Site factors and management influence short-term host resistance to spruce budworm, Choristoneura fumiferana (Clem.), in a species-specific manner

BACKGROUND: This study examined the interactions between thinning and soil drainage classes on the resistance of balsam fir, Abies balsamea (L.) Mill, white spruce, Picea glauca (Moench) Voss, and black spruce, P. mariana (Mill.) BSP, to spruce budworm, Choristoneura fumiferana (Clem.), defoliation 1 year after treatment. To estimate host tree resistance, foliage production and larval foliage consumption were determined to generate an index of resistance quantifying the amount of residual foliage available for photosynthesis after insect defoliation. RESULTS: Significant interactions on tree resistance and foliage chemistry were detected between thinning and soil drainage in balsam fir. Drainage class affected spruce budworm performance, foliar chemistry and balsam fir resistance to spruce budworm, whereas no effect was found in white spruce. Thinning had a significant effect on the foliar chemistry of balsam fir and white spruce, but no effect on black spruce. CONCLUSION: Thinning reduced balsam fir resistance to spruce budworm defoliation. This response is due to increased defoliation linked to reduction in concentrations of certain monoterpenes, and a decrease in foliage production, except on hydric drainage, demonstrating the importance of drainage class to tree resistance. The results suggest that the use of Bacillus thuringiensis might be required when conducting stand thinning during spruce budworm outbreaks. Copyright © 2011 Society of Chemical Industry     

Foliar Persistence and Residual Activity of Tebufenozide Against Spruce Budworm Larvae

A field study was conducted to investigate the persistence of tebufenozide in white spruce foliage. An aqueous suspension concentrate formulation, RH-5992 2F, was sprayed over single trees at three dosage rates, 35, 70 and 140 g of the active ingredient (AI), in 2·0 litre ha⁻¹, using ground application equipment. Foliage was collected at different intervals of time up to 64 days after treatment and tebufenozide residues were measured by high-performance liquid chromatography. Foliage was also fed to laboratory-reared 4th- and 6th-instar spruce budworm (Choristoneura fumiferana Clemens). The data indicated that tebufenozide residues in foliage declined with time according to first-order kinetics. The average rate-constant and half-life of disappearance (DT₅₀) were 0·0340 and 20·45 days, respectively. Larval mortality declined gradually, corresponding to the residues, but was still appreciable (49 to 70%) when the larvae were fed with foliage collected 64 days after treatment. The amount of foliage consumed by the larvae decreased when foliar residues of tebufenozide increased, thus indicating anti-feedant activity of the chemical. The LD₅₀ values for both instars were similar and averagedc.25 ng per insect, but the LD₉₀ values were significantly lower for 4th-instar than for 6th-instar, at 63·6 and 96·1 ng per insect respectively. This implies that, theoretically, at a foliar concentration of 1·0 μg tebufenozide g⁻¹ foliage (fresh wt), the spruce budworm larva needs to consume 65 to 100 mg of foliage in 10 days to cause mortality in about 90% of a population of the insect.     

Insect Mobility and the Philosophy of Crop Protection with Reference to the Sudan Gezira

Abstract

Mobility results in movement of insects from their birth place (emigration) to another site (immigration). The scale, both in time and in space, on which such migration occurs may determine rates of increase or decrease in numbers in a fixed geographical area or plot. This is self evident in the case of mobile insects, such as locusts. Other documented examples include the spruce budworm in Canada and the Queensland fruit fly.

In the Sudan Gezira the distribution of the major insect pest of cotton, Heliothis armigera Hb., was found to conform to a common temporal pattern over probably some thousands of square kilometres, and other major pests, Empoasca libyca de Berg and Bemisia tabaci Gen., are considered to be similarly distributed, suggesting that their occurrence in damaging numbers may be dominated by transport and concentration by major windfields rather than by natality and mortality within a field or area. This posibility was investigated using a Pilatus Turbo-Porter aircraft fitted with Doppler Navigator equipment and an insect collecting net, and densities of flying insects monitored by a ground-based Marine-type Radar.

The results of this study will make it possible to determine the spatial extent of a threatening population and the time during which that population is present, so that control action may be taken on a commensurate scale. Such matching of scale of operations to insect mobility is of particular importance when repeated invasions occur during periods of rapid crop growth, because it enables non-persistent insecticides to be employed, thus providing potentially better utilisation of parasites and predators than can be achieved by maintaining the crop as an environment lethal to insects. These procedures, connoted ‘synoptic survey’ and ‘synchronous control’, require that the control is applied on a scale determined by pest mobility rather than by the boundaries of fields or other artificial constraints. Evidence is accumulating regarding the importance of insect mobility, in particular adaptive dispersal, in population dynamics and this may require re-assessment of farmer and government responsibilities in crop protection.     

Wood losses and economical threshold of Btk aerial spray operation against spruce budworm

BACKGROUND: Spruce budworm, Choristoneura fumiferana (Clem.), causes cumulative defoliation and hence annual growth loss of the balsam fir, Abies balsamea (L.) Mill, host tree. Annual growth increments of mixed balsam fir stands were measured by stem analysis over a 9 year period (1994–2002), when Bacillus thuringiensis ssp. kurstaki (Btk) was applied to control spruce budworm defoliation. With this approach, it was possible to quantify the change in stand volume growth after aerial spray applications of Btk. RESULTS: Differences between the periodic volume increment of protected and unprotected plots were statistically significant, while differences between protected and budworm‐free plots were not significant. After 9 years, the difference in periodic increment between protected and unprotected plots was 20 m³ ha^?1, and the difference in periodic mortality was 20.5 m³ ha^?1. CONCLUSION: An economic assessment of Btk treatments indicates that biopesticide aerial spraying operations are justified, as they prevented substantial balsam fir mortality and growth losses over the 9 year study. Copyright © 2009 Society of Chemical Industry     

Further observations on the use of fungicides to control Peronosclerospora sacchari (T. Miyake) Shirai and K. Hara in sugarcane in Papua New Guinea

Abstract

Many biologists perceive organisms as constantly evolving and therefore consider the host plant ranges of biological control agents as labile. Host plant ranges are thus likely to undergo adaptive change should environmental conditions change, for example following successful biological control. As a consequence, the introduction of biological control agents against weeds is considered by many to be an inherently unsafe practice with non‐target plants at risk of attack. However, despite the introduction of over 600 insect species from one geographic region to another for biological weed control during this century, there are relatively few documented cases of changes in host plant range. Purported instances are discussed in relation to behavioural and genetic concepts. It is concluded that apparent additions to the host range can, in all of the cases examined, be explained in terms of established behavioural concepts of pre‐adaptation, threshold change resulting from host deprivation, and effects of experience (learning). The inappropriateness of the often‐used term host shift’ to describe these cases is demonstrated, and it is concluded that evidence from biological weed control contradicts some aspects of ecological and evolutionary theory.     

Types of bark beetle (Coleoptera: Scolytidae) infestation in spruce forest stands affected by air pollution, bark beetle outbreak and honey fungus (Armillaria mellea)

583 spruce stands in an area affected by air pollution and bark beetle outbreak in Eastern Slovakia were studied in 1996. According to bark beetle infestation of dominant and codominant trees, stands were classified into following types of spruce stand decline:Ips typographus-A,Ips typographus-B,Polygraphus poligraphus, I. typographus/P. poligraphus—A,I. typographus/P. poligraphus—B. The presence of attacked trees in forest edges, bark beetle spots and forest interior was the key important factor for the classification. Data from forest inventory and forest management evidence together with data on types of spruce stands decline were used in further analyses. Results shows that the distribution of forest stands classified into different types or uninfested stands is related mainly to host size and site quality. The percentage of spruce, exposition of stands and stand density showed significant effects. The mechanisms of spreading of studied bark beetle outbreak could be explained by direct effects of stress of trees caused by an abrupt increase of level of solar irradiation and by weakening of trees by the honey fungus.     

Persistence and activity of mexacarbate and its metabolites against spruce budworm larvae

This study was conducted to determine if metabolites of mexacarbate contribute to its residual toxicity to spruce budworm (Choristoneura fumiferana) larvae. Potted white spruce (Picea glauca) trees were treated with ‘Zectran’ UCZF # 19 at 100 g a.i. ha^?1 and kept in a glasshouse. Mexacarbate residues declined by 98–99% within three days and reached non-detectable levels 10 days after treatment. Mortality of larvae fed on buds from these trees declined more gradually and was still 19–27% when exposed 10 days after treatment. The very low levels of mexacarbate (<0.07 μg g^?1) found after three days did not produce such mortality. Gas chromatographic analysis of metabolites in needles revealed that after three days, 4-methylformamido-3,5-xylyl N-methylcarbamate was present at levels 20–30 times higher than the parent compound. This metabolite was about 50 times less toxic than mexacarbate to larvae when applied topically but was only 7 times less toxic when ingested. Two other methylcarbamate metabolites, the amino, and methylamino analogues were detectable for one day following treatment but not at later time points. They were as toxic as mexacarbate both topically and orally. Based on these findings, the methylformamido analogue could contribute to the residual toxicity of mexacarbate treatments of spruce.     

气候变暖对农业害虫及其天敌的影响

全球气候的持续变暖引起了人类的高度关注。农业害虫是关系到农业生产顺利进行的一个特殊的昆虫类群,已经受到温度升高的影响。本文从气候变暖对农业害虫的发生、为害以及与天敌间关系的影响等三方面进行了综述。温度升高导致农业害虫的发生区域扩张,发生期提前和延长,高温适生种群发生量增大;农业害虫的为害时期改变,为害程度加重,为害物种之间产生新的竞争关系;农业害虫与寄主植物、天敌之间的同步性发生改变,继而影响到农业害虫的生物防治。本文最后对当前的研究工作进行了评述,就气候变暖形势下农业害虫的防治提出建议。     

Effects of kaolin-based particle film on spruce budworm (Choristoneura fumiferana (Lepidoptera: Tortricidae)) oviposition in the laboratory

A laboratory study conducted in 2003 determined the influence of a kaolin-based particle film (Surround WP Crop Protectant) on spruce budworm (Choristoneura fumiferana (Clem)) oviposition. Three concentrations (15, 30 and 60 g litre(-1) spray carrier) were applied to white spruce (Picea glauca (Moench) Voss). When presented with different paired choices of oviposition surfaces, spruce budworms laid very few egg masses overall and showed no significant (P < 0.05) preference between kaolin-coated and untreated foliage. During no-choice tests, spruce budworms were significantly (P < 0.05) less inclined to oviposit on the 60 g kaolin litre(-1) treated foliage than on the controls, but no kaolin treatment completely inhibited spruce budworm oviposition. Egg mass size and percentage hatch were unaffected by the kaolin treatments, and overall the percentage of egg masses laid on foliage was inversely proportional to treatment concentration. It is unlikely that kaolin-based particle film would be practical for wide use in natural forests without significant adaptations to current pesticide application equipment and methods. However, the technique might be feasible in selected urban settings.     

褐飞虱寄生性天敌两索线虫生活史的研究

两索线虫(Amphimermis sp.)的幼虫寄生于褐飞虱、灰飞虱等害虫的体内,使宿主产生一系列的病理变化,直至死亡。本文较详细地报导了湖北省褐飞虱寄生性天敌两索线虫的生活史。在实验室内用感染期幼虫作感染褐飞虱的试验获得成功。根据该虫的生活史和生态习性,在汉阳县的两索线虫孳生田里,采用与水稻高产栽培相结合的保护线虫措施,可以在褐飞虱中等发生量的年份,有效地控制褐飞虱的危害。     

Fate of spinosad in litter and soils of a white spruce plantation in central Ontario

Spinosad is a natural insecticide with potential as a novel biorational control agent for spruce budworm (Choristoneura fumiferana [Clem]), the most destructive insect defoliator of spruce and balsam fir in Canada. Concurrent terrestrial fate experiments were conducted under full coniferous canopy and in a natural opening of a mature white spruce (Piecea glauca [Moench]) plantation of central Ontario to examine the fate and persistence of spinosad in the forest floor and underlying soils. Mean initial residues of spinosyn A and D were approximately 0.2 and 0.02 microgram g-1, respectively, in thatch and exposed soils, but were substantially higher, 2.72 and 0.36 micrograms g-1, in litter under coniferous canopy. Results demonstrated that spinosad residues in spruce litter, graminaceous thatch and exposed sandy loam soils dissipated rapidly, following hyperbolic or exponential decline models. Dissipation time (DT50) values ranged from 2.0 to 7.8 days, depending on matrix and experimental conditions. Transient increases in demethylated metabolite residues confirmed that the parent product was degraded in situ. No evidence of vertical mobility of any of the analytes was observed.     

棉铃虫寄主植物种类及其适合性程度

通过江苏淮南、淮北棉区棉铃虫寄主植物种类凋查,已查明60种栽培植物、34种野生植物为棉铃虫寄主,它们分属24个科,其中以禾本科、豆科、菊科、葫芦科、十字花科、锦葵科、百合科、旋花科、藜科种类居多。运用选择系数法和适合性指数法定量测定了30种常见寄主植物对棉铃虫的适合性程度,建立了选择强度与适合性程度估测模型,据此将棉铃虫众多寄主划分为适宜寄主、较适宜寄主与次要寄主三大类。并在上述工作基础上,结合寄主植物种植面积情况,明确了各代次棉铃虫主要栽培寄主种类,以优化棉铃虫测报与防治技术。     

基于MaxEnt和DIVA-GIS的亮壮异蝽潜在地理分布预测

亮壮异蝽Urochela distincta Distant为中国特有种,具有结群迁飞和抱团越夏的习性,近年在江西武功山和仙姑坛风景区暴发成灾,为使相关自然保护区及风景名胜区做好对亮壮异蝽种群暴发的早期预警和监测,采用Max Ent和DIVA-GIS软件,基于该虫在江西、湖南、贵州等地的分布数据及相关的20个环境变量,对其潜在地理分布进行了预测。结果表明,影响亮壮异蝽分布的主要环境变量包括最干月降雨量、海拔、昼夜温差月平均值、最暖季降雨量、最冷月最低温、昼夜温差与年温差比值、最干季平均温和最湿季平均温,其中最干月降雨量和海拔是最重要的因素,贡献率分别为64.9%和19.5%。该虫在我国的高适生区多属于海拔700~1 500 m且最干月降雨量为25~130 mm的地区,主要集中在我国动物地理区划的华中区、华南区和西南区东部的部分区域,如江西与湖南交接的罗霄山脉,江西与福建接壤的武夷山山脉,以及重庆、湖南、贵州和湖北四交之地的武陵山脉等;非适生区包括我国的北部地区、西部地区、华中部分地区及华南的小部分区域。     

烟粉虱大发生对其不同寄主作物上其他主要害虫的影响研究

在对海门地区烟粉虱大发生状态下茄果类、瓜类及棉花等寄主作物上其他主要害虫发生情况进行系统监测的基础上,阐述了不同寄主作物上烟粉虱大发生对其他害虫产生的影响,比较了对其他各类不同为害习性害虫的影响大小,深入剖析了出现的干扰效应,明确了烟粉虱对寄主空间生态位的占有及对寄主刺吸为害造成寄主作物汁液口味变化等是引起其他害虫逐渐减少的根本原因。     

赤眼蜂实验种群生命表的编制与应用

利用以寄生变黑卵或仔代成蜂数量作为繁殖力估计等方法,编制了3种赤眼蜂在5种不同寄主卵上繁殖的实验种群生命表。分析比较表明,生命表参数能较好地反映“蜂-卵”组合的适合程度和寄生效能。初步认为,赤眼蜂实验种群生命表的编制,可以作为室内评估“蜂种与目标害虫”和“蜂种与中间寄主”的组合适合度和寄生效能的重要方法。其作用类似于农药的室内毒力测定。可供“育蜂治虫”实践参考。     

The International Centre of Insect Physiology and Ecology

Abstract

A method for assessing the damage by insect pests to cowpeas is presented. A crop life table for cowpeas grown in northern Nigeria shows the estimated losses due to insect attack at various stages of growth of the plants. The potential loss in yield due to insects is over 90%, with 70% of this loss occuring during the flowering and pod formation stages.     

Comparative efficacy of indigenous heterorhabditid nematodes from north western Himalaya and Heterorhabditis indica (Poinar,Karunakar & David) against the larvae of Helicoverpa armigera (Hubner)

The efficacy of three Heterorhabditis spp of entomopathogenic nematodes (EPNs) from north western Himalaya, India was studied against the larvae of pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), under the laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the concentrations of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also compared against commercially available entomopathogenic nematode, H. indica. Appreciably good performance was achieved by H. bacteriophora (HRJ), which showed 73.3% mortality of insect larvae in 96 h exposure time against third instar larvae, while H. indica produced 80.0% mortality. However it was noticed that with the advancement of larval stage its mortality rate reduced and vice versa with the exposure period. All tested EPNs were also found to reproduce within the host and maximum production of IJs was recorded in H. bacteriophora (26.0 ± 3.76 × 10³ IJs/larva) at the concentration of 40 IJs/larva.     

Advances in insect phototaxis and application to pest management: a review

Many insects, especially nocturnal insects, exhibit positive phototaxis to artificial lights. Light traps are currently used to monitor and manage insect pest populations, and play a crucial role in physical pest control. Efficient use of light traps to attract target insect pests is an important topic in the application of integrated pest management (IPM). Phototactic responses of insects vary among species, light characteristics and the physiological status of the insects. In addition, light can cause several biological responses, including biochemical, physiological, molecular and fitness changes in insects. In this review, we discuss several hypotheses on insect phototaxis, factors affecting insect phototaxis, insect‐sensitive wavelengths, biological responses of insects to light, and countermeasures for conserving beneficial insects and increasing the effect of trapping. In addition, we provide information on the different sensitivities to wavelengths causing positive phototactic behavior in > 70 insect pest and beneficial insect species. The use of advanced light traps equipped with superior light sources, such as light‐emitting diodes (LEDs), will make physical pest control in IPM more efficient. © 2019 Society of Chemical Industry