Veteran farmer warns disease, heat, drought will hurt yam, sweet potato crops

A top root crop grower has predicted a shortage of sweet potatoes and yams in the next few months as a result of low rainfall coupled with a heatwave during this year’s wet season.

But veteran farmer Richard Armstrong has painted an even bleaker picture of ever-shrinking yields of the staples with the triple threat of crop disease, extreme heat and drought, as he urged the authorities and the University of the West Indies to team up to come to the rescue.

“We are past a crisis level,” said Armstrong, whose Armag Farms has produced the Sunbury Harvest brand of sweet potato fries for the past ten years. In an interview with Barbados TODAY, he said that if this year’s rainy season was marred by sweltering heat, especially during the months of August and September, it would significantly affect the staples’ yields, prompting scarcity.

Both crops were already under severe threat from microorganisms and the unusually hot weather made the situation worse, he said.

2023 was the hottest year on record, about 1.37 degrees Celsius higher than pre-industrial levels.

Armstrong, who has been in farmer for over 40 years, said: “If we get the heat levels we got in August and September last year again this year over an extended period of time, you will get problems with the yam yields and sweet potato yields. My yam crop last year was half the amount of the previous year and I put it down to nothing other than that heat and dry spell we had during those two months. If we get the heat and get some showers in between, the plant might still do something, but last September we got no rain and the temperatures were up to 34 degrees Celsius.

“For six weeks we didn’t get rain and the plants were so stressed out that they stopped growing. I think it is inevitable [that we will get the same conditions] but we have to hope for some showers of rain in between,” he said, pointing out that sweet potato production had reached critical levels due to a complexity of viruses.

“It is a complex of about three to four different viruses that cause our yields to be very poor, especially in the old varieties that locals like. We are at the point where we only get half the volume of potato now in terms of yields, that we did over 20 years ago and we spend more money on them.”

The St Philip-based farmer said the virus complex did not affect the sweet potato itself; rather, it stunted the vine’s growth, drastically reducing its photosynthesis abilities – how plants use sunlight to synthesise their food from carbon dioxide and water. The main carrier of the virus was white flies and there is no cure, he noted.

Plant scientists in Peru, investigating a devastating virus disease wreaking havoc on sweet potato crops in 1990 isolated and characterised a new virus that appeared to be the major culprit – the sweet potato chlorotic stunt virus (SPCSV). The virus was found to cause severe stunting and chlorosis – a deficiency of the green pigment found in plants that allows them to absorb sunlight and use that energy to produce food.

The virus was found to be part of complex viruses like the sweet potato feathery mottle virus (SPFMV). In 2002, researchers in Uganda reported the first complete genome sequence of an SPCSV isolate in the East African country that contained key differences from the Peruvian type.

The effects of changing climate with more extremes in heat and rainfall coupled with the viral disease have led to a perfect storm of potential disaster for the crops at a time when Caribbean Community (CARICOM) governments have zeroed in on roots and tubers like sweet potato and yam as key elements of a regional food security drive.

Armstrong stressed that a “crisis” in sweet potato production was linked to environmental conditions rather than reduced cultivation.

“You don’t get the yields from sweet potato now that you got in the past and that is one of the reasons why you get these shortages all the time,” he said. “It is not that the crop isn’t being planted, it is just that you are not getting the yields from the acreage that you planted . . . . So our production cost has gone through the roof and the yields are down. The cost to produce has gone up by 50 per cent and the yields have dropped by 30 to 50 per cent, and in some cases by more. The newer farmers are finding it difficult and sometimes they don’t even harvest a potato.”

Armstrong plants about 100 to 105 acres in sweet potatoes each year. In the past, he was confident of a yield of 25 000 pounds per acre but now had to settle for 15 000 pounds per acre, he said.

Yam production has not been spared the effects of disease, as the anthracnose fungus is also drastically reducing yam yields here. Armstrong noted yam scarcity over the last decade requiring the importation of clean planting material to help farmers make a comeback, but that was interrupted with the advent of the COVID-19 pandemic.

The farmer and food processor said there was a dire need for the development of a national tissue culture laboratory, pointing out that despite the advocacy of many of the island’s plant pathologists over the years, nothing had been done.

He suggested that the University of the West Indies work with the Ministry of Agriculture on the tissue lab, noting a similar project in the United States after farmers there were struck by a similar virus. With the help of university researchers, American farmers were able to develop virus-free slips, he said.

With the government in talks with farmers about exporting tonnes of sweet potatoes, Armstrong said the low yields would limit the project’s sustainability.

Five sweet potato varieties are mainly grown here which are currently sold at $1.30 to 1.50 per pound or $25 per rod.

sheriabrathwaite@barbadostoday.bb