Sugarcane aphid populations have been low in south Texas

Sugarcane aphid populations have been low in south Texas.

Wet fields may be keeping sugarcane aphid numbers in check

Texas has received an average 7.54 inches of rain so far this May, besting the previous record of 6.66 inches recorded in June of 2004.

It's official. This month is the wettest May on record in Texas. In fact, with a few days remaining in May, the National Weather Service has already titled May 2015 as the wettest month ever in the Lone Star State.

According to State Climatologist John Nielsen-Gammon, Texas has received an average 7.54 inches of rain so far this May, besting the previous record of 6.66 inches recorded in June of 2004. Nielsen-Gammon, a professor of atmospheric science at Texas A&M University, says state records go back more than 100 years and the El Niño-driven storms that dropped exceptional rains across the state this month have saturated Texas soils and any additional rain will only serve to increase massive floods that have been occurring in several parts of the state.

“It has been one continuous storm after another for the past week to 10 days in several regions of the state, and many creeks and rivers are already above flood stage,” he warned.

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Monthly rainfall amounts exceeding 20 inches of rain in May through May 27 have been reported in isolated areas of the state including in water logged Harris County where over 10 inches of rain fell on Monday. Austin has recorded nearly 17 inches of rain this month so far and Wichita Falls, which was experiencing exceptional drought conditions just weeks ago, has received over 13 inches of rain already in May.  

See also: Yellow ground poses concerns for cotton alternatives

Corpus Christi has received nearly 14 inches of rain in May; Amarillo reported 9.26 inches of rain for the same period and most major rivers across the state are still above flood levels.

Officials at Lake Texoma, a reservoir impounding the Red River on the Texas-Oklahoma border, have reported the lake is at 100 percent capacity, as is Lake Corpus Christi in the Coastal Bend. Flood gates at both reservoirs are fully open in spite of flooding on the rivers below the dams. At Lake Texoma, officials report flood gates are inadequate to handle the flow volume and water was spilling over the dam on Thursday (May 28).

Water rescues continue in Hays County where nine people are still missing as the Blanco and San Marcos Rivers continue to flow out of their banks. Search efforts continue near Wimberly where multiple homes were swept away by raging waters and at least 9 people were still reported missing.

Blame El Niño

Nielsen-Gammon says there is little doubt that the exceptional wet weather this spring has been caused by an active El Niño, which has steered storm clouds into the jet stream sending heavy rains all across the U.S. Southwest and Mexico. He warns that forecast models indicate the probability of continuing moderate to heavy rains in the days ahead that could rage across the state well into June.

For farmers across Texas, the unexpected but badly needed rains this spring are a “Catch 22.” While suffering through a multi-year drought, farmers and ranchers across the Southwest desperately needed rain, stretching as far back as 2011. Persistent drought parched pastures and decreased or destroyed crop yields in some areas, and ranchers culled herds. But with late summer and early fall rains last year offering some needed water, hopes soared when forecasters reported that a possible El Niño could form by the end of the year bringing a fair chance of a wet winter.

It was a wet winter, but with the arrival of spring, southern oscillation in the Pacific increased low pressure systems on the Mexican coast that were quickly caught up in the jet stream, colliding with moisture laden air funneling into the Southwest from the Gulf of Mexico bringing any heavier rains.

Now, at the start of June, the rains continue.

A few areas in Oklahoma and in north and southeast Texas have received as much as 25 inches of rain over the last 30 days (ending May 29), much of it coming this past week.

But in spite of planting delays and for many a late start to the season—or no planting at all—most farmers agree that after many years of little rain and little or no soil moisture, the rains this year, while excessive, have been welcomed. Soil moisture has been largely restored, reservoirs are filling and those lucky enough to get a crop planted are reporting some healthy plant conditions.

Low sugarcane aphid populations

Another benefit of steady rains in South Texas is how it may have slowed sugarcane aphid development in grain sorghum, especially in the Lower Rio Grande Valley where some farmers were able to get seed planted early in the season.

Danielle Ortiz, IPM Extension agent at the Texas AgriLife Extension in Weslaco, reports some fields with high SCA populations were being sprayed last week, mainly in eastern Cameron County and reaching as far north as the Willacy County line, and also in the mid Valley area in Hidalgo and Cameron counties.

However, in a lot of the LRGV grain sorghum fields farmers were finding sugarcane aphid in very low numbers.

"We have yet to reach the threshold of 100 SCA per leaf at the station in Weslaco, but have had continuous sugarcane aphid presence and presence of winged SCA at the station, but natural predator populations seem to be keeping SCA numbers low, below 20 per leaf or even lower counts," Ortiz said.

Continuous rainfall and overcast days may have inhibited the SCA from reaching the high populations of last year. By the first week of June last season many farmers were reporting as many as 2,000 aphids per leaf.

In spite of the current low numbers, however, county agents are advising farmers to continue scouting fields as SCA populations are expected to grow as warmer weather sets in.

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