I’m sure there have been a few studies published looking at the impact of biological control in agriculture, measuring the impact and effectiveness of biological control both on its own and in tandem with careful application of pesticides (integrated pest management).
I go to an agricultural college- I wrote an essay on the positive influence of bats and birds on agriculture- we learnt about it at school.
They are starting to use wasps to control caterpillars in broccoli- https://www.accessscience.com/content/ichneumon-wasps-as-biological-control-agents/BR0622151
I don’t know about lizards, spiders or mantids tho…
don’t they eat pollinators like bees , butterflies
Welcome to the forum @abhijatshakya
With a recent lizard population explosion in my garden, this is something I have wondered about as well.
I have certainly noticed a sharp decline in weevil damage in my garden the corresponds to an increase in the number of tree frogs in my garden.
The Xerces Society has some good webinars about IPM and biological controls. One of them talked about providing host plants for hoverflies because their larvae are excellent aphid predators. A nursery in California placed hanging baskets of Alyssum to attract hoverflies and it has reduced their use of pesticides.
Biological control is a great , sustainable and sometimes dreamy it seems ,but sure it has some side effects as
1)It does not completely wipe out pests
So what do you think guys what should be the sustainable method is your veiw to control pests
Given the demand for food to feed an ever-growing human population, we likely won’t get 100% away from the use of chemicals. There’s been a considerable amount of research done, so following where the science leads would be best. A couple of good resources on IPM are here:
Here’s a paper that you might find interesting: https://royalsocietypublishing.org/doi/10.1098/rsbl.2012.0948
Excerpt from the abstract: “(…)Because all spiders are silk-producing carnivores, we hypothesized that silk alone would signal other arthropods and enhance non-lethal effects of spiders.”
And from the discussion: “Silk has many remarkable properties; these results add plant protection to the list and suggest that strategies promoting spiders and silk production could be important to integrated pest management programmes.”
The short answer is yes. The longer answer is perhaps. IPM came to the fore when, in the 1960’s, all major cotton pests became resistant to all registered pesticides. The problem with most modern crops is that they are a monoculture, and not much lives in the fields except the crops, the pests, and some introduced ‘Pest controllers’. Many of the NA pests are introduced, or have few natural predators. There has been work done on introducing parasites and diseases, and sterilised male biting insects. All of them reduce the pest load, but in modern agriculture maximum yield is essential. So while biological pest control can reduce the amount of pesticide used, especially in smaller plots, it is much harder in large farms.
Speaking from the perspective of someone in agriculture - spiders, mantises and lizards not so much, particularly since they are also cannibalistic in times of prey shortage and are generalists.
Parasitic wasps, ladybirds, lacewings and entomopathogens work much better. For vertebrate predators, birds do a decent job as they will scour large areas and flock towards concentrations of insects.
The thing is completely wiping out pests is not necessary and probably not possible. Even if it were possible, the colleterial damage is unacceptable. Pesticides can’t tell a beneficial insect from a pest. The point is to keep damage to an acceptable level. There are several videos on YouTube of people soaking their strawberries in salt water and being horrified when fruit larva come out. The truth is anyone who has ever eaten a strawberry has probably eaten a few larvae. For the most part it is not a problem. A little bit of fruit gets spoiled when the infestation is too bad, and in exchange we get to keep the birds and bees.
I also heard not only pesticides but also neem and eucalyptus leaves are able to repell pests.
I wonder how agricultural practices were taken without these chemicals
Spiders, wasps, and mantises especially are very good to have in your agricultural areas. Certain ladybug species are also good allies, as are dragonflies.
Bats, and a wide range of birds are also major benefactors.
Not sure about the impact of lizards though.
I used to work in a winery/vineyard and while I was there we switched over to entirely organic agriculture. One of the big questions was how to handle insect pests and the research we did indicated that the most effective thing to do was to establish large native plant buffers on the margins of the vineyard, establish native plant habitats within the vineyard, use a permanent cover-crop to provide a diversity of habitat, to do what ecological restoration we could in other areas, and to place bird perches and bat-boxes on the property.
The idea is to reestablish a predator-prey balance. You accept that you’ll have some crop damage, but that if you have a good amount of naturally occurring predators (as well as other species competing for the pest niche), the over-all amount of crop damage is minimal.
Doing this at the vineyard scale (not a large on, only about 126 acres) took a few years to get established, but once it was it worked really well. We did this back in 2003 or so and I left in 2005. I’ve kept in contact with the owners and some of the folks working there and it’s still operating very well and effectively.
Two of the best projects I saw were ones where spraying was contraindicated. With Bertha Armyworms in Manitoba, farmers often sprayed when they saw larvae at the top of Canola crops. Some of the guys I worked with showed that by then, most of the damage had already been done, and spraying was a waste of money. Practice changed. Another study in Manitoba showed that the second spraying for aphids in peas was a waste. Again, by that time the damage had been done. Those studies were done by Agriculture Canada - I’m not sure they would be done now given the shift in funding models. Chemical companies don’t want work that decreases the need for their product.
Good to hear that
That sounds great and the way that should be utilized much more often!
My wife is an IPM advisor to retail nurseries. She comes home with a lot of horror stories. The sad thing is a lot of research has been done, and the information is on the label, but no one reads the labels. That includes the nursery “professionals.” There are many critters that can only be killed in the larval stage, which often can’t be seen. By the time the adults are out, the damage has been done, and pesticides not only don’t work, but kill beneficials.
She also regularly gets questions about what pesticide to use on bees. People place flowering plants near their doors, bees come, they are afraid of getting stung, so want to kill the bees. She calmly explains there is no retail pesticide listed for killing bees, using pesticides contrary to the packaging is a violation of federal law, and they should just remove the plant.
Neem and eucalyptus oil are fairly benign and effective.
By “these chemicals” do you mean things like neem and eucalyptus or the various pesticides that are in common use now?
There are a number of documentaries about returning farm land to biodiverse farming operations.
One set I enjoyed watching detail the transformation of Apricot Lane Farm in Moorpark, CA. I remember one part where they learned to welcomed back the coyotes for their role in pest management.