Why insect pests love monocultures, and how plant diversity could change that
For all Science-fanatic, world-hunger apologetic supporting chemical mono-culture farming.
And same mono-culture is forced on humans as there is wave of globalization going on killing native diversity. Once you start living synthetic global life-style, you are prone to insects and pests, ending life earlier than expected.
We are hitting own legs with axe!
Diversity as Natural Pesticide
The problem with monocultures
The problem with monocultures, Wetzel said, is if an insect likes the crop, that insect has a large food supply to draw from all in one place. Conversely, a field containing a variety of plants does not offer a large block of food for the insect, so it will not get the nutrients it needs to survive and thrive.
“A monoculture is like a buffet for plant-eating insects where every dish is delicious,” Wetzel said. “A variable crop is like a buffet where every other dish is nasty.”
Variability in plant nutrients reduces insect herbivore performance
Left to its own defenses, a farm field growing a variety of plants tends to attract fewer insect pests than a field growing just one type of crop. While scientists and farmers have noted that difference for years, the reasons behind it have been poorly understood.
A study led by the University of California, Davis, and published Oct. 12 in the journal Nature explains that much of the discrepancy may have to do with the nutritional needs of insects. Returning plant diversity to farmland could be a key step toward sustainable pest control.
“Insects have a perfect nutrient level that they really like,” said lead author William Wetzel, a doctoral student in Population Biology at UC Davis at the time of the study and currently an assistant professor at Michigan State University. “When it’s too high or too low, they do poorly.”
The performance and population dynamics of insect herbivores depend on the nutritive and defensive traits of their host plants1. The literature on plant–herbivore interactions focuses on plant trait mean values2, 3, 4, but recent studies showing the importance of plant genetic diversity for herbivores suggest that plant trait variance may be equally important5, 6. The consequences of plant trait variance for herbivore performance, however, have been largely overlooked. Here we report an extensive assessment of the effects of within-population plant trait variance on herbivore performance using 457 performance datasets from 53 species of insect herbivores. We show that variance in plant nutritive traits substantially reduces mean herbivore performance via non-linear averaging of performance relationships that were overwhelmingly concave down. By contrast, relationships between herbivore performance and plant defence levels were typically linear, with variance in plant defence not affecting herbivore performance via non-linear averaging. Our results demonstrate that plants contribute to the suppression of herbivore populations through variable nutrient levels, not just by having low average quality as is typically thought. We propose that this phenomenon could play a key role in the suppression of herbivore populations in natural systems, and that increased nutrient heterogeneity within agricultural crops could contribute to the sustainable control of insect pests in agroecosystems.