The mysterious absence of an insect pest is making for a bountiful harvest of spring onions in South Texas, according to an expert with the Texas AgriLife Extension Service.

“I can’t explain why, but onion thrips just disappeared,” said Dr. Juan Anciso, an AgriLife Extension vegetable specialist in Weslaco. “With all the hot, dry weather we’ve had, we should have had lots of them, but we didn’t. Something’s going on, but I don’t know what.”

Thrips are tiny insects that slash onion crop yields and quality by rasping the green off leaves and sucking juices from the onion bulbs, he said.

To manage populations, growers spend thousands of dollars each season spraying insecticides.

“When it’s rainy and damp we suffer losses from fungal diseases,” Anciso said. “And when it’s dry, we battle thrips. But this year we got neither, so yields and quality are excellent.”

Rains in October slowed and delayed planting, leading to early speculation that this year’s crop would be damaged, said John McClung, president of the Texas Produce Association in Mission.

“We had trouble getting them in," McClung said, “but it dried up and we’re getting better yields than expected. The quality is good and the size is not bad. Not as large as we’d like, but not bad.”

McClung has his own theory of why thrips populations are low.

“Maybe Hurricane Dolly just drowned them all last summer,” he said. “It’s a big mystery, but we’ll take what we can get.”

Anciso estimates growers are harvesting 800 to 950 50-pound bags per acre, about twice the amount harvested when disease and insect pressures are high.

“The harvest is relatively young,” he said. “It started the first week of March. But so far, so good. We’ve probably harvested a little over 10 percent of the crop, so we’re looking at finishing up by mid-May. Hopefully it won’t go into June because the onions get sun scalding and go soft.”

Growers in the four-county Lower Rio Grande Valley planted only 8,200 acres this year, compared to 9,000 acres last year, when yields were said to be phenomenal, Anciso said.

“Unfortunately, market prices for onions were very low last year and that, coupled with the high cost of fuel and fertilizers, led to fewer acres being planted this year,” he said.

Prices early this season were high, in the $8 to $10 per bag range, then dropped off to between $5 and $7 per bag, but could rise again, Anciso said.

“Mexico is delivering a lot of onions to the U.S. right now, so prices are on the down side. But once Mexico quits shipping, usually in mid-April, things could change.”

The Valley’s onion harvest grosses an average of $150 million in farm gate receipts. While some are sold locally, most South Texas onions are shipped north.

“Our onions are sold all over the country, but most go straight up a corridor through Dallas, into the Midwest and even into New York,” Anciso said.

Over the years, Texas onions have gotten a reputation of being mild, with only a few now carrying the famous 1015 label, he said.

“The industry itself decided that to be labeled as a 1015, onions had to be tested for low levels of pyruvic acid," Anciso said. "But few have been tested this year, probably because all our onions are now considered to be mild or sweet and of good quality.”