Publications by authors named "Norman C Leppla"

9 Publications

  • Page 1 of 1

Analysis of the Spatial Distribution and Development of Sequential Sampling Plans for Heteropteran-Associated Fruit Injury in Florida Peaches.

J Econ Entomol 2021 Jun 14. Epub 2021 Jun 14.

USDA-ARS Southeastern Fruit and Tree Nut Research Station, 21 Dunbar Road, Byron, GA 31008, USA.

Catfacing and gummosis/sap-type injury associated with a heteropteran pest complex were sampled at five peach orchards in southern Florida during two consecutive growing seasons. Trapping and visual surveys indicate that Euschistus servuis (Say) (Hemiptera: Pentatomidae) was the dominant heteropteran pest in the study orchards. The spatial arrangement of injury indicated a random distribution, as determined by Taylor's power law. Spatial analysis by distance indices indicated a random arrangement of fruit injury in a majority of the sample site × date combinations and analysis of local clustering did not provide evidence of patches of fruit injury occurring near orchard borders. The coefficients from Taylor's power law were used to develop sequential sampling plans based on hypothetical injury thresholds. Sequential sampling plans were compared to a simple random sample of 15 sample units using a simulation approach. The sequential sampling plan was able to achieve equivalent levels of accuracy when compared to the 15-unit fixed sampling plan while reducing the number of sample units required to an average of 7.99. The sequential sampling plans developed in this study are an improvement over simple random sampling; however, further research is needed to determine how to best implement sequential sampling of fruit injury in Florida peach orchards to better inform management decisions.
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http://dx.doi.org/10.1093/jee/toab106DOI Listing
June 2021

Wireworm (Coleoptera: Elateridae) Species Composition and Management in Sweet Potato Grown in North Florida Using Chemical Insecticides and Entomopathogenic Nematodes.

Environ Entomol 2020 12;49(6):1415-1426

Entomology and Nematology Department, UF-IFAS, Gainesville, FL.

Wireworms are immature stages of click beetles (Coleoptera: Elateridae) and are considered a serious threat to sweet potato production in the southern United States. The major wireworm species collected in North Florida sweet potato fields in 2017 and 2018 were Conoderus scissus, C. rudis, C. amplicollis, and C. falli. These species vary in their behavior and biology. During a 2-yr study period, we conducted two insecticide field trials using eleven insecticides belonging to organophosphates, neonicotinoids, pyrethroids, and botanical classes, and three field trials using entomopathogenic nematode (EPN) species to control wireworms. In 2017, all insecticide treatments significantly reduced new feeding holes and total holes (old + new + other) as compared to the untreated control. In 2018, the result was similar with a few variations. In both years, all insecticides showed a percentage reduction in wireworm damage holes (2017: 34.88-96.19%; 2018: 12.38-97.02%) with the highest by Regent. In the EPN field study, one application of EPN near planting significantly reduced soil insects. In a laboratory study conducted at the Tropical Research and Education Center, UF-IFAS, chlorpyrifos caused higher percentage mortality of C. rudis (55.5%) than C. scissus (22.2%). At the present experiment rates, none of the insecticides caused the mortality of C. amplicollis. Heterorhabditids strain 'FL-2122' was more susceptible to chlorpyrifos than other strains of EPN.
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http://dx.doi.org/10.1093/ee/nvaa113DOI Listing
December 2020

Trap-Based Economic Injury Levels and Thresholds for Euschistus servus (Hemiptera: Pentatomidae) in Florida Peach Orchards.

J Econ Entomol 2020 06;113(3):1347-1355

USDA-ARS Southeastern Fruit and Tree Nut Research Station, Byron, GA.

Populations of the brown stink bug, Euschistus servus (Say), in Florida peach orchards were monitored during the 2017 and 2018 growing seasons using yellow pheromone-baited pyramid traps. Peaches were evaluated at harvest for the presence of stink bug injury. A relationship between E. servus trap capture and fruit injury was used to estimate the economic injury level (EIL) for varying scenarios of crop price, per-hectare yield, and control costs. Economic thresholds were then set based on observed E. servus population trends and expected rates of increase. Thresholds were lowest in the period immediately following shuck split due to the rapid increase in E. servus populations during this period. Euschistus servus trap capture trended downward at the time of harvest. Therefore, increased E. servus management early in the Florida peach season provides the greatest overall benefit, whereas late season populations decline independent of management actions. The proposed EIL for Florida peaches determined by this study is 5.53 E. servus per trap over a 14-d trapping period, which was surpassed in only 16 of the 60 recorded trapping periods. This suggests that the current recommended spray frequency may not be economically justified.
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http://dx.doi.org/10.1093/jee/toaa044DOI Listing
June 2020

Effect of Ephestia kuehniella (Lepidoptera: Pyralidae) Larval Diet on Egg Quality and Parasitism by Trichogramma brassicae (Hymenoptera: Trichogrammatidae).

J Insect Sci 2019 Jul;19(4)

USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology (CMAVE), Gainesville, FL.

Trichogramma spp., among the most common parasitoids used for augmentation biological control, often are mass-reared on eggs of the Mediterranean flour moth, Ephestia kuehniella (Zeller). To evaluate removal of nutritional components from the E. kuehniella larval diet and reduce production costs, colonies were maintained using one of three diets: a standard diet consisting of eight ingredients, a reduced diet containing whole wheat flour, glycerol, and Brewer's yeast, or a third minimal diet of only whole wheat flour. The standard diet sustained the fastest larval development, female pupae with the greatest mass, the highest level of adult emergence, and production of the most eggs per female. Eggs from moths reared as larvae on the standard or reduced diet had equivalent mass, length, and percent hatch. Females from larvae fed the minimal diet produced eggs with the least mass that were shorter and had the lowest percent hatch. Eggs from the three E. kuehniella colonies were exposed separately to Trichogramma brassicae Bezdenko females to determine their acceptance for oviposition. More of the eggs from the standard diet were parasitized by the females, eggs from the reduced and minimal diets being less acceptable. The percent emergence of the parasitoids was the same regardless of diet; however, the largest wasps emerged from the standard diet eggs and a greater proportion of them were females. Consequently, the standard E. kuehniella larval diet resulted in the highest rate of reproduction and robust eggs that produced superior T. brassicae wasps.
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http://dx.doi.org/10.1093/jisesa/iez076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6638262PMC
July 2019

Tritrophic Interactions of Cucumber Cultivar, Aphis gossypii (Hemiptera: Aphididae), and Its Predator Hippodamia variegata (Coleoptera: Coccinellidae).

J Econ Entomol 2019 08;112(4):1774-1779

Moghan College of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran.

The melon aphid, Aphis gossypii Glover, is a cosmopolitan pest that infests and damages a wide range of crop plants, especially cucurbits. It is a host of the coccinellid predator, Hippodamia variegata (Goeze), that has the potential to suppress the pest on leaves of cucumber plants grown in greenhouses. Melon aphids were reared on either Storm or Khasib cucumber cultivars to determine whether there would be a difference in their development and reproduction. The aphids from each cultivar were fed to H. variegata adults to assess their effects on the life history of the predator. The aphid population reared on Khasib leaves increased faster than the population on Storm leaves; however, the predators fed aphids from Storm leaves had a higher rate of population growth. Thus, the intrinsic rate of increase and net reproductive rate were greater for aphids reared on Khasib leaves but lower for H. variegata fed those aphids compared with aphids reared on the Storm cultivar. Additionally, clean and aphid-infested leaves from both cultivars were analyzed for total flavonoids, phenol, and chlorophyll, and the density of leaf trichomes was measured. The Storm leaves contained higher amounts of flavonoids and phenol, less chlorophyll, and a greater density of trichomes. Regardless of cucurbit cultivar, aphid feeding increased the flavonoids and phenol content and decreased the amount of chlorophyll.
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http://dx.doi.org/10.1093/jee/toz072DOI Listing
August 2019

History of the International Organization for Biological Control Global Working Group on Mass Rearing and Quality Assurance.

J Insect Sci 2019 Mar;19(2)

Laboratory of Agrozoology, Department of Plants and Crops, Ghent University, Coupure Links, Ghent, Belgium.

The International Organization for Biological Control Global Working Group on Mass Rearing and Quality Assurance (MRQA) was established in 1980 as the Working Group on Quality Control (WGQC) to assure success of insect mass rearing for pest management that was being developed in the 1950s and 1960s. Due mostly to the efforts of WGQC, quality control became institutionalized in several insect mass rearing facilities during the 1980s. After addressing autocidal control programs, the WGQC concentrated on entomophagous insects, especially testing the quality of commercial biological control products. Universal Implementation of Quality Control for Mass-Reared Arthropods was finally achieved in the 1990s, having encompassed all aspects from insect production to field application and evaluation. This increased scope prompted a name change from WGQC to Arthropod Mass Rearing and Quality Control (AMRQC). Subsequently, the scope of the Working Group was expanded again and it was renamed MRQA to include a range of applications for mass-reared beneficial invertebrates. The geographic range of MRQA recently was extended beyond North and South America and Europe to include India. This expansion continued as insects for food and feed, networking and instruction, and legal and ethical issues were added to the most recent workshop held in Mexico. Thus, the MRQA continues to evolve as additional invertebrate organisms are mass produced for both established and novel applications.
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http://dx.doi.org/10.1093/jisesa/iey125DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403476PMC
March 2019

Life Table Parameters and Oviposition Preference of Plutella xylostella (Lepidoptera: Plutellidae) on Six Brassicaceous Crop Plants.

J Econ Entomol 2019 03;112(2):932-938

Entomology and Nematology Department, University of Florida, Gainesville, FL.

The oviposition preferences and larval development of the diamondback moth, Plutella xylostella (L.), were evaluated in the laboratory on canola, Brassica napus L. and five Brassica oleracea L. cultivars: broccoli, cauliflower, kohlrabi, red cabbage, and white cabbage. Adults from larvae fed on cauliflower and canola lived longer than those fed other cultivars, whereas the oviposition period was longest for cauliflower (5.54 d) and shortest for females reared on kohlrabi (2.68 d). The oviposition period for canola and broccoli was relatively long compared with white cabbage, red cabbage, and kohlrabi. Significantly more eggs were oviposited on cauliflower (163.71 eggs per female) than on canola (139.23 eggs per female) and the other B. oleracea cultivars, although broccoli also was preferred over white cabbage, red cabbage, and kohlrabi. The differences in total development times of immature stages on Brassica plants tested were significant, being shortest on cauliflower (17.60 d) and longest on kohlrabi (21.12 d). The moths reared on cauliflower and Kohlrabi, respectively, had the highest (65.46 offspring per individual) and lowest (12.71 offspring per individual) R0 values. Also, moths reared on cauliflower had significantly higher r value (0.200 d-1). The lowest r value was obtained when individuals fed on Kohlrabi (0.105 d-1). In free-choice situation, oviposition on canola and cauliflower was similar, but numbers of eggs deposited on these plants exceeded other plants. The amounts of glucosinolate were significantly greater in canola and cauliflower, intermediate in white cabbage, lower in broccoli and kohlrabi, and the lowest in red cabbage.
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http://dx.doi.org/10.1093/jee/toy384DOI Listing
March 2019

Linear Dispersal of the Filth Fly Parasitoid Spalangia cameroni (Hymenoptera: Pteromalidae) and Parasitism of Hosts at Increasing Distances.

PLoS One 2015 10;10(6):e0129105. Epub 2015 Jun 10.

Entomology and Nematology Department, University of Florida, PO Box 110620, Gainesville, Florida, 32611, United States of America.

Release of parasitic wasps (Hymenoptera: Pteromalidae) as biological control agents for house flies and stable flies in livestock confinements has had variable success. In part, this may reflect a lack of knowledge regarding the optimal distance to be used between parasitoid release stations. In the current study, we assessed the effect of linear distance on host parasitism by the wasp Spalangia cameroni Perkins. In open fields at distances ranging from 1 m to 60 m from a central point, house fly puparia were placed in a mixture of pine shavings soiled with equine manure, urine, and alfalfa hay. Releases of S. cameroni then were made using a 5:1 host: parasitoid ratio. Host pupae were parasitized at all distances, with the highest rate of total parasitism (68.9%) recorded ≤ 5 m from the release site. Analyses of results using non-linear and linear models suggest that S. cameroni should be released in close proximity to host development areas. Additionally, releases may not be suitable in pasture situations where long-distance flight is required for control. However, further testing is needed to examine the effect of density-dependent dispersal and diffusion of S. cameroni.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0129105PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4465169PMC
April 2016

Post-hire asthma among insect-rearing workers.

J Occup Environ Med 2012 Mar;54(3):310-7

Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.

Objective: To evaluate the incidence of post-hire asthma (PHA) among insect-rearing workers, defined as asthma, the symptoms of which appeared after hire at the current workplace.

Methods: We surveyed the health of workers at three insect-rearing facilities and an associated office facility. We calculated the incidence and estimated hazard ratios for PHA.

Results: Post-hire asthma incidence in 157 insect-rearing workers was 16.2 per 1000 person-years compared with 9.2 per 1,000 person-years in 70 office workers. Workers with predominant exposure to Lepidoptera had an incidence of 26.9 per 1000 person-years and a hazard ratio of 5.5 (95% confidence interval: 1.6 to 23.9) adjusted for sex, race, and parental asthma. In contrast, the presence of specific immunoglobulin E to Lepidoptera antigens was not associated with PHA.

Conclusion: Insect-rearing workers had a high incidence of PHA, primarily accounted for by workplace exposure to Lepidoptera.
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http://dx.doi.org/10.1097/JOM.0b013e31823fe098DOI Listing
March 2012
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