Field Scouting Research Articles

Fixed-Time Classification and Detection Plans for Alfalfa Snout Beetle (Coleoptera: Curculionidae)

Practical scouting plans are described that categorize the economic status of the alfalfa snout beetle, Otiorhynchus ligustici (L.), from direct visual counts of adults during 30-min field inspections. Plans were derived by fixing field-sampling time requirements as a linear function of beetle density and computing with the t statistic the probability that true mean beetle density μ differs from the economic injury level, given estimated mean beetle density (x) from field scouting. Consequences of classification errors are stated as probability of financial gains and losses to dairy farmers. Worst-case yield loss scenarios are presented as a simple decision aid that dairy farmers can consult to minimize the probability of catastrophic losses. Survey and detection plans are derived from a geometric series for Poisson frequencies of beetle occurrence; plans can be used by regulatory personnel to identify the probability of detecting beetle infestations when field inspection is restricted to arbitrary time limits. General guidelines for implementing both sampling plans are discussed. Concurrent studies of alfalfa snout beetle population dispersion detected aggregation among soilborne larvae as well as among beetles emerging from soil overwintering sites. In contrast, dispersion of beetles on the soil surface following spring emergence was random.

Potential Use of Visual Mold Ratings to Predict Mycotoxin Contamination of Grain Sorghum

The suggested association between zearalenone contamination and Fusarium grain mold, along with documented cases of zearalenone and deoxynivalenol contamination in sorghum [Sorghum bicolor (L.) Moench], prompted an investigation into a determination if field scouting could be used to predict contamination level. Several sorghum hybrids were examined for bird damage and visible grain mold prior to harvest at seven locations in 1986 and 1987. Zearalenone and deoxynivalenol levels were analyzed in the harvested samples. Bird damage, Fusarium grain mold, zearalenone, and deoxynivalenol were detected in 68, 87, 67, and 88% of all samples, respectively. There appeared to be no correlation between bird damage and mycotoxin levels; however, highly significant correlation coefficients of 0.38** and 0.39** were found between grain mold and zearalenone and deoxynivalenol levels, respectively. Of the 13% of the samples with no visible grain mold, all were contaminated with one or both of these mycotoxins. With 96% of the samples showing signs of mold and later revealing detectable levels of zearalenone or deoxynivalenol, it would appear that visible grain mold can indicate possible mycotoxin contamination; however, absence of any grain mold does not necessarily assure the grain is free from contamination.

Relationship of Adult European Corn Borer (Lepidoptera: Pyralidae) in Action Sites with Egg Masses in the Cornfield

A relative sampling method for second flight adult European corn borer, Ostrinia nubilalis (Hubner), was used to predict egg mass levels within hybrid seed cornfields ( Zea mays L.). An aluminum bar (1 m) was swept through adult aggregation areas of giant and green foxtail grass ( Setaria spp.) and adults were counted as they flushed from the grass. Numbers of scouted egg masses in the field were regressed onto numbers of flushed adults during early to late silking stages of corn. Egg masses were dependent on the number of European corn borer adults in aggregation areas (example: predicted 0.5 egg masses per corn plant with an average of 52 moths flushed from 10 m2 grass at 5% silking or an average of 66 moths flushed from 10 m2 grass at 80% silking). This relationship between flushed adults and egg masses can be used to determine the need and timing of field scouting by consultants or seed companies for second-generation egg masses in the Corn Belt.

Operation of a brown planthopper surveillance system in the Tanjung Karang Irrigation Scheme in Malaysia

A surveillance system for the brown planthopper (BPH) was set up in the Tanjung Karang Irrigation Scheme, Selangor, Malaysia after an extensive outbreak of the pest in 1977. The system has since grown to cover all major rice-growing schemes in Peninsular Malaysia. However, the Tanjung Karang Irrigation Scheme remained the most advanced area in terms of operating an early warning system for BPH. This paper describes how the data are collected, analysed and appropriate action taken to manage BPH. Information of the incidence of BPH and its natural enemies were obtained by field scouting, light trapping, and aerial net trapping. The data obtained would be supplemented by information on plant growth, farm practices and weather. A rice planthopper control committee existed in the Scheme to examine the surveillance data and using pragmatic threshold levels together with prey: predator ratios, decisions on management of the BPH would be issued for immediate implementation. As a result of the surveillance system operating in the Tanjung Karang Irrigation Scheme, the number of outbreaks of the BPH has decreased since 1977. In addition, the availability of early warning information has encouraged the implementation of integrated pest control programmes in the scheme. The incorporation of natural enemies in the collection of data and the recognition of predators in decision making has highlighted the importance of natural enemies in managing BPH and this in turn has discouraged indiscriminate use of insecticides.

Control of European Corn Borer on New Sweet Corn Varieties, 1987

Abstract A Windsor sandy loam field at the University of Vermont Horticultural Research Center, South Burlington, was planted on 3 Jun to 25 varieties of SE or EH type sweet corn, having elevated sugar levels, and two standard varieties. This field was used to evaluate the efficacy of Dipel 10G and Pounce 3.2EC in a multiple variety situation. Treatments were applied to 9 row plots, 52 ft long on 24-inch centers superimposed across varieties. A randomized complete block design with 3 replicates per treatment was used. Timing of treatments was based on attainment of an infestation level of 15% as determined by scouting. Initial field scouting of 100 plants, selected at 5 randomly chosen locations across the field, 20 plants/location, occurred on 13 Jul when the corn was in the whorl stage, 24-36 inches high. Further scouting was conducted on 16, 19, and 27 Jul and involved assessing the new growth on 33 plants/plot, a total of 99 plants/treatment, for larvae or damage. Insecticides were applied on 13 Jul and 20 Jul using a Solo backpack hand pumped sprayer at 30 psi or a hand crank spinner for the liquid and granular insecticides, respectively. Corn was harvested, based on maturity, over four dates, 19, 24, 26, and 31 Aug. Seven ears/variety/replicate, a total of 189 ears/treatment, were evaluated for external or internal damage. Data were analyzed using a square root transformation were appropriate.

Monitoring Adult Corn Flea Beetles (Coleoptera: Chrysomelidae) in Sweet Corn Fields with Color Sticky Traps

Sticky traps of various colors were used to monitor adult flea beetles in sweet corn fields. Twenty-two flea beetle species were collected; however, the corn flea beetle (CFB), Chaetocnema pulicaria Melsheimer, represented 94.4% of the total number of specimens captured. Saturn yellow and lightning yellow traps captured significantly more CFB adults than all other colors tested. Traps hung closest to the ground (0.6 m) captured significantly more CFB than traps at 1.2 or 1.8 m aboveground. Saturn yellow traps placed within the cornfield captured significantly more CFB than traps placed along the field edge or in the weedy border. The relationships between trap captures, degree-days, and the current field scouting method were investigated and resulted in tentative action thresholds for CFB management. Relationships between both adult monitoring methods (traps and field scouting) and flea beetle feeding injury were also determined.

Human Capital, Adjustments in Subjective Probabilities, and the Demand for Pest Controls

AbstractIn addition to risk aversion, farmer behavior in an uncertain environment is governed by subjective probability estimates of random events. The estimates given here lend support to the idea that human capital development can improve farmers' ability to estimate pest damage probabilities. More accurate assessment of subjective probabilities leads to lower pesticide use and increases the use of labor‐intensive pest controls. The human capital variables with the largest effects are formal schooling and farmer experience, with smaller impacts from field scouting and extension schools.

Western Corn Rootworm (Coleoptera: Chrysomelidae) Beetle Counts as a Means of Making Larval Control Recommendations in Nebraska

A larval damage prediction method for Diabrotica virgifera virgifera LeConte was evaluated in west central and northeastern Nebraska from 1978–1980. Cornfields averaging 1 beetle per plant on any sampling date were considered to be indeterminant with respect to a damage prediction; the growers were advised to use a soil insecticide as a precautionary measure. With the possible exception of a few fields in northeastern Nebraska, in which yield difference probably was not due to D. virgifera virgifera larval feeding, the prediction method was reliable >80% of the time. The study indicated that lowering the treatment threshold to 0.75 or 0.90 beetles per plant increased the prediction accuracy to >90% (root damage ratings <2.75), with none of the fields with prediction errors being seriously damaged (root damage ratings <3.1). As a result of this study, only 158 and 263 of ca. 3,050 ha of field corn in the west central study area were treated with soil insecticide for D. virgifera virgifera in 1981 and 1982, respectively. No serious problems were reported in the untreated fields by the field scouts. Before the IPM program, ca. 90%of the fields were treated with corn rootworm larvicides.

Pest management for potatoes in Wisconsin— A pilot program

A potato integrated pest management program was conducted from 1979–82 by University of Wisconsin-Extension in two of Wisconsin’s major potato producing areas. The program utilized trained field scouts for intensive pest monitoring, and economic thresholds for pest control recommendations; also a grower fee to pay for the scouting service. The program scouted between 1360 ha and 3240 ha during 1979–1982 growing seasons on a weekly basis for pest problem development in the field and worked with approximately 50 commercial potato growers each year. In general, program participants used more fungicide applications and fewer insecticide applications than the control group. The pesticide usage pattern on potatoes by the IPM grower group supports the integrated pest management concept of ‘fine-tuning’ pesticide usage to individual fields, weather conditions and pest problems.

A SEQUENTIAL DECISION PLAN FOR MANAGEMENT OF THE ALFALFA BLOTCH LEAFMINER, AGROMYZA FRONTELLA (DIPTERA: AGROMYZIDAE)

AbstractA sequential decision plan, based on the negative binomial distribution and providing for two infestation classes, has been derived for use in management of the alfalfa blotch leafminer, Agromyza frontella (Rond.), in southern Ontario. It utilizes counts of the eggs in leaflets of alfalfa, and in economic situations will provide growers with sufficient lead time to consider alternative action strategies. An appraisal of the plan by field scouts showed that it rated the infestation status of the leafminer correctly in 48 of 51 cases. Sampling time averaged 25 min per scout per field.

Evaluation of Insecticide Usage in the New York Processing-Cabbage Pest Management Program1

Insecticide usage in the Cornell University Processing (sauerkraut) Cabbage Pest Management Pilot Program was evaluated over the 4-year period from 1978 to 1981. Insecticide load was assessed in terms of dose equivalents. Insecticide efficacy was measured by percent reduction of Lepidoptera and percent reduction of plants infested with onion thrips, Thrips labaci Lindeman. Total insecticide load, in average dose equivalents per field, decreased every year from 1978 to 1980, but increased in 1981. The increase in dose equivalents in 1981 was due to multiple applications of insecticides by growers to suppress high populations of thrips. However, during the 4-year period, most insecticides were applied to control Lepidoptera, and comparing 1981 with 1978, the amount of insecticides used against Lepidoptera decreased by 49%, whereas their effectiveness increased by 54%. These results are attributed to better insecticide selection and improved timing of applications due to development of action thresholds used in conjunction with weekly field scouting. Methamidophos and the pyrethroids consistently provided the most effective control of Lepidoptera. Control of thrips by foliar insecticides was inadequate for present Food and Drug Administration standards.

Development of cotton-pest management in Zimbabwe

Use of insecticides on cotton is kept to a minimum in Zimbabwe by the recommendation that applications are timed on the basis of routine crop-inspection (scouting) data. Greater acceptance of field scouting by large-scale cotton producers was achieved by providing training for farm scouts. The syllabus for courses financed from a crop levy included recognition of insect pests and methods of recording their numbers. Subsequently, courses on data interpretation improved the timing of spraying, but scouting efficiency was increased most markedly by an on-farm check scouting scheme. Small-scale cotton farmers also are now provided with courses. Training schemes have been an important factor in the adoption of a pest-management programme. Cotton production has increased from less than 3000 t of lint in 1964 to over 70 000 t in 1982.

Design of a Field-Sampling Simulator

Demonstration of the design and operation of sampling systems to entomology students and field scouts in integrated pest management (IPM) programs is often difficult. Laboratory exercises may be unrealistic, and the use of field populations unreliable. Particular difficulties can be experienced in demonstrating the effects of different insect distributions on sampling efficiency, since it is difficult to manipulate natural insect populations. Complexities of seasonal trends also preclude many field exercises.

Pest Information Markets and Integrated Pest Management

Integrated pest management (IPM) programs vary from employing field scouts to planting trap crops, as inputs in production, to control crop losses. Scouts provide pest information, helping to determine the need for pesticide applications. This increased information may indicate a reduction of periodic application, which would diminish the negative external effects that such treatments have on environmental quality.Recent research in this area has determined the need for pest information (Regev et al.) and the rationale for established information markets (Feder). Currently, such sources exist throughout the United States, and both public and private consultants supply information to agricultural producers.

Pheromone Trap Index System for Predicting Need for Overwintered Boll Weevil Control12

Studies were conducted during 1977–79 to determine if grandlure baited traps could be used to predict the need to treat for overwintered Anthonomus grandis grandis Boheman. A positive relationship was established between the mean number of overwintered weevils captured per trap per field just prior to the appearance of squares suitable for oviposition and the percent oviposition damaged squares during the early 1/3-grown square period. A trap index threshold was developed and applied to actual field situations. The accuracy of the trap index system in determining the need for overwintered boll weevil control was compared to conventional field sampling. The trap index method was more accurate than field scouting in providing a warning of overwintered weevil infestation before squares of a suitable size for oviposition were present. The system was equally effective in indicating when overwintered weevil control was unnecessary.