Reports of an impending heat wave can conjure up dire images of corn leaves pointing skyward and vines browning on cracked earth.
Pennsylvania experienced its first major heat wave of the summer last week, with Harrisburg hitting 90 degrees every day of the week, peaking at 97 on July 18, according to the National Weather Service.
Fortunately, the heat wave was “long enough to make us a little concerned, but not long enough to have any lasting effect,” said Lancaster County Extension educator Tim Elkner.
Although the heat may have caused some leaves to curl a little, corn has tropical origins and can withstand some heat, said Jeff Graybill, a Lancaster County Extension agronomy educator.
High heat causes plants to pull moisture through their systems faster to cool themselves by evaporation.
“Anything above 80 is not really conducive of additional growth” because it forces the corn to expend energy on cooling rather than developing kernels, he said.
Over 86 degrees, pollen survives for only a few hours. Late corn plantings, accounting for perhaps 15 to 20 percent of local corn acreage, were still pollinating last week. These fields might see some barrenness and missing kernels, he said.
If conditions are hot and dry, the kernels could abort or end up much smaller than normal, diminishing yields.
“That’s not happened yet, but we need timely rains,” about an inch every 10 days, Graybill said.
The tobacco crop, too, has benefited from the sun.
“Tobacco actually likes a period of warm, dry weather,” he said.
Those conditions toughen the leaves and give them more weight, he explained. If the heat spell had become prolonged, the leaves might have stayed small and lost some yield.
The weather in the last two weeks of July has great importance to yields because agronomic crops are setting their fruit during these weeks, he said.
Graybill had predicted that this season would be ripe for disease, and gray leaf spot has been a notable issue.
The dryness significantly reduced the incidence of disease, which had spiked with the earlier wet weather. Rain could allow diseases to flare up again, he said.
Diseases “do have a toehold” in the soil, and the ailments are visible on the lower leaves in almost any cornfield, he said.
Graybill hopes no-till practices will help crops in hot times by keeping cover on the ground to preserve moisture. Good weed control can also help in hot weather, saving the crops from having to compete for food and water, he said.
The heat also helped grass and grain growers. The USDA reported that “harvesting of wheat and barley really took off” last week after wetter conditions had postponed harvesting.
Mark Madden, a Sullivan County Extension educator, said farmers made a lot of hay in his area last week, “much to the discomfort of the operators.”
The hay was still a little hard to get dry and was a little late, but the second cutting should look good, he said.
Some crops were showing signs of heat stress in the western part of the county, but the crops benefited from the wet period that preceded the heat, he said.
Soybeans, a small but expanding crop in Sullivan County, are also looking good, he said.
Vegetables had more mixed results with the heat.
Tomatoes and peppers are vulnerable in hot weather, Elkner said.
If the crops did not get irrigated enough, growers might see bottom-end rot in a few weeks, but by that time they will not be able to do anything about it, he said.
Without adequate leaf cover, bell peppers in particular can get sunburned. This will be immediately observable, he said.
On the other hand, the cucumbers at the Landisville Extension farm “really grew a lot last week,” he said.
Elkner said he regretted not getting a cantaloupe from a farm stand last week. Sunny weather produces “good, sweet melons,” he said.
The record rainfall in June helped lessen the detrimental effects of the heat wave, but crops will soon need rain again or they may show heat and drought stress, Graybill said. If the fields dry out too much after so much rain, the ground will harden and be difficult for the roots to penetrate.
The half-dozen farmers interviewed by The Citizens Voice newspaper in Luzerne County agreed with Graybill that rain will be key to surviving after the heat wave.
Albert Broyan, of Broyan’s Farm Produce in Nescopeck, told The Citizens Voice, “If we don’t get rain, then I have to irrigate out of our spring pond and that’s all extra work. If we have to, we pump water, but it’s very labor-intensive.”
A storm during the night of July 22-23 provided some relief to many Pennsylvania farmers. It delivered at least an inch of rain across the state.
The National Weather Service reported that the storm dumped more than 7 inches on parts of Lebanon County.
That sent Daryl Alger, a crop farmer at Lebanon-based Mark Hershey Farms, out the next morning checking for damage from yet another dramatic weather change.
“It just kept raining” last night, he said while inspecting a field.
Alger expected some erosion but said the storm, which did not have high winds or lightning, was “nothing too alarming.”