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Serving: Central

Sweet potato yields drop with late-season problems

In 2008, Louisiana bumped sweet potato acreage up to approximately 15,000. That includes about 1,000 acres in south Arkansas that are planted by Louisiana producers and brought back to their packing sheds.

Until late-season rains and hurricanes arrived, that acreage appeared set for a fine harvest. “We were expecting at least a solid yield,” says Tara Smith, LSU AgCenter sweet potato specialist who works out of the Sweet Potato Research Station in Chase, La. “It just wasn’t to be.”

Early in the season, it was wet and that delayed planting. “It did dry out fairly quickly, though, and the crop was put in the ground in a reasonable timeframe. Actually, the tail-end of the planting — say late June through early July — was made under moisture-stressed conditions.”

Following planting, “the crop shaped up nicely. Insect pressure was moderate through the season. Most producers sprayed as needed based on thresholds and scouting schedules. The predominant pest we scout for is cucumber beetles, but we also have white fringe beetles, white grubs (in south Louisiana) and sporadic sugarcane beetle presence throughout the state.”

The start of August was extremely dry. Avoyelles Parish, which has about 3,000 acres of sweet potatoes each year, was among the driest. Those with irrigation capabilities throughout the state utilized them at full capacity.

Later in the month, even before a pair of hurricanes ripped through the state, rains came. In north Louisiana, some operations received 10 to 15 inches of rain in August alone.

“So, when Gustav came through and dumped 18-plus inches of rain, it was on soils that were already saturated. The hurricanes just added insult to injury.”

Prior to the August rains, “the crop was very good. I was in fields that, without hesitation, I can say were in the 650- to 700-bushel range. It was a very nice crop and I believe the yielding quality would have surpassed the 2007 crop.”

Water damage

Between hurricanes and frequent rains, some fields were wet for three weeks or more.

“Anytime there is prolonged soil saturation and oxygen is limiting or excluded from the soil, actively-growing sweet potatoes will begin to break down and sour. That’s what we’ve seen.”

Sunburned or “green top” sweet potatoes have also been a thorn in the industry’s side. Green tops result when rains wash soil off row tops and the root top is exposed, compromising the marketability of the potato.

“Right now, we’re sitting at an approximate crop loss of 50 percent statewide. Some of the loss is attributed to roots that will go unharvested. Others will be harvested — but it’s impossible to cull all the damage in the field, and we do expect losses in storage as we pack out the 2008 crop.”

Most yields being reported are in the neighborhood of 200 to 250 bushels per acre. However, yields have been much improved in areas less affected by adverse conditions.

“Our average state yield last year was 385 bushels per acre, so this is a very difficult time for many producers.”

This season, farmers must deal with more unharvested potatoes than normal. “Because of insect concerns — primarily the sweetpotato weevil in south Louisiana — it’s a bad idea to just let the roots rot in the field. We always go in and disk the fields after harvest. That’s going on this year, too.”

Northeast Louisiana (where 80 percent of the state’s production is located) is considered “weevil-free.” The entire state (including commercial fields, seed beds and storage houses) is trapped and monitored for the presence of sweetpotato weevil, which is endemic to south Louisiana production areas.

The Louisiana Department of Agriculture and Forestry maintains a statewide trapping program and mandatory spray program in south Louisiana to keep the pest contained and out of northeast Louisiana production areas and to maintain the quality and integrity of south Louisiana commercial production. The trapping and spray program, coupled with producer awareness, has resulted in much lighter weevil pressure in recent years.

As in growing sugarcane, sweet potato growers save a portion of this year’s crop as seed for the coming season. Because of all the problems, Smith says there could be seed shortages next season.

Variety news

While the growing season was a struggle, Smith says there are plenty of bright spots in the industry. Among things heading the list is a new variety, Evangeline, released in 2007 from Don Labonte’s breeding program at the LSU AgCenter.

Evangeline is comparable to Beauregard in its production characteristics and, to date, yields have been on par with Beauregard in research plots. About 1,000 acres of Evangeline were planted in the state this year and early harvest reports were favorable.

“What we wanted was a non-biased, disaster-free look at the variety. Unfortunately, that wasn’t in the cards. But what we have seen that piqued our interest — and this may be something very beneficial — is it doesn’t seem to have broken down as much as Beauregard in some of the stressed fields. If that holds through the storage season, it will be a definite positive attribute of the variety.”

One quirk Smith and colleagues found in Evangeline is that it isn’t quite the plant producer Beauregard is. Seed bed research is being done to find out how best to address that issue.

More research

Other key research — primarily Arthur Villordon’s work at the Sweet Potato Research Station — is honing in on early-season management of sweet potatoes.

“He is doing a lot of work on storage root initiation and the various factors and variables that may affect it,” says Smith. “That includes drought stress, transplant quality, and fertilization regimes. Results being gleaned from this research can immediately benefit producers.”

Another positive for sweet potatoes is increased utilization of the crop, the increase in the number of sweet potato products. Those include “pre-packaged, consumer-friendly foods. With good nutrition and health on the minds of everyone, sweet potatoes use is growing. French fries, chips, baby food, cookies and juices are all using more sweet potatoes. Per capita consumption of the crop is inching up every year.

“So, even though this is a bad crop year for Louisiana sweet potato producers, the industry has a bright future and is looking ahead to what we hope will be a much improved 2009 crop.”


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