A good way to avoid such silent intruders that destroy farmers' corp in natural farming is to make sure that there is enough vegetation for predators like wasps, birds to come and attack the bugs. Unless there is a food chain that is isn't broken whatever non-biological methods that are used aren't sustainable.
The best practices in our own experiences are
Have a good green cover over the soil and encourage all kinds of predators.
Grow a combination of cover crops, shrubs, creepers, bushes, small trees, large trees so that they can host all the types of predators that are required for biological control.
Treat or control their population growth by increasing plant immunity - Done through application of Jiwamrita