Hi There,
I don’t necessarily think their choice of chemical was bad. Rather my guess is that it was a matter of the timing of the sprays - I say that as you wrote “during all these attacks”…
Its rare to find an insecticide that can take down a fully grown or even adolescent caterpillars (bigger than 1 cm). A fair number of products like lambda- cylohalothrin and others act as an ovicide - an egg killer in them and they will effectively kill moth larvea/ catterpillar eggs and as an insecticide. Systemic products will enter the plant and when baby caterpillars start chomping away they will get sick and die.
Now, ideally, farmers should be monitoring their plants and they should know what the eggs look like so that they can spray if they see a heavy egg lay. At times farmers will monitor the moth numbers… trapping techniques for monitoring exist. They should be in their crops at least twice a week and looking for the eggs and small larvea - they are small, they should sample the field well (in number of places). They should have product and be ready to spray so they don’t waste a week or two tracking it down and getting ready. Be armed, ready and watching!
If farmers are not doing this (good sampling and spraying when there are eggs or baby caterpillars) and instead wait until they see the tell tale signs of an infestation (holes on the leaves as they grow out) you are already too late.
These army worm burrow down the stalks… burrow into the ears of corn… Hence protecting themselves from the contact action of insecticides and once they are in there, I don’t care what type of chemical you use it is incredibly hard to kill the things (the ones you say that died were likely the ones that were exposed when the crop was sprayed), the insecticide which enters the plant tissue might well make adults sick and slow them down but I’d be very surprised if it killed them all…and then generally you have secondary infections of mould or rot or disease that cause damage as well.
What I see in one of your photos is a man spraying a crop. From the leaves I can see the signs of damage. I don’t think the treatment was necessarily wrong but rather I think the timing was likely wrong. I think farmers in your area need to understand the limitations of the products (that they should be used on eggs and young caterpillars) and be monitoring more and applying the products earlier if they want to have good crop protection.
Study the life cycle of the pest. Do they know what the parents look like? Study your enemy. If you spray late once… and it looks like some die and you get attacked again and spray late again… and the the ones of the leaf surfaces die and then you spray a 3rd time late again… it won’t surprise me if you’ll be disappointed with the results.
Another things is - read up well on the product. Is it systemic / contact? Does it act as an ovicide? Etc… what stage of the life cycle of the pest does it target. A quick Google search for me showed that it is systemic and targets eggs as well - looks like a good choice. Double check they are calibrating their sprayers correctly and applying at the correct rates. The right medicine applied at the wrong dosage or in the wrong way won’t be effective.
On a side note: I wouldn’t waste my cash on the foliar fertilizer but that’ another discussion and its not the end of the world.
That they know how to spray is good! Also, their maize otherwise looks well fertilized - it seems the farmers their are doing lots of things right! Encourage them!
I hope something in all that helps, God bless!
