Reduced risk insecticides to control scale insects and protect natural enemies in the production and maintenance of urban landscape plants

Armored scale insects are among the most difficult to manage and economically important arthropod pests in the production and maintenance of urban landscape plants. This is because of morphological traits that protect them from contact insecticides. I compared initial and season-long control of euonymus scale, Unaspis euonymi Comstock (Hemiptera: Diaspidae), by reduced-risk insecticides (insect growth regulators [IGRs], neonicotinoids, spirotetramat) to determine if they controlled scale as well as more toxic insecticides such as the organophosphate, acephate, and pyrethroid, bifenthrin. I also evaluated how these insecticides affected natural enemy abundance on experimental plants and survival when exposed to insecticide residue. All insecticides tested reduced first generation euonymus scale abundance. In 2009, reinfestation by second generation euonymus scale was highest on plants treated with acetamiprid and granular dinotefuran. In 2010, systemic neonicotinoids and spirotetramat prevented cottony cushion scale infestation 133 d after treatment whereas scale readily infested plants treated with bifenthrin and horticultural oil. Encarsia spp. and Cybocephalus spp. abundance was related to scale abundance. These natural enemies were generally less abundant than predicted by scale abundance on granular dinotefuran treated plants and more abundant on granular thiamethoxam treated plants. Bifenthrin residue killed 90-100% of O. insidiosus and E. citrina within 24 h. My results indicate that reduced risk insecticides can provide season-long scale control with less impact on natural enemies than conventional insecticides. This could have economic and environmental benefits by reducing the number of applications necessary to protect nursery and landscape plants from scale.     

人工长白落叶松树干边材、心材和树皮密度预测模型

基于黑龙江省林口林业局、东京城林业局和东北林业大学帽儿山实验林场的35株人工长白落叶松的解析样木数据,构建长白落叶松的边材、心材和树皮密度的Beta回归模型,采用赤池信息准则、决定系数、平均绝对偏差、均方根误差和似然比检验对模型的拟合优度进行比较评价,进而选取边材、心材和树皮密度的最优模型,最后采用刀切法对选择出的最优模型进行检验,评价模型预测能力。结果表明: 边材、心材和树皮密度的最优模型的自变量不完全相同,其中,边材密度与树木年龄、树高、相对高度和相对高度的平方关系较好,而心材密度最优模型的自变量为年生长量、相对高度和相对高度的平方,树皮密度最优模型的自变量为树木年龄、年生长量、相对高度和相对高度的平方。对最优模型分析可知,从树干基部到树梢,边材密度逐渐减小,心材密度先减小后增加,树皮密度先增加后减小。本研究所建立的Beta回归模型可以预估该研究区域的人工林内长白落叶松的边材、心材和树皮任意位置的木材密度,为树干平均密度和生物量的研究奠定基础。     

Decreased resistance and increased tolerance to native herbivores of the invasive plant Sapium sebiferum

Release from natural enemies may favor invasive plants evolving traits associated with reduced herbivore‐resistance and faster‐growth in introduced ranges. Given a genetic trade‐off between resistance and tolerance, invasive plants could also become more tolerant to herbivory than conspecifics in the native range. We conducted a field common garden study in the native range of Sapium sebiferum using seeds from native Chinese populations and invasive North American populations to compare their growth and herbivory resistance. We also performed a cage‐pot experiment to compare their resistance and tolerance to Bikasha collaris beetles that are specialist feeders on S. sebiferum trees in China. Results of the common garden study showed that Sapium seedlings of invasive populations relative to native populations were more frequently attacked by native herbivores. Growth and leaf damage were significantly higher for invasive populations than for native populations. Growth of invasive populations was not significantly affected by insecticide spray, but insecticide spray benefited that of native populations. In the bioassay trial, beetles preferentially consumed leaf tissue of invasive populations compared to native populations when beetles had a choice between them. Regression of percent leaf damage on biomass showed that invasive populations tolerated herbivory more effectively than native populations. Our results suggest that S. sebiferum from the introduced range had lower resistance but higher tolerance to specialist herbivores. Both defense strategies could have evolved as a response to the escape from natural enemies in the introduced range.     

Factors influencing bark beetle outbreaks after forest fires on the Iberian Peninsula

Fires are among the most globally important disturbances in forest ecosystems. Forest fires can be followed by bark beetle outbreaks. Therefore, the dynamic interactions between bark beetle outbreaks and fire appear to be of general importance in coniferous forests throughout the world. We tested three hypotheses of how forest fires in pine ecosystems (Pinus pinaster Alton and P. radiata D. Don) in Spain could alter the population dynamics of bark beetles and influence the probability of further disturbance from beetle outbreaks: fire could affect the antiherbivore resin defenses of trees, change their nutritional suitability, or affect top-down controls on herbivore populations. P. radiata defenses decreased immediately after fire, but trees with little crown damage soon recovered with defenses higher than before. Fire either reduced or did not affect nutritional quality of phloem and either reduced or had no effect on the abundance, diversity, and relative biomass of natural enemies. After fire, bark beetle abundance increased via rapid aggregation of reproductive adults on scorched trees. However, our results indicate that for populations to increase to an outbreak situation, colonizing beetles must initiate attacks before tree resin defenses recover, host trees must retain enough undamaged phloem to facilitate larval development, and natural enemies should be sufficiently rare to permit high beetle recruitment into the next generation. Coincidence of these circumstances may promote the possibility of beetle populations escaping to outbreak levels.     

Laboratory and field experiments towards the development of an attract and kill strategy for the control of the codling moth, Cydia pomonella

A viscous formulation based on castor oil containing the pyrethroid insecticide cyfluthrin and E8, E10-dodecadienol, the main component of the codling moth sex pheromone, (Cydia pomonellaL.: Tortricidae, Olethreutinae) was developed. The insecticidal performance of the formulation was evaluated in the laboratory using a tarsal-contact bioassay. The pheromone dosage required to attract male moths to the formulation was determined in behavioural tests performed in a wind tunnel. The efficacy of formulations applied to seedlings of the host plant was further investigated in glasshouse experiments conducted with male moths in small wire-gauze cages. The laboratory tests resulted in a formulation for preliminary field trials containing 4% cyfluthrin and 0.1% pheromone. During the 1995 growing season, experiments were conducted in apple orchards at three locations in Germany. The formulation was first applied to the bark of apple trees (Malus domestica) in mid May and then again in late July. A good level of control, comparable with a spray treatment using the insect growth regulator Alsystin was achieved. The potential of the attract and kill strategy, combining selective attraction of a pest species with the efficacy associated with a pyrethroid insecticide treatment, as a means of controlling the codling moth in commercial apple growing, is discussed.     

Evaluation of Agrilus planipennis (Coleoptera: Buprestidae) control provided by emamectin benzoate and two neonicotinoid insecticides, one and two seasons after treatment

Effective methods are needed to protect ash trees (Fraxinus spp.) from emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive buprestid that has killed millions of North American ash (Fraxinus spp.) trees. We randomly assigned 175 ash trees (11.5-48.1 cm in diameter) in 25 blocks located in three study sites in Michigan to one of seven insecticide treatments in May 2007. Treatments included 1) trunk-injected emamectin benzoate; 2) trunk-injected imidacloprid; 3) basal trunk spray of dinotefuran with or 4) without Pentra-Bark, an agricultural surfactant; 5) basal trunk spray of imidacloprid with or 6) without Pentra-Bark; or (7) control. Foliar insecticide residues (enzyme-linked immunosorbent assay) and toxicity of leaves to adult A. planipennis (4-d bioassays) were quantified at 3-4-wk intervals posttreatment. Seven blocks of trees were felled and sampled in fall 2007 to quantify A. planipennis larval density. Half of the remaining blocks were retreated in spring 2008. Bioassays and residue analyses were repeated in summer 2008, and then all trees were sampled to assess larval density in winter. Foliage from emamectin benzoate-treated trees was highly toxic to adult A. planipennis, and larval density was < 1% of that in comparable control trees, even two seasons posttreatment. Larval densities in trees treated with trunk-injected imidacloprid in 2007 + 2008 were similar to control trees. Dinotefuran and imidacloprid were effectively translocated within trees treated with the noninvasive basal trunk sprays; the surfactant did not appreciably enhance A. planipennis control. In 2008, larval densities were 57-68% lower in trees treated with dinotefuran or imidacloprid trunk sprays in 2007 + 2008 than on controls, but densities in trees treated only in 2007 were similar to controls. Highly effective control provided by emamectin benzoate for > or = 2 yr may reduce costs or logistical issues associated with treatment.     

Reducing insecticide volume and nontarget effects of ambrosia beetle management in nurseries

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are increasingly important pests of nursery-grown trees because of the arrival of several invasive species. Ambrosia beetles bore into young trees and inoculate them with ambrosia fungus, which interferes with vascular transport resulting in limb or tree death. In spring, when beetles are active, growers make frequent applications of pyrethroid insecticides to susceptible tree species to deter beetles from boring into trees. Applications often are made with airblast sprayers that forcefully release insecticide mist that billows through nursery beds. Our objective was to compare the environmental, nontarget, and economic effects of airblast sprayer applications to applications made with a new dual-nozzle spray wand that makes targeted applications only to tree trunks where beetles attack. Through replicated experiments at commercial nurseries, we found that 5 times more insecticide was released by airblast sprayers than the manual spray wand. The extra insecticide from airblast applications landed on tree canopies, between rows, and left the nursery beds as drift. As a consequence of not spraying tree canopies, 50% more natural enemies and 50% fewer spider mites were captured in nursery beds treated with the manual spray wand than beds treated with the airblast sprayer. Manual applications require 12 times more labor than airblast applications. However, increased need for expensive miticide applications may make manual applications an economically feasible strategy for integrated pest management (IPM) of ambrosia beetles in nurseries.     

Predation and bark beetle dynamics

Bark beetle populations may undergo dramatic fluctuations and are often important pests in coniferous forests. Their dynamics are thought to be primarily driven by factors affecting the resistance of the host tree to attack, i.e., bottom-up forces, while natural enemies are usually assigned a minor role in these systems. I present behavioral experiments that suggest that the clerid beetle Thanasimus dubius may be an important source of mortality for the bark beetle Dendroctonus frontalis during attack of the host tree, and determine the nature of the functional response of T. dubius under conditions close to natural. I also examine the numerical response of T. dubius to large-scale fluctuations in D. frontalis density, and the relationship between bark beetle population trends and predator density, and find that beetle populations tend to decline when predator densities are high. Combined with the effects of clerid larvae on bark beetle broods, these results suggest that top-down forces generated by natural enemies could also be an important component of bark beetle dynamics. The implications of these results for bark beetle dynamics are discussed in relation to the prolonged life-cycle of clerid beetles. Received: 23 January 1997 / Accepted: 5 April 1997     

Effects of Multiple Disturbances (Fire and Hurricane) on Epiphyte Community Dynamics in a Subtropical Forest,Florida, U.S.A.1

We addressed the interacting effects of a natural large–scale fire and a subsequent major hurricane on relative positions of epiphytes in a subtropical forest. In Everglades National Park, subtropical hammocks (hardwood tree “islands”; burned and unburned) during the Ingraham Fire (1989) were surveyed for trees and epiphytic bromeliads (Tillandsia spp.) one year before, as well as one and five years after, Hurricane Andrew (1992). We measured trees (species, diameter, and status [alive/dead]) and epiphytes (species, height, host tree characteristics, substrate life status, and density). The fire decreased the height of epiphytes during the hurricane because branches and bark of trees killed by the fire were unstable epiphyte substrates in the high winds. Proportions of epiphytes on Quercus virginiana were equally increased after the hurricane in both unburned and burned hammocks; the large size and bark characteristics resulted in greater proportional survival of epiphytes on this species. During the five years following the hurricane, changes in the distributions of epiphytes generally were toward pre–hurricane distributions, but recovery was faster in unburned than burned hammocks. We conclude that disturbances that kill trees are likely to amplify the vertical reduction of epiphytes during a subsequent hurricane and that effects of a single disturbance on plant populations can be influenced by the disturbance history of the system, including different types of disturbances.     

Effects of fertilizer and low rates of imidacloprid on Adelges tsugae (Hemiptera: Adelgidae)

Healthy hemlock trees, Tsuga canadensis (L.) Carrière, and hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), populations should favor retention and population growth of adelgid predators such as Laricobius nigrinus Fender (Coleoptera: Derodontidae) and Sasajiscymnus tsugae (Sasaji & McClure) (Coleoptera: Coccinellidae). Eastern hemlock trees between 15 and 38 cm diameter at breast height (dbh) were treated with 0, 10, or 25% of 1.5 g imidacloprid (Merit 75 WP) per 2.5 cm dbh and were either fertilized or not, in a 3 by 2 factorial design. After 2 yr, imidacloprid reduced the numbers of ovisacs and eggs found on trees in a dosage-dependent manner, while enhancing tree growth parameters such as new shoots or needles and the length of new shoots. Fertilized trees had greater adelgid fecundity, which was positively correlated with total foliar N in both winter generations. In February 2009 (27 mo after imidacloprid treatment), higher imidacloprid dosages to unfertilized trees resulted in reduced adelgid fecundity. Concentrations of N, P, and K were higher in the foliage of trees treated with insecticide, whereas foliar aluminum concentrations were consistently lower in trees with higher insecticide dosages. Trees treated with low rates of imidacloprid were healthier than untreated trees, but only trees treated with the 0.1 x dosage had sufficient adelgids to possibly sustain predators over extended periods.     

A decision-support tool to predict spray deposition of insecticides in commercial potato fields and its implications for their performance

Approximately US $1.3 billion is spent each year on insecticide applications in major row crops. Despite this significant economic importance, there are currently no widely established decision-support tools available to assess suitability of spray application conditions or of the predicted quality or performance of a given commercial insecticide applications. We conducted a field study, involving 14 commercial spray applications with either fixed wing airplane (N=8) or ground rig (N=6), and we used environmental variables as regression fits to obtained spray deposition (coverage in percentage). We showed that (1) ground rig applications provided higher spray deposition than aerial applications, (2) spray deposition was lowest in the bottom portion of the canopy, (3) increase in plant height reduced spray deposition, (4) wind speed increased spray deposition, and (5) higher ambient temperatures and dew point increased spray deposition. Potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), mortality increased asymptotically to approximately 60% in response to abamectin spray depositions exceeding around 20%, whereas mortality of psyllid adults reached an asymptotic response approximately 40% when lambda-cyhalothrin/thiamethoxam spray deposition exceeded 30%. A spray deposition support tool was developed (http://pilcc.tamu.edu/) that may be used to make decisions regarding (1) when is the best time of day to conduct spray applications and (2) selecting which insecticide to spray based on expected spray deposition. The main conclusion from this analysis is that optimization of insecticide spray deposition should be considered a fundamental pillar of successful integrated pest management programs to increase efficiency of sprays (and therefore reduce production costs) and to reduce risk of resistance development in target pest populations.     

Interactions of light intensity, insecticide concentration, and time on the efficacy of systemic insecticides in suppressing populations of the sweetpotato whitefly (Hemiptera: Aleyrodidae) and the citrus mealybug (Hemiptera: Pseudococcidae)

The impact of light intensity on the uptake and persistence of the systemic neonicotinoid insecticides, imidacloprid and dinotefuran, were evaluated in poinsettia (Euphorbia pulcherrima Willd.) and yellow sage (Lantana camara L.). Insecticide residues were measured in leaves sampled from the treated plants at four time intervals after treatment to determine the relationship between insecticide concentration and efficacy against two insect pests: sweetpotato whitefly, Bemisia tabaci Gennadius, and the citrus mealybug, Planococcus citri Risso. The insecticides were evaluated at their respective label rate and at the comparable label rate of the other insecticide under two different light environments: ambient and shade. The uptake of dinotefuran into yellow sage was more rapid at both treatment rates than both rates of imidacloprid, resulting in higher percent mortality of whitefly nymphs (89.8-100) compared with imidacloprid (14.1-89.2) across all 4 wk. Additionally, plants that received both rates of dinotefuran had fewer whitefly pupae (< 1.0) at week 4 compared with imidacloprid-treated plants (23.7-25.3). The uptake of dinotefuran into poinsettia plants was also more rapid and resulted in quicker and higher percent mortality of whitefly nymphs (89.5-99.6) compared with imidacloprid (14.1-89.2) across all 4 wk. However, despite efficient uptake, the efficacy of both systemic insecticides was less for citrus mealybug where percent mortality values were <50% among all the treatments across the 4 wk. The use of the two systemic insecticides evaluated in regards to pest management in horticultural cropping systems is discussed.     

Mesostigmatid Mites (Acari: Mesostigmata) on Rainforest Tree Trunks: Arboreal Specialists, but Substrate Generalists?

Predatory mites (Acari: Mesostigmata) on tree trunks without significant epiphytic growth in a subtropical rainforest in Eastern Australia were assessed for habitat specificity (i.e. whether they are tree trunk specialists or occupying other habitats) and the influence of host tree and bark structure on their abundance, species richness and species composition. The trunks of nine tree species from eight plant families representing smooth, intermediate and rough bark textures were sampled using a knockdown insecticide spray. In total, 12 species or morphospecies of Mesostigmata (excluding Uropodina sensu stricto) were collected, most of which are undescribed. Comparison with collections from other habitats indicates that epicorticolous Mesostigmata are mainly represented by suspended soil dwellers (six species), secondarily by generalists (four species) and a bark specialist (one species). A typical ground-dwelling species was also found but was represented only by a single individual. In terms of abundance, 50.5% of individuals were suspended soil dwellers, 40.7% bark specialists, and 8.3% generalists. Host species and bark roughness had no significant effect on abundance or species richness. Furthermore, there was no clear effect on species composition. The distribution of the most frequently encountered species suggests that most mesostigmatid mites living on bark use many or most rainforest tree species, independent of bark roughness. These findings support the hypothesis that some epicorticolous Mesostigmata use tree trunks as ‘highways’ for dispersing between habitat patches, while others use it as a permanent habitat.     

Resprouting of Quercus suber in NE Spain after fire

Abstract. Many Mediterranean species have evolved strategies that allow them to survive periodic wildfires. Quercus suber trees resprout after fire, some from stem buds and others from basal buds only. In the former case the canopy recovers quickly. In the latter case the stem dies but the tree survives and regrows from basal sprouts. The probability of stem death and the degree of height recovery were studied after a fire in a Q. suber forest in NE Spain using logistic regression analysis. The results suggest that most trees survive after fire; the probability of stem death is negatively related to tree diameter; and recovery is positively related to tree diameter and to bark thickness. Implication for management and conservation of cork-oak forests are discussed.     

Prospects for improved off-crop habitat management for pollen beetle control in oilseed rape

There is an urgent need to develop sustainable and environmentally benign integrated pest management (IPM) strategies for arable crops. The enhancement and manipulation of naturally occurring populations of the natural enemies of crop pests through habitat management for ‘conservation biological control’, as well as habitat management to manipulate populations of the pests themselves, have the potential to become major components of successful IPM strategies. We review the studies that have contributed to our current understanding of how the crop margin, local landscape, and regional landscape can influence pollen beetle Brassicogethes aeneus (syn. Meligethes aeneus) (Coleoptera: Nitidulidae) abundance and damage to oilseed rape crops (Brassica napus), and the efficacy of their natural enemies. We also discuss how habitat management across these multiple scales may improve pollen beetle control, reducing the need for insecticide use and contributing towards sustainable production of this important crop which is grown on increasing areas for both food and fuel.     

天敌昆虫抗药性研究进展

天敌昆虫抗药性研究在协调害虫化学防治和生物防治中有着重要的理论和现实意义,其研究的最终目的在于更好地推进抗性天敌在害虫综合治理(IPM)中的应用。抗药性天敌昆虫具有潜在的巨大价值。鉴于此,本文系统地综述了天敌昆虫抗药性最新研究进展,包括杀虫剂对天敌昆虫的影响、天敌昆虫抗药性现状、抗药性机理和限制天敌昆虫抗药性发展因素等。文章最后还对抗药性天敌昆虫的应用前景进行了展望。     

Ant-exclusion to promote biological control of soft scales (Hemiptera: Coccidae) on woody landscape plants

Ant-exclusion to facilitate biocontrol by endemic natural enemies was investigated for suppressing infestations of two coccids, calico scale, Eulecanium cerasorum (Cockerell), and magnolia scale, Neolecanium cornuparvum (Thro), in landscape settings. Application of sticky bands combined with basal trunk sprays resulted in 92-100% reduction in counts of honeydew-seeking ants, mainly Formica subsericea Say, ascending large, scale-infested sugar maple (Acer saccharum Marshall) trees. Ant-exclusion was associated with increased numbers of green lacewing, mainly Chrysoperla rufilabris (Burmeister), larvae and spiders on multiple sample dates, and 54 and 69% fewer surviving scale nymphs after the first and second growing seasons. Foliar sooty mold accumulation was also significantly reduced where ants were excluded. In feeding trials, C. rufilabris larvae collected from the tree canopies consumed large numbers of settled scale nymphs. On another site, ant-exclusion led to 82% reduction in magnolia scale densities on Magnolia stellata (Siebold & Zuccarini) Maximowicz, compared with controls, after 1 yr. Nine and 10 ant species were found tending calico and magnolia scales, respectively, at landscape sites in central Kentucky, and in situ observation trials showed that many of them aggressively attack approaching lacewing larvae. Our results suggest that where ants are closely associated with soft scales on woody landscape plants, ant-exclusion has potential as a sustainable pest management strategy.     

Phylogenetic congruence of armored scale insects (Hemiptera: Diaspididae) and their primary endosymbionts from the phylum Bacteroidetes

Insects in the sap-sucking hemipteran suborder Sternorrhyncha typically harbor maternally transmitted bacteria housed in a specialized organ, the bacteriome. In three of the four superfamilies of Sternorrhyncha (Aphidoidea, Aleyrodoidea, Psylloidea), the bacteriome-associated (primary) bacterial lineage is from the class Gammaproteobacteria (phylum Proteobacteria). The fourth superfamily, Coccoidea (scale insects), has a diverse array of bacterial endosymbionts whose affinities are largely unexplored. We have amplified fragments of two bacterial ribosomal genes from each of 68 species of armored scale insects (Diaspididae). In spite of initially using primers designed for Gammaproteobacteria, we consistently amplified sequences from a different bacterial phylum: Bacteroidetes. We use these sequences (16S and 23S, 2105 total base pairs), along with previously published sequences from the armored scale hosts (elongation factor 1alpha and 28S rDNA) to investigate phylogenetic congruence between the two clades. The Bayesian tree for the bacteria is roughly congruent with that of the hosts, with 67% of nodes identical. Partition homogeneity tests found no significant difference between the host and bacterial data sets. Of thirteen Shimodaira-Hasegawa tests, comparing the original Bayesian bacterial tree to bacterial trees with incongruent clades forced to match the host tree, 12 found no significant difference. A significant difference in topology was found only when the entire host tree was compared with the entire bacterial tree. For the bacterial data set, the treelengths of the most parsimonious host trees are only 1.8-2.4% longer than that of the most parsimonious bacterial trees. The high level of congruence between the topologies indicates that these Bacteroidetes are the primary endosymbionts of armored scale insects. To investigate the phylogenetic affinities of these endosymbionts, we aligned some of their 16S rDNA sequences with other known Bacteroidetes endosymbionts and with other similar sequences identified by BLAST searches. Although the endosymbionts of armored scales are only distantly related to the endosymbionts of the other sternorrhynchan insects, they are closely related to bacteria associated with eriococcid and margarodid scale insects, to cockroach and auchenorrynchan endosymbionts (Blattabacterium and Sulcia), and to male-killing endosymbionts of ladybird beetles. We propose the name "Candidatus Uzinura diaspidicola" for the primary endosymbionts of armored scale insects.     

Phenology, natural enemies, and efficacy of horticultural oil for control of Chionaspis heterophyllae (Homoptera: Diaspididae) on Christmas tree plantations

Pine needle scale, Chionaspis pinifoliae (Fitch), and Chionaspis heterophyllae Cooley are important pests of Scots pine, Pinus sylvestris L., and other conifers in much of North America. On Christmas tree plantations, these insects are typically controlled by spraying broad-spectrum insecticides when the vulnerable immature stages are present. However, effective control of bivoltine populations can be difficult to achieve due to asynchronous hatch and development of the second generation. Our objectives were to 1) determine the phenology of the second generation of C. heterophyllae in Michigan; 2) characterize the natural enemy complex; and 3) assess the effectiveness of horticultural oil for control of C. heterophyllae on P. sylvestris Christmas tree plantations. We monitored scale populations in three counties in lower Michigan for 3 yr. Scale phenology was consistently associated with cumulative degree-days base 10 degrees C (DD(10 degrees C)). Second-generation egg hatch began at approximately 1230-1300 DD(10 degrees C), and continued for approximately 3 wk. The peak of the second instar coincided with 1500-1600 DD(10 degrees C). Common predators included the coccinellids Chilocorus stigma (Say) and Microweisia misella (LeConte). On average, 70% of the C. heterophyllae population in unsprayed fields was killed by predators in 1999. Two endoparasitic wasps, Encarsia bella Gahan and Marietta mexicana Howard (Hymenoptera: Aphelinidae), also were recovered. In 2000 and 2001, we applied a highly refined horticultural spray oil with a backpack mist blower at 1500-1600 DD(10 degrees). Scale mortality on trees treated with oil ranged from 66 to 80% and was similar to control achieved using conventional insecticides in both years.     

Impact of a nucleopolyhedrovirus bioinsecticide and selected synthetic insecticides on the abundance of insect natural enemies on maize in southern Mexico

The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), and pyrethroid (cypermethrin) insecticides on insect natural enemies was compared with that of a nucleopolyhedrovirus (Baculoviridae) of Spodoptera frugiperda (J. E. Smith) (Lepidoptera Noctuidae) in maize grown in southern Mexico. Analyses of the SELECTV and Koppert Side Effects (IOBC) databases on the impact of synthetic insecticides on arthropod natural enemies were used to predict approximately 75-90% natural enemy mortality after application, whereas the bioinsecticide was predicted to have no effect. Three field trails were performed in mid- and late-whorl stage maize planted during the growing season in Chiapas State, Mexico. Synthetic insecticides were applied at product label recommended rates using a manual knapsack sprayer fitted with a cone nozzle. The biological pesticide was applied at a rate of 3 x 10(12) occlusion bodies (OBs)/ha using identical equipment. Pesticide impacts on arthropods on maize plants were quantified at intervals between 1 and 22 d postapplication. The biological insecticide based on S. frugiperda nucleopolyhedrovirus had no adverse effect on insect natural enemies or other nontarget insect populations. Applications of the carbamate, pyrethroid, and organophosphate insecticides all resulted in reduced abundance of insect natural enemies, but for a relatively short period (8-15 d). Pesticide applications made to late-whorl stage maize resulted in lesser reductions in natural enemy populations than applications made at the mid-whorl stage, probably because of a greater abundance of physical refuges and reduced spray penetration of late-whorl maize.