Performance of a Low-Cost Acoustic Insect Detector System with Sitophilus oryzae (Coleoptera: Curculionidae) in Stored Grain and Tribolium castaneum (Coleoptera: Tenebrionidae) in Flour.

Reduction of postharvest losses is gaining increased priority in warm regions where insect infestation may cause rapid deterioration of staple commodities. Acoustic detection can be used to assess the likelihood of insect infestations in bags of grain, flour, and other commodities that are stored in small holdings in developing countries, enabling rapid targeting of treatments. A portable postharvest insect detection system was developed with the goal to provide low-cost capability to acoustically assess infestations in small-scale storage facilities. Electret microphones input pest insect sounds to a 32-bit microcontroller platform that digitized and stored the signals on a digital memory card transferable to a portable laptop computer. The insect sounds then were analyzed by custom-written software that matched their spectra to those of known pests. Infestations of Sitophilus oryzae (L) in 2.6-kg bags could be detected down to densities of 1.9 adults/kg in grain and Tribolium castaneum (Herbst) down to 3.8 adults/kg in flour in laboratory settings. Also, differences in the rates of sounds per insect in treatments with different numbers ranging from 5 to 50 insects suggested that the sound rates of adults of different species at different population densities may be noticeably affected by aggregation pheromones or other behaviorally active semiochemicals. Further testing is needed but previous experience with acoustic detection systems suggests that the prototype has potential for use in small storage facilities where early detection of infestations is difficult to provide.

Effects of Hermetic Storage on Adult Sitophilus oryzae L. (Coleoptera: Curculionidae) Acoustic Activity Patterns and Mortality.

Hermetic storage is of interest to farmers and warehouse managers as a method to control insect pests in small storage facilities. To develop improved understanding of effects of hermetic storage on insect pest activity and mortality over time, oxygen levels, acoustic signals, and observations of visual movement were recorded from replicates of 25, 50, and 100 adult Sitophilus oryzae (L.) (Coleoptera: Curculionidae) hermetically sealed in 500- and 1,000-ml glass jars. Recordings were done for 28 d; twice daily for the first 6 d and twice weekly thereafter. Insect sounds were analyzed as short bursts (trains) of impulses with spectra that matched average spectra (profiles) of previously verified insect sound impulses. Oxygen consumption was highest in treatments of 100 insects/500-ml jar and lowest in 25/1000-ml jars. The rates of bursts per insect, number of impulses per burst, and rates of burst impulses per insect decreased as the residual oxygen levels decreased in each treatment. Activity rates <0.02 bursts s-1, the acoustic detection threshold, typically occurred as oxygen fell below 5%. Mortality was observed at 2% levels. The time to obtain these levels of insect activity and oxygen depletion ranged from 3-14 d depending on initial infestation levels. Acoustic detection made it possible to estimate the duration required for reduction of insect activity to levels resulting in negligible damage to the stored product under hermetic conditions. Such information is of value to farmers and warehouse managers attempting to reduce pest damage in stored crops.

Wingbeat Frequency-Sweep and Visual Stimuli for Trapping Male Aedes aegypti (Diptera: Culicidae).

Combinations of female wingbeat acoustic cues and visual cues were evaluated to determine their potential for use in male Aedes aegypti (L.) traps in peridomestic environments. A modified Centers for Disease control (CDC) light trap using a 350-500 Hz frequency-sweep broadcast from a speaker as an acoustic stimulus, combined with a black poster-board half-cylinder behind the trap as a visual stimulus, captured a significantly greater proportion of males in a laboratory arena during daylight than a CDC trap with the visual stimulus alone or a CDC trap alone without stimuli. Traps of each treatment type captured relatively more males when they were placed at darker positions in the arena. Potential applications are discussed for the incorporation of these findings into trapping programs to reduce transmission of human pathogens vectored by Ae. aegypti.

Disrupting Mating Behavior of Diaphorina citri (Liviidae).

Severe economic damage from citrus greening disease, caused by 'Candidatus Liberibacter asiaticus' bacteria, has stimulated development of methods to reduce mating and reproduction in populations of its insect vector, Diaphorina citri (Hemiptera: Liviidae). Male D. citri find mating partners by walking on host plants, intermittently producing vibrational calls that stimulate duetting replies by receptive females. The replies provide orientational feedback, assisting the search process. To test a hypothesis that D. citri mating can be disrupted using vibrational signals that compete with and/or mask female replies, courtship bioassays were conducted in citrus trees with or without interference from female reply mimics produced by a vibrating buzzer. Statistically significant reductions occurred in the rates and proportions of mating when the buzzer produced reply mimics within 0.4 s after male courtship calls compared with undisturbed controls. Observations of courtship behaviors in the two bioassays revealed activity patterns that likely contributed to the reductions. In both disruption and control tests, males reciprocated frequently between structural bifurcations and other transition points where signal amplitudes changed. Males in the disruption bioassay had to select among vibrational signals combined from the buzzer and the female at each transition point. They often turned towards the buzzer instead of the female. There was a statistically significant reduction in the proportion of males mating if they contacted the buzzer, possibly due to its higher vibration amplitude and duration in comparison with female replies. Potential applications of D. citri mating disruption technology in citrus groves are discussed.

Acoustic Detection of Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae) and Oryctes elegans (Coleoptera: Scarabaeidae) in Phoenix dactylifera (Arecales: Arecacae) Trees and Offshoots in Saudi Arabian Orchards.

Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae) larvae are cryptic, internal tissue-feeding pests of palm trees that are difficult to detect; consequently, infestations may remain hidden until they are widespread in an orchard. Infested trees and propagable offshoots that develop from axillary buds on the trunk frequently are transported inadvertently to previously uninfested areas. Acoustic methods can be used for scouting and early detection of R. ferrugineus, but until now have not been tested on multiple trees and offshoots in commercial date palm orchard environments. For this report, the acoustic detectability of R. ferrugineus was assessed in Saudi Arabian date palm orchards in the presence of commonly occurring wind, bird noise, machinery noise, and nontarget insects. Signal analyses were developed to detect R. ferrugineus and another insect pest, Oryctes elegans Prell (Coleoptera: Scarabaeidae), frequently co-occurring in the orchards, and discriminate both from background noise. In addition, it was possible to distinguish R. ferrugineus from O. elegans in offshoots by differences in the temporal patterns of their sound impulses. As has been observed often with other insect pests, populations of the two species appeared clumped rather than uniform or random. The results are discussed in relation to development of automated methods that could assist orchard managers in quickly identifying infested trees and offshoots so that R. ferrugineus infestations can be targeted and the likelihood of transferring infested offshoots to uninfested areas can be reduced.

Acoustic Assessment of Beauveria bassiana (Hypocreales: Clavicipitaceae) Effects on Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae) Larval Activity and Mortality.

Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae) is an economically important pest of palm trees in the subtropics. Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Clavicipitaceae), has been shown to be pathogenic against R. ferrugineus in laboratory and field studies. However, because they remain inside the trunks until adulthood, the slowing of feeding and increases in mortality of internally feeding R. ferrugineus larvae over time after B. bassiana treatment has not been established. To explore the potential of acoustic methods to assess treatment effects, sound impulses produced by untreated, 10(4)-, and 10(6)-conidia ml(-1) B. bassiana-treated larvae in palms were recorded for 23 d, after which the palms were dissected and the larvae examined. Analyses were performed to identify trains of impulses with characteristic patterns (bursts) produced frequently by moving and feeding larvae but only rarely (3-8% of the larval rate) by interfering background noise or tree vibrations. The rates of bursts, the counts of larval impulses per burst, and the rates of impulses in bursts decreased significantly over time in both B. bassiana treatments but not in the control. This supports a hypothesis that larvae had briefer movement and feeding bouts as they became weaker after infection, which reduced the counts of larval impulses per burst, the rates of bursts, and the rates of impulses in bursts. There is considerable potential for use of acoustic methods as tools for nondestructive assessment of effects of biological control treatments against internally feeding insect pests.

Applications and mechanisms of wax-based semiochemical dispenser technology for disruption of grape root borer mating.

Grape root borer, Vitacea polistiformis (Harris) (Lepidoptera: Sesiidae), is an important pest of cultivated grapes (Vitis spp.) in the eastern United States from Michigan to Florida. There are few registered insecticides for control of this pest, and their efficacy is limited. Pheromone-based mating disruption is a potential alternative to insecticides for management of V. polistiformis. Wax-based Specialized Pheromone & Lure Application Technology (SPLAT) was tested as a mating disruption method. Deployment densities of 150 dispensers per ha dosed with 5 mg of V. polistiformis pheromone were sufficient to achieve 95% mating disruption during a 7-wk trapping period. The disruption mechanism was determined to be competitive attraction. The release rate of pheromone from these dispensers was quantified to be approximately linear, 77.4 microg/g SPLAT/d. At this release rate, a minimum initial load of 5.4 mg of pheromone per dispenser would be needed to maintain disruption over a 9-10-wk V. polistiformis flight season, approximately 19 August to 21 October in central Florida. It should be noted, however, that the main pheromone component alone, (E,Z)-2,13-octadecadienyl acetate (ODDA), was effective (presumably by a noncompetitive mechanism) at higher loads per area of crop. Due to the cost of synthesis of highly pure isomers of the V. polistiformis pheromone components, mating disruption of V. polistiformis may be more practical with higher doses of commercially produced Zeuzera pyrina L. blend [95% (E,Z)-2,13-ODDA:5% (E,Z)-3,13-octadecadien-1-ol] or with (E,Z)-2,13-ODDA alone than with the V. polistiformis blend at lower rates.

Acoustic indicators for targeted detection of stored product and urban insect pests by inexpensive infrared, acoustic, and vibrational detection of movement.

Crawling and scraping activity of three stored-product pests, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), and Stegobium paniceum (L.) (Coleoptera: Anobiidae), and two urban pests, Blattella germanica (L.) (Blattodea: Blattellidae) and Cimex lectularius L. (Hemiptera: Cimicidae), were monitored individually by infrared sensors, microphones, and a piezoelectric sensor in a small arena to evaluate effects of insect locomotory behavior and size on the ability of an inexpensively constructed instrument to detect insects and distinguish among different species. Adults of all species could be detected when crawling or scraping. The smallest insects in the study, first-fourth-instar C. lectularius nymphs, could not be detected easily when crawling, but could be detected when scraping. Sound and vibration sensors detected brief, 3-10-ms impulses from all tested species, often grouped in distinctive trains (bursts), typical of impulses in previous acoustic detection experiments. To consider the potential for targeting or focusing detection on particular species of interest, indicators were developed to assess the likelihood of detection of C. lectularius. Statistically significant differences were found between C. lectularius and other species in distributions of three measured variables: infrared signal durations, sound impulse-burst durations, and sound pressure levels (energy) of impulses that best matched an averaged spectrum (profile) of scraping behavior. Thus, there is potential that signals collected by an inexpensive, polymodal-sensor instrument could be used in automated trapping systems to detect a targeted species, 0.1 mg or larger, in environments where servicing of traps is difficult or when timeliness of trapping information is important.

Acoustic detection of Oryctes rhinoceros (Coleoptera: Scarabaeidae: Dynastinae) and Nasutitermes luzonicus (Isoptera: Termitidae) in palm trees in urban Guam.

Adult and larval Oryctes rhinoceros (L.) (Coleoptera: Scarabaeidae: Dynastinae) were acoustically detected in live and dead palm trees and logs in recently invaded areas of Guam, along with Nasutitermes luzonicus Oshima (Isoptera: Termitidae), and other small, sound-producing invertebrates and invertebrates. The low-frequency, long-duration sound-impulse trains produced by large, active O. rhinoceros and the higher frequency, shorter impulse trains produced by feeding N. luzonicus had distinctive spectral and temporal patterns that facilitated their identification and discrimination from background noise, as well as from roaches, earwigs, and other small sound-producing organisms present in the trees and logs. The distinctiveness of the O. rhinoceros sounds enables current usage of acoustic detection as a tactic in Guam's ongoing O. rhinoceros eradication program.

Acoustic detection of melolonthine larvae in Australian sugarcane.

Decision support systems have been developed for risk analysis and management of root-feeding white grubs (Coleoptera: Scarabaeidae: Melolonthinae) in Queensland, Australia, sugarcane (Saccharum spp.), based partly on manual inspection of soil samples. Acoustic technology was considered as a potential alternative to this laborious procedure. Field surveys were conducted to detect the major pests Dermolepida albohirtum (Waterhouse) near Mackay, and Antitrogus parvulus Britton near Bundaberg. Computer analyses were developed to identify distinctive scrapes and other sounds produced by D. albohirtum and Antitrogus species and to distinguish them from sounds of nondamaging white grubs (Rutelinae, Dynastinae), as well as from extraneous, wind-induced tapping signals. Procedures were considered for incorporating acoustic methods into surveys and sequential sampling plans. Digging up and inspecting sugarcane root systems requires 10-12 min per sample, but acoustic assessments can be obtained in 3-5 min, so labor and time could be reduced by beginning the surveys with acoustic sampling. In a typical survey conducted in a field with low population densities, sampling might terminate quickly after five negative acoustic samples, establishing a desired precision level of 0.25 but avoiding the effort of excavating and inspecting empty samples. With a high population density, sampling might terminate also if signals were detected in five samples, in which case it would be beneficial to excavate the samples and count the white grubs. In intermediate populations, it might be necessary to collect up to 20 samples to achieve desired precision, and acoustic methods could help determine which samples would be best to excavate.

Detection of Anoplophora glabripennis (Coleoptera: Cerambycidae) larvae in different host trees and tissues by automated analyses of sound-impulse frequency and temporal patterns.

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), an invasive pest quarantined in the United States, is difficult to detect because the larvae feed unseen inside trees. Acoustic technology has potential for reducing costs and hazards of tree inspection, but development of practical methods for acoustic detection requires the solution of technical problems involving transmission of resonant frequencies in wood and high background noise levels in the urban environments where most infestations have occurred. A study was conducted to characterize sounds from larvae of different ages in cambium, sapwood, and heartwood of bolts from three host tree species. Larval sounds in all of the tested trees and tissues consisted primarily of trains of brief, 3-10-ms impulses. There were no major differences in the spectral or temporal pattern characteristics of signals produced by larvae of different ages in each tissue, but larval sounds in sapwood often had fewer spectral peaks than sounds in cambium and heartwood. A large fraction, but not all background sounds could be discriminated from larval sounds by automated spectral analyses. In 3-min recordings from infested bolts, trains containing impulses in patterns called bursts occurred frequently, featuring 7-49 impulses separated by small intervals. Bursts were rarely detected in uninfested bolts. The occurrence of bursts was found to predict infestations more accurately than previously used automated spectral analyses alone. Bursts and other features of sounds that are identifiable by automated techniques may ultimately lead to improved pest detection applications and new insight into pest behavior.

Acoustic indicators for mapping infestation probabilities of soil invertebrates.

Acoustic and traditional excavation methods were used in consecutive summers to conduct two geospatial surveys of distributions of white grubs and other soil invertebrates in two forage fields. Indicator variables were constructed from listener- and computer-based assessments of sounds detected at each recording site and then applied in geostatistical analysis, contingency analysis, and spatial analysis of distance indices (SADIE) of soil invertebrate distributions. Significant relationships were identified between the acoustic indicators and the counts of sound-producing soil invertebrates in a majority of the geostatistical and contingency analyses. Significant clusterings and overall spatial associations were identified also in most of the SADIE analyses. In addition, significant local spatial associations were identified between acoustic indicators and counts of sound-producing soil invertebrates that could be of potential value in selection of specific sites as targets for treatment or for untreated reserves in integrated pest management programs. An example is presented of the relative efficiency of acoustic surveys for targeting of white grub treatments.

Geophone detection of subterranean termite and ant activity.

A geophone system was used to monitor activity of subterranean termites and ants in a desert environment with low vibration noise. Examples of geophone signals were recorded from a colony of Rhytidoponera taurus (Forel), a colony of Camponotus denticulatus Kirby, and a termite colony (undetermined Drepanotermes sp.) under attack by ants from a nearby C. denticulatus colony. The geophone recordings were compared with signals recorded from accelerometers in a citrus grove containing Solenopsis invicta Buren workers. Because of their small size, all of these insects produce relatively weak sounds. Several different types of insect-generated sounds were identified in the geophone recordings, including high-frequency ticks produced by R. taurus and C. denticulatus, and patterned bursts of head bangs produced by Drepanotermes. The S. invicta produced bursts of ticks with three different stridulation frequencies, possibly produced by three different-sized workers. Overall, both systems performed well in enabling identification of high-frequency or patterned pulses. The geophone was more sensitive than the accelerometer to low-frequency signals, but low-frequency insect sound pulses are more difficult to distinguish from background noises than high-frequency pulses. The low cost of multiple-geophone systems may facilitate development of future applications for wide-area subterranean insect monitoring in quiet environments.

Broadcasts of wing-fanning vibrations recorded from calling male Ceratitis capitata (Diptera: Tephritidae) increase captures of females in traps.

Female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), from the sterile-male rearing facility in El Pino, Guatemala, were exposed to broadcasts of wing-fanning vibrations recorded from males engaged in calling behavior to investigate the feasibility of developing a female-selective acoustic trap. The recorded signals had frequent amplitude fluctuations and peak frequencies approximately 350 Hz, typical of signals observed in previous studies of Mediterranean fruit fly acoustic behavior. Females did not exhibit long-distance phonotaxis, but remained near a speaker significantly longer when the sounds were broadcast at 103-107 dB than when the speaker was silent. In addition, significantly higher percentages of females were captured by yellow adhesive traps next to a broadcasting speaker than by traps next to a silent mimic. Additional bioassays were conducted with synthetic, 350-Hz tones produced by a thermoacoustic tube as well as with silent mimics of the different sound sources to examine the relative responsiveness of female Mediterranean fruit flies to traps with different acoustic and visual features. The visual attributes of the different sound source assemblies significantly affected capture rates. The range over which the broadcast significantly increased the percentage of female captures was <0.5 m, which may limit the utility of these acoustic cues in large-scale trapping programs. However, the findings of this study do justify further testing of whether optimized short-range acoustic signals could be used to augment longer range pheromonal and visual cues to improve the efficacy of female-selective traps.

Microwave radar detection of stored-product insects.

A microwave radar system that senses motion was tested for capability to detect hidden insects of different sizes and activity levels in stored products. In initial studies, movements of individual adults or groups of Lasioderma serricorne (F.), Oryzaephilus surinamensis (L.), Attagenus unicolor (Brahm), and Tribolium castaneum (Herbst) were easily detected over distances up to 30 cm in air. Boxes of corn meal mix and flour mix were artificially infested with 5-100 insects to estimate the reliability of detection. The likelihood that a box was infested was rated by the radar system on a quantitative scale. The ratings were significantly correlated with the numbers of infesting insects. The radar system has potential applications in management programs where rapid, nondestructive targeting of incipient insect infestations would be of benefit to the producers and consumers of packaged foods.

Acoustic detection of termite infestations in urban trees.

A portable, low-frequency acoustic system was used to detect termite infestations in urban trees. The likelihood of infestation was rated independently by a computer program and an experienced listener that distinguished insect sounds from background noises. Because soil is a good insulator, termite sounds could be detected easily underneath infested trees, despite the presence of high urban background noise. Termite sounds could be detected also in trunks, but background noise often made it difficult to identify termite signals unambiguously. High likelihoods of termite infestation were predicted at four live oak (Quercus virginiana Mill, Fagacae), two loblolly pine (Pinus taeda L., Pinacae), and two baldcypress (Taxodium distichum Rich. Pinacae) trees that wood-baited traps had identified as infested with Coptotermes formosanus Shiraki. Infestations also were predicted at two pine trees with confirmed recoveries of Reticulitermes flavipes (Kollar). Low likelihoods of infestation were predicted in four oak trees where no termites were found. Additional tests were conducted in anechoic environments to determine the range of acoustic detectability and the feasibility of acoustically estimating termite population levels. There was a significant regression between the activity rate and the number of termites present in a wood trap block, with a minimum detectable number of approximately 50 workers per liter of wood. The success of these field tests suggests that currently available acoustic systems have considerable potential to detect and monitor hidden infestations of termites in urban trees and around building perimeters in addition to their present uses to detect and monitor termite infestations in buildings.

Acoustic surveying of subterranean insect populations in citrus groves.

Subterranean insect pests cause considerable economic damage but their concealment makes detection difficult. A portable acoustic system was developed and tested for its potential to rate the likelihood that trees in citrus groves were infested with Diaprepes abbreviatus (L.) larvae. The likelihood was rated independently by a computer program and an experienced listener that distinguished insect sounds from background noises. Diaprepes abbreviatus, Phyllophaga spp., or other pest insects were excavated from all 11 sites rated at high likelihood of infestation but were absent from 20 of 25 low-rated sites. There was a significant regression between the activity rate and the number of pest organisms present at recording sites although the correlation was weaker than between activity rate and likelihood of infestation. Although the system is at an early stage of development, the success of these field tests suggests that it has considerable potential as a tool to detect and monitor hidden infestations of insects in soil.

Mapping of soil insect infestations sampled by excavation and acoustic methods.

Geostatistical analysis was used to map traditionally and acoustically sampled populations of soil invertebrates at two different times in a hayfield at Grove Hill, AL, and once in an Auburn, AL, hayfield. The distributions of nearly all the soil invertebrates and their sounds were nonrandom in all three mapping studies. The maps constructed by excavation and acoustic sampling methods were compared by correlating the estimated (kriged) soil invertebrate counts with the estimated (kriged) counts of sounds per minute (pulse rate). Acoustic and traditional estimates were positively correlated in the Auburn study. Kriged estimates for green June beetle grub counts overlapped significantly with kriged estimates of sound pulse rate (R2 = 0.47). Overlap with sound pulse rates increased slightly when other soil organisms were counted along with green June beetle grubs: estimates of sound pulse rates were significantly correlated with counts of all white grubs (R2 = 0.50), all white grubs with earthworms (R2 = 0.52), all white grubs with earthworms and earwigs (R2 = 0.59), and total invertebrates (R2 = 0.59). The correlation between acoustic and traditional estimates was not significant at Grove Hill in either year, possibly because of a lack of experience in signal analysis or because the soil invertebrates may not have generated enough sounds to be detected above the background noise levels. These results suggest that acoustic technology is a promising tool for detecting insect pests in soil, but that further study and additional analysis are needed to improve interpretation of acoustic data obtained in the field.

Monitoring insect pests in retail stores by trapping and spatial analysis.

Stored-product insects are a perennial problem in retail stores, where they damage and contaminate susceptible merchandise such as food products and animal feed. Historically, pest management in these stores has relied heavily on chemical insecticides, but environmental and health issues have dictated use of safer methods, and these require better monitoring. A monitoring procedure that employs an array of moth and beetle traps combined with spatial (contour) analysis of trap catch was tested in three department stores and two pet stores. The rate of capture increased with the level of infestation but was essentially constant over 4- to 5-d trapping periods. Contour analysis effectively located foci of infestation and reflected population changes produced by applications of the insect growth regulator (S)-hydroprene. The most abundant insects were Plodia interpunctella (Hiibner), Lasioderma serricorne (F.), Oryzaephilus mercator (Fauvel), Tribolium castaneum (Herbst), and Cryptolestes pusillus (Schönherr). The results indicate that contour analysis of trap counts provides a useful monitoring tool for management of storage pests in retail stores. It identifies trouble spots and permits selection, timing, and precision targeting of control measures to achieve maximum pest suppression with minimum pesticide risk. It permits managers and pest control operators to visualize pest problems over an entire store, to monitor changes over time, and to evaluate the effectiveness of control intervention. The contour maps themselves, along with records of control applications and stock rotation, provide permanent documentation of pest problems and the effectiveness of pest management procedures.

Eavesdropping on insects hidden in soil and interior structures of plants.

Accelerometer, electret microphone, and piezoelectric disk acoustic systems were evaluated for their potential to detect hidden insect infestations in soil and interior structures of plants. Coleopteran grubs (the scarabaeids Phyllophaga spp. and Cyclocephala spp.) and the curculionids Diaprepes abbreviatus (L.) and Otiorhynchus sulcatus (F.) weighing 50-300 mg were detected easily in the laboratory and in the field except under extremely windy or noisy conditions. Cephus cinctus Norton (Hymenoptera: Cephidae) larvae weighing 1-12 mg could be detected in small pots of wheat in the laboratory by taking moderate precautions to eliminate background noise. Insect sounds could be distinguished from background noises by differences in frequency and temporal patterns, but insects of similarly sized species could not be distinguished easily from each other. Insect activity was highly variable among individuals and species, although D. abbreviatus grubs tended to be more active than those of O. sulcatus. Tests were done to compare acoustically predicted infestations with the contents of soil samples taken at recording sites. Under laboratory or ideal field conditions, active insects within approximately 30 cm were identified with nearly 100% reliability. In field tests under adverse conditions, the reliability decreased to approximately 75%. These results indicate that acoustic systems with vibration sensors have considerable potential as activity monitors in the laboratory and as field tools for rapid, nondestructive scouting and mapping of soil insect populations.