Herbivorous insects not only destroy the food itself, but also carry pathogens such as viruses, causing huge losses to agriculture. At present, plants have evolved a lot of mechanisms to defend themselves against herbivorous insects, including morphological, chemical and biochemical defenses. Among them, chemical defense is considered to be more important in increasing defense against herbivorous insects. A typical chemical defense of plants is to produce specialized metabolites as insecticides. Throughout history, specialized metabolites of plants have been exploited by people because of their anti-insect property. Commercial insecticides are often based on plant metabolites and further modified to give them specific physicochemical properties. The development and application of these insecticides has made it possible to scale up the production and increase crop yields of global food.
Applications
The 350000 extant species of vascular plants are consumed by about 400000 species of herbivorous insects. Although all plants are attacked by at least some herbivorous insects, any individual plant species is resistant to the vast majority of herbivorous insects. This is because that many of the more than 600000 known metabolites in plants provide protection against herbivorous insects[1]. Several examples of metabolites used as insecticides are listed below.
- Alkaloids used as insecticides
Alkaloids are plant metabolites and approximately 20% of plants produce them. Alkaloids affect the ionic pathways, neuro-transmitter receptors, transporters and enzymes, which may lead to significant changes in the physiology and behavior of herbivorous insect. Probably the best know alkaloid is nicotine that has been shown to be essential for protecting wild tobacco species from a wide variety of herbivorous insect such as Diabrotica undecimpunctata, Spodoptera exigua and Trimerotropis spp. In addition, plants of the nightshade family, such as potatoes, are known for the toxic alkaloids in their leaves. In potatoes, the alkaloids α-solanine and α-chaconine cause toxicity to the tuber-eating larvae of the Guatemalan potato moth[2].
- Terpenoids used as insecticides
Terpenoids are also one of the most reported plant metabolites associated with herbivorous insects. Many terpenoids are lipophilic metabolites that attack the bio-membranes surrounding the living cells and intracellular compartments. Volatile terpenoids could be used as repellents, preventing or decreasing the contact between plants and herbivorous insect and the transmission of disease. For example, the sesquiterpene 7-epizingiberene from Solanum habrochaites, repels the silverleaf whitefly Bemisia tabaci, a vector for begomoviruses. Another well-described repellent sesquiterpene is (E)-β-caryophyllene that has inhibitory effect on the Asian citrus psyllid Diaphorina citri.
- Other metabolites used as insecticides
Apart from the above plant metabolites, tannins, phenolics, acylsugars, cyanogenic glucosides, and saponins are also used as insecticides in agriculture. One part of these metabolites is highly toxic to herbivorous insects or can be converted into toxic substances in herbivorous insects. Another part of these metabolites can repel herbivorous insects by their smell to protect the plant.
What Can We Do?
Alfa Chemistry has a profound research foundation in the field of insecticides. In our company, you can find the appropriate metabolites for the research of insecticides. Alfa Chemistry will serve you with the most abundant experience and affordable price. Please feel free to contact us if you have a need.
References
- Zhou, S.; Jander, G. Engineering insect resistance using plant specialized metabolites. Current Opinion in Biotechnology. 2021, 70: 115-121.
- Kortbeek, R. W. J.; et al. Endogenous plant metabolites against insects. European Journal of Plant Pathology. 2019, 154: 67-90.
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