Plant Trials – Natural Pesticides & Biochar

Today is the first in what will hopefully be an ongoing stream of posts by our interns about the projects they’re carrying out on the farm. We hope that these will not only provide useful information that we collect in our own experiments to other farms, but give potential interns an idea of what we’re doing and what they could potentially get involved in.

Kiara is an expert in integrated pest management who’s been working with us for a number of months in the development of natural pesticides and fertilizers. Before leaving this week she wrote us up a short post to let our readers know what she’s been doing.



During my time as a work trade at Bona Fide I worked on a number of projects in the gardens with Nevis.

Insecticide/repellent trial

Using Nevis’s recipes from a local workshop, we produced 3 products which are supposed to help with insect problems.  One product was made with zorillo and meca leaves, one was made with cedro leaves, and one was made with neem.  The idea for testing these three products specifically was that they can be found on the farm or within a short distance and the only cost is labour.  They are very time consuming to produce though!


To create the zorrillo and cedro products:

-collected leaves

-cut them up with scissors or tore them with our hands until they were small pieces

-put them through a hand grinder

-mixed with hands in water for about 5min

-left the pulp to soak in water overnight

-strained the liquid the next day

-put the liquid in pop bottles and left for over a month to ferment

-the lids had to be opened at least daily in the beginning to release gases

To create the neem product:

-deshelled neem seeds

-they had to be carefully sorted because almost all of the neem seeds (which were collected in the wet season) had some sort of fungus. We used the cleanest seeds we could.

-the seeds were put through the hand grinder

-mixed with hands in water for about 5min

-left to soak overnight

-strained the liquid the next day

-left in a bottle to ferment for a bit less than a month

natural pesticide

Because we did not have enough space at the farm to properly space out the treatments, the products were tested on squash plants at Hector’s house in town.  The treatments were zorillo, cedro, neem and a water control.  Four replicates were set up for each treatment.  Single leaves about six inches wide were flagged, leaving a minimum spacing of one foot, and they were also marked with a permanent marker.  The backs of each squash leaf were covered with aphids so we ended up having to reduce our number of replications and plot size.  We cut the selected leaves in half and counted aphids on the underside of two replicates.  One person completed each replicate.   The other two replicates which were not counted, were simply observed.  The products were then sprayed in the late afternoon when the sun was not strong.  The products were diluted with water and soap was added to the neem product by lathering soap in water until it was foamy.  Aphid numbers were then counted again six days post spray.  It appears that neem may have an ability to kill aphids and zorillo and cedro may have repellent effects on squash plants.  No conclusions can be made yet because we need to statistically analyse the data.




A trial has been set up to view the effect of biochar in combination with different fertilizers.  The five treatments we have are: biochar, biochar and worm compost, biochar and urine, biochar and worm compost and urine, and a water control.  The biochar source was mainly corn cobs and these were broken down into fine bits.  For the treatments with urine, the biochar was soaked/inoculated with the urine for at least a week.  The worm compost was mixed with biochar a few days before mixing it with soil.  In order to inoculate the biochar with worm compost, water was added so an equal amount of water was added to all of the treatments because we know that biochar has an effect on water.  We have two replicates in the garden, each in a different bed.  The beds were made by digging up the soil and adding fine gravel, rice hulls and finely chopped rice straw.  The plots are six inches by twenty four inches and are separated by eighteen inches.  Bricks were also placed in a line between the plots to stop nutrients and water from moving from one plot to another.  The treatments were mixed into the soil within the top four inches and then covered with straw.  Three days later, healthy basil transplants were planted in the plots- four per plot and spaced with four inches in between them.  Lettuce and misuna plants were seeded around the basil plants, outside of the treatment areas.  Measurements of width, height and maximum leaf number per node have been taken weekly and will continue to be taken.  So far it appears that the plants growing with urine and biochar and urine, compost and biochar are much healthier than the other treatments.  Because biochar is supposed to have long term effects on the soil, we will continue to observe the treatments.


We can see the greener rows here, which contain biochar inoculated with urine. As time progresses these rows have seen markedly improved growth.


Other tests

-zorillo and meca leaf pulp does not appear to repel rats from eating planted bean seeds

-pop bottle containers can be used to protect planted beans from being eaten by rats

-bay leaves do not appear to repel weevils from eating sorgum

-Bromner’s peppermint soap diluted with water does not appear to function very well to kill aphids

-fresh cow manure mixed with water as a foliar fertilizer works really well but the USA regulations on the preharvest interval for raw manure, foliar sprays is about four months



-tested the germination of some seeds

-started a batch of effective microorganisms using whey, molasses sugar water, untouched forest floor leaves and dirt and rice germ

effective microorganisms

-bed covers could be created out of a fine netting which can be bought in Managua to protect plants from insects (same material which is used to make mosquito nets)

-lots of umbels should be planted within the beds to attract beneficial insects- you have to let them go to seed

-beds are compacted but could be improved with lots of mulch


If you want more information you can contact

Kiara Jack

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