Sampling for the sugarcane borer (Lepidoptera: Crambidae) on sugarcane in Louisiana.

A 3-yr study was conducted in 0.6- to 2.0-ha sugarcane fields throughout south Louisiana under varying sugarcane borer, Diatraea saccharalis (F.), density levels to determine the spatial dispersion of infestations and to develop a sequential sampling plan. Infestations of D. saccharalis were randomly dispersed. Infestation levels (percentage of stalks infested) ranged from 0.6 to 33.3%. Frequency distributions of the number of infested stalks indicated that the Poisson distribution best fit the data Tests of other distributions (negative binomial [aggregated], binomial [uniform], geometric, and hypergeometric) resulted in poorer fits. The sequential sampling plan devised, with lower and upper D. saccharalis infestation limits of 2 and 5% and 5 and 10%, required maximum average sample numbers of 7.1 and 5.5 (20-stalk samples), respectively, to make terminating management decisions. It is our assessment that implementation of these plans would decrease sampling effort by 50-60% when compared with sampling programs currently in use for D. saccharalis management decisions in Louisiana.     

Evaluation of sequential presence-absence sampling plans for the diamondback moth (Plutellidae: Lepidoptera) in cruciferous crops in Australia

Two sets of sequential presence-absence sampling plans for decision-making in the management of diamondback moth, Plutella xylostella (L.), were developed and evaluated. One set of sampling plans targeted the classification of proportions of infested plants, and the other set of sampling plans targeted the classification of larval density. The action thresholds investigated were 0.15, 0.25, 0.35, and 0.45 proportion of plants infested with larvae, and 0.2, 0.4, 0.6, and 0.8 larvae per plant. They are representative of the action thresholds currently practiced by Australian crucifer growers. For each sampling plan, the population range within which a minimal correct decision rate of 95% can be expected at a maximal average sample size of 50 plants (OC95ASN50) was specified. The closeness of an OC95ASN50 range to the target action threshold is a measure of the expected performance of the sampling plan. A closer distance reflects better performance. The OC95ASN50 ranges of the proportion-classification sampling plans were within 33-53% of the target action thresholds. The width of these OC95ASN50 ranges represents 73-87% of the entire population range (0-1). For the classification of larval density, an empirical proportion-density model was first established using data from different states and different cruciferous crops. The OC95ASN50 ranges of the density-classification sampling plans were within 57-75% of the target action threshold. Simulated sampling of 20 independent data sets showed that for most data sets the correct classification rate was at least 98% and the matching average sample size was <50 plants.     

Sequential sampling plans for western flower thrips (Thysanoptera: Thripidae) on greenhouse cucumbers

The development of cost-effective and reliable sampling programs for the management of western flower thrips, Frankliniella occidentalis (Pergande), on greenhouse cucumbers is important for getting growers to adopt economic injury levels and economic thresholds. The objectives of this study were to develop two sequential sampling plans. A fixed-precision sequential sampling plan was designed for estimating F. occidentalis adult density at a fixed-precision level on cucumber flowers. Also, a sequential sampling plan for classifying thrips population levels as below or above economic thresholds was developed to assist in decision making for the timing of pesticide applications. Both sequential sampling plans were validated using a resampling simulation technique on nine independent data sets ranging in density from 1.25 to 12.95 adults per flower. With the fixed-precision sampling plan, average means obtained in 100 repeated simulation runs were within the 95% CI of the estimated mean for all data sets. Appropriate levels of precision for the different population densities were recommended based on the simulation results. With sequential sampling for classifying the population levels of thrips in terms of an economic threshold, it has the advantage of requiring smaller sample sizes to determine the population status when the population densities differ greatly from the critical density (i.e., economic threshold). However, this plan needs a great number of samples when population density is close to the critical density. In this case, use of a combination of both sampling plans is recommended.     

Evaluation of action thresholds and spinosad for lepidopteran pest management in Minnesota cabbage

Action thresholds, based on the percentage of plants infested, for the lepidopteran pest complex in fresh-market cabbage Brassica oleracea variety capitata were evaluated in 1996 and 1997 in southern Minnesota. Three lepidopteran pests are common in Minnesota, including the imported cabbageworm, Pieris (=Artogeia) rapae (L.), diamondback moth, Plutella xylostella (L.), and the cabbage looper, Trichoplusia ni (Hübner). Most of the thresholds tested included all three pests. However, because T. ni is often the most consistent and damaging pest in Minnesota, two thresholds were based solely on the percentage of plants infested with T. ni eggs and larvae. Action thresholds were also evaluated for their compatibility with a recently labeled biologically based insecticide, spinosad, and a conventional pyrethroid, permethrin. Although all three lepidopteran pests were present in both years of the study, P. rapae provided most of the pest pressure in 1996, and T. ni was most abundant in 1997. Compared with the 0% larval infestation treatment (approximately weekly sprays from early heading to harvest), all action thresholds resulted in less insecticide use (17- 80%), while maintaining high levels of marketability. Despite variable pest pressure between years, one of the thresholds based solely on T. ni (10% of plants infested with eggs or larvae) performed as well as each of the thresholds based on all three species combined. For both years, and compared with a weekly spray schedule from early heading to harvest (average of 5.5 sprays per year), use of the 10% T. ni egg or larval threshold resulted in an average of 36.5% (3.5 sprays) and 65% (2.0 sprays) fewer applications of spinosad and permethrin, respectively, with no significant loss in marketability. The results indicate that a variety of incidence-based action thresholds can be used to ensure the production of high-quality cabbage in the midwestern United States with only minimal applications of spinosad or permethrin.     

Evolution of acaricide resistance: phenotypic and genotypic changes in field populations of Rhipicephalus (Boophilus) microplus in response to pyrethroid selection pressure

There have been few, if any, studies of arthropod field populations quantifying the kinetics of evolution of phenotypic and genotypic resistance to chemicals in response to the presence or absence of selection pressure. A prospective intervention study was undertaken over 2 years in Mexico to measure changes in resistance phenotype and genotype in the presence or absence of pyrethroid selection pressure on field populations of Rhipicephalus (Boophilus) microplus ticks on 11 farms with varying degrees of pyrethroid resistance. The resistance phenotype was evaluated by bioassay in a larval packet test expressed as the resistance factor (RF) derived from probit analysis of dose mortality regressions, and resistance genotype by an allele-specific PCR (AS-PCR) to determine the frequency of a sodium channel mutation (F1550I) associated with pyrethroid resistance. To validate the AS-PCR, a Pyrosequencing? method was developed to detect the F1550I mutation. There was good concordance with the genotypes identified by both Pyrosequencing? and AS-PCR (Kappa: 0.85). On five farms cypermethrin (CY) was exclusively used at intervals and on six farms amitraz was used. On two of the five CY-treated farms, the experiment was prematurely terminated due to unacceptably high levels of tick resistance. For all five farms, after 8–24 months of continued selection pressure with CY, the RF had increased 2–125-fold. The frequency of the resistance allele increased on all five farms from a starting range of 5–46% to a range of 66–95% after 8–24 months. On six farms treated with amitraz neither the RF nor the frequency of the resistance allele changed. A clear correlation between the phenotype and genotype was found in three of four treated farms confirming that the F1550I mutation is a major cause of synthetic pyrethroid resistance in Mexico. These results show that the pyrethroid resistance trait is stable (> 2 years) and that resistance is acquired much faster than it is lost. Hence, alternation of pyrethroid acaricide with other chemicals is likely to lead to the stepwise acquisition of synthetic pyrethroid resistance but not additional prolongation of its efficacious lifespan.     

Binomial sampling for pest management of stable flies (Diptera: Muscidae) that attack dairy cattle.

A binomial sampling plan for pest management of the stable fly, Stomoxys calcitrans (L.), was developed. Counts of stable flies on front legs of the same animal were independent and each leg from the same animal was considered a sample unit. The relationship between the mean number of flies per leg and the variance was determined and did not vary among farms. The relationship between the mean number of flies per leg and the proportion of legs with zero, one or less, and two or less flies (P0, P1, and P2) was determined and used as the basis of the binomial sampling plan. Predicted values of the mean number of flies per leg from P0, P1, and P2 were close to observed values of the mean number of flies per leg. Equations are presented for calculating the variance of a predicted value of the mean number of flies per leg using values of P0, P1 and P2 determined by sampling. Operating characteristic (OC) curves are also presented for determining the probability of making a treatment decision error at an economic threshold of one fly per leg (P0 = 0.47) using binomial sampling or direct counting. OC curves for binomial sampling with n = 50 legs were close to those for direct counting with n = 10 legs. Recommendations concerning the use of binomial sampling for stable flies are presented.     

Spatial pattern and sequential sampling of squash bug (Heteroptera: Coreidae) adults in watermelon

Spatial distribution patterns of adult squash bugs were determined in watermelon, Citrullus lanatus (Thunberg) Matsumura and Nakai, during 2001 and 2002. Results of analysis using Taylor's power law regression model indicated that squash bugs were aggregated in watermelon. Taylor's power law provided a good fit with r2 = 0.94. A fixed precision sequential sampling plan was developed for estimating adult squash bug density at fixed precision levels in watermelon. The plan was tested using a resampling simulation method on nine and 13 independent data sets ranging in density from 0.15 to 2.52 adult squash bugs per plant. Average estimated means obtained in 100 repeated simulation runs were within the 95% CI of the true means for all the data. Average estimated levels of precision were similar to the desired level of precision, particularly when the sampling plan was tested on data having an average mean density of 1.19 adult squash bugs per plant. Also, a sequential sampling for classifying adult squash bug density as below or above economic threshold was developed to assist in the decision-making process. The classification sampling plan is advantageous in that it requires smaller sample sizes to estimate the population status when the population density differs greatly from the action threshold. However, the plan may require excessively large sample sizes when the density is close to the threshold. Therefore, an integrated sequential sampling plan was developed using a combination of a fixed precision and classification sequential sampling plans. The integration of sampling plans can help reduce sampling requirements.     

Presence-absence sequential sampling plan for northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae), on caged-layer hens

Caged-layer hens were scored as infested or uninfested by visual examination of the vent region, and the number of northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago), per hen was estimated. The proportion infested and average number of mites per hen were shown to have a highly significant, positive relationship (r = 0.936). Sampling among houses within a flock, and rows and sections within houses were analyzed to determine the reliability of sampling a representative portion of a flock. Low- and moderate-tolerance treatment thresholds, based on percentage of hens infested with mites, were developed from sampling 1 wk before and 1 wk after acaricide treatments determined necessary by the producer. These thresholds were used to compare a fixed (single) sampling plan, a curtailed procedure of the fixed sampling plan, and a sequential sampling plan based on a sequential probability ratio test, by sampling 174 hens (the maximum number needed for the single sampling plan). The sequential sampling plan required fewer hen examinations on average to reach a treatment decision than did the other plans, depending on the infestation tolerance limits. Using a low tolerance approach in which infestations below 15% are considered noneconomic (safe threshold) and infestations above 25% are considered economically important (action threshold), as few as 5 hens required examination to reach a treatment decision. Sequential sampling plan graphs are presented for 2 tolerance threshold scenarios (a 15% safe-threshold paired with a 25% action threshold and a 35% safe-threshold paired with a 45% action threshold). These sequential sampling plans using presence absence assessments should greatly facilitate monitoring and treatment decisions for this important pest.     

Enumerative and binomial sequential sampling plans for the multicolored Asian lady beetle (Coleoptera: Coccinellidae) in wine grapes

To develop a practical integrated pest management (IPM) system for the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in wine grapes, we assessed the spatial distribution of H. axyridis and developed eight sampling plans to estimate adult density or infestation level in grape clusters. We used 49 data sets collected from commercial vineyards in 2004 and 2005, in Minnesota and Wisconsin. Enumerative plans were developed using two precision levels (0.10 and 0.25); the six binomial plans reflected six unique action thresholds (3, 7, 12, 18, 22, and 31% of cluster samples infested with at least one H. axyridis). The spatial distribution of H. axyridis in wine grapes was aggregated, independent of cultivar and year, but it was more randomly distributed as mean density declined. The average sample number (ASN) for each sampling plan was determined using resampling software. For research purposes, an enumerative plan with a precision level of 0.10 (SE/X) resulted in a mean ASN of 546 clusters. For IPM applications, the enumerative plan with a precision level of 0.25 resulted in a mean ASN of 180 clusters. In contrast, the binomial plans resulted in much lower ASNs and provided high probabilities of arriving at correct "treat or no-treat" decisions, making these plans more efficient for IPM applications. For a tally threshold of one adult per cluster, the operating characteristic curves for the six action thresholds provided binomial sequential sampling plans with mean ASNs of only 19-26 clusters, and probabilities of making correct decisions between 83 and 96%. The benefits of the binomial sampling plans are discussed within the context of improving IPM programs for wine grapes.     

Sequential sampling plan for Cameraria ohridella (Lepidoptera: Gracillariidae) on horse chestnut tree

A fixed precision sequential sampling plan for estimating the density of the horse chestnut, Aesculus hippocastanum L., leafminer Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae) was developed. Data were collected from 2002 to 2004 in Turin, northwestern Italy, with the aim of developing a sampling strategy for estimating populations of C. ohridella mines. Taylor's power law was used as a regression model. Sampling parameters were estimated from 216 data sets, and an additional 110 independent data sets were used to validate the fixed precision sequential sampling plan with resampling software. Covariance analysis indicated that there were not significant differences in the coefficient of Taylor's power law between heights of the foliage, months, and years. Dispersion patterns of C. ohridella were determined to be aggregated. The parameters of the Taylor's power law were used to calculate minimum sample sizes and sampling stop lines for different precision levels. Considering a mean density value of five mines per leaf, an average sample number of only 49 leaves was necessary to achieve a desired precision level of 0.25. As the precision level was increased to 0.10, the average sample size increased to 303 leaves. The sequential sampling plan should provide an effective management of C. ohridella in the urban areas, minimizing sampling time and cost, and at the same should be an effective tool to reduce insecticide applications and prevent the esthetic damage.     

Economic injury level and sequential sampling plan for Bemisia tabaci in outdoor tomato

Abstract:  This work aimed to determine the economic injury levels and to establish sequential sampling plans for nymphs and adults of the whitefly Bemisia tabaci Genn. (Sternorrhyncha: Aleyrodidae) in tomato fields. Densities of nymphs and adults, as well as crop yield were evaluated in 13 commercial tomato fields to determine the economic injury levels. The whitefly nymphs were sampled by direct counting in a leaf from the lower part of the canopy and the adults were sampled by beating an apical leaf against a white plastic tray. The sequential sampling plan was based on data collected in eight commercial tomato fields. The validation of the sequential sampling plan was carried out based on the curves of operational characteristics and average sample numbers. The decisions reached with the conventional and the sequential sampling plans in 21 commercial fields were compared for the intended validation of the sequential plan. The economic injury levels were four nymphs per leaf and one adult per tray. The decisions taken based on the sequential sampling plan were similar to those obtained through the conventional sampling plan. Most of the decisions taken with the sequential sampling plan were obtained through the minimum number of seven samples per field for nymphs and 11 samples per field for adults, with reductions of 84.44% and 54.17% in the number of samples required to reach a decision with the sequential sampling plan compared with the conventional sampling plan.     

Sampling plans for estimating pepper fruit damage levels by Oriental tobacco budworm,Helicoverpa assulta (Guenee), in hot pepper fields

Sequential sampling programs for the management of Oriental tobacco budworm, Helicoverpa assulta (Guenee), on red hot peppers were developed using the data of damaged pepper fruits by H. assulta. Taylor's power law indicated that the damaged pepper fruits were distributed randomly in hot pepper fields. A fixed-precision-level sequential sampling plan for classifying fruit damage density levels at a critical density of 2 damaged fruits per plant was developed to assist in decision making. The sequential classification sampling plan was evaluated using the operating characteristic (OC) and the average sample size (ASN) curves. The OC and ASN curves indicated that this sampling plan was robust and properly classified the population density. A resampling simulation demonstrated that average actual sampling precision value at D = 0.25 was ≤ 0.25. With sequential sampling for classifying the damaged fruit levels in terms of a critical density, sample size was fixed to 18 plants. The fixed-precision-level sequential sampling plan developed in this study should greatly enhance the monitoring efficacy and provide practical solutions suitable for reliable decision-making process in the management of H. assulta.     

Enumerative and binomial sequential sampling plans for soybean aphid (Homoptera: Aphididae) in soybean

Since the discovery of the soybean aphid, Aphis glycines Matsumura, in midwestern U.S. soybean, Glycine max L., in 2000, the aphid has become a significant economic pest. Basic information about estimating population density within fields is unknown. Therefore, we developed two sampling plans to efficiently characterize A. glycines densities. Enumerative and binomial sequential plans were developed using 89 data sets collected from 10 commercial fields sampled during 2001-2003. Re-sampling software was used to validate the enumerative plan on whole plant counts, based on Taylor's power law parameters (a = 9.157 and b = 1.543). For research applications, the enumerative plan was modified to provide an actual precision level of 0.10 (SE/mean), which resulted in an average sample number of 310 individual plants. For integrated pest management (IPM) purposes, we developed an enumerative plan with an actual precision of 0.25, which resulted in an average sample number of 38 individual plants. For IPM applications, the binomial plan will likely be more practical. Binomial plans were developed using two tally thresholds at five action thresholds. Final analysis of the operating characteristic curve for each plan indicated that the tally threshold of > or = 40 aphids per plant, and an action threshold of 0.837 (84% of the plants infested) provided the most correct treat (4%) and no-treat (95%) decisions, with very low incorrect treat (0.5%) and no-treat (0.5%) decisions. A tally threshold of > or = 40 aphids per plant and action thresholds of 84% of plants infested is equivalent to a mean density of 250 aphids per plant, a recently recommended economic threshold. Using this threshold, the minimum required sample number for the binomial plan was 11 plants.     

Sampling a weighted pest complex: caterpillars in North Korean cabbage (Brassica oleracea var. capitata) crops

The lepidopteran pests Plutella xylostella L. (Plutellidae) and Pieris rapae L. (Pieridae: Pierini) are responsible for major yield losses of cabbage, Brassica oleracea L. (Brassicaceae), in North Korea. Preliminary integrated pest management (IPM) programmes using economic thresholds (ETs) to schedule insecticide applications have proved promising and have demonstrated marked increases in yield compared to standard farming practice, which relies heavily on synthetic insecticides. To use ETs effectively on a routine basis, farmers need efficient yet sufficiently precise methods of surveying crops for pests. Here we construct and validate binomial sequential sampling plans for the two-species pest complex and for P. rapae alone. The recommended plans would be practical to implement, demanding maximum sample sizes below 50 plants, and proved very slightly conservative with respect to classifying the population relative to the ET (i.e., they were slightly more likely to suggest control at the ET than not).     

Within-plant distribution and binomial sampling of Pentalonia nigronervosa (Hemiptera: Aphididae) on banana

The banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae), infests banana (Musa spp.) worldwide. Pentalonia nigronervosa is the vector of Banana bunchy top virus (family Nanoviridae, genus Babuvirus) the etiological agent of Banana bunchy top disease (BBTD). BBTD is currently the most serious problem affecting banana in Hawaii. Despite the importance of this vector species, little is known about its biology or ecology. There are also no sampling plans available for P. nigronervosa. We conducted field surveys to develop a sampling plan for this pest. Ten plots were surveyed on seven commercial banana farms on the island of Oahu, HI, for the presence of P. nigronervosa on banana plantlets. We found aphids more frequently near the base of plants, followed by the newest unfurled leaf at the top of the plant. Aphids were least likely to be located on leaves in between the top and bottom of the plant. Aphid infestation on surveyed plots ranged from 8 to 95%. We developed a sequential binomial sampling plan based on our surveys. We also discovered that the within-plant distribution of P. nigronervosa is an important factor to consider when sampling for this pest. Our sampling plan will assist in the development of sustainable management practices for banana production.     

A dynamic binomial sequential sampling plan for Plutella xylostella (Lepidoptera: Plutellidae) on broccoli and cauliflower in Australia

Binomial sequential sampling plans have been used widely for monitoring invertebrate pest populations. Such plans are typically based upon a single action threshold (AT), which represents the level of infestation that the grower is prepared to accept before using a control measure. For many cropping systems this acceptable infestation level is likely to vary, being dependent on factors such as the growth stage of the crop and the value or demands of the destination market (e.g., local or high-quality export). We developed and validated a computer-assisted plan that uses a dynamic AT. The plan has been developed for monitoring diamondback moth, Plutella xylostella (L.) on broccoli (Brassica oleracea variety botrytis L.) and cauliflower (Brassica oleracea variety botrytis L.), but the concepts and methodologies could be readily applied to other systems.     

Cost-effective binomial sequential sampling of western bean cutworm, Striacosta albicosta (Lepidoptera: Noctuidae), egg masses in corn

Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a native pest of dry beans (Phaseolus vulgaris L.) and corn (Zea mays L.). As a result of larval feeding damage on corn ears, S. albicosta has a narrow treatment window; thus, early detection of the pest in the field is essential, and egg mass sampling has become a popular monitoring tool. Three action thresholds for field and sweet corn currently are used by crop consultants, including 4% of plants infested with egg masses on sweet corn in the silking-tasseling stage, 8% of plants infested with egg masses on field corn with approximately 95% tasseled, and 20% of plants infested with egg masses on field corn during mid-milk-stage corn. The current monitoring recommendation is to sample 20 plants at each of five locations per field (100 plants total). In an effort to develop a more cost-effective sampling plan for S. albicosta egg masses, several alternative binomial sampling plans were developed using Wald's sequential probability ratio test, and validated using Resampling for Validation of Sampling Plans (RVSP) software. The benefit-cost ratio also was calculated and used to determine the final selection of sampling plans. Based on final sampling plans selected for each action threshold, the average sample number required to reach a treat or no-treat decision ranged from 38 to 41 plants per field. This represents a significant savings in sampling cost over the current recommendation of 100 plants.     

Fixed precision sampling plans for white apple leafhopper (Homoptera: Cicadellidae) on apple

Constant precision sampling plans for the white apple leafhopper, Typhlocyba pomaria McAtee, were developed so that it could be used as an indicator species for system stability as new integrated pest management programs without broad-spectrum pesticides are developed. Taylor's power law was used to model the relationship between the mean and the variance, and Green's constant precision sequential sample equation was used to develop sampling plans. Bootstrap simulations of the sampling plans showed greater precision (D = 0.25) than the desired precision (Do = 0.3), particularly at low mean population densities. We found that by adjusting the Do value in Green's equation to 0.4, we were able to reduce the average sample number by 25% and provided an average D = 0.31. The sampling plan described allows T. pomaria to be used as reasonable indicator species of agroecosystem stability in Washington apple orchards.     

Sequential sampling of Aphis gossypii Glover (Hemiptera: Aphididae) and Frankliniella schultzei Trybom (Thysanoptera: Thripidae) on cotton crop

The goal of this research was to use the sequential probability ratio test to establish a sequential sampling plan for Aphis gossypii Glover and Frankliniella schultzei Trybom infesting cotton. Field work was conducted at the agricultural experimental station of the Universidade Federal da Grande Dourados during the 2003/2004 and 2004/2005 agricultural years. Aphid colonies and individual thrips in the sampling area were counted and their numbers were recorded. The spatial distribution pattern of A. gossypii and F. schultzei in the cotton culture was aggregated. Sequential sampling plans were developed for aphids and thrips with type I and type II errors set at 0.1, common Kc = 0.6081 (aphids) and = 0. 9449 (thrips), and safety and management levels of 20% (aphids) and 40% (thrips) of infested plants. The sampling plans resulted in two decision boundaries for each species, as follows: the upper boundary, indicating when management (population control) is recommended: S1 = 4.6546 + 0.2849n (aphids), and S1 = 3.6514 + 0.1435n (thrips); and the lower boundary, indicating when population control is not necessary: S0 = -4.6546 + 0.2849n (aphids) and S0 = - 3.6514 + 0.1435n (thrips). The highest probability of error when making a decision was 3% for aphids and 2% for thrips, respectively. The maximum number of samples required to reach a decision was 63 for aphids and 95 for thrips.     

Accounting for cluster sampling in constructing enumerative sequential sampling plans

Green's sequential sampling plan is widely used in applied entomology. Green's equation can be used to construct sampling stop charts, and a crop can then be surveyed using a simple random sampling (SRS) approach. In practice, however, crops are rarely surveyed according to SRS. Rather, some type of hierarchical design is usually used, such as cluster sampling, where sampling units form distinct groups. This article explains how to make adjustments to sampling plans that intend to use cluster sampling, a commonly used hierarchical design, rather than SRS. The methodologies are illustrated using diamondback moth, Plutella xylostella (L.), a pest of Brassica crops, as an example.