Comparative Epidemiology of Three Virus Diseases on Zucchini Squash

Abstract

Zucchini yellow mosaic virus (ZYMV), Papaya ringspot virus – type W (PRSV‐W) and Zucchini lethal chlorosis virus (ZLCV) cause important diseases on zucchini squash crops in Brazil. ZYMV and PRSV‐W belong to the genus Potyvirus and are transmitted by aphids, whereas ZLCV belongs to Tospovirus and is transmitted by the thrips Frankliniella zucchini. These three viruses may occur simultaneously in the field, and the epidemiology of the corresponding diseases may be determined by interactions among viruses, hosts and vectors. In this work, the progress of the diseases caused by these viruses was studied over a temporal and geographic range for three planting seasons (PS). For the lethal chlorosis (ZLCV), a monomolecular model was found to be the best fit for the data, though only during the third PS. For data collected during the first two PS, the Gompertz model was found to fit the data best. The spatial distribution of disease indicated disease aggregation at the end of the crop cycle. For the yellow mosaic (ZYMV), the model that best fit in the 1st PS was the logistic and in the 2nd and 3rd PS was monomolecular. The spatial pattern of the disease was random when the disease incidence was low but aggregated when the disease incidence was high. The common mosaic (PRSV‐W) showed the lowest incidence in all three PS. An exponential model was the best fit for data collected during all PS, and the spatial pattern of the disease was random. Interactions among the three viruses apparently did not result in changes in the epidemiology of the diseases. Removal of sources of inoculum and planting at an unfavourable time for reproduction of virus vectors are the two main measures recommended for the control of these diseases. The use of insecticide is indicated only for the control of the F. zucchini.

IDENTIFICATION AND EFFECTS OF MIXED INFECTION OF Potyvirus ISOLATES WITH Cucumber mosaic virus IN CUCURBITS

“…Kim et al (2010) observed that the symptoms in C. pepo plants doubly infected with ZYMV and CMV in the field were peculiarly similar to those symptoms caused by CMV alone. According to Moreira, Filho and Rezende (2015) mixed virus infections in cucurbits are very common in natural conditions and can present biological and epidemiological variations, resulting in several effects on the infected hosts, as well as distinct levels of virus accumulation in the infected host tissues. In others mixed infections with CMV and species of the Potyvirus genus, CMV was present in low concentrations as assessed by PTA-ELISA; herein, the virus was also detected by RT-PCR (Figure 1).…”

Can Winged Aphid Abundance Be a Predictor of Cucurbit Aphid-Borne Yellows Virus Epidemics in Melon Crop?

“…In the present study, CABYV progress over time (expressed as days after planting or fleece removal) was successfully described by the logistic model. This model commonly used to describe the temporal dynamics of plant viruses [16][17][18][19] has three parameters (µ, γ, α) with a biological sense (epidemic precocity, carrying capacity, epidemic speed) that were considered as dependent variables in statistical analyses and data mining. Parameters were uncorrelated.…”