When you grow some cultures in your farm you need to use some products against some "unfriendly" things that might harm your crops.
What word could be used for generalization of the words that I have bolded?
I think your definition for the term pesticide is perhaps too narrow.
Per Saunders Comprehensive Veterinary Dictionary, 2nd Ed., pesticide is defined as (p. 865):
a poison used to destroy pests of any sort
And it defines pest (p. 865) as
an organism that injures, irritates, or damages livestock or crops
Therefore, I think your answer for the general word is pesticide.
See also this comprehensive definition in Wikipedia for pesticide.
Pesticides are substances that are meant to control pests or weeds.[1] The term pesticide includes all of the following: herbicide, insecticide, insect growth regulator, nematicide, termiticide, molluscicide, piscicide, avicide, rodenticide, predacide, bactericide, insect repellent, animal repellent, antimicrobial, fungicide, disinfectant (antimicrobial), and sanitizer.[2] The most common of these are herbicides which account for approximately 80% of all pesticide use.[3] Most pesticides are intended to serve as plant protection products (also known as crop protection products), which in general, protect plants from weeds, fungi, or insects.
There is also the word biocide, which is not as much in general use. It is defined by Merriam-Webster as:
a substance (such as an algicide or fungicide) that destroys or inhibits the growth or activity of living organisms
It is a term used by environmental groups, such as in this post by the Green Party of California.
You could possibly call those bolded works blights:
Blight
noun, BrE
- a person or thing that mars or prevents growth, improvement, or prosperity.
I can't think of a single word that neatly and unambiguously fits your description. The best words that I can think of are more generic than your specific usage, and refer to the organisms being unwanted, an annoyance and likely to cause harm. If you use these, you would probably have to define what you meant first. You could use words such as:
I would put the word blight under this type of word, but add a note of caution to its use. There are several plant diseases (fungal infections, I think) that are called blight (e.g. potato blight), so this may be what people take it to mean.
You could also use words that imply a large number of organisms causing damage, such as:
But, probably the best word to use would just be pests as this doesn't have to be limited to animal pests.
You could use the word parasite.
an organism living in, with, or on another organism in parasitism
an intimate association between organisms of two or more kinds; especially : one in which a parasite obtains benefits from a host which it usually injures
Since all of the organisms you mention benefit from feeding off the crops (or, in the case of weeds, competing for sunlight and water) to the detriment of the crops, you could say that the fungi, insects, and weeds are all parasites.
The Illinois farmers and agronomists my shop has interviewed tend to use the term pressure as a generic for all the factors which threaten yield: 'weed pressure', 'disease pressure', 'drought pressure', 'wildlife pressure', and so forth.
Plague and Pestilence is a common phrase to describe forces that usually ravage a farm if not a countryside, or even a whole country. It couples nicely with famine and war as well as loot and plunder.
Things that prevent growth and usually kill what is already there in a generalized sense would be a blight. While it may be defined for the prevention of growth, it almost always implies that it also kills or destroys what is already there. There are some popular phrases that use blight, like encroaching blight.
I would choose one of these two, depending on the context, preferring blight.
