Pheromone Trap Data Research Articles

Phenology of the spruce bark beetle Ips typographus in the UK under past, current and future climate conditions

Summary The European spruce bark‐beetle, Ips typographus, is a major pest of Norway spruce across mainland Europe; however, until 2018, it was considered absent from the United Kingdom (UK). The finding of a breeding population of I. typographus in Kent, England, in 2018 and subsequent findings in pheromone traps across the southeast of England, has led to an urgent need to improve understanding of environmental suitability across the UK. Two distinct published phenological models for I. typographus, developed in Sweden and Austria, were adapted for use in the UK and validated against pheromone trap data collected at the original site of infestation and in the surrounding area from 2019 to 2022. Both models captured some, but not all, of the within‐season variation in trap catches. One, the PHENIPS model, more accurately captured early season flight patterns. The climate in the southeast of England is mild enough to facilitate two generations of the beetle, while further north the pest is expected to be univoltine. At high altitude in Scotland, there is insufficient thermal warming within a season for the completion of one annual generation. Phenological modelling does not explain why the pest failed to establish in England prior to 2018 including when a large amount of infested material was imported to sawmills in the 1940s. Under 2 and 3°C global warming scenarios, we might expect to see an increase in potential voltinism across the UK in the next few decades, increasing the risk of large outbreaks of I. typographus were it allowed to establish. Societal impact statementIn 2018, a breeding population of the European spruce bark‐beetle, Ips typographus, was discovered in woodland in southeast England. Ips typographus is a major forest pest in continental Europe; however, despite previous findings at ports and sawmills, this was the first recorded infestation in the UK. The number of generations per year (voltinism) varies with latitude and altitude. Applying a phenological model, we find that the current climate in southern UK could support two generations, while temperature accumulation in parts of Scotland may be insufficient to support one generation. Global warming will increase voltinism and hence the risk of establishment.

Phenological Features of the Spongy Moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), in the Northernmost Portions of Its Eurasian Range.

The spongy moth, Lymatria dispar, is a classic example of an invasive pest accidentally introduced from Europe to North America, where it has become one of the most serious forest defoliators, as in its native range. The present study was aimed at (i) identifying the current northern limit of L. dispar's Eurasian range and exploring its northward expansion in Canada using pheromone trap data, and (ii) comparing northern Eurasian populations with those from central and southern regions with respect to male flight phenology, the sums of effective temperatures (SETs) above the 7 °C threshold necessary for development to the adult stage, and heat availability. We show that the range of L. dispar in Eurasia now reaches the 61st parallel, and comparisons with historical data identify the average speed of spread as 50 km/year. We also document the northern progression of L. dispar in southern Canada, where the actual northern boundary of its range remains to be identified. We show that the median date of male flight does not vary greatly between northern and southern regions of the spongy moth range in Eurasia despite climate differences. Synchronization of flight at different latitudes of the range is associated with an acceleration of larval development in northern Eurasian populations. Similar changes in developmental rate along a latitudinal gradient have not been documented for North American populations. Thus, we argue that this feature of spongy moths from northern Eurasia poses a significant invasive threat to North America in terms of enhanced risks for rapid northward range expansion.

Common pheromone use among host-associated populations of the browntail moth, Euproctis chrysorrhoea, displaying different adult phenologies

The diversity of herbivorous insects may arise from colonization and subsequent specialization on different host plants. Such specialization requires changes in several insect traits, which may lead to host race formation if they reduce gene flow among populations that feed on different plants. Behavioural changes may play a relevant role in host race formation, for example if different races evolve distinct sexual communication signals or adult phenology. Previous research has revealed differences in larval phenology in different host-associated populations of the browntail moth, Euproctis chrysorrhoea (Lepidoptera: Erebidae). Here, sex pheromones among populations of this species are compared, and pheromone trapping data obtained is used in the field to build a phenological model that tests whether populations that feed on different plants differ in their adult flight period. The chemical and electrophysiological analyses revealed that two E. chrysorrhoea populations (on Prunus and on Arbutus unedo) use the same sex pheromone component for mate finding. Our trapping data, however, showed that males fly on average 25 days earlier in populations whose larvae feed on A. unedo compared to those whose larvae feed on Quercus species. Although the shifted phenology described here may underlie host-plant specialization in E. chrysorrhoea, and adults of this species are short-lived, the use of a common sexual pheromone and a large overlap in flight periods suggest that host race formation via allochronic isolation is unlikely in this moth. (Less)

Examining population structure of a bertha armyworm, Mamestra configurata (Lepidoptera: Noctuidae), outbreak in western North America: Implications for gene flow and dispersal.

The bertha armyworm (BAW), Mamestra configurata, is a significant pest of canola (Brassica napus L. and B. rapa L.) in western North America that undergoes cyclical outbreaks every 6–8 years. During peak outbreaks millions of dollars are spent on insecticidal control and, even with control efforts, subsequent damage can result in losses worth millions of dollars. Despite the importance of this pest insect, information is lacking on the dispersal ability of BAW and the genetic variation of populations from across its geographic range which may underlie potential differences in their susceptibility to insecticides or pathogens. Here, we examined the genetic diversity of BAW populations during an outbreak across its geographic range in western North America. First, mitochondrial cytochrome oxidase 1 (CO1) barcode sequences were used to confirm species identification of insects captured in a network of pheromone traps across the range, followed by haplotype analyses. We then sequenced the BAW genome and used double-digest restriction site associated DNA sequencing, mapped to the genome, to identify 1000s of single nucleotide polymorphisms (SNP) markers. CO1 haplotype analysis identified 9 haplotypes distributed across 28 sample locations and three laboratory-reared colonies. Analysis of genotypic data from both the CO1 and SNP markers revealed little population structure across BAW’s vast range. The CO1 haplotype pattern showed a star-like phylogeny which is often associated with species whose population abundance and range has recently expanded and combined with pheromone trap data, indicates the outbreak may have originated from a single focal point in central Saskatchewan. The relatively recent introduction of canola and rapid expansion of the canola growing region across western North America, combined with the cyclical outbreaks of BAW caused by precipitous population crashes, has likely selected for a genetically homogenous BAW population adapted to this crop.

Biology and Management of the Pecan Nut Casebearer (Lepidoptera: Pyralidae)

Abstract The pecan nut casebearer, Acrobasis nuxvorella Neunzig, is a key pest of pecan nut production throughout the pecan producing regions of the central and southwestern United States and northern Mexico. Economic loss is primarily due to first-generation larvae that feed internally in developing nutlets soon after pollination in the spring. Damage by second-generation and third-generation larvae can also result in economic loss. We summarize pecan nut casebearer distribution, life history, crop injury, and current management practices including orchard scouting, monitoring adult activity with pheromone traps, and chemical, biological and regulatory controls. Insecticides are the sole means of controlling pecan nut casebearer but must be properly timed to kill young larvae before they tunnel into pecan nuts. Effective management requires orchard scouting to assess egg abundance and nut entry by larvae to determine the need for and optimum timing of insecticide treatment. An on-line, degree-day model, PNCforecast, uses pheromone trap data to predict oviposition activity and optimum dates for sampling orchards to assess pecan nut casebearer egg infestations. This IPM program is enhanced by the availability of diacylhydrazine insecticides that are toxic to Lepidoptera larva but preserve beneficial insects that suppress secondary pests of pecans.

Phenology and pest status of Agrotis segetum in a changing climate

Insects are strongly dependent on climatic factors, especially temperature. For this reason, changes in insect phenology are predicted to be one of the many effects of climate change. We analysed the effect of climate warming on Agrotis segetum (Denis & Schiffermüller) in Denmark. Agrotis segetum is an agricultural pest that causes root crop damage. Extensive registers of root crop damages by A. segetum in Denmark were kept between 1905 and 1980. These records show a correlation between A. segetum outbreaks and hot, dry summers. The last outbreak in Denmark, in 1976, prompted the implementation of pheromone trap monitoring. Data from these pheromone traps, for the periods between 1981–1991 and 1997–2009, show a decline in the number of A. segetum individuals during 2000–2009. We used this pheromone trapping data to test the hypothesis that temporal changes in phenology and abundance are correlated with temperature and precipitation patterns. As phenological fixed points, we use the time of capture (first, 10%, 50%, 90% and last) of 1st generation A. segetum together with the 10%–90% capture period and the total capture per location for a statistical comparison of the period 1981–1990 versus 2000–2009. We also analysed the effect of temperature on the timing of fixed points and the effect of precipitation on the mean total capture from the summer and the preceding winter. Our analyses showed an earlier occurrence of A. segetum during 2000–2009 than during 1981–1990: all phenological fixed points advanced by 6–9 days. Trap captures of the 1st generation roughly halved from the 1981–1990 decade to the 2000–2009 decade, and a much larger 2nd generation of moths developed in the latest decade. When a second generation occurs, populations in following years decrease because the larval offspring of the 2nd generation cannot successfully overwinter. Our analyses further indicated that increased precipitation during the summers and mild winters contributed to an overall decline in the populations of this pest. The presence of A. segetum remains sufficient to be a potential threat to yields. Forecasting an economically important attack of A. segetum is challenging because of the early emergence of A. segetum and more variable local weather conditions than 20 years ago; forecasting relies on the timely and correct delivery of monitoring results. Farmers are a vital source of information for monitoring, for estimating control requests and for timing the emergence of A. segtum. However, the growing frequency of no-risk forecasts has reduced the interest and lowered the motivation of farmers to participate in monitoring programs.

Pheromone production, male abundance, body size, and the evolution of elaborate antennae in moths.

The males of some species of moths possess elaborate feathery antennae. It is widely assumed that these striking morphological features have evolved through selection for males with greater sensitivity to the female sex pheromone, which is typically released in minute quantities. Accordingly, females of species in which males have elaborate (i.e., pectinate, bipectinate, or quadripectinate) antennae should produce the smallest quantities of pheromone. Alternatively, antennal morphology may be associated with the chemical properties of the pheromone components, with elaborate antennae being associated with pheromones that diffuse more quickly (i.e., have lower molecular weights). Finally, antennal morphology may reflect population structure, with low population abundance selecting for higher sensitivity and hence more elaborate antennae. We conducted a phylogenetic comparative analysis to test these explanations using pheromone chemical data and trapping data for 152 moth species. Elaborate antennae are associated with larger body size (longer forewing length), which suggests a biological cost that smaller moth species cannot bear. Body size is also positively correlated with pheromone titre and negatively correlated with population abundance (estimated by male abundance). Removing the effects of body size revealed no association between the shape of antennae and either pheromone titre, male abundance, or mean molecular weight of the pheromone components. However, among species with elaborate antennae, longer antennae were typically associated with lower male abundances and pheromone compounds with lower molecular weight, suggesting that male distribution and a more rapidly diffusing female sex pheromone may influence the size but not the general shape of male antennae.

Structural fumigation efficacy against Tribolium castaneum in flour mills

Structural fumigations of food processing plants to manage stored-product insects have been a major component of pest management programs, but limited information on field efficacy is available. Efficacy, based on pheromone trapping data, consists of initial reduction in captures after treatment and recovery in trap captures over time after treatment (i.e., rebound). Patterns of Tribolium castaneum reduction and rebound were evaluated after 21 fumigations in two flour mills. Influence of time of year fumigation occurred, environmental conditions, and impact of other pest management tactics on efficacy was determined as well. Information generated can be used to guide fumigation decisions, including the development of risk thresholds for levels of pheromone trap captures. Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Normale Tabelle; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Times New Roman; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Keywords: Tribolium castaneum , Fumigation, Flour mills, Efficacy, Methyl bromide

Long-Term Monitoring of <I>Tribolium castaneum</I> Populations in Two Flour Mills: Rebound After Fumigation

Structural fumigations of food processing plants to manage stored-product insects has been a major component of pest management programs, but limited information on field efficacy is available. Efficacy, based on pheromone trapping data, consists of initial reduction in captures after treatment and rebound in trap captures over time. Pattern of Tribolium castaneum (Herbst) rebound was evaluated after 21 fumigations in two flour mills. Rebound in mean number of beetles captured and the probability of a trap capturing one or more beetles was evaluated. Rebound to a threshold mean beetle capture of 2.5 beetles per trap per 2-wk period took 174 +/- 33 d and rebound took longer after fall (248 +/- 50 d) than spring (104 +/- 21 d) fumigations. Rebound to the probability of capture threshold of 0.50 was 120 +/- 21 d, but there was no significant effect of season. Improvement in integrated pest management (IPM) practices in one of the mills was associated with an increase in time to reach mean beetle capture threshold (49 +/- 15 d before and 246 +/- 71 d after) but not in time to reach the probability of capture threshold (38 +/- 14 d before and 165 +/- 46 d after). There was a negative correlation between number captured after fumigation and time to rebound to threshold. After improved IPM there was a significant reduction in the number of beetles per trap immediately after fumigation. Above these two thresholds the degree of change in trap captures is significantly greater than below, which suggests they might be useful in evaluating risk in a pest management program.

Seasonal Abundance, Life History, and Parasitism of <I>Caloptilia porphyretica</I> (Lepidoptera: Gracillariidae), a Leafminer of Highbush Blueberry

The leafminer Caloptilia porphyretica Braun (Lepidoptera: Gracillariidae), has become a frequent pest in commercial highbush blueberries, Vaccinium corymbosum L., in New Jersey, but little is known about its seasonal abundance, life history, and parasitism rates. Monitoring programs were conducted from 2003 to 2006 on seven blueberry farms to determine the relative abundance of this leafminer by using pheromone-baited traps and by sampling vegetative and flower/fruit clusters and new shoot growth. We found at least three distinct generations per year, with populations reaching their highest peak in the second generation. Laboratory studies characterized the life history of C. porphyretica and its parasitoid Pholetesor sp. prob. salalicus (Mason). The developmental period of C. porphyretica, from egg to adult, took 927, 838, and 912 degree-days (DD) at 20, 25, and 30 degrees C, respectively, by using a developmental threshold of 4.8 degrees C. This was equivalent to an average of 892 DD to complete development to adult, which compared with 870 and 880 DD between the first and second, and second and third generations, respectively, by using pheromone trap data averaged from 2004 to 2006. Although C. porphyretica populations varied greatly, the number of larvae in cluster and new shoot samples was highly correlated with the number of adults in traps. Field parasitism rate was -29%, with the braconid Pholetesor sp. the most abundant parasitoid. Ten of the 13 parasitoid species collected belonged to the family Eulophidae. When different ages of leafminers were exposed to Pholetesor sp., we found that the parasitoid attacks 9-15-d-old instars that reside in the mines of leaves.

Bioclimatic Model of the Spined Soldier Bug (Heteroptera: Pentatomidae) Using CLIMEX: Testing Model Predictions at Two Spatial Scales

A bioclimatic model of the polyphagous predator, Podisus maculiventris (Say) (Heteroptera: Pentatomidae), was developed using CLIMEX software (Hearne Scientific Software, Melbourne, Australia). Calibration distribution was fitted using known distribution records for the United States and Canada, after which the model was used to generate a potential distribution map for the entire world. As expected, potential distribution maps agreed with known distribution records for North America. However, apparent mismatches were found for distributions in Europe, South America, midAfrica, and Southeast Asia. Using historical weather data, CLIMEX “growth indices” (measures of climate suitability for insect development) were compared against multiyear pheromone trap counts in the northern (Indiana) and southern (Florida) United States. Growth index curves did not appear to match pheromone trap data in either location when examined separately by year, location and insect sex. However, a weak relationship was found between trap counts and growth index when data were pooled across years, locations and sex.

(321) Development of a GIS-based Model for Predicting Sweetpotato Weevil Infestation Risk in Louisiana: Progress, Problems, and Prospects

The sweetpotato weevil [SPW, Cylas formicarius (Fabricius)] is an important economic pest in “pink-tagged” or SPW-infested areas of Louisiana. From time to time, sweetpotato weevils are detected in “green-tagged” or SPW-free locations. When sweetpotato weevils are detected in “green'tagged” areas, the produce is quarantined and may not be shipped to locations that do not allow “pink-tagged” sweetpotatoes. As part of the statewide SPW monitoring program, the Louisiana Department of Agriculture and Forestry (LDAF) conducts a statewide pheromone-based trapping program to monitor SPW presence in beds and fields. We used SPW presence-absence data with a GIS-based logistic regression modeling tool to assess the feasibility of developing a model for predicting SPW risk in sweetpotato beds. Using pheromone trap data from 2001–03, we performed stepwise logistic regression experiments to assess the role of various weather variables (daily mean maximum and minimum temperature, rainfall) in the occurrence of SPW in beds. Our modeling experiments showed a strong relationship of mean daily minimum temperature during the winter months with SPW occurrence in beds. In particular, a logistic regression equation developed from 2003 trap data and mean April daily minimum temperature created a spatially accurate map of SPW risk for 2002. However, the same model did not accurately predict the 2001 SPW risk. These results indicate that additional variables are needed to improve the predictive ability of the model. Spatial risk mapping can be a potentially useful tool for decision makers in choosing between risk-averse and -prone decisions.

Synchrony and geographical variation of the spruce bark beetle (Ips typographus) during a non‐epidemic period

AbstractSpatio‐temporal analyses of non‐epidemic bark beetle populations may provide insight in dynamics predisposing for outbreaks. The present article presents a spatio‐temporal analysis of the population dynamics of Ips typographus based on pheromone trap data from southeast and mid‐Norway in the post‐epidemic period 1979–2002. The analyses include regression analyses, hierarchical cluster analysis, and analysis of spatial synchrony of beetle time series and climatic data by means of nonparametric spatial covariance functions. The mean abundance of beetles declined linearly with latitude. In addition, the time series means were higher in areas with high forest productivity and rocky soils predisposed to drought. The time series patterns differed significantly between northern and southern study areas. The regional synchrony of the time series was fairly high (0.38), indicating that some large‐scale climatic factor may influence the dynamics. Windfelling was the external variable showing the most parallel pattern of correlation to the beetle dynamics. We thus posit that large windfall events may be a major instigator and synchronizer of beetle outbreaks in areas subjected to regionalized weather systems.

Predicting spring moth emergence in the pink bollworm (Lepidoptera: Gelechiidae): implications for managing resistance to transgenic cotton.

Cultural control methods have been central in the southwestern United States for reducing pink bollworm, Pectinophora gossypiella (Saunders), damage to cotton. Nevertheless, it is not clear at present how such methods could be integrated within the novel pest management framework allowed by introduction of cotton producing a toxin from Bacillus thuringiensis (Bt) for pink bollworm control. Using statewide pheromone trapping and climatic data in conjunction with deterministic simulation models, we investigated whether manipulation of cotton planting date and use of other cultural control methods could represent valuable tactics for control of the pink bollworm in Arizona. Accumulation of heat units from one January accurately predicted the rate of pink bollworm emergence from diapause in 15 cotton-producing regions. Significant variation in rate of emergence from diapause was present among regions, with earlier emergence at higher altitudes. Most adults emerge from diapause too early to reproduce successfully on cotton, a phenomenon known as suicidal emergence. A method for prediction of the fraction of suicidal emergence resulting from adoption of a given cotton planting date is presented. Results from simulation models suggest that manipulation of planting date and implementation of other control cultural methods reduce the rate of application of insecticides and delay the evolution of resistance to Bt cotton in the pink bollworm.

Analysis of Gypsy Moth (Lepidoptera: Lymantriidae) Population Dynamics in Michigan Using Geographic Information Systems

We studied the 9-yr (1986-1994) statewide gypsy moth, Lymantria dispar (L.), population distribution dynamics in Michigan using geographic information systems (GIS) based on an analysis of pheromone trap data of male moth catch from more than 3,000 permanent sites. A time series of male moth contour maps with 7 density categories (0, 1-25, 26-100, 101-200, 201-300, 301-400 and >400 moths.trap -1 year -1 ) was created using the GIS. The statewide gypsy moth population expanded at an alarming rate of 6,053 km 2 /yr with the largest area infested being 128,164 km 2 (85% of the state) in 1993. The population-weighted mean center stayed in the Lower Peninsula, but a low density population was developing in the Upper Peninsula during the 9-yr period. Map analysis showed that the statewide population gradually increased from 1986 to 1990 and then became relatively stable thereafter. Both the highest weighted average density (191 moths.trap - ryear -1 ) and the greatest coefficient of relative dispersion (307%) occurred in 1990. Linear regression slopes between successive years were >1.0 before 1990 and 70%). In the 9-yr study, 55% of the population cells stayed in the same density class in the following year. A general pattern of population density shifts was that increase prevailed over decrease. Research methodology, population distribution, temporal dynamics, and density shifts are discussed.

Establishment, Spread, and Impact of Teretriosoma nigrescens (Coleoptera: Histeridae), an Exotic Predator of the Larger Grain Borer (Coleoptera: Bostrichidae) in Southwestern Benin

Studies were carried out between 1992 and 1997 in southwestern Benin to investigate the establishment, spread, and impact of Teretriosoma nigrescens Lewis, a natural enemy of the larger grain borer, Prostephanus truncatus (Horn). Trap data, using the 2-component synthetic aggregation pheromone of P. truncatus , from 5 different surveys, carried out twice yearly over a 3-yr period, showed a rapid establishment and spread of the predator throughout the region. Increasing numbers of T. nigrescens in the pheromone traps were associated with decreasing numbers of P. truncatus . Pheromone trap data, collected weekly at a small number of sites over the entire study period, revealed a yearly bimodal peak in flight activity of P. truncatus in 1992, 1993, and 1994. The 1st peak in flight activity of P. truncatus was sharply reduced in 1995, 1996, and 1997, accompanied by increasing numbers of T. nigrescens in the pheromone traps. Data from on-farm storage experiments and from surveys in farm-stored maize, Zea mays L., showed a considerable reduction of P. truncatus infestation, and decreasing losses of maize, coinciding with the increasing presence of T. nigrescens .

Leafroller phenology and parasitism in Hawkes Bay, New Zealand, canefruit gardens

Abstract Pheromone traps together with leaf and fruit samples were used to measure the seasonal occurrence and relative pest status of three species of leafrollers (Lepidoptera: Tortricidae) in two berryfruit gardens in Hawkes Bay, New Zealand. The pheromone trap data detected slight differences in the seasonal phenology of male flights between the two properties, but reflected the relative pest status of larvae infesting leaves and fruit at only one property. Numbers of larvae of the different species found in leaves, on the other hand, were good predictors of pest status at harvest. Three species of larval parasitoids (all Hymenoptera) were reared, and their seasonal occurrence noted, but the data were inadequate to allow life‐table compilation or measurement of population regulation of their hosts.

Distribution of Quadraspidiotus perniciosus (San José scale) in Switzerland based on interpolated pheromone trap data

A geographic information system was used to create a surface representation of 1990 pheromone‐trap catch data of Quadraspidiotus perniciosus (San José scale) in Switzerland. The interpolation took the mountainous topography into consideration. The comparison of Q. perniciosus‐infested regions and regions of tree‐fruit production indicates that major tree‐fruit production regions of Switzerland at risk are still free from Q. perniciosus.

Areawide Management of Cotton Bollworm and Tobacco Budworm (Lepidoptera: Noctuidae) through Application of a Nuclear Polyhedrosis Virus on Early-Season Alternate Hosts

A field trial was done in 1990 using aircraft to treat all vegetation in a 259-km2 area with the nuclear polyhedrosis virus from the cotton bollworm, Helicoverpa zea (Boddie), to control the first generation of bollworm and tobacco budworm, Heliothis virescens (F.). Bioassays of early-season hosts from the treated area indicated that ≍12% as much virus and 8% as many spray droplets were deposited on the plants compared with results of a previous small-area study. Although the area-wide viral coverage on target plants was inadequate, results of pheromone trap data indicated that populations of emerging adults were reduced 19-38% compared with adults from untreated areas. The virus remained active on the host plants (i.e., 47% of the original virus activity remained 9 dafter treatment). In cage testing areas where bioassays indicated that somewhat more virus was deposited, we detected a 41% average reduction in adult emergence in cages placed over treated wild hosts compared with untreated areas.

Factors Associated with Flight Patterns of the Peach Twig Borer (Lepidoptera: Gelichiidae) Observed Using Pheromone Traps

Sixty-three season-long pheromone trapping data sets of peach twig borer, Anarsia lineatella Zeller, were collected in California almond and stonefruit orchards during 1975-1985. The data sets were analyzed with corresponding weather data to determine potential causal factors associated with the occurrence of a commonly observed bimodal flight pattern. The factor best fitting the twin-peaks phenomenon was temperatures below a threshold of 14-16 degrees C during the nightly flight period (2400-0400 hours PDT). Results indicate the generation time of 600 degree-days (DD) currently recommended is correct and does not vary by flight pattern (e.g., unimodal or bimodal), generation, or location. This conclusion was confirmed with observations of spring larval emergence.