Azadirachta
indica (Neem)
Meliaceae
Azadirachta
indica fact sheet (ICRAF)
Neem is a fast-growing tree wihch is native to the
Indian subcontinent, where its medical and insecticidal properties are
well known. It is widely distributed throughout Southeast Asia, East and
Sub-Sahelian Africa, Fiji, Mauritius and parts of Central America. It
grows well in climates from semi-arid to sem-humid and will thrive even
in places with less than 500 mm of rain per year. Its soil requirements
are modest and neem grows equally well on poor, shallow, sandy or stony
soil. The trees fruit when they are 4-5 years old, yielding on average
30-50 kg of fruits per tree. The oil content of the seeds is between 35
and 45%. The effective ingredients are present in all parts of the tree
but are most highly concentrated in the seeds.
Pest control using extracts from the neem
tree is currently practised in more then 55 countries throughout the world,
and neem products have been in use in parts of Asia, such as Burma and
India, for over 2,500 years.
Seeds
The seeds should be dried well so that they do not produce the toxic aflatoxins
which impair their pest control properties and which are highly toxic
to humans. When harvesting neem seeds, care must be taken that the fruit
colour is neither greenish-yellow nor brownish-yellow but plain absolute
yellow. Greenish yellow fruits are not fully mature and are low in azadirachtin
content. For the collection of the fruits, spread a plastic sheet or cloth
under the tree. Thus the seeds do not come in contact with the soil and
the danger of fungus attack and aflatoxin development is reduced. After
collection, the fruit pulp should be removed. The seeds are then dried
for one day in the sun, and the following three days in the shade, during
which they are regularly stirred. Stored neem kernels should be kept in
well aerated containers or jute bags to prevent mould, which reduces effectiveness
and produces highly toxic aflatoxins. Seeds between 3 and 8-10 months
after harvest have the highest quantity of azadirachtin. Germination of
neem seeds will decrease about one month after harvest and if exposed
to temperatures higher than 45C.
Leaves
The advantage of using neem leaves lies in the fact that leaves are available
all year round and do not have to be processed for storage. It is reported
that a mature tree of about 8-10 m in height can produce about 360 kg
of fresh leaves per year.
The insect-controlling substances are
primarily azadirachtin A and B. In addition, neem contains a number of
other chemical substances such as Salannin and Meliantriol, which have
primarily repellent effects, and Nimbin/Nimbidin, which seem to have antiviral
effects. Some substances support each other, thus creating synergiestic
effects.
Insecticidal, repellent, antifeedant, acaricidal, growth-inhibiting, nematocidal,
fungicidal, antiviral
Neem compounds act mainly as a stomach poison and systemic.
The compounds are most effective against insects of the following
orders:
Coleoptera (beetles and their larvae), Lepidoptera (caterpillars = larvae
of butterflies and moths), Orthoptera (nymphs and adults of grasshoppers
and locusts). Results against some bugs, leafhoppers and whiteflies have
also been good.
Field insects |
|
American bollworm |
Helicoverpa armigera |
Ants |
general |
Banana pseudostem borer |
Odoiporus longicollis |
Bean pod borer |
Maruca testulalis |
Brown rice planthopper |
Nilaparvata lugens |
Bunch caterpillar |
Andraca bipunctata |
Cabbage worm |
Mamestra brassicae |
Citrus leaf miner |
Phyllocnistis citrella |
Cockchafer grub |
Lachnostema impressa |
Colorado beetle |
Leptinotarsa decemlineata |
Cutworms |
Agrotis spp. |
Desert locust |
Schistocerca gregaria |
Diamondback moth |
Plutella xylostella |
Fall armyworm |
Spodoptera jrugiperda |
Flea beetle |
Podagrica uniforma |
Gram pod borer |
Clavigralla tomentosicollis |
Green rice leafhopper |
Nephotettix virescens |
Leafhopper |
Empoasca jlavescens |
Leaf miner |
Liriomyza spp. |
Mexican bean beetle |
Epilachna varivestis |
Migratory locust |
Locusta migratoria |
Mites |
general |
Red coffee mite |
Oligonychus coffeae |
Red crevice tea mite |
Brevipalpus phoenicis |
Rice leaffolder |
Cnaphalocrocis medinalis |
Rice gall midge |
Orseolia oryzae |
Rice stemborers |
general |
Rhinoceros beetle |
Oryctes rhinoceros |
Scales |
Chrysomphalus aonidium |
Stem borers |
Busseola jusca, Chilo suppresalis |
Termites |
Coptotermes jormosanus |
Thrips |
Heliothrips spp. |
Whitefly |
Bemisia tabaci |
White-backed rice planthopper |
Sogatella jurcifera |
Storage insects |
|
Cowpea weevil
|
Callosobruchus maculatus |
Khapra beetle |
Trogoderma granarium |
Lesser grain borer |
Rhyzopertha dominica |
Rice weevil |
Sitophilus oryzae |
Maize weevil |
Sitophilus zeamais |
Field diseases |
|
Grey leaf spot |
Pestalotiopsis palmarum |
Powdery mildew |
|
Basal stem rot |
Ganoderma lucidum |
Viruses |
many types |
Spiders, ants and birds are not affected. The ladybird beetle has been
found to suffer minor mortality of 3% under field conditions. Bees sometimes
are unable to hatch or have crippled wings. Rice fields treated with neem
products house more natural enemies than untreated fields. Earthworms
do not like to penetrate into soil treated with neem, but if they do,
they grow better and have higher fertility. IRRI reported that neem was
relatively non-toxic to most parasitoids and predators of rice pests.
In Mauritius, no adverse effects on the development and emergence of the
introduced larval parasitoid of the diamondback moth, Apanteles plutellae,
were found.
The fungus Aspergillus flavus easily develops on seeds with a
moisture content of more than 14%, producing carcinogenic aflatoxins and
thus posing a health hazard to humans.
• For sprays with neem seeds, only seeds which are green inside
have a high azadirachtin content. If they are brown inside, they should
be discarded.
• The pulp of the fruits has no insect control properties and should
best be removed.
• Per ha, about 30 g of azadirachtin is required. In neem seeds,
contents between 2 and 9 mg/g can be found. Therefore it is best to get
the seeds analyzed, where possible, in order to establish the optimum
ratio for preparing extracts.
• Azadirachtin is highly sensitive to ultraviolet light. Therefore
spraying in the evening is highly recommended.
• Applications against viruses must be conducted preventively before
the infestation occurs in order to be effective.
Seed protection
This treatment is used against rice gall midge, thrips, brown rice
planthoppers, soilborne insects and crabs.
Prepare a container with sufficient volume to submerse the required quantity
of water and seeds. Then dissolve the appropriate amount of powdered neem
kernels into the container. A rate of 1 kg neem powder per 16 kg of rice
seeds is suggested. The bagged rice seeds are submersed in the neem solution
and soaked overnight. Then they are ready to be broadcast into the prepared
seedbed.
Aqueous seed extracts
Pure azadirachtin is poorly soluble in water. But it is almost
completely dissolved in water extracts of seed powder, due to the action
of cosolvents. Therefore, water extracts can be as effective as a commercial
neem extract. As general guidelines, the following quantities are recommended.
Basic neem formula |
Low incidence
of pests or control
of highly susceptible pests, g/ltr water |
High incidence
of pests or control
of moderately susceptible pests, g/ltr water |
Seed powder: |
15 - 30 |
40 - 60 |
Kernel power: |
10 - 20 |
30 - 40 |
Seed cake powder: |
15 - 30 |
40 - 60 |
Kernel cake powder: |
10 - 20 |
30 - 40 |
50 g of neem seeds
(or 25 g of kernels) is required for use in 1 litre of water. The neem
kernels are pounded gently so that no oil comes out. If the seed coat
has not been removed, 75 g is required. This mixture is extracted overnight.
The next day it is filtered and mixed with liquid soap at a rate of 1
ml soap per litre of extract. Other recommendations are 25-50 g of neem
kernel per one litre of water, depending on the situation). Successful
control against the diamondback moth have been found at concentrations
of 1% to 3%. For effective control of citrus leaf miner, Phyllocnistis
citrella, this neem emulsion should be applied after the emergence
of new leafflush at 10 day intervals.
Hot neem
seed kernel extract
A neem seed kernel extract at 2% is prepared by soaking 1 kg of seed powder
in two litres of hot water for three days. The resultant decoction is
filtered and filled up with water to obtain the 2% concentration. Liquid
soap is added at 0.1% as an emulsifier.
To control major
pests in tea such as spider mites (Oligonyehus coffeae, Brevipalpus
phoenieis), thrips (Heliothrips haemorrhodalis), leaf hoppers
(Empoasca jlaveseens), and bunch caterpillars (Andraca bipunetata),
the following spray can be made by 2.5 kg of crushed seeds in 20 litres
of water. After soaking for 16-18 hours, the resulting filtrate is filled
up to 200 litres with water and ready for application. This volume is
roughly sufficient for 1 hectare. This spray was used during conversion
to organic tea cultivation. In the first year of conversion two complete
rounds of spraying were conducted. The above spray was alternated with
neem oil cake extract and neem oil soapnut extract (description under
neem cake and neem oil). After this, only spot spraying was applied as
needed, using one of the three extracts, depending on the pests and effectiveness.
This approach kept pests under control and encouraged beneficial insects.
In the second year the incidence of insect pests was already reduced and
beneficial insects increased their activity. From the third year onward,
a total ecological balance was achieved.
Neem seed/kernel
powder application
Neem kernel powder is mixed with sawdust or dry clay at a ratio of 1:1
and placed into the funnel of young maize plants for the control of maize
stalkborer. This mix is applied in the whorl of maize or sorghum plants
at a rate of 0.5 -1.0 g per plant. Application time starts 2-3 weeks after
germination. Another 1-2 applications at intervals of 2-3 weeks are necessary.
Applications make sense only in late sown maize when the pressure of maize
stalkborers is high. For an average field of 25,000 maize plants per ha,
about 12.5 kg of the mixture of neem seed and inert material is necessary.
This equals 6.25 kg neem seed powder per ha and application. Treatments
should be repeated every 8-10 days. Roughly 3 applications are sufficient
for an effective control of stalkborers. This treatment should be applied
on young plants before flowering. Similarly, farmers in Honduras use neem
kernel powder against fall armyworm in maize. The seeds are peeled and
crushed and the resulting 'cake' is crumbled into the whorl of maize plants.
Some farmers use a mixture of ground neem seeds and soil in the same way.
Admixing inert material is necessary to avoid phytotoxicity.
The same treatment
can be applied against the rhinoceros beetle in coconut. Crown application
of neem seed powder + inert material has proven quite as effective as
chemical treatment. Incorporation of neem seed kernel powder in manure
pits reduces the population of rhinoceros grubs in these breeding sites.
Neem oil/emulsion
Neem oil can control sucking insects like aphids, whiteflies and stemborers.
30-40 ml of neem oil is added to 1 litre of water, stirred well and then
an emulsifier added, e.g. liquid soap at 1 ml per litre. It is essential
to add the emulsifier and mix properly. It should be used immediately
otherwise oil droplets start floating. A knapsack sprayer is better for
neem oil spraying than a hand sprayer. Per hectare ca. 500 l of the finished
liquid is required. This spray is effective in controlling cockchafer
grubs (Lachnosterna impressa), scales (Chrysomphalus aonidium)
and tea mosquito bug (Helopeltis theivora) in organic tea cultivation.
An emulsion is formed by mixing 2 litres of neem oil with 1 kg of soapnut
powder (Sapindus emerginatus) which is then filled up to 200
litres with water. For effective control of the grubs, ground application
around the collar of the tea plant is important. Against tea mosquito
bug complete drenching of the tea bush covering the frame and ground around
the collar is recommended.
Neem cake extract
100 g of neem cake is required for 1 litre of water. The neem cake is
put in a muslin cloth and soaked in water overnight. It is then filtered
and liquid soap is added as emulsifier at a rate of 1 ml/litre of extract.
In tea cultivation a neem cake extract is used against the major tea pests,
particularly spider mites, thrips and leafhoppers. It is prepared by soaking
2.5 kg of neem cake in 20 litres of water for about 12 hours. The filtrate
is then filled up to 200 litres with water which is roughly enough to
spray 1 hectare.
Neem Soil incorporation
Neem cake protects eggplants against fruit and shoot borer (Leucinodes
orhonalis) and tomatoes against nematodes and leaf spot disease.
Farmers in India's Pune district plough in 1-2 tiha of neem cake. 250-2,000
kg/ha is recommended to suppress nematodes and certain fungi in the root
system and to reduce denitrification. Another method of using neem cake
is by putting 8 kg of it in a sack. After tying, it is placed in the irrigation
channels of paddy crop for control of rice stem borer, rice gall midge
and bacterial wilt. This practice is first applied 18 to 20 days after
transplanting and renewed every 25 days.
Neem leaf extracts
Neem leaves should be used before flowering occurs. This extract is effective
against leaf-eating caterpillars, grubs, locusts and grasshoppers. For
5 litres of water, 1 kilogram of fresh neem leaves are required. The leaves
are chopped and soaked overnight in water. The next day, the extract is
filtered and liquid soap is added at 1 ml per litre as a sticker. Since
the quantity of leaves required for preparation of this extract is quite
high (nearly 80 kg for 1 hectare), this practice is more appropriate for
nurseries and kitchen gardens.
Used against whitefly and aphids in tomatoes
in Honduras in the following proportions: 2 kg pounded neem leaves, 30
g soap. Mix the ingredients together and leave them to soak overnight
(the solution was found to be less effective if used straight away rather
than left to soak overnight). The next day, sieve the solution, take 5
litres of the stock solution and fill up to 20 litres with water. These
quantities make four tanks, which is enough for 0.22 ha of tomatoes or
0.18 ha of maize. Tomatoes are sprayed at four and then at eight days
after germination whilst in the seedbed, and two to four times a week
once transplanted to avoid whitefly problems.
Neem leaf extracts are also used in the
following concentrations against fall armyworm, grasshoppers and white
grubs in maize. Pound 1.25-2 kg leaves and leave them to soak overnight
in some water. Sieve the resulting solution and fill it up to 10-12 litres
in total, which is sufficient for ca. 1,000 m2 of maize. The solution
is either blanket sprayed or spot applied. Fall armyworm in areas which
had been sprayed in the morning were dead by the afternoon. For white
grubs, the spray was directed at the foot of affected plants. Leaf extracts
using 350 g fresh leaves per litre of water is effective against thrips
(Megalurothrips sjoestedti), the bean pod borer (Maruca testulalis)
in beans and the American bollworm.
Neem seed powder - storage insects
Most stored grain pests are susceptible to neem's effect, except the saw-toothed
grain beetle (Oryzaephilus surinamensis), which breeds well on
neem.
There are three methods to apply neem in storage protection:
1. neem seed powder
2. neem seed slurry
3. neem oil
The Indian Agricultural Research Institute
(lARI) in New Delhi has tested the effectiveness of neem seed powder in
storage protection against rice weevil, lesser grain borer and khapra
beetles. Neem seed powder was mixed with wheat at rates of O.5, 1.0 and
2.0% by volume. The results showed that the 1.0 and 2.0% admixture protected
the seed against rice weevils, lesser grain borers and khapra beetles
for 269, 321 and 379 days, respectively. This method should be of interest
to village farmers storing grain in smaller quantities. Seeds from legumes
were similarly treated and were shown to suffer no deterioration in germination
properties.
In another test the IARI examined the
effect of neem seed kernel powder against the khapra beetle and the lesser
grain borer when mixed with wheat at the rate of O.5%, 1.0%, 2.0% and
4.0%. This showed that the khapra beetles were more vulnerable to neem.
After 240 days 24% of the wheat was found to have suffered khapra damage
when treated with 0.5% neem, but only 8% in the case of the 4.0% admixture.
On the other hand, neem seed kernel powder had no effect on the lesser
grain borer, for even with the 4.0% treatment, 92% of the wheat suffered
insect damage. This result contradicts the foregoing one obtained by the
same research institute.
Neem seed slurry
A pplying plant powders as slurry preparations fared better as protectants
against the larger grain borer (Prostephanus truncatus) than
the powder preparations. An explanation of the superiority of the slurries
over the powders is that with the slurry treatment, the grains are more
thoroughly coated. With the powder treatment, the powders tend to settle
at the bottom of the container. Slurries are prepared by weighing out
the seed powder and adding water to give the respective concentration.
At 10% and 5% (w/w) the weight losses were kept below 5%. The neem kernel
slurry at 1% was clearly more effective than the neem leaf slurry at 10%.
Neem oil
To produce neem oil by hand, use the dried kernels. These first have to
be decorticated. In a mortar they are lightly cracked so that the outer
husks are freed from the inner seed. The husks are then removed by winnowing.
The decorticated seeds are returned to the mortar where they are pounded
until they form a brown, slightly sticky mass. A little water is added
so as to form a workable paste which forms an almost solid ball. This
ball is kneaded for several minutes over a bowl until oil collects on
the surface. Then it is firmly pressed. Oil will come out in drops. Alternate
kneading and squeezing will separate the oil. With this method 100-150
ml of oil can be extracted from one kg of neem kernels. This is about
half the oil content (440). Neem oil is now commercially available in
an increasing number of countries.
In the Sudan, for the control of the potato tuber moth (Phthorimaea
operculella), the tubers are sprayed with an aqueous neem seed extract.
Afterwards they are bagged in jute sacks. This practice significantly
reduces damage. Results of experiments conducted in Thailand suggest that
admixing neem oil to mung bean seeds at a rate of 2-5 ml/kg mung beans
can effectively control cowpea weevils (Callosobruchus maculatus)
for up to 8 months with a damage of less than 15%.
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