Heat stress noted among many dryland crops as high temperatures persist

• Writer: Adam Russell, 903-834-6191, adam.russell@ag.tamu.edu
• Contact: Dr. Lee Tarpley, 409-752-2741, ltarpley@tamu.edu
  Dr. Ted Wilson, 409-752-3045, lt-wilson@tamu.edu

BEAUMONT — Heat is stressing crops, pastures and gardens throughout Texas.

The majority of Texas A&M AgriLife Extension Service districts reported daytime temperatures exceeding the high 90s, with several reporting temperatures beyond 105 degrees. Increased daytime and nighttime heat is taking a toll on croplands and forages as moisture levels in non-irrigated fields continue to decline.

Lee Tarpley, Texas A&M AgriLife Research plant physiologist, Beaumont, said higher than normal temperatures around the state could impact yields and quality for producers.

Tarpley said there were reports from rice fields west of Houston regarding stress from high nighttime temperatures. High nighttime temperatures can affect rice flowering, which could hurt fertility and ultimately grain production.

A healthy range of nighttime temperatures for rice is below 73 degrees, Tarpley said. Anything above 77 degrees can noticeably damage plants.

Temperatures and heat stress can affect plants in several ways at different growth stages, he said.

During vegetative growth, heat stress can cause oxidative stress, which hurts plant photosynthesis, Tarpley said. Damages can impact yields.

Heat stress during flowering and seed setting, as with the rice fields near Houston, can impact fertilization and effectively reduce seed set and fruit or grain numbers, depending on the crop, he said. After the plant’s grain or fruit has started to develop, heat stress can hurt harvest quality.

Tarpley said high temperatures also impact plant transpiration, the process of water moving through a plant with most eventually being lost from aerial parts, especially leaves stems and flowers, as the plant exchanges gas with the atmosphere during photosynthesis. Transpiration has a cooling effect on plants, so can help reduce heat stress effects.

“At a point though, if the plant gets too stressed it will tend to shut down transpiration to leaves and flowers,” he said. “Dryland crops could be suffering without water. They try to take up more water, which indirectly takes even more energy.”

Tarpley said various crops are facing stress at different points in their growth cycle based on regional planting schedules and whether producers were delayed due to spring rains.

Delays that shift plant development deeper into summer usually have a detrimental effect on yields, said Dr. Ted Wilson, Texas A&M AgriLife Research and Extension Center director, Beaumont, because later maturing rice experiences higher temperatures, which increase plant stress.

A multi-year analysis of yields from over 10,000 rice fields showed yields decreased by 315 pounds per acre each week harvest was delayed past the week maximum yield occurs.

“If they’re delayed six weeks, you’re looking at almost 2,000 pounds per acre and that is significant,” he said.

The heat has different effects on various vegetative plants, but high temperatures cause stress for most crops at some point, Wilson said. Heat stress has been shown to reduce fruit sets in tomatoes, and a study on cotton by the University of California at Berkeley showed stressed plants began aborting young squares in which the plant has invested the least amount of energy so it might save bolls with heavy energy investment.

AgriLife Extension district reporters compiled the following summaries:

CENTRAL: The district was hot and dry. Dryland corn silage harvest was turning out well. Pastureland started to show some signs of stress. The weather forecast showed no sign of rain anytime soon. Irrigation of cotton was going strong. Some sorghum fields were sprayed with Roundup to prepare for harvest. Sugarcane aphid populations were on the rise, and some fields were treated. Livestock and cattle were in good condition. Overall crop conditions were 90 percent good, and 75 percent of the counties reported soil moisture as fair.

ROLLING PLAINS: Summer storms produced some hail and heavy rains that washed out some cotton. Extreme lightning caused a dozen reported wildfires. Some fleahopper pressure was seen in fields. Cotton continued to look good although increased daily temperatures started to affect the plants. Cattle were in good condition.

COASTAL BEND: The district was hot and dry with some windy conditions. Corn harvest was bringing in 80-100 bushels per acre, and grain sorghum harvest neared completion with above–average yields being reported. Cotton was holding on but could use some rain. Some bolls were beginning to open. Bollworms were still an issue. Fields were parched and very dry with hot spots beginning to show up in some pastures, but all in all forage conditions were still good. Hay making was in full swing with big yields. Cattle were in good condition.

EAST: Extremely hot and dry conditions remained around the district. Weather forecasts predicted little or no rain, but all counties needed moisture. Pond levels were dropping. Pasture and range conditions were mostly good. Most counties reported adequate subsoil and topsoil conditions. Some areas in Gregg County were under burn bans as topsoil moisture conditions were very short. Drought conditions have set in for most of Houston County. Panola County expected to enter a short-period drought if the heat and high winds continue. Wildfire chances increased due to abundant underbrush growth from spring rains. Hay was being cut and baled. Some pastures have shown little regrowth after cutting and have started to turn brown. Producers in Trinity County made one cutting of hay, but few made a second. Baling slowed down in most counties. Smith County producers were worried that without rain, hay supplies could be a little short this year. Gardens were drying up. Corn in Houston County had almost completely turned brown from the base up. Only a small percentage of fields were still green but not expected to stay that way for long. One field was cut down completely. Fall planting was going on in Jasper County. Cattle were in good condition. Prices were holding steady in Gregg County. Shelby County reported large numbers of cattle at sale barns with the market down some. In Trinity County, some producers were selling market-ready calves while others were holding off. Feral hogs were very active. Horn and barn flies were in great numbers. Producers were checking for armyworms and grasshoppers in forages.

SOUTH PLAINS: Hot, dry weather continued. Floyd County finally received some rain, from 0.3 of an inch to 2 inches. Scattered rains helped dryland cotton, but with temperatures remaining very high, fields will need more rain to keep going. Some cotton was blooming. Lubbock County experienced extreme heat, with four consecutive days of 104 to 108 degree highs. Corn was in the tassel to milk stages. Pollination appeared good in the majority of fields in spite of the heat. Sugarcane aphids were found in adjacent counties in grain sorghum.

PANHANDLE: The district continued with hot, dry and windy weather. Temperatures were above average for most of the district. A cool front dropped temperatures into the lower 90s briefly. Some moisture was received. Amounts ranged from a trace to 1.50 inches in a few areas. Soil moisture varied from very short to adequate with most reporting short. Hot weather was affecting all summer crops negatively. Ranges were drying out. If current weather conditions continue supplemental feeding will start soon. Grasshoppers were becoming a problem. Corn was beginning to silk and was stressed from the very high temperatures. Some corn was already behind in soil moisture. Lightning caused a few range fires. Producers irrigated around the clock trying to keep up with crop water demands with the above-normal temperatures. Earlier-planted corn was holding, however the later plantings were suffering because of the lack of water and 100-plus degree days. Decisions will be made soon regarding some crop abandonment to save half circles of corn. Cotton was coming along, but it, too, needed irrigation. However, most cotton was still young enough to hold on. Grain sorghum was looking good since most of the crop remained in the vegetative stage, but heat was taking its toll. Weeds were a problem in fields, and plowing was taking place. Cattle on pasture looked good. Insects were a problem.

NORTH: Topsoil moisture ranged from adequate to short and decreasing amid dry, hot conditions with temperatures near 100 and strong southerly winds. A slight chance of rain was in the forecast. Irrigation of crops, gardens and lawns took place. Corn and grain sorghum were starting to mature. Soybeans were blooming, and some fields were setting pods. Grain sorghum looked decent. Pastures still looked decent given the weather conditions. Hay fields needed rain. Hay producers continued to bale mostly second cuttings on Bermuda grass and some first cuttings on native grasses. Producers said yields were about average on most fields. Livestock were in good condition. Grasshopper activity picked up. Some pressure from sugarcane aphids on some milo fields was reported.

FAR WEST: The district experienced temperatures above 100 degrees with spotty showers and extreme lightening, which led to a high fire danger in some counties. Ward and Brewster counties were the only counties to receive a significant amount of rainfall, from 1-1.5 inches. Cattle in those counties were in excellent condition headed into the fall. Crops and pastures were starting to suffer from the extensive heat and no measurable rainfall. Early cotton began blooming. Sorghum entered hard dough stage, and corn was approaching 50 percent starch as watermelon harvesting continued.

WEST CENTRAL: Dry, hot, windy conditions prevailed as temperatures remained in the triple digits. Burn bans were being issued. Pastures were drying out, and fire dangers increased. Field activities, including fertilizer and pest applications, continued as producers prepared for fall planting. Grasshoppers were becoming a concern. Cotton crops were fully emerged and growing. Wheat harvest was mostly complete. Yields were not as good as expected due to excessive rains that delayed harvest and damaged some crops. About 60 percent of grain wheat was not harvested. Grain sorghum looked good and progressed well. Row crops were starting to show signs of heat and moisture stress. Cutting and baling hay continued and was mostly complete. Range and pasture conditions were declining. They were no longer lush and green but were beginning to show heat stress and dry out fast. Livestock remained in fair to good condition. Cattle prices went down. Pecans seemed to be holding where irrigation was available. Native pastures were in good condition.

SOUTHEAST: Dry conditions continued. A few scattered showers were reported in Jefferson County. High, above average temperatures were affecting crop and pasture growth. Some hay was still being baled. Rice and other crop conditions looked good, however, a good rain would not hurt as the ground continued to dry. Soil moisture levels throughout the region ranged widely from adequate to surplus, with most adequate. Rangeland and pasture ratings varied widely too, from excellent to good, with fair ratings being the most common.

SOUTHWEST: Warm and dry conditions continued with temperatures over 100 degrees. Wildfire dangers increased. Soil moisture levels were depleting rapidly. Pastures and fields dried considerably and rapidly. The corn and milo harvest began. Rangelands were dry, and livestock were in fair condition.

SOUTH: Extremely hot temperatures and high winds continued throughout the district. The combination quickly dried rangeland of any good soil moisture levels remaining. Temperatures were unusually high, and daily highs near 110 were recorded in some areas. A few watermelons and cantaloupes remained in fields in parts of Maverick County. Corn and sorghum harvesting was in full swing. Some corn fields reported uncommonly high yields, upwards of 120 bushels per acre. Early planted sorghum harvesting should be completed soon, and later-planted sorghum should be ready for harvest within the next two weeks. Irrigated sorghum continued to receive water. Cotton was in the boll-opening stage. Early planted peanuts were beginning to peg, and all peanut fields were under constant irrigation. Range and pasture conditions continued to decline. Some ranges and pastures have gone dormant, and forage quality declined some. Soil was dry and cracked, and no moisture was visible on topsoil or in the subsoil in some areas. Supplemental feed was increasing, and body condition scores on cattle remained in good condition. Overall soil moisture conditions were 65 to 100 percent very short. Livestock markets reported increased offerings, but prices slipped some in most classes of beef cattle. Supplemental feeding of cattle continued in some areas.

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