One of the subjects i believe are more recurrent and there is always a lot of questions about, it’s pest control.
I wanted to contribute in a way that everyone can see what results i got with these two products.
Feel free to add more.
Azadirachtin
Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing functional groups, including an enol ether, acetal, hemiacetal, tetra-substituted epoxide and a variety of carboxylic esters.
Contents
1 Chemical Synthesis
2 Occurrence and Use
3 Biosynthesis
Chemical synthesis
Azadirachtin has a complex molecular structure; it presents both secondary and tertiary hydroxyl groups and a tetrahydrofuran ether in its molecular structure, alongside 16 stereogenic centres, 7 of which are tetrasubstituted. These characteristics explain the great difficulty encountered when trying to prepare this compound from simple precursors, using methods of synthetic organic chemistry.
Hence, the first total synthesis was published over 22 years after the compound’s discovery: this first synthesis was completed by the research group of Steven Ley at the University of Cambridge in 2007.[1][2] The described synthesis was a relay approach, with the required, heavily functionalized decalin intermediate being made by total synthesis on a small scale, but being derived from the natural product itself for the gram-scale operations required to complete the synthesis.
Occurrence and use
Initially found to be active as a feeding inhibitor towards the desert locust (Schistocerca gregaria),[3] it is now known to affect over 200 species of insects, by acting mainly as an antifeedant and growth disruptor. It was recently found that azadirachitin possesses considerable toxicity towards African cotton leafworm (Spodoptera littarolis), which are resistant to a commonly used biological pesticide, Bacillus thuringiensis. Azadirachtin fulfills many of the criteria needed for a good insecticide. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals (the LD50 in rats is > 3,540 mg/kg making it practically non-toxic).
This compound is found in the seeds (0.2 to 0.8 percent by weight) of the neem tree, Azadirachta indica (hence the prefix aza does not imply an aza compound, but refers to the scientific species name). Many more compounds, related to azadirachtin, are present in the seeds as well as in the leaves and the bark of the neem tree which also show strong biological activities among various pest insects [4][5] Effects of these preparations on beneficial arthropods are generally considered to be minimal. Some laboratory and field studies have found neem extracts to be compatible with biological control. Because pure neem oil contains other insecticidal and fungicidal compounds in addition to azadirachtin, it is generally mixed at a rate of 1 ounce per gallon (7.8 ml/l) of water when used as a pesticide.
Azadirachtin is the active ingredient in many pesticides including TreeAzin,[6] AzaMax,[7] BioNEEM,[8] AzaGuard,[9] and AzaSol[10], Terramera Proof and Terramera Cirkil.
Azadirachtin has a synergistic effect with the biocontrol agent Beauveria[11]
Biosynthesis
Azadirachtin is formed via an elaborate biosynthetic pathway, but is believed that the steroid tirucallol is the precursor to the neem triterpenoid secondary metabolites. Tirucallol is formed from two units of farnesyl diphosphate (FPP) to form a C30 triterpene, but then loses three methyl groups to become a C27 steroid. Tirucallol undergoes an allylic isomerization to form butyrospermol, which is then oxidized. The oxidized butyrospermol subsequently rearranges via a Wagner-Meerwein 1,2-methyl shift to form apotirucallol.
Apotirucallol becomes a tetranortriterpenoid when the four terminal carbons from the side chain are cleaved off. The remaining carbons on the side chain cyclize to form a furan ring and the molecule is oxidized further to form azadirone and azadiradione. The third ring is then opened and oxidized to form the C-seco-limonoids such as nimbin, nimbidinin and salannin, which has been esterified with a molecule of tiglic acid, which is derived from L-isoleucine. It is currently proposed that the target molecule is arrived at by biosynthetically converting azadirone into salanin, which is then heavily oxidized and cyclized to reach azadirachtin.
Potassium Insecticidal Soap
Insecticidal soap is based on potassium fatty acids and is used to control many plant pests. Because insecticidal soap works on only direct contact with the pests, it is sprayed on plants in way such that the entire plant is wetted. Soaps have a low mammalian toxicity and are therefore considered safe to be used around children and pets and may be used in organic farming.
Contents
1 Composition
2 Mechanism of action
3 Affected organisms
4 Use
Composition
Insecticidal soap should be based on long-chain fatty acids (10–18 carbon atoms),[1] because shorter-chain fatty acids tend to be damaging for the plant (phytotoxicity). Short (8-carbon) fatty-acid chains occur for example in coconut oil and palm oil and soaps based on those oils. Recommended concentrations are typically in the range 1–2 percent.[2][3][4] One manufacturer recommends a concentration of 0.06% to 0.25% (pure soap equivalent) for most agricultural applications.;[5][6] another one[7] recommends concentrations of 0.5 to 1% pure soap equivalent. In the European Union, fatty acid potassium salts are registered and allowed as insecticide[8] at a 2% concentration.[9]
Insectidal soap is most effective if it is dissolved in soft water, since the fatty acids in soap tend to precipitate in hard water, thereby reducing the effectivity.[1][5]
Insecticidal soap is sold commercially for aphid control. Labels on these products may not always use the word soap, but they will list “potassium salts of fatty acids” or “potassium laurate” as the active ingredient. Certain types of household soaps (not synthetic detergents) are also suitable,[1] but it may be difficult to tell the composition and water content from the label. Potassium-based soaps are typically soft or liquid.
Mechanism of action
The mechanism of action is not exactly understood.[1] Possible mechanisms are:[1][10]
Soap, which enters via the insect’s trachea, may disrupt cell membranes, resulting in the cell contents leaking from the damaged cells (cytolysis).
Soap may dissolve the wax layer on the cuticle (“skin”), which leads to water loss by evaporation.
Soap may block breathing openings or trachea, which leads to suffocation.
Soap may interfere with growth hormones.
Soap may affect insect metabolism.
Affected organisms
Insecticidal soap works best on soft-bodied insects and arthropods such as[2][5] aphids, adelgids, mealybugs, spider mites, thrips, jumping plant lice, scale insects, whiteflies, and sawfly larvae. It can also be used for caterpillars and leafhoppers, but these large-bodied insects can be more difficult to control with soaps alone. Many pollinators and predatory insects such as lady beetles, bumblebees, and hoverflies are relatively unaffected. However, soap will kill predatory mites that may help control spider mites.[2][11] Also, the soft-bodied aphid-eating larvae of lady beetles, lacewing, and hoverflies may be affected negatively. According to one study[11] a single soap application killed about 15% of lacewing and lady-beetle larvae, and about 65% of predatory mites (Amblyseius andersoni).
Green peach aphids are difficult to control[12] since they reproduce quickly (one adult female can deposit up to four nymphs per day) because they tend to reside under the leaves and in leaf axils (“leaf armpits”), where they may not be wetted by a soap spray. Manufacturers[5][7] indeed state that their insecticidal soaps are only suitable for controlling green peach aphids if used in combination with another insecticide, whereas the same soaps can control other aphids on their own. Among green peach aphids that are in contact with a 2% soap solution, around 95% of the adults and 98% of nymphs die within 48 hours.[12] At 0.75% concentration, the mortality rates are reduced to 75% and 90%, respectively.
Since 2011, insecticidal soap has also been approved in the United States for use against powdery mildew.[5][7] In the European pesticide registration, its use as an insecticide is listed for aphids, white fly, and spider mites.[9] At different concentrations, it may also be used against algae and moss.[9]
Use
Insecticidal soap solution will only kill pests on contact; it has no residual action against aphids that arrive after it has dried. Therefore, the infested plants must be thoroughly wetted. Repeated applications may be necessary to adequately control high populations of pests.
Soap spray may damage plants, especially at higher concentrations or at temperatures above 32 °C (90 °F).[3][4] Plant injury may not be apparent until two days after application. Some plant species are particularly sensitive to soap sprays. Highly sensitive plants include:[5] horse chestnut, Japanese maple (Acer), Sorbus aucuparia (mountain ash), Cherimoya fruit, Lamprocapnos (bleeding heart), and sweet pea. Other sensitive plants are, for example:[4][5] Portulaca, some tomato varieties, Crataegus (hawthorn), cherries, plum, Adiantum (maidenhair fern), Euphorbia milii (crown of thorns), Lantana camara, Tropaeolum (nasturtium), Gardenia jasminoides, Lilium longiflorum (Easter lily). Conifers under (drought) stress or with tender new growth are sensitive as well.
Damage may occur as yellow or brown spotting on the leaves, burned tips, or leaf scorch. Plants under drought stress, young transplants, unrooted cuttings and plants with soft young growth tend to be more sensitive. Sensitivity may be tested on a small portion of a plant or plot before a full-scale application.
One manufacturer recommends that applications are done with 7- to 14-day intervals, with a maximum of three applications,[5] as repeated applications may aggravate phytotoxicity. In addition, water conditioning agents can increase phytotoxicity.[citation needed]
Thanks to its low mammalian toxicity, application of insecticidal soap is typically allowed up to the day of harvest.