CLIMATOLOGICAL ELEMENT RELATIVE HUMIDITY AS POTENTIAL INDICATOR FOR CROPS DISEASES IN PARANÁ STATE

The relative humidity (%) of the air expresses the amount of vapor of water existing in the atmosphere at a given time relative to the maximum amount of water vapor that could be contained in air. The objective of this study was to carry out to verify the potential of RH above 90 % as an indicator of the occurrence of the key fungal diseases exist in Paraná state, Brazil, of remarkable crops cultivated in Paraná state (soybean and wheat) and perennial (grape fruit), aiming at rationalizing the use of fungicides and helping the farmer in decision-making. For that, daily data of RH weather stations located at Londrina (North), Palmas (South), Cascavel (West) Guarapuava (Center), Guaratuba (East), Paranavaí (Northwest) and Ponta Grossa (South Center) were grouped from a historical average from 1975 to 2021. Analyzes of frequency were carried out by a moving 10 days scales (for example, September 1st to 10th; September 2nd to 11th; September 3rd to 12th and so on. This procedure avoids the omission of consecutive 10 days scales periods with relative humidity above 90 % occur when considering only the 1-10, 11-20, and 20-30 deciles of each month, from January to December from 1975 to 2021. There are risks of incidences of phytosanitary problems in Paraná state for annual cycle crops, soybean and wheat crops, especially for grape fruits which are more susceptible to diseases due to a high number of hours with relative humidity above 90 %. However, due the climate change, the crops are more susceptible to fungal diseases, especially for grape fruits due the excess of rainfall increase the wetness period on the leaf of plants.