Gareth Manning, Gleaner Writer
Farmer Jervis Rowe (left), along with Garnet Malcolm (centre),
general manager of AgroGrace and Cyril Chambers, project development officer, examine sweet peppers growing in a greenhouse in Hopeton, Manchester, for disease and other defects. - CONTRIBUTED
DESPITE THE intervention of the Ministry of Land and Agriculture, the scourge of diseases and pests is crippling agricultural production, says senior plant protection specialist at the Rural Agricultural Development Authority (RADA), Marina Young.
She says while there is a strategy to manage pests and diseases - by using
the integrated pest management system (IPM) - viral diseases in particular are having a debilitating effect on crop production. Some of those hard-hit crops are non-traditional exports such as papaya.
VIRUSES YOU'LL SEE
"You'll see viruses like papaya ring spot and tomato yellow leaf coral virus, pepper leaf spots. It is (a) significant reduction," she says.
She is not able to quantify, however, how many crops are lost each year due to these diseases, but says the loss is significant.
"Even considering that we are even managing them, they are still a problem," she adds.
But one of the traditional exports that has suffered at the hands of viral diseases is citrus. Since 1993, the whole industry has been under siege from the citrus tristeza virus. In 2004, the sector declined by six per cent when compared to 2003. It produced only 131,364 tonnes of citrus as opposed to over 140,000 tonnes in 2003. Citrus production fell even further by 4.4 per cent in 2005 to just over 125,000 tonnes. The Planning Institute of Jamaica says this was due mainly to the effects of the tristeza virus.
Technical manager at Jamaica Citrus Growers Group of Companies, Dr. Percy Miller, explains that the citrus tristeza virus has always been in Jamaica, in fact from as early as the 1950s. However, it was not a problem then because it was isolated.
But in 1993 the disease became rampant due to the advent of the brown citrus aphid. This aphid acts as a vector for the virus, which led to an outbreak in Jamaica.
"Before 1993 the level of infected citrus plants was less than one per cent. When the vector came it was a totally different story to the point now where we are in 2006 and I would say over 80 per cent of all orchards in Jamaica are infected and are in decline," Dr. Miller says.
The brown citrus aphid affects citrus grown from the sour orange rootstock. In 1993, Dr. Miller explains, 95 per cent of citrus was grown from that rootstock, which constituted a crisis for the industry.
There are no known chemicals that can contain or kill the citrus tristeza virus, so once a plant becomes infected, it dies. The disease affects trees by blocking the xylem and phloem vessels or the veins of the plant that carry water and nutrients to and from the root to the leaves. This blockage normally occurs at the bud union. When the vessels become blocked, the roots are starved and the plant eventually dies.
"You won't get up tomorrow morning and see everything dead, but over time the whole thing will go," he says.
In 2000 Government initiated the Citrus Replanting Programme to make loans available to farmers to replant 7,500 acres of citrus on resistant rootstock. The project was not successful, however, simply because farmers did not apply for the loans and most could not provide the collateral necessary. As such, only 1,950 acres of citrus have been replanted through this programme, the Planning Institute of Jamaica says.
"So the industry is still in crisis because in 1993 when the epidemic begun, Jamaica had 24,000 acres, 95 per cent of which was on sour orange rootstock that would have to be replanted and we arrived at a situation where in 2006 and over 19,000 acres of the national acreage is still on sour orange rootstock which will die," Dr. Miller said. "So we really haven't begun to address the problem in a meaningful way on resistant rootstock," he emphasised.
There are other viral diseases affecting some of our other major exports. The black sigatoka disease, for example, has seriously blighted banana in Jamaica. The disease is caused from a fungus that is easily spread and difficult to control. Spores of black sigatoka fungi can travel long distances and remain viable under ultraviolet (UV sunlight) radiation in tropical conditions for up to six hours.
Luckily, the disease is not as taxing on the industry as the tristeza virus is to citrus. President of the Jamaica Producers Group, Dr. Marshall Hall, explained in an earlier interview that much has been done to reduce incidence of the disease through tissue culture. Tissue culture, which is a simple biotechnological process, has helped the industry to produce many disease-resistant plants at low cost to farmers. The plants also grow faster and produce more fruit.
Crop Type - - Pest - - - - - - Disease
Plantain/ Banana - - Root nematodes, banana borer - Black sigatoka
Coffee - - - Coffee borer - - - Cercospora leaf spot, - - - - - - - - - - coffee rust, American leaf-spot disease
Citrus - - - Leaf miner - - - Citrus tristeza virus, phytophtora fruit rot
Papaya - - - Mites - - - - Ring spot virus
Peppers - - - Mites - - - - Fungal bacterial wilts, leaf - - - - - - - - - - spots, virus diseases
Tomato - - - Nematodes, stink bug - - Yellow leaf curl virus, - - - - - - - - - - early and late blights
Cucumber/ Pumpkin - Melon worm, cucumber beetle - Downy mildew virus
- Source: RADA
