Controlamos la plaga a fin de que no afecte la albahaca.

A fin de que means so that or in order that. It introduces a purpose.

So the structure is:

• Controlamos la plaga = we control the pest
• a fin de que no afecte la albahaca = so that it does not affect the basil

This expression is correct, but it sounds fairly formal. In everyday speech, many speakers would be more likely to use para que.

Because a fin de que triggers the subjunctive.

In Spanish, when you express a goal, intention, or purpose with expressions like:

• para que
• a fin de que
• con el fin de que

the verb in the following clause normally goes in the subjunctive.

So:

• no afecta = indicative, stating a fact
• no afecte = subjunctive, expressing the intended result or purpose

Here, the idea is not that the basil is already being affected as a fact. The idea is that we control the pest so that this does not happen.

Afecte is the present subjunctive, third-person singular.

It comes from the verb afectar.

A quick breakdown:

• infinitive: afectar
• present indicative yo form: afecto
• remove the -o
• add subjunctive endings

So you get:

• yo: afecte
• tú: afectes
• él/ella/usted: afecte

In this sentence, it is third-person singular because the understood subject is la plaga.

Controlamos is the present indicative of controlar, first-person plural: we control.

Depending on context, Spanish present tense can mean different things in English, such as:

• we control
• we are controlling
• sometimes even we do control

So this sentence could describe:

• a general practice: We control the pest so that it does not affect the basil
• a current action: We are controlling the pest so that it does not affect the basil

The wider context tells you which English translation sounds best.

Because both nouns are feminine singular nouns, and Spanish uses articles more often than English does.

• la plaga = the pest / the infestation
• la albahaca = the basil

A few useful points:

• plaga is feminine, so it takes la
• albahaca is also feminine, so it takes la
• Spanish often keeps the definite article with plant names and other nouns where English may sometimes drop it

So la albahaca sounds natural in Spanish.

Because la albahaca is a thing, not a person.

The personal a is mainly used before a specific human direct object, and sometimes with pets or animals treated very personally.

Compare:

• Veo a María = I see María
• Veo la albahaca = I see the basil

In this sentence, afectar takes a direct object, and la albahaca is that object, so no a is used.

Great question, because after que, the subject is not repeated.

The clause is:

• que no afecte la albahaca

The understood subject is still la plaga.

So the full idea is really:

• a fin de que la plaga no afecte la albahaca

Spanish often leaves out the subject when it is clear from context.

Why is la albahaca not the subject?

• Semantically, it makes sense that the pest affects the basil, not the other way around
• afecte is singular and matches the understood subject la plaga
• la albahaca functions as the direct object after the verb

Yes. That would be very natural and probably more common in everyday Spanish.

So these are both fine:

• Controlamos la plaga a fin de que no afecte la albahaca.
• Controlamos la plaga para que no afecte la albahaca.

The difference is mostly one of tone:

• para que = more common, neutral, everyday
• a fin de que = more formal, more written, sometimes more careful or technical sounding

Yes, but only if the structure works with an infinitive.

Compare these:

• Controlamos la plaga a fin de que no afecte la albahaca.
• Controlamos la plaga a fin de proteger la albahaca.

Both are correct, but they are built differently:

• a fin de que + conjugated verb
• a fin de + infinitive

The second version is often simpler when the subject stays the same.

So if you want to say in order to protect the basil, you can use:

• a fin de proteger la albahaca

But if you want a full clause with its own verb, use:

• a fin de que no afecte la albahaca

Sometimes, but not always.

In this sentence, plaga most naturally means something like:

• pest
• infestation
• blight or pest problem, depending on context

If you are talking about gardening or agriculture, plaga usually refers to harmful insects, organisms, or infestations damaging plants.

So here, the pest or the infestation is a more natural English idea than the disease-related meaning of plague.

Because in Spanish, no normally goes directly before the conjugated verb.

So:

• no afecte = does not affect / may not affect

That is standard Spanish word order.

You would not normally place no somewhere else in this clause.