Neem Oil used against animal health (Cattle Tick)

A study on the effect of neem oil on the life cycle of the cattle tick (Boophilus microplus) by John Farries a report of a trial undertaken in a dairy herd in Thailand an addition to the current research literature on neem as a natural pesticide of interest to agricultural researchers and practitioners in the developing world.

ABSTRACT

Ticks of all stages were collected and treated with solutions of neem oil diluted in
water in concentrations of 0.1%, 0.2%, 0.4%, 0.6%, 0.8% and 1.0%. These were compared with a control of water only. It was found that in the greater dilutions, the immature ticks as well as the gravid ticks laid ticks before dying. The dilution of 1.0% had the greatest mortality with least egg laying.

Eggs from treated and non-treated ticks were hatched and the resultant nymphs were also treated with dilutions of 0.1%, 0.2%, 0.4%, 0.6%, 0.8% and 1.0%. Viability and hatchability was affected by the different dilutions: the dilution of 0.1% had least effect on the viability of the eggs laid and had the greatest hatchability, while the dilutions of 0.8% and 1.0% had the greatest effect, with 60-75% of the eggs non-viable.

The eggs of the treated ticks were smaller and paler in colour than those of the non-treated ticks. The time of incubation did not vary and was around 21 days. Nymphs from eggs of treated ticks were paler and had less mobility than those from eggs of untreated ticks, although heat and light stimulated allstantly by the alcohol rather than by the concentration of neem oil.

When collecting ticks from the cattle, it was found that there were smaller darker ticks in the container after collection. These were considered to be male ticks which had attached to the underside of the female ticks in the act of fertilisation. These small dark ticks were also more active, indicating that they may fertilise more than one female, the main aim of which is to engorge with blood and reproduce. In the treatment, the small dark ticks died before the female ticks.

METHOD

Eight-legged ticks of immature and gravid stages were collected from cattle at the dairy at Rachamangale Institute of Technology, Pitsanuloke. These were then segregated into screwtop containers. Natural conditions such as soil and moisture were provided for some ticks. Tissue paper soaked with bovine blood was also provided. This did not prove to be effective in feeding any tick that was not gravid. Some ticks were given a dry container - no natural conditions. These were usually single ticks or pair of ticks.

Untreated ticks were watched and maintained until hatching. Fungus appears to be the main predator of untreated gravid ticks, especially were moisture has been added.

Ticks which were treated were in batches of 5-10 depending upon the number of ticks collected and available. The replication tests were carried out with greater numbers. The tests were replicated two times.

Two methods were used to treat ticks in order to to simulate
1. whether the tick was already on the animal when the animal was sprayed
or
2. whether the tick crawled onto the animal after spraying.

To simulate the first case, the relevant dilution was brushed onto the ticks with a brush. For the second, the ticks were put in a screwtop bottle on top of a tissue soaked with the relevant dilution of neem oil and water, and application was by sensory touch of the tick. The effects of the two methods were relatively similar.

In moist conditions, eggs from untreated ticks develop embryos in 12 days. The eggs from treated ticks are slower to develop and there is a greater incidence of eggs collapsing and drying out in dilutions of 0.4%, 0.6% and 0.8%.

At hatching, nymphs from untreated ticks were distributed into screwtop bottles with tissue paper soaked in the six dilutions. There was a control bottle with water only. Numbers per bottle varied from 50-200 depending on the replication. Regular counting of live/dead nymphs took place thereafter until all nymphs were dead or had expired through loss of energy.

When nymphs hatched from the eggs of treated ticks, further diluent was added to maintain moisture content within the bottle. Live/dead counts were taken of these groups also.

RESULTS

Treated ticks

As the table shows, the number of immature ticks which attempt to complete their life cycle by laying eggs is similar to those in the control group for all dilutions, except when treated with 1.0% solution.

Treatment % of ticks laying eggs Mean of 3 replications
Control 25 : 30 : 43 32%
0.1% 23 : 20 : 22 22%
0.2% 22 : 35 : 27 28%
0.4% 43 : 25 : 8 25%
0.6% 50 : 22 : 33 34%
0.8% 66 : 9 : 10 28%
1.0% 0 : 10 : 10 6%

When hatching and subsequent activity is considered, there was a much greater significance between treatments.

Treatment Hatchability Mean Activity
Control dried out : 0 : 95 : 95 63% Highly active
0.1% 85 : 80 : 75 80% Highly active
0.2% 55 : 65 : 66 62% Highly active
0.4% 75 : 65 : 0 46% Slow to hatch, active
0.6% 50 : 60 : 12.5 41% Slow to hatch, active
0.8% 50 : 30 : 7.7 29% Slow to hatch, active
1.0% 0 : 0 : 40 13% 40% Hatch from 1 gravid tick,active

(Zero hatchability mens that no embryos developed from the eggs laid.)

The results of the treatments from untreated ticks were analysed for statistical variance and are summarised below.

ANALYSIS OF VARIANCE

Time (days Coefficient of variance Significant @ 1.0%
(ns = not significant)
1 18.7% 14.26
3 21.4% 12.67
6 28.9% 6.88
10 34.0% 5.11
13 45.4% 3.09 @ 5%
17 57.0% n.s.
21 70.7% n.s.
24 90.8% n.s.
27 149.0% n.s.

TREATMENTS

ns = not significant
* = significant at 5%
** = significant at 1%

Day Control 0.1 0.2 0.4 0.6 0.8 1.0

1 means 83.10 70.87 67.17 72.33 57.40 27.03 22.93

difference - - -12.34 ns -15.93 ns -10.77 ns -25.70* -56.07* -60.17**

3 means 81.93 69.63 66.53 71.93 50.77 27.03 18.13

difference - - -12.30 ns -15.40 ns -10.00 ns -31.17** -54.90** -63.80**

6 means 70.63 67.67 62.40 67.13 43.67 25.90 16.43

difference - - -2.97 ns -8.23 ns -3.50 ns -26.97* -44.73** -54.20**

10 means 60.70 55.40 60.20 60.70 42.77 21.50 13.33

difference - - -5.30 ns -0.50 ns -0.50 ns -17.93ns -39.20** -47.37**

13 means 58.50 41.50 45.77 50.33 37.20 17.07 11.50

difference - - -17.00 ns -12.75 ns -8.17 ns -21.30 ns -41.43** -47.00**

17 means 45.10 35.07 42.10 43.90 33.73 11.67 8.40

difference - - -10.03 ns -3.00 ns -1.20 ns -11.3 ns -33.43* -36.70*

After 17 days, the differences between treatments ceased to be significant. It is considered that there were two main reasons for this. It is accepted that after 17 days the effect of the neem oil will have diminished in spite of the closed container. The other reason is that there is a great range in the natural vitality of the newly hatched nymphs. Some ticks have more energy than others and since they are selected at random for the treatments, the law of averages dictates that there would be an average number of high vitality ticks in each treatment.

To extrapolate the results into a practical situation, the recommendation to spray every 2 weeks (14 days) in order to control ticks is considered acceptable. At no stage was it the intention of the experiment to eliminate the tick, as it has been proven that a certain number of ticks are essential to control the incidence of tick fever and to maintain the natural balance.

CONCLUSION

From the results of this experiment, it is considered that a dilution of neem oil in water of 1.0% contains sufficient botanical insecticide in the form of Azadirachtin to affect the life cycle and to control the cattle tick.

It cannot be emphasised too strongly that a botanical insecticide acts in a different way to a chemical insecticide. The results are not immediate as is the case with chemicals, but there is a gradual build-up in control with no side effects at the dilutions used in this trial.