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October 4, 2012

Adverse Spring Weather Impacts Crops in R. Grande do Sul

Adverse springtime weather in the state of Rio Grande do Sul has been detrimental for the developing wheat crop and the recently planted corn crop in the state. Over the last several weeks there have been repeated episodes of heavy rain, hail, strong winds, and even freezing temperatures.

Springtime rains are a common occurrence in southern Brazil, but the freezing temperatures, which were even accompanied by light snow at the higher elevations, are rare indeed. Unfortunately, more heavy rain and hail is forecasted again to move across the state this week. Heavier than normal rainfall is expected in southern Brazil whenever there is a transition from La Nina to El Nino, but this spring, the rains have been exceptionally heavy.

The wheat crop in the state has been the crop most impacted by the weather. There have been widespread reports of hail damage to the wheat crop across the state, but the most severe damage was restricted to localized areas. The strong winds accompanying the hail also resulted in lodging of the wheat.

The most unusual aspect of this year's spring weather has been the freezing temperatures reported last week all across the state. If there is a frost or freezing temperatures in southern Brazil, it usually occurs during the coldest months of July or August. Having a frost in southern Brazil during late September is a very rare event for the state.

The cold temperatures caused damage to the wheat because the crop had already entered into a sensitive stage of development. When the cold temperatures hit, approximately 50% of the wheat was flowering and 40% had already entered into the grain filling period. Freezing temperatures during either of these two stages can cause damage, but it usually takes a week or two to determine the extent of the damage. State agricultural officials have announced that they will survey the wheat crop in the state next week to determine the extent of the damage.

Some early planted corn was also damaged by the cold temperatures. The earliest planted corn that had five or more fully developed leaves was probably damaged enough that the corn will need to be replanted. If the corn had less than five leaves, it will probably regrow new leaves and will not need to be replanted. At the time of the freezing temperatures, approximately 35% of the state's 2012/13 corn crop had already been planted.

Temperatures across the state last week were in the upper 20's and low temperature records were set in many locations.