Heat & Light Stress

Heat & Light Stress

Heat & Light Stress. I’m Greg Martin with today’s Fruit Grower Report.

When it comes to stress, humans are not the only ones that exhibit symptoms. Larry Schrader with WSU says that tree fruit can easily suffer from heat and light stress.

SCHRADER: I think anytime we have a maximum air temperature exceeding 90 degrees Fahrenheit we begin to impose stress on fruit and I’m going to talk principally about apples. You add to that the very high light intensities that we experience on almost a daily basis. I’ve listed a photon flux density of 2200. I’ve actually measured more than that on a number of days. 

He says that 2000 is considered full sunlight.

SCHRADER: You see we’re maybe 10% above that so that exacerbates the situation and creates even more stress. And you add to that the low relative humidities we experience and the days we have little or no wind. All of those are conditions that really become a stress environment for the fruit.

All that means is that fruit is going to start experiencing a bit of heat stress.

SCHRADER: The fruit experiences fruit surface temperatures or FST’s that run 20 to 30 degrees Fahrenheit above the maximum air temperature. So if you’ve got a 90 degree day we’re talking fruit surface temperatures that 110 to 120 degrees.

More tomorrow.

That’s today’s Fruit Grower Report. I’m Greg Martin on the Ag Information Network.

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