Facts About Botanical Pesticides from Dr . Pio Javier, IPM expert
Interview by : Eric Jhon dG . Cruz & Sarah Jane B . Manaday Photos : PA Javier
Dr. Pio A. Javier, multi awarded researcher and faculty of CPC has recentlyretired from a 40 year dedicated and meritorious service at the Crop Protection Cluster-National Crop Protection Center. He was one of the pioneers of integrated pest management and biological control projects and studies that the cluster continues to be proud of.
To name a few, researches on Trichogramma parasitoids, biological control against Asian corn borer, was one of his pioneering tasks at NCPC. He also initiated researches on earwigs, effective predators of corn borer as well as pests of coconut and banana. He received numerous awards from local and national agricultural entities due to his hard works as researcher, extension worker and for the last years as cluster, a faculty. With the advent of organic agriculture, he has been doing serious studies on botanical pesticides.
The following are highlights of his studies on BPs:
WHAT ARE Botanical Pesticides (BPs)?
Botanical pesticides or plant extracts are naturally occurring toxins obtained from plants that is intended to reduce pest populations. Specifically, botanical insecticides are plant extracts intended for the control of insect pests. There are plants that have evolved for several million years and to defend themselves from frequent insect infestation they were able to biosynthesize any of the compounds like alkaloids, steroids, phenols, flavonoids, glycosides, glucosinolates, quinones, tanins and terpenoids that are toxic against insects. If you see plants that are quite healthy and free from insect damage, suspect that these plants might contain compounds that may exhibit toxicity against insect pests. The use of plant extracts as insecticides dates back as the Roman Empire wherein dry flowers of pyrethrum was used in delousing children.
Not all plants can be a safe source of botanical pesticides because some plants may exhibit high toxicity to mammals and maybe carcinogenic like the yellow bell. The tubli (Derris elliptica), a botanical insecticide that exhibits toxicity against wide range of insect pests could not be recommended since it is quite toxic to fish.
Therefore, not all plants that are reported to be toxic against insect pests could be used as a safe source of botanical insecticides. Examples of plant extracts that can be sources of BPs are makabuhay, oregano, luyang dilaw, langkauas, marigold, lantana, name, black pepper, lagundi, lemon grass and many others. Fortunately, most of these plants also have medicinal values, hence, they can be considered as safe source of botanical insecticide.
How are BPs prepared and applied?
The common practice of obtaining plant extracts from plants is by using expensive solvent systems like hexane, methanol and others; but the use of solvent systems are not allowed in organic agriculture, instead vinegar, wine and water are being recommended.
MODE OF ACTION OF BPs
Although plant extracts kill insects through contact toxicity (applied directly to insects), do not expect that the application of BP will cause an immediate and abrupt reduction in insect pest populations. Many of the plant extracts are less toxic to insects than synthetic insecticides. The residual action of plant extracts is short since they are rapidly degraded by UV light, therefore, BP should be applied more frequently. BPs do not leave residues on treated plant parts, hence they are safe to non-target organisms and insect resistance development to BP is not common. Botanical pesticides exhibit antioxidant activity which suggests that insects could feed on the treated plants but there is significant reduction in food intake until the insects die of starvation. Botanical pesticides also exhibit repellent action wherein the insect are driven away after exposure to treated plant parts without necessarily initiating the feeding activity. Another mode of action of BP is that they possess growth inhibitory effects. Insects that feed on plants treated with BP results to the emergence of abnormal pupae and adults and produce eggs that are partially sterile. With the above properties of BP, the use of plant extracts could be an important component of integrated pest management since they are safe to the population of biological control agents which played a significant role in regulating pest population. This will be better than the synthetic insecticides which will kill majority of the insect pests but at the same time will decimate the biological control agents in the field.
Do you prepare crude extracts only or are the bioactive components being identified? What can you say about the stability of the final product?
Initially, we prepared crude water extracts only but the extracts should be immediately applied within 48 h because they are unstable. After 48 hours, some materials, especially langkauas and oregano will have a foul smell, an indication that the crude plant extracts are unstable which will reduce their insecticidal activity. We observed that farmers are adding molasses in their extracts and lately, we also add molasses in our plant extracts and fortunately we noticed that development of foul odor was prevented and the activity of the extracts is maintained. Consequently, we always add molasses to our crude plant extracts to extend the shelf-life. With regards to the identification of the active components of the plant extracts is not a part of our project and we don’t have the capacity to do the identification. However, the active components of the different botanical insecticides had already been identified and this could be searched in the internet.
How effective are BPs? What is the mortality rate of the pests?
There are so many plant extracts that were reported to be toxic against many insect pest species. When we conducted the contact toxicity tests, majority of the reported plants showing toxicity to insect pests are not that toxic. Remember that insect mortality using plant extracts can not be compared with the synthetic pesticides since the concentration of the active component is quite low. The effectiveness of the plant extract will vary depending on the target pest to be controlled. For example, mortality can be as high as 100% for black bean aphids using oregano, 90% against flea beetle of eggplant using langkauas, 70% for cutworms, and 30-70% for others. However, mortality should not always be the yardstick in determining the effectiveness of the plant extract.
BPs also exhibit other mode of action like anti -oxidant activity wherein the insect will also feed but their food intake in treated plant parts will be significantly reduced until the insect die from starvation. Some BPs possess repellent effect wherein the insects will be driven away after exposure to treated plants parts even if there is no feeding. BPs could also cause insect growth regulatory effects.
Feeding on plants treated with plant extracts may results to the emergence if abnormal pupae and adults.
In terms of commercialization are there companies marketing BPs already? How much will it cost to purchase these botanical pesticides?
Foreign companies have started to market these BPs but for local companies, some are importing these BPs. Local producers are encouraged to register their material but the registration procedure is not yet intact. It’s on-going and around 90% finished by BAFPS. There is a cooperative in Tayabas, Quezon that sells plant extracts at less than 100 pesos for 1 Liter. I believe botanical insecticides are cheaper than synthetic insecticides.
Is there a necessity for personal protective equipment (PPE)?
It is not that strict as compared with the application of synthetic insecticides but it is still recommended due to some ingredients in the BPs that may act as irritant (example is sili).
In terms of usage, can you say that farmers have been using BPs significantly?
BPs are primarily used by organic crop producers; in fact, they are major line of defense used by organic growers that reduce pest infestation. Therefore, almost all of them are now using botanical pesticides in their crops except for ordinary farmers, because of the low mortality rate against pests. They have to protect their crops against pests because consumers demand crops that are free from pest damage .
Are there botanical fungicides or herbicides for fruits also?
We do not have projects on fruit trees but there should be an evaluation of botanicals against major pests of fruit trees especially in mangoes. However, Dr. Candida B. Adalla had already registered luyang dilaw extracts against scale insects in lanzones. For the botanical fungicides, I had a project with Mr. Carlos L. Padilla, study leader in my previous PCAARRDfunded project and existing DA-BAR project but based on our results, there are very few botanical pesticides with fungicidal activity. Generally, it can be used for preventive application when the infestation is still low.