All about potatoes.pdf - Vegetableipmasia.org

6.
INSECT ECOLOGY
How to use it: Squeeze plant roots in clean water and leave them to soak overnight.
The water can then be sprayed directly onto the plants. As with neem, you should
spray in the late afternoon, and make sure the mixture is not too concentrated.
The benefits of natural pesticides are:
• They are often cheap and easy for farmers to make.
• They are generally not toxic to humans or livestock.
• They do not pollute the environment, because their residues are easily broken
down.
• They rarely lead to insect immunity.
Drawbacks are:
• Materials are not always readily available to farmers.
• They must be applied appropriately and repeatedly.
• Some natural pesticides also poison natural enemies.
• It is difficult to determine the correct doses to apply.
• Bits of plants often block sprayer nozzles.
6.6.2 Mechanical control
Mechanical control strategies include using traps and trap crops, and manually
removing insect pests.
Effective trap crops for leafminer flies are all kinds of beans, as the flies prefer these
plants to potatoes to lay eggs on. Trap crops contribute to increasing the role of
parasitoids, and can be used as follows:
• Plant beans at the same time as potatoes on the edges of potato beds.
• One week after emergence conduct observations of these plants. Collect leaves
affected by leafminer flies and put them in the parasitoid release cage. Continue to
do observations every other day.
Yellow sticky traps are only appropriate for leafminer flies, as they are attracted to the
color yellow. Initially yellow traps were only used for observing the presence and
quantity of these insect pests, but recently many farmers have been using them as a
means for reducing leafminer fly populations.
Anything yellow such as yellow plastic, yellow painted boards, oil bottles etc. can be
used for making traps. Smear them with something sticky such as glue, starch
solution or old engine oil, then put them in the field about 10-20 cm above the tops of
the plants. You can use bamboo stakes for supporting the yellow boards. Normally
about 80 traps will be used for 1 ha. Position flat traps in line with the path of the sun
(west-east). Traps that gleam in sunlight will be more effective.
Many farmers have changed their insecticide use patterns as a result of the success
of yellow traps. When farmers find lots of leafminer flies on their traps, they feel they
are controlling them successfully and no longer spray insecticide. This supports the
development of natural enemies, increasing their numbers, diversity and impact.
Finally, natural enemies can control leafminer flies by themselves.
Drawbacks of yellow traps are:
• They only trap adult insects, while the actual pest is the larva. Trapped insects
may have already laid their eggs on leaves. Hence, the effects of such traps on
population regulation are limited.
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ALL ABOUT POTATOES