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<p>Corn stunt complex disease (CSCD) poses a severe threat to maize production in Brazil, with persistent outbreaks and substantial crop losses. This disease complex involves two bacterial pathogens, the maize bushy stunt phytoplasma (“<i>Candidatus</i> Phytoplasma asteris”) and <i>Spiroplasma kunkelii</i>, both transmitted by the corn leafhopper <i>Dalbulus maidis</i> (Hemiptera: Cicadellidae). Studies to assess the epidemic dynamics of CSCD are scarce. This study aimed to comprehensively assess disease incidence and progression in experimental fields in Chapecó, Santa Catarina, Brazil. Symptom assessments were done on 2,860 and 6,336 maize plants in the 2018/19 and 2019/20 seasons, respectively, with binary data recorded for the presence (1) or absence (0) of symptoms during crop development. The observed CSCD incidence was 7.62% and 4.58% for the each season, respectively. Goodness-of-fit comparison indicated that the 2018/19 data confirmed to a binomial distribution, consistent with a random spatial pattern, while the 2019/20 data were better described by a beta-binomial distribution, indicating aggregation (clustered distribution) among infected plants. This shift from a random to an aggregated pattern highlights the progression from widespread primary vector-borne inoculation to localized secondary disease spread within the field. Semivariogram analysis confirmed the uniform distribution of diseased plants across the study fields. Geostatistical examination of the field scale spatial distribution of diseased plants unveiled low spatial dependence, with an index of aggregation around 1 and an intracluster correlation coefficient of ≤ 0.03. Although visual assessments were conducted at the late vegetative stage (63–81 days after sowing), the long incubation period of the pathogens indicates that primary infections likely occurred early in the crop cycle, at the V1–V3 stages. The absence of pronounced spatial clustering emphasizes the critical significance of a widespread distribution throughout the field, highlighting the imminent risk of rapid plant infestation and underscoring the necessity for early-season control measures to prevent potential extensive damage.</p>

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Spatial distribution and initial spread of corn stunt complex disesase in Santa Catarina, Brazil

  • 期刊论文

  • 发表日期：

    2026年6月29日

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  • Maria Cristina Canale,
  • Rodolfo Vargas Castilhos,
  • Marcos Vinicius Silva de Andrade,
  • Cristiano Nunes Nesi,
  • Mohamed Cassim Mohamed Zakeel

摘要

Corn stunt complex disease (CSCD) poses a severe threat to maize production in Brazil, with persistent outbreaks and substantial crop losses. This disease complex involves two bacterial pathogens, the maize bushy stunt phytoplasma (“Candidatus Phytoplasma asteris”) and Spiroplasma kunkelii, both transmitted by the corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae). Studies to assess the epidemic dynamics of CSCD are scarce. This study aimed to comprehensively assess disease incidence and progression in experimental fields in Chapecó, Santa Catarina, Brazil. Symptom assessments were done on 2,860 and 6,336 maize plants in the 2018/19 and 2019/20 seasons, respectively, with binary data recorded for the presence (1) or absence (0) of symptoms during crop development. The observed CSCD incidence was 7.62% and 4.58% for the each season, respectively. Goodness-of-fit comparison indicated that the 2018/19 data confirmed to a binomial distribution, consistent with a random spatial pattern, while the 2019/20 data were better described by a beta-binomial distribution, indicating aggregation (clustered distribution) among infected plants. This shift from a random to an aggregated pattern highlights the progression from widespread primary vector-borne inoculation to localized secondary disease spread within the field. Semivariogram analysis confirmed the uniform distribution of diseased plants across the study fields. Geostatistical examination of the field scale spatial distribution of diseased plants unveiled low spatial dependence, with an index of aggregation around 1 and an intracluster correlation coefficient of ≤ 0.03. Although visual assessments were conducted at the late vegetative stage (63–81 days after sowing), the long incubation period of the pathogens indicates that primary infections likely occurred early in the crop cycle, at the V1–V3 stages. The absence of pronounced spatial clustering emphasizes the critical significance of a widespread distribution throughout the field, highlighting the imminent risk of rapid plant infestation and underscoring the necessity for early-season control measures to prevent potential extensive damage.