Part A :
I'm here today to present the findings from our research into pesticides and alternatives to using them.
I'd like to begin by talking about some of the environment effects of pesticide use.
As most of you will be aware, pesticides have proven to be very harmful to our environment.
The principal reason for this is because nearly all pesticides along water channels such as rivers, where they are then transported downstream.
In order situations, particularly when they are dropped by plane,
the wind blows pesticides into wild areas where they are not wanted. These areas can be up to several kilometers away.
We also need to think about the effects of pesticides on animals.
Pesticides can cause illness and even death in many animals, including birds and aquatic life.
Animals can also be affected, however, when pesticide use eliminates their food source and causes them to starve or migrate to other areas.
When pesticides don't travel into neighbouring environments,
they tend to seep into the soil.
There they degrade the quality of the soil and in addition, they can weaken biodiversity -studies of pesticide - contaminated soil show a much lower count of organisms compared to healthy soil.
There's a final consideration to take into account,
and that's the environmental effects of pesticides in terms of pest numbers.
In the short term, pesticides significantly reduce the number of pests in an area, as might be expected.
After long-term, regular use, however, insects tend to become immune to certain kinds of pesticide and are no longer negatively affected by them.
As the number of insecticide resistant pests grows, this creates the need for new varieties of pesticide,
and further exacerbates the pesticide problem.
Let's move on now to look at some possible alternatives to pesticide use.
As l' II explain, although these techniques can help reduce our dependence on pesticides,
they do have their own drawbacks too.
The first technique will be familiar to any of you who have even a small vegetable garden at home.
You see a slug on a piece of lettuce,
and what do you do? Put on some gloves, walk right up to the plant and pick the slug off with your hands.
This is called handpicking.
Handpicking is remarkably effective and requires little in the way of money to implement.
But while it may be sufficient for the home gardener,
the time-consuming nature of handpicking makes it unsuitable for large-scale operations.
Owners of larger crops and orchards require a more systematic approach to pest management,
and they have a few options here.
You may be familiar with a technique known as biological control.
This involves the strategic use of what we call 'good'insects - that is,
insects which eat pests, rather than plants. When they eat the pests,
they also protect the crop environment.
Unfortunately, biological control is always risky because we can never know for sure how insects will behave in a particular environment,
and the results are therefore unpredictable.
A safer option is companion planting,
where certain plants are grown together.
Garlic, for example, fends off spider mites and aphids,
and basil drives away the tomato hornworm,
making it a good companion for tomatoes.
This is because some varieties of plant can repel specific breeds of insects,
so planning them alongside and around more vulnerable vegetables will discourage the insects from coming near.
Of course, all these extra plants begin fighting for space and
competing with the protected plants for access to water
and nutrients in the soil.
A final possibility is crop rotation. This involves alternating plants every harvest,
which forces insects to migrate in an attempt to locate their food source.
Crop rotation is unappealing for large-scale commercial operations, however, because the high cost of constantly changing crops cuts into their profits.
As you can see, there's still no easy answer to the question of how to keep plants free from the scourge of pests.
I'm happy to take any questions...
How the 1670 lever-based device worked
Question 35 - 40
Complete the table below:
Write NO MORE THAN THREE WORDS AND/OR A NUMBER for each answer.
Remove insects with gloves
Effective and low-cost; but so not useful for large farms
Breed 'good' insects to attack pests
Risky due to outcomes
Use plants with ability to certain insects
Low risk, but additional plants compete for space and soil nutrients
Change plant varieties after each harvest -insects must to access food
Unappealing for big businesses as are reduced
35. time-consuming|time consuming
36. biological|Biological control