ST. CLOUD (AP) - Some maple syrup producers in central Minnesota are worried that last weekend's warmup could affect production.

Temperatures were near 70 degrees over the weekend. The weather is similar to the 2012 syrup production season, which is one of the lowest on record.

St. John's University biology professor Steve Saupe says that 50-degree highs and 20-degree lows are ideal for syrup operations. Such conditions cause suction in trees that helps replace fluids lost in the daytime.

Saupe, who's also a board member at the Minnesota Maple Syrup Producers Association, says warmer temperatures during the sap run's peak mean more mold and bacteria growth. And once buds appear on trees, the sap takes on an off-taste.

Saupe says the sap run typically begins in earnest around March 20.