All about potatoes.pdf - Vegetableipmasia.org

6.
INSECT ECOLOGY
• SLIGHTLY HAZARDOUS (Class III): Pesticides with the active ingredients
trichlorfon, dicofol.
• UNLIKELY TO PRESENT ACUTE HAZARD IN NORMAL USE (Class IV):
Pesticide formulations unlikely to present acute hazard in normal use such as
those with the active ingredients zineb, benomyl and maneb.
D. How to apply pesticides
The effectiveness of a pesticide is highly dependent upon:
• Appropriate target: The pesticides used should be appropriate for the organisms
they are targeting. For example, to control leafminer attack, an insecticide able to
kill larvae inside the leaves should be used. A list of target living organisms can be
seen on the labels of the packaging.
• Appropriate timing: Timing should be based on the behavior of the targeted pest
and the weather at the time of application. If a pest is active in the morning, it is
best to apply the pesticide in the morning too. Weather, especially rain and sun
shine, can be very influential. Many pesticide types cannot resist washing by
rainwater and long hours of sunshine.
• Appropriate quantities: Recommended quantities are shown on the pesticide
packaging. These should be adhered to, as inappropriate quantities will cause
negative effects, such as ineffectiveness and build-up of resistance.
• Appropriate application methods: Pesticides should not be mixed when they are
applied, as some will counteract each other and reduce toxicity to target
organisms.
The amount of pesticide the spraying equipment releases can also influence
effectiveness. Generally, a finer spray is better because the smaller droplets will
adhere better to the plants and the bodies of targeted pests, provide better coverage
and will reduce the amount of water and pesticide required. The problem of a finer
spray is that it can be blown away by the wind.
When spraying, consider wind direction to prevent poisoning from becoming covered
with pesticide.
E. Resistance and resurgence
Evidence shows that the more farmers use pesticides, the more problems arise with
pests and diseases. Examples of this are increasing numbers of brown plant hoppers
on rice crops and leafminer flies on potatoes as a result of insecticide use.
The processes causing increased numbers of insects after insecticide application are
as follows:
• Insecticide causes resistance in insect pests. In a population, each individual
insect reacts differently to the insecticide applied. Sensitive ones will die when
coming into contact with insecticide. However, somewhat resistant insects will
survive. When the survivors reproduce, their offspring will be resistant, too.
Through selection the population will be more and more resistant until the
insecticide is totally ineffective. The same process applies to fungi and fungicides.
• Insecticides kill natural enemies. Natural enemies, particularly parasitoids, are
generally more sensitive to insecticide than insect pest. Without natural enemies,
pest insect populations can increase rapidly. This process is called resurgence.
A HANDBOOK TO THE ECOLOGY AND INTEGRATED MANAGEMENT OF POTATO 37