Bacterial diseases in beans are your crop’s biggest threat
Bacterial diseases in beans are your crop’s biggest threat
Bacterial diseases are such a threat that the US state of Idaho, for instance, has been declared a quarantine state. Seed from outside of that state has to first be grown in quarantine in a greenhouse with favourable conditions for bacterial diseases to develop.
Only seedlings that show no sign of bacteria are then planted outdoors.
In the field, inspectors are clothed in outfits that a trout fisherman would wear. He or she would have a knapsack sprayer on their bakkie and spray themselves with disinfectant before entering each field.
If even one plant is found to be infected with a bacterial disease, the whole field is placed under quarantine and, if necessary, destroyed. The frequency of inspections would be increased in the whole neighbourhood. None of the production fields are allowed to use overhead irrigation, and areas for seed production have to be dry.
Fully disease-free seed comes at a price due to all the precautions required, but this is like paying for insurance.
Checking each batch
As a further check, when the harvested beans are sorted in the packhouse, any discoloured beans that are removed in the process are ground up and soaked in water.
This solution is then sprayed over a bean variety in the hothouse that is very susceptible to bacterial diseases.
This is done to check that there is no possibility of any bacteria being present in that batch. The batch is then treated with various products and packed in bags of 100 000 seeds.
There was a suggestion by the industry in South Africa to have an area in the Northern Cape declared a quarantine region for clean seed production, but government refused on the grounds that this would infringe on the rights of individual farmers in the area.
There are various races of bacterial diseases, so having resistant genes is not a complete solution to this hazard but rather a very important benefit to restrict damage to the crop.
When seed is produced in an area that has been declared disease free, it is still possible to find the odd infected plant in your land, as the bacteria can hitch a ride on a bird
from an infected farm in another area.
In order to reduce risk, should there be an infected plant or two, one should never work on a bean land when dew is still on the leaves, because humans or tractors moving in the land can spread the bacteria further.
I once came across a farmer who had a very clean land, but one row was infected for about 100m and stood out like a sore thumb.
Seed companies can request that laboratories in South Africa examine batches of seed for any disease that may be present.
If the seed on offer has not been produced in a certified disease-free area, the buyer should insist on having a copy of the laboratory test.
Using seed that is infected can cause a whole crop to be unmarketable. Some countries, such as Australia, will only allow importation of seed produced in Idaho or California, even if a laboratory certificate is presented. Not even seed samples are allowed to enter those countries.
