Crop production and animal production probably provide 90% of the world human population’s food needs. Very few people on earth live as hunter-gatherers (maybe those who do are the lucky ones) while the rest of us rely on agriculture to supply our food. Food crops are very sophisticated biological entities with high yield potential under ideal conditions but we are hampered not only by the challenges of climate change but also by the pressure of crop pests (invertebrates and vertebrates), weeds (competing plants) and plant diseases (pathogens and microbes). Historical events still reverberate in our minds to caution us against devastating crop pests, weeds and diseases like the late blight that killed potatoes in Ireland between 1845 and 1849 and caused severe famine and mass human mortality. The challenges of climate add the pressures of pests and makes life interesting if not stressful for modern farmers.
Can modern crops succeed under pest pressure without pest management?
A fair percentage of the world’s human population have no idea what crop production means. People buy their food from the retail outlets and demand healthy, tasty and good-looking fresh produce and processed foods without understanding that it is produced in a constant “war” situation – that “war” is waged against crop pests, weeds and diseases. Question is why plant pests and diseases are in such competition with us? The answer is quite logical: we managed to select certain traits like high yields, growth form, short growth cycle in cultivation but in the process the natural compatibility or resistance against pests and diseases are sacrificed. A second rationale for the challenges we face with plant pests and diseases is the agricultural practice we use for food production, namely large tracts of land planted with dense stands of monocultures. Any arthropod species will cash in on such abundant food supply while pathogens are very easily spread between individual plants while proliferating in magnitude to epidemic proportions. Fact is that our modern crops are highly susceptible to plant pests and disease while weeds are omnipresent in crop production. There is no way in which we can produce enough food the 8.5 billion people without supporting our crops with sound pest management. Nature’s little beasts are simply to numerous and competitive to be left without control.
Arthropod and nematode pests
Insects and arachnids like mites are considered serious crop pests. Nematodes are often forgotten due to their small size, but they can be totally devastating to many crop species.
Sporadic pest outbreaks
The recent red locust outbreak in central Africa is an example of how a single insect species can destroy virtually all crops in a short period of time. We have a similar species namely the migratory locust in South Africa that damages natural veld, but if left unchallenged it invades cash crops like maize. Another pest that occurs sporadic in many crops is the African bollworm. There were outbreaks in the Western Cape canola and wheat in 2018 and 2019 that caught farmers off guard. Our African armyworm is another sporadic pest that often “appears out of nowhere”, damages veld and grazing and even spills over into crops. The sporadic pests are perhaps more dangerous than the endemic pests because the farming community does not expect such pests and are unprepared to deal with it. The agricultural sector and state agriculture organs need to develop efficient early warning systems for such sporadic pests to prepare farmers better to combat them.
The fall armyworm that invaded South Africa in 2016 is a pest that sent the shivers through the agricultural network and destroyed cash crops of a large percentage of small farmers and some commercial farmers in South Africa. Had it not been for genetically modified maize that has an inherent control mechanism for Lepidoptera (worm) pests, the maize crop in South Africa would have been devastated. We also see other invasive pests like different fruit flies that arrive uninvited in South Africa and jeopardise fruit crops. The problem with invasive pests is that there are often no registered pesticides available, leaving farmers at a loss for suitable and effective control mechanisms. Another problem is that such invasive pests establish themselves as endemic pests within a short period time and add to the frustration of farmers and costs of production. South Africa recently also experienced the arrival of the polyphagous shot hole borer that invades ornamental and crop trees, inoculates it with very the dangerous Fusarium fungus and we have not effective control mechanism for this pest yet.
Farmers are usually acquainted with the “standard” pest like stalk borers, thrips, whitefly, loopers and various nematodes (there are many, many others!) and their cyclic nature coincide with crop cycles and spray programmes are established to control such pests. We seldom see a real problem with endemic pests that cannot be controlled effectively and if such problems do arise, it is mostly because of poor agricultural practices or incorrect application of pesticides.
The threat posed by and nematodes to food security
One may think that the physical damage caused by pests to crops is the only impact we are concerned about, and yes, physical crop damage either in the larger plant itself or the part that should be harvested like fruit or an ear of wheat, can wipe out a farmer’s prospects of sending his produce to the market. Physical damage like nematodes in potatoes and bananas, worms in maize, whitefly in tomatoes and thrips in fruit crops can destroy a crop completely but the secondary effects may also be as devastating. That is when a biting and sucking insect inoculates the crop with a plant pathogen, virus or bacterium that kills the plant or damages it to the point where it is not able to yield a harvest. Thrips and plant lice are tiny plant pests that can destroy a crop by establishing a disease in a crop. Damage caused by such pests can be tertiary of nature when fungal spores are carried into the crop by wind and enter the damaged areas; it is not necessarily only insect borne diseases that damage crops. On the commercial scale the physical and secondary damage to crops may not really be a threat to food security but for a small farmer or the subsistence grower, it may take out his or her food supply for an entire season. If we, however, remove plant protection from commercial agriculture, as much as one quarter of the national crop may be wiped out by plant pests which leaves a serious national food security risk for a nation.The full article is for subscribed members only. To view the full article please subscribe. It’s FREE!Log In Register
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