vegetable patch management
pest control
the percentage factor
The first thing you should do when there are signs that pests are damaging your crops is to consider the percentage factor.  By this I mean what percentage of your crop is being damaged and whether it is enough to warrant doing something about it.

Our unrealistic expectations
Shoppers in many Western countries have been conditioned to expect perfect vegetables.  By a combination of intensive pesticide spraying, heavy use of artificial fertilisers and  the culling of any vegetables with blemishes or insect damage people have been  led to believe that it is possible to grow perfect vegetables.  But there is no such thing as a perfect vegetable crop.  Even intensive chemical agriculture cannot remove all threat of damage and certainly a home gardener has no chance of achieving such an outcome. 

There will always be some damage caused by insects, birds, and disease.  But just because a cabbage has some tattered leaves or that a few pea shoots are eaten off when young does not mean you will not end up with healthy vegetables to eat.

the percentage factor
The Percentage Factor is an acceptance that a percentage of your vegetables will always be eaten or damaged, and that you only need to take drastic action to protect them if the percentage of damage goes above an acceptable level.

Photo of a cockatoo eating a wallnut
Cockatoo in the late afternoon sun eating a walnut.  The cockatoos visit our walnut tree at harvest time but as they only feed from the top of the tree there is no need to net the tree or try and scare off the birds.  they eat less than 20% of the tree's crop, leaving plenty for us.
What level of crop damage you see as acceptable is up to you.  Mine sits at an imaginary figure of around twenty percent.  There is no need to reach for deadly sprays and powders  when the level of damage is  below that figure.

However The Percentage Factor does not mean you do nothing to protect your vegetables when the amount of damage being done is relatively low.  But your response should be proportional to the level of damage.  There is no need to reach for powerful insecticides as soon as you see the first signs of damage by pests.

To control pests based on the level of damage they are doing I use a three stage system, which I have described as The Three D's.

Another point worth mentioning is that, while I describe insects and birds that damage my fruit and vegetables as pests I feel it is a somewhat misleading label as I do not in fact see them as pests.  To me they are competitors.  Pests are vermin - something that cannot be tolerated and have to be destroyed.  On the other hand competitors may not be liked but they are to be respected. And after all, without competitors you have no race. 

Keeping this in mind makes it much easier to accept damage to your vegetables without getting annoyed.  In fact most insects only inflict  minor damage to vegetables.  I never try to deliberately kill insects that inflict only minor damage, even when I can see them on plants.  The damage they do is so low that the best response is to simply ignore them.  After all, they have to make a living too!