Field sanitation critical to prevent plant diseases

Saturday May 22 2021
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Weeds in the garden can host pathogens and vector populations. Photo | George Katongole

By George Katongole

Most farmers think that use of pesticide is the most effective strategy for combating diseases. 

But according to Dr Christopher Bukenya, Manager of technical and agribusiness services at the National Agricultural Advisory Services (Naads) that is a fallacy.

According to Bukenya, sanitation is one of the effective tactics in disease management strategy in the field. 

Field sanitation includes any practices that aims to prevent the spread of pathogens by removing diseased and asymptomatic infected tissue, as well as decontaminating tools, equipment and washing hands.

Dr Bukenya says that good field sanitation reduces pathogen inoculum which is also termed as “seeds” of the pathogen. “Consistent and effective sanitation practices,” he says, “greatly increases the chances of raising healthy plants.”

Planting
Dr Bukenya says that sanitation in the field needs to take place before, during and after the growing season.

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He says that prior to planting, fine-tune your weed management plan. He explains that most weeds are reservoirs for plant pathogens and insects. By controlling weed populations in your fields, you can reduce pathogens and their vector populations.

James Mugerwa, a retired extension worker in Mukono, adds that weeds create a lot of pressure for farmers. “But knowing the weed profiles and learning how to keep fields clean is crucial,” he says.

Mugerwa, therefore, recommends early planting to deal with weed resistance.
“The earlier you plant, the longer the window weeds have to grow.” Mugerwa explains. He adds that delayed weed control leads to a sizable percentage loss of potential yield.

Keeping weeds under control also means keeping the surroundings of your farm free of weeds, unless they are maintained and intended as habitat for natural enemies or as barriers.

Clean and disinfect farm tools
Dr Asher Wilson Okurut, an agronomist at the National Agricultural Research Laboratories (NARL) Kawanda, says that farm tools can be a big vehicle through which diseases are transmitted on the farm or between farms.
Dr Okurut suggests that farmers ought to be vigilant and clean farm equipment from the previous season’s residue.

He suggests placing equipment like hoes and machetes to a flame of fire or using dilute bleach such as Jik to disinfect equipment before it is used on another farm.

Additionally, Mugerwa recommends washing soil off of farm equipment, including brushing off soil particles from farm shoes.
“This is an effective way to stop the spread of soil borne pathogens such as White mold and different species of Fusarium.

He recommends washing tools with soapy water and dip or wiped in ethanol-based products. 
Tool sanitation, he says, goes hand in hand with hand-washing to minimise plant-to-plant spread of diseases caused by several bacteria and viruses.

For example, if spider mites are present on a crop they will surely move to the newly planted. If the old infested crop is upwind the pests will almost certainly be blown onto the new crop. If possible, get rid of the old crop first.

In vegetable farming, where bamboo poles are used to support crops such as tomato, they should be disinfected before being used for a second time as disease pathogens and pests may be present on them.

Remove infected plants
Doreen Nampamya, a research associate at Korea programme on International Agriculture (Kopia), who partners with NARL on vegetable production, says as soon as symptoms appear, destroy or pile diseased material.

According to Nampamya, removing infected plants from the field can reduce the amount of pathogen inoculum that could move into healthy plant parts.
She adds that in the case of tomatoes, the farmer should make sure to destroy the plants.

“It is not advisable to put them in your compost bin,” she cautions.
She recommends proper disposal of all the infected plants and crop residues after harvesting. Crop residues can be composted, buried underground or burnt.

Use resistant plants or cultivars
Dr Okurut says that diseases such as black sigatoka, which cause enormous losses in banana plantations, can be managed through hybrids especially NaroBan 1,2,3,4 and 5. 

The latest variety, NaroBan 5 (M30) is resistant to weevils, nematodes, and black sigatoka on top of having desired food qualities.
“Researchers are increasingly focusing on disease-resistant varieties and it is these that should be adopted,” Dr Okurut adds.

Ploughing
Dr Michael Otim, the senior research officer in charge of entomology in maize at the National Crops Resources Research Institute (NaCRRI), says that ploughing is a helpful intervention in farming.
He says fields should be ploughed under the crop residues and organic mulches. This is one of the interventions in managing the fall armyworm.

“This not only improves soil condition, it also helps to disrupt the pest’s lifecycle. The pests are exposed to extreme temperature, mechanical injury, and predators,” he says.

Vigilant workforce
Dr Bukenya explains that sanitation requires detail-oriented employees.
“There is a lot of work involved in field sanitation right from planting to harvesting. This calls for vigilant workers,” he says.

He says that planting materials should be inspected before being introduced in the field. 
“Instruct employees on how to recognise common disease symptoms and pests. The more eyes available to look at your plants in the field, the more chances issues can be identified earlier,” he says.

Nampamya recommends personal hygiene on the farm as key to disease control. “Farmers should always bear in mind that they might be the carrier of diseases and insect pests while moving from one plant to another or between fields,” says Nampamya. 

Crop rotation
Soil borne pests and diseases such as nematodes, club root in cabbage, damping-off and many others are prevented from building up. Avoid rotating crops of the same family.
“The goal of crop rotation is to reduce the amount of the pest population present in the soil,” Mugerwa says.

Continuously cropping the same crop builds up the population levels of any soil borne pathogen of that crop that may be present. 
The populations can potentially build up so large that it becomes difficult to grow that crop without yield losses. 

Growing a crop that is not a host plant for that pathogen will lead to the pathogen dying out and its soil population levels lowering. Most pest populations will decline in two to three years without a suitable host.

Crop sanitation 
Field sanitation is the practice of safe hygiene in field conditions to maintain environmental health. It is used by travelling militaries, field workers harvesting crops, campers, and other people who spend time outdoors in environments which lack urban sanitation.

Sanitation practice:
•Remove plant debris and infected plants as soon as symptoms appear
•Disinfect knives, shears and other harvesting tools often.
•Frequent hand-washing with clean water and soap.
•Wash soil off farm equipment and shoes.
•Keep weeds under control at all times.

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