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.     

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.     

Correlations between wireworm damages in potato fields and landscape structure at different scales

Wireworms, the larvae of click beetles are world-wide pests of arable and vegetable crops. Many studies have shown that arthropods are influenced by landscape context. Therefore, for successful wireworm risk assessment, it is important to gain more information on relationships between landscape structure and wireworm infestation level. The aim of this study was to investigate if different landscape variables are related to wireworm infestation, represented by the proportion of wireworm damaged potato tubers. Based on aerial photographs and field surveys landscape variables, such as landscape composition, landscape complexity and ecological variables were characterised around 14 randomly selected potato field plots alongside the gradient from the lower warm-dry “Weinviertel” (region 1) to the cool-humid “Waldviertel” (region 2) in the North-East of Austria at three scales (1, 9 and 25 ha). Relationships between landscape variables and wireworm damage ratings were described by Spearman correlations coefficients. Our results showed that wireworm damage was higher in region 2 than in region 1 and tended to be higher in soils with higher sand content. Among the tested landscape variables only landscape composition, especially grassy field margins were significantly positively correlated with wireworm damage at the 25 ha scale. In areas with high proportion of such grassy habitats, farmers should pay more attention to field characteristics, such as sand content in soil, and management, like crop rotation. Further investigations on appropriate management regimes for grassy landscape elements suppressing wireworm populations but ensuring the maintenance of natural pest control should be conducted.     

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.     

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.     

Wireworm damage to wheat seedlings: effect of temperature and wireworm state

We describe the results of four laboratory studies designed to measure the effect of temperature and wireworm appetence, weight, and degree of Metarhizium infection on their ability to damage wheat seedlings. Wireworm activity, measured from wireworm speed, increased linearly from 6 to 18 °C and leveled off thereafter. Plant emergence and growth increased exponentially from 6 to 22 °C for wheat cultivars AC Barrie and AC Unity VB. Plant root:shoot ratio at Zadoks 13 was highest at 14 °C and lowest at 22 °C for AC Barrie. Wireworm weight and degree of infection with Metarhizium did not affect their ability to kill wheat seedlings, but wireworms in a feeding state caused significantly more damage than those in a non-feeding state when wheat was grown at 10, 14, 18, and 22 °C. Wireworms (ww) in a feeding state destroyed 1.8 seedlings/ww in 14 days at 22 °C if there were 1 or 2 wireworms in a pot, and 1.5 seedlings/ww if there were 4 wireworms in a pot. If 5 wireworms were placed in a pot, wireworms in a feeding state destroyed 0.3, 1.0, 0.9, 1.3, and 1.4 seedlings/ww in 46, 32, 25, 25, and 25 days at 6, 10, 14, 18, and 22 °C, respectively. Wireworm mortality from Metarhizium during 60 days of containment in pots in the study was higher in non-feeding than in feeding wireworms, and higher if wireworms were selected from a Metarhizium-infected colony than those selected from a non-infected colony. Some of the implications of these results for wireworm management and laboratory trials are discussed.     

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.     

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.     

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     

Influence of the surrounding landscape on the colonization rate of cereal aphids and phytovirus transmission in autumn

Ecological control has often focused on factors enhancing control of pests by their natural enemies, while factors reducing the colonization rate of crops by pests have been comparatively neglected. We present an approach to assess landscape influence on the intensity of wheat colonization by a major crop pest, the aphid Rhopalosiphum padi. We used trays containing wheat seedlings to monitor field colonization by R. padi and barley yellow dwarf viruses’ transmission in two areas in France in autumn. We assessed the influence of landscape components likely affecting aphid colonization, i.e. maize and grasslands as source of migrants on the number of aphids landing per tray, as well as the host plant of origin and the viruliferous potential of migrants. During the survey, maize was the main source of migrants. Virus transmission was detected in a few cases (4 % positive assays). Colonization was increased by the presence of maize, but reduced by the presence of grasslands at the landscape scale considered here (i.e. at a radius of 1000 m). Our study contributes to a better understanding of disease dynamics in agricultural landscapes. By identifying features of the landscape that surrounds fields and affects these dynamics, growers can develop more efficient crop protection strategies relying on habitat manipulation and rational use of pesticides.     

金针虫控制技术及其研究进展

金针虫是一类重要地下害虫,其控制技术一直是植物保护工作的难点.文章从作物栽培管理、生物防治、土壤处理、化学防治及成虫诱杀5个方面综述了国内外金针虫控制技术的研究现状及进展,并提出了在金针虫不同发育阶段协调多种控制手段的综合治理策略.     

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.     

潮棕壤不同利用方式土壤氮的垂直变化及氮储量

对中国科学院沈阳生态实验站潮棕壤在水稻田、玉米地、撂荒地和林地等经过14年不同利用方式后0-150cm各土层(2003年11月取样)N的剖面分布及N储量进行研究的结果表明不同利用方式下土壤全N、碱解N、NH4+-N和NO3--N含量发生明显的剖面差异;土壤N储量为林地>玉米地>撂荒地>水稻田,NO3--N含量为玉米地>水稻田>林地>撂荒地,说明不同利用方式下生物量差异及N的生物循环对N行为的影响。100cm深度林地土壤平均N储量为11.41t穐m-2,分别是水稻田和玉米地土壤的1.65和1.25倍,而玉米地和撂荒地的土壤N储量无显著差异。玉米地和水稻田相对较高的NO3--N含量可能由于过量施用N肥和人为干扰所致。土壤碱解N与全N含量呈线性正相关关系(R20.929,p<0.001),而自然生态系统(林地和撂荒地)中的相关性略高于农田生态系统(水稻田和玉米地)。过量施用N肥还导致耕地土壤中比撂荒地和林地积累更多的NO3--N。研究结果表明,农林复合系统对于作物生产和环境保护具有重要的潜在贡献。图2表5参23。     

Crop production on soil under some forest plantations in the Sahel

The production of maize (Zea mays L.), guinea corn (Sorghum vulgare L.) and groundnuts (Arachis hypogea L.) grown in pots on soils sampled under neem (Azadiracta indica A. Juss), Eucalyptus camaldulensis Dehnh, and Prosopis juliflora Swartz, plantations in the Sahel region of Nigeria was investigated. Ordinary field soil adjacent to the plantation formed the control against which forest and species effects on the soil were compared.Crops, particularly maize and sorghum, produced higher dry matter on forest influenced soil than on ordinary field soil. The leguminous groundnuts however, appeared to have fixed its own nitrogen and therefore depended less on the inherent fertility advantages of the forest soil. The highest crop yield was obtained on the soil under neem followed by Prosopis, Eucalyptus and ordinary field. Since forest species differed in their effects on crop yield, further indentification, categorization and development of species with positive effects on crop yield was suggested for priority attention.     

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.     

Hauptprobleme der landwirtschaftlichen Entomologie in Jugoslawien

Summary A survey of the most important entomological problems on wheat, maize and sugar beet in Yugoslavia is given. The causes of some new problems, such asEurygaster spp. on wheat, some new pests of maize, and leaf cutworms on sugar beets, so as the problem of wireworms control with new insecticides, are especially pointed out.     

Land use alters the abundance of herbivore and predatory insects on crops: the case of alfalfa

We assess the effects of changing land use and crop management on alfalfa insect abundance by comparing it in 50 alfalfa fields when they were inserted in landscapes with different proportions of arable crops and orchards. Land use in a buffer of 500 m was assessed, and alfalfa insect abundance was estimated with sticky yellow traps. The number of catches of several herbivores and predators was related to the proportion of landscape components and several field variables. Results indicated that the proportion of orchards in the buffer negatively affected the abundance of predators on alfalfa, likely because orchards treated with pesticides are a sink for predators moving in the landscape, among other possible causes. Other landscape variables such as noncrop habitats, winter cereals, and landscape diversity analysed by the Shannon index had a minor influence. Among field variables, field size influenced positively the abundance of insects on alfalfa, whereas alfalfa growth stage and age affected positively or negatively the different herbivores and predators. Of course, abundance of predators and prey was affected by the abundance of prey and predators, respectively. These findings suggest that a high proportion of intensively managed crops (orchards) in the landscape interferes with the role of alfalfa as a reservoir of predatory insects for adjacent crops and that the responses to local and landscape structures are temporal and species-specific as previously concluded for maize. Consequently, landscape and field management strategies to improve pest control must consider both types of variables as well as their changing influence when we modify them.

     

北京密云水库集水区森林景观生态分类研究

以遥感影像和地形图件为基础,结合二类调查资料和GPS实地布点,借助于ARC View和Fragstats软件,从不同尺度将集水区森林景观进行了分类归并,包括2个森林景观类、3个森林景观系、6个森林景观组、5个森林景观型和9个森林景观亚型。其中,生态型森林景观系是研究区域内的森林景观主体,森林景观多为幼龄林和疏林,针阔混交林的比重相对较低。各种森林景观类型景观斑块面积较破碎、形状较规则,受人类活动干扰普遍较为严重,宜以培育水源涵养与水土保持功能为主要目标,加强森林抚育,发展多种模式的混交造林。