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Diseases and pests: Limiting factors of productivity – part 2

IN OUR last article we discussed how low and wrong fertiliser usage has been a limiting factor of productivity in Zambia especially amongst the small-scale farmers.
Indeed, we went further to emphasise a point that not all that plant seed are farmers. It is similar to the law of fraternity; not all that have studied law are lawyers, many of them have been sieved off at ZIALE. Unfortunately, in agriculture we don’t have a ZIALE otherwise; we could not be in this ‘mess’ we are in.
Those are side, because the future looks bright. For now let’s discuss how disease can be a limiting factor in attaining desired productivity.
To discuss this point allow me to pose a question to all those people that are above 60 years; how many of you have never taken panadol or some herbs of some sort?
To paraphrase this question, how many of you senior citizens have reached that age without falling sick? I will be very surprised, if not perplexed if any one of them claims to have grown to that advanced age without falling sick.
We are living things and normally fall sick and die if we delay in taking medication. Plants and crops to be specific, are living things that also get attacked by diseases and pests.
There are so many diseases and pests that attack crops and sometimes, symptoms of these attacks manifests similar to nutrient deficiency.
For instance, yellowing in crops might be a sign of either nitrogen or sulphur deficiencies, however, this might also mean blights in certain crops.
In Zambia, we will never attain national average yields of above 6Mt in maize for instance or 2.5Mt in soybeans if we only think that the inputs we need in crop production is seed and fertilizers’.
This is so critical, especially now that our production is becoming more permanent on the same piece of land. It is different in a few years ago when most of the small-scale farmers used to practice shifting cultivation as they had abundant land to shift to.
Now, one is forced to cultivate on the same piece of land until one tires because of land pressure. Many of our old timers think this is not possible and they have ended up moving from one chiefdom to the other seeking new virgin land.
Many of them have moved from Southern and Central provinces to the far north and have only been stopped from getting into Congo because of nationality issues. I will not be surprised to find some Zambian farmers cultivating on the no-man’s land.
The satisfying point to note is that one can use the same piece of land sustainably for as long as one lives. I have always given an example of York Farms in Makeni area. That farm is about 400ha and they have farmed on that piece of land for more than 30 years.
Besides, each piece of land is cultivated for 365 days of the year; meaning no piece of land is left furrow. They also use fertilisers and pesticides in their growing of vegetables and flowers. I was lucky to have done my practicals at that farm; as a matter of fact, I did my fifth year dissertation at that farm. I wanted to know the effectiveness of their cultivation practices in maintaining soil organic matter and avoiding soil compaction.
There are so many diseases that affect our crops, but the broad category of diseases is bacterial, fungal, and viral, Out of this, like you would guess, it is the viral diseases which have no cure just like in human beings.
These are diseases that are caused by virus. Just like human viruses, these normally can’t survive outside a host. This means your crop will never be infected because viruses are moving in the air. The main carriers of viruses in plants are pests such as aphids and grasshoppers.
It is therefore imperative to control the vectors or pests before they transmit viral disease because the only cure of plants attacked by viruses is to uproot that plant and destroy them away from healthy plants. Nonetheless, the most common of the diseases in most crops are fungal diseases.
The spores of these diseases can overwinter on seed, crop leftover (stover), in the soil and water. This is the reason that we need to spray preventatively of all our crops before they are attacked because by the time we are seeing the symptoms, the disease would have done so much damage that our yields can be reduced as much as 40 percent from the potential.
This is very important to know especially nowadays when breeders are breeding varieties for yield. You will note that the more the variety has yield potential, the more susceptible it is to disease attack.
So never risk by investing so much in seed, fertiliser, herbicides and forget about fungicides. There are so many fungicides on the market but you need to seek advice before buying one for your crop. I’m offering free advice for those that want to buy genuine fungicides.
This author is an Agribusiness Practitioner.