of soil characteristics, climate conditions, the presence of wireworms and the identity of predominant species, agricultural practices, field history and local landscape features on the damage caused by wireworms in maize. Boosted regression trees, a statistical model originating from the field of machine learning, were fitted to survey data and then used to hierarchize and weigh the relative influence of a large set of variables on the observed damage. Our study confirmed the relevance of an early assessment of wireworm populations to forecast crop damage. Results have shown that climatic factors were also major determinants of wireworm damage, especially the soil temperature around the sowing date, with a strong decrease in damage when it exceeds 12 °C. Soil characteristics were ranked third in importance with a primary influence of pH, but also of organic matter content, and to a lesser extent of soil texture. Field history ranked next; in particular, our findings confirmed that a long-lasting meadow appeared favourable to wireworm damage. Finally, agriculture practices and landscape context (especially the presence of a meadow in the field vicinity) were also shown to influence wireworm damage but more marginally. Overall, the predicted damage appeared highly correlated with the observed one allowing us to produce the framework of a decision support system to forecast wireworm risk in maize crop.     

Physical exclusion of adult click beetles from wheat with an exclusion trench

Click beetles, the adult stage of wireworms, will enter fields of their preferred hosts (i.e., grasses, pasture, and cereals) from various reservoir habitats, and lay eggs which give rise to wireworm problems in subsequent years. To prevent click beetles, Agriotes obscurus, from immigrating into fields, a portable trench barrier composed of an extruded, PVC plastic trough was evaluated in 2001 in Agassiz, British Columbia, Canada. Plots of wheat or bare ground that were surrounded by trenches had significantly lower numbers of males in pheromone traps and females in pitfall traps relative to non-trenched plots. Exclusion was more pronounced in the first part of the study (about 75 % reduction) than later in the study (30–42 %), likely due to gradual within plot emergence of overwintered beetles and/or flight activity. The potential for use of exclusion devices for click beetle control and future directions for research are discussed.     

Seasonal population dynamics of wireworms in wheat crops in the Pacific Northwestern United States

Insect pests often exhibit predictable seasonal population dynamics in response to temperature and other environmental drivers. Understanding these dynamics is critical to developing effective integrated pest management strategies. Here we studied the seasonal phenology and feeding activity of two wireworm species that are major pests of wheat crops in the Pacific Northwestern United States, Limonius californicus and L. infuscatus. We conducted monthly sampling of the damaging larval stages of both species in commercial spring wheat fields in Washington and Idaho throughout 2013 and 2014. These data were used to model the seasonal phenology and feeding activity of each species in relation to soil temperature. We found larvae of both species were most abundant relatively early in the season, with total wireworms captures in soil cores declining as the season progressed. Larvae of both species were collected predominantly in the top 70 cm of the soil profile, suggesting that they primarily feed on plant roots and seeds up to this depth. While patterns of seasonal abundance of both species were similar, feeding activity varied significantly between the two species. Our results indicate that as spring moves into summer L. californicus feeds more aggressively, whereas the activity of L. infuscatus decreases as the crop season progresses. These differences might help explain why L. californicus is generally a more economically damaging pest that also threatens winter crops, while damage from L. infuscatus is generally limited to the spring. Accordingly, management strategies for each species should be tailored to their specific seasonal dynamics.     

The molecular identification and genetic diversity of economically important wireworm species (Coleoptera: Elateridae) in Canada

Click beetle larvae (wireworms) are significant crop pests in Europe and North America. In Canada, there are ~30 economically important species which are morphologically difficult to identify, but for which sequence data are lacking. Accurate knowledge of damage-causing species and the population genetics and phylogeography of elaterids will provide insight into their sustainable management. Here, we use interspecific variation in mitochondrial 16S rRNA as a robust method of identification, consider the intra- and interspecific genetic variation of some important Canadian wireworm pests and assess the genetic structure and isolation by distance for a re-emerging major pest species, Hypnoidus bicolor Eschscholtz. Wireworms were sampled from Canada and the USA, identified as morphospecies, and sequenced at the 16S rRNA region (294–442 bp). Within some species unusually high intraspecific genetic distances between samples suggested the possibility of cryptic wireworm species or misidentifications, though this was <1 % for most species. Phylogenetic analyses gave some indication of the likely identity of these ambiguous samples. There was a significant correlation between genetic and geographic distance and significant genetic structuring within and between H. bicolor populations, which appeared to be composed of two species comprising several haplotypes. These data provide a starting point for determining the distribution of damage-causing species throughout Canada. The inclusion of data from other nuclear and mitochondrial loci, and use of sequence data from known adult samples, would further aid identification and relationships of wireworm species.     

Validation of a sequential sampling plan for wireworms (Coleoptera: Elateridae) at sugarcane planting

Wireworms in Florida are primarily a pest in newly planted sugarcane, and growers usually apply a soil insecticide at planting to protect germinating seedpieces from wireworm damage. However, studies have suggested that this application in many cases may not be necessary. The objective of this research was to test a sequential sampling method to determine the need for soil insecticide at sugarcane planting. Testing was conducted on fields located on King Ranch near South Bay, Florida. Wireworm samples were taken in a transect across the length of each field. We used an economic injury level of nine or more wireworms per 25 samples. Sugarcane yield parameters for each whole field were obtained through standard commercial harvesting procedures. Using our sampling method, 38 fields were judged as not needing insecticide application. There was no significant difference in yield in these fields with versus those without insecticide application.     

筛胸梳爪叩甲监测技术及应用

正害虫预测预报是进行害虫风险评估及制定防治决策的基础,使用有效的监测技术能准确地预测林间害虫发生的时间、种群动态等重要参数,可为害虫防治指标的确定和综合防治措施的实施提供参考依据。当前,我国已有近百种重要害虫建立了系统的监测技术[1]。金针虫是鞘翅目(Coleoptera)叩甲科(Elateridae)昆虫幼虫的通称,广布于世界各地,是一种极为重要的地下害虫[2-3]。金针虫隐蔽性强,且能随环境变化改变活动及危害深度,其虫口密度     

Wireworm damage reduction in potatoes with an attract-and-kill strategy using <Emphasis Type="Italic">Metarhizium brunneum</Emphasis>

Innovative wireworm control strategies are required to implement integrated pest management on the basis of the (EC) No regulation 1107/2009 and Directive 2009/128/EC. Entomopathogenic fungi, such as Metarhizium brunneum (Metschnikoff) Sorokin, are potential biological control agents for wireworm control but do not achieve high control efficacies in the field when applied as a conidia suspension. In a 2-year study, wireworm control with a novel attract-and-kill strategy aimed at enhancing M. brunneum efficacies in organic potato production systems in Lower Saxony, Germany. The approach is based on the attraction of wireworms (Agriotes spp. Eschscholtz) towards an artificial carbon dioxide-emitting source, using baker’s yeast (Saccharomyces cerevisiae Meyen ex Hansen) in combination with M. brunneum conidia for wireworm infection. Both components were encapsulated in alginate as a carrier material and applied in a mixture with two types of beads (one for encapsulated yeast and one for M.brunneum conidia). An application of these beads within the potato rows during potato planting reduced wireworm tuber damage by 37–75% relative to the untreated control and was able to enhance the efficacy of M. brunneum by up to 35% through an attract-and-kill approach compared to beads without a carbon dioxide source only. This strategy offers a high potential to promote biological wireworm control as an alternative to insecticide use by potentially reducing the inoculum compared to an inundate M. brunneum conidia release strategy.     

Evaluation of spinetoram and spinosad for control of Prostephanus truncatus,Rhyzopertha dominica,Sitophilus oryzae,and Tribolium confusum on stored grains under laboratory tests

Spinetoram and spinosad have been evaluated against certain stored-product insect pests with success but there are no data available on the comparison of the efficacy of these two novel compounds in stored grains. Thus, laboratory bioassays were conducted to compare spinetoram and spinosad as grain protectants against Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) adults, and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) adults and larvae. Factors such as treatment (1 ppm spinetoram, 1 ppm spinosad, 0.1 ppm spinetoram + 0.9 ppm spinosad, 0.5 ppm spinetoram + 0.5 ppm spinosad, and 0.9 ppm spinetoram + 0.1 ppm spinosad), exposure interval (1, 2, 7, and 14 days), temperature (20, 25, and 30 °C), and commodity (barley, maize, rye, and wheat) were evaluated. Progeny production was assessed after 60 days of exposure. Concerning temperatures, for P. truncatus adults, after 14 days of exposure, all adults were dead in treatments except of the case of spinosad alone at 20 °C. Offspring emergence was completely suppressed in all treatments at 20 and 25 °C. For R. dominica adults, after 7 days of exposure, the overall mortality ranged from 92.8 to 100 %. After 14 days of exposure, all adults were dead in all treatments of the combined use of spinetoram and spinosad at 25 and 30 °C. Progeny production was completely suppressed in all treatments at 30 °C. For S. oryzae adults, after 7 days of exposure, all S. oryzae were died at 25 and 30 °C in all treatments except in the case of spinosad alone. Offspring emergence was very low in all treatments and temperatures except in the case of spinosad alone at 30 °C. For T. confusum adults, after 1, 2, and 7 days of exposure, the overall mortality was low in all treatments and temperatures. Concerning commodities, for R. dominica adults, after 7 and 14 days of exposure, the overall mortality was >97 %. Offspring emergence was very low in all commodities. For S. oryzae adults, after 7 and 14 days of exposure, the overall mortality was increased exceeding 91 % except in the case of spinosad alone 7 days after exposure in barley. Progeny production was high in barley and rye in all treatments. For T. confusum adults, after 7 and 14 days, the overall mortality was low in barley, rye, and wheat. No offspring emergence was recorded in all treatments and commodities. For T. confusum larvae, after 14 days of exposure mortality was further increased, but did not reach 100 % for any of the combinations tested. The results of the present study suggest that the simultaneous application of spinetoram and spinosad was generally equally effective with the use of either spinosad or spinetoram alone. Furthermore, the increase of dose of either compound resulted in the same mortality levels. Thus, no benefits were achieved when spinetoram and spinosad were used simultaneously on grains, regardless of the proportion of each ingredient. These issues should be seriously considered when control measures against stored-product insects are designed.     

The impact of climate change on the growth of tropical agroforestry tree seedlings

Several studies have been conducted on the response of crops to greater concentrations of atmospheric CO₂ (CO₂ fertilization) as a result of climate change, but only few studies have evaluated this effect on multipurpose agroforestry tree species in tropical environments. The objectives of this study were to quantify differences in growth parameters and in leaf carbon (C) and nitrogen (N) concentrations of Cedrela odorata L. and Gliricidia sepium (Jacq.) Walp. seedlings under current ambient temperature (32°C daytime, 22°C night time) and CO₂ (360 ppm) (AMB); CO₂ fertilization (800 ppm, 32°C daytime, 22°C night time) (_fCO₂); elevated ambient temperature (360 ppm, 34°C daytime, 25°C night time) (TEMP); and a combination of elevated temperature (32°C daytime, 22°C night time) and CO₂ fertilization (800 ppm) (TEMPx_fCO₂). Results showed significant differences (P < 0.05) in seedling growth parameters (seedling height, number of stem leaves, leaf area ratio, shoot and root biomass, and shoot/root ratio) between treatments for both tree species. The greatest increases in growth parameters occurred in the TEMP and TEMPx_fCO₂ treatments compared to the AMB treatment for both tree species. However, growth parameters were significantly lower (P < 0.05) in the _fCO₂ treatment compared to that of the AMB treatment. Leaf N concentration was 1.1 to 2.1 times lower (P < 0.05) in all treatments when compared to current ambient conditions (AMB) in both tree species, but no significant changes in leaf C concentrations were observed. Results from our study suggested that _fCO₂ had the greatest negative impact on tree growth parameters, and leaf N concentrations were affected negatively in all treatments compared to current ambient conditions. It is expected that such changes in growth parameters and plant N content may impact the long-term cycling of nutrients in agroforestry systems.     

Low soil temperatures increase carbon reserves in Picea mariana and Pinus contorta

? Context

Soil temperature can limit tree growth and function, but it is often unaddressed in understanding the successional status of trees.

? Aims

We tested how soil temperature affected carbon allocation strategies of two dominant co-occurring boreal conifer species, Pinus contorta and Picea mariana.

? Methods

We measured nonstructural carbon (NSC) concentrations, biomass, and photosynthesis of dormant and actively growing 2-year-old seedlings in response to three soil temperatures (5, 10, and 20 °C) under a common ambient air temperature.

? Results

For both species, variation in carbon reserves with soil temperature was more pronounced following seedling growth than during dormancy. For both species and all organ types (roots, needles, and stems), NSC concentrations were highest when seedlings were grown at 5 than 20 °C. Mass adjusted for NSC content was negatively correlated with NSC concentration for all organ types of both species. Soil temperature had a marginally significant effect on photosynthesis of pine; seedlings grown at 10 or 20 °C acquired more carbon than seedlings grown at 5 °C. Spruce seedlings photosynthesized more when grown at 20 °C than at 5 or 10 °C.

? Conclusion

Interspecific differences in allocation of carbon may underlie the responses of P. mariana and P. contorta to cold soils and consequently their successional status.     

Toward improved understanding of the cell-wall density and porosity of wood determined by gas pycnometry

The main objective of this study was to evaluate the effect of sample preparation on cell-wall density and porosity using gas pycnometry. Native and thermally modified twin samples of Norway spruce (Picea abies (L.) Karst.), sycamore maple (Acer pseudoplatanus L.), and European ash (Fraxinus excelsior L.) were analyzed. The samples differed in terms of shape, geometry, and climatic state. On the one hand, the samples were oven dry as usual and, on the other hand, conditioned at 22 °C and 95 % relative humidity. Furthermore, the samples were processed using solvent exchange drying. In addition to helium, nitrogen was used as a displacement gas. The tests show i.a. how this can lead to misinterpretation of the cell-wall density or porosity of wood determined by gas pycnometry. The results show that native spruce has a lower cell-wall density and higher porosity compared with native maple and ash. Due to thermal modification, the cell-wall densities are decreased. The investigations show that the determined cell-wall density and porosity of the wood are strongly dependent on the sample geometry and climatic state. The cell-wall densities of all investigated wood species in the conditioned state at 22 °C and 95 % relative humidity are significantly higher compared with the oven-dry cell-wall densities.     

Temperature-dependent development of Sesamia nonagrioides

The effect of various constant temperatures on survival, development and adult longevity of Sesamia nonagrioides Lefébvre (Lepidoptera: Noctuidae) was studied under laboratory conditions. The following temperatures were tested: 14, 17, 21, 25 and 31 °C. The percentage of individuals that completed development at each temperature as well as the days needed for the emergence of the pupa and adult eclosion were measured. Adult longevity was estimated under the same conditions. Development time decreased significantly with increasing temperature within the range 14–25 °C. Survival was higher at medium temperatures (17–25 °C) in comparison with that at more extreme temperature regimens (14 and 31 °C). Egg and first larval instars were the stages where S. nonagrioides suffered the highest mortality levels at all temperatures. The highest survival was recorded with experimental individuals aging between the third and fifth larval instar. Thermal requirements of development (developmental thresholds, thermal constant, optimum temperature) of S. nonagrioides were estimated with application of linear and one nonlinear models (Logan I). Upper and lower developmental thresholds ranged between 31.2 and 36.2 and 7.0 and 10.3 °C, respectively. The optimum temperature for development (where maximum rate of development occurs) was estimated at between 28.1 and 30.3 °C. The thermal constant for total development was estimated at 1,000.0 degree-days. Adult longevity was also affected by temperature, as it was significantly reduced at higher temperatures (21–31 °C) compared to the lower ones (14 and 17 °C). This information would be useful in determining the critical temperatures which may affect the distribution of S. nonagrioides concerning potential climate change.     

Effect of temperature on the biology of Acyrthosiphon gossypii Mordvilko (Homoptera: Aphididae) on cotton

Acyrthosiphon gossypii is a widespread, major pest of cotton in central Asia. Effects of specific temperatures on A. gossypii development and survival are unknown and would be useful in helping interpret population dynamics and devising management tactics for this pest. In this paper, the effect of temperature on the life table of A. gossypii reared on cotton was evaluated under laboratory conditions using temperatures of 18, 21, 24, 27, and 30 °C. The developmental rate of immatures increased exponentially from 18 to an optimum around 27 °C and then declined. The estimated lower developmental threshold was 8.0 °C, and 107.5 degree days were required for development from the first instar to adult. The percentage survival of immature stages varied from 81 to 91 % within the range of 18-27 °C. Survival declined to 27 % at 30 °C. The average longevity of adult females was 15.7, 11.7, 8.2, 5.2, and 2.8 days, and the average number of offspring produced per female was 46, 38, 20, 14, and 0, at temperatures of 18, 21, 24, 27, and 30 °C, respectively. From 21-27 °C, the intrinsic rate of increase of A. gossypii was significantly higher than at 18 °C, indicating that 21–27 °C was within the optimal range for the growth of A. gossypii, and that 30 °C constant is beyond the upper limit for reproduction. The observations will form the basis of a forecasting system and could account for the decline of the species on cotton in central Asia as well as other regions during hot summer months.     

Laboratory evaluation of five novel pyrrole derivatives as grain protectants against <Emphasis Type="Italic">Tribolium confusum</Emphasis> and <Emphasis Type="Italic">Ephestia kuehniella</Emphasis> larvae

Several naturally discovered or laboratory-synthesized pyrrole compounds have insecticidal, acaricidal and microbial properties. The novel sulfanyl 5H-dihydro-pyrrole derivatives exhibit certain antioxidant activities. However, there is a knowledge gap whether these substances are potent grain protectants against stored-product insect pest species. In this context, we evaluated the insecticidal activity of five novel pyrrole derivatives (under the trivial names 3a, 3g, 3l, 3m, 3h), against larvae of Tribolium confusum Jaquelin du Val and Ephestia kuehniella Zeller at different doses (0.1, 1 and 10 ppm), exposure intervals (7, 14 and 21 days or 1, 2, 7, 14, 21 days), temperatures (20, 25 and 30 °C), relative humidity (RH) (55 and 75 %) levels and commodities (wheat, maize, barley). The pyrrole derivative 3a exhibited the highest insecticidal activity, while 3g, 3l, 3m and 3h caused similar mortality against larvae of T. confusum. Apart of the level of efficacy, all tested pyrrole derivatives performed similarly according temperature. We found that increase in temperature increased mortality in the majority of the tested combinations. Generally, the pyrrole derivatives caused the highest mortality levels at 30 °C. The pyrrole derivatives 3a, 3g, 3l and 3m were affected by relative humidity at almost all combinations tested. The 75 % level of RH moderated the efficacy of the pyrrole derivatives, while the 55 % enhanced it. Mortality of T. confusum and E. kuehniella on maize was much lower on treated maize than barley or wheat. However, 100 % control of both species was recorded only on treated barley. The results of the present study indicate that the pyrrole derivatives tested could serve as grain protectants against noxious stored-product insects under certain biotic and abiotic conditions.