الآفة النباتية قرب البرعم.

In Arabic, adjectives normally come after the noun they describe.

So here:

• الآفة = the noun
• النباتية = the adjective describing it

This is the normal Arabic order:

• noun + adjective

That is different from English, where adjectives usually come before the noun.

It is not an iḍāfa.
Here, النباتية is an adjective.

A good way to tell is that the adjective matches the noun in:

• definiteness
• gender
• number
• case in fully vowelled Arabic

So:

• الآفة = definite, feminine, singular
• النباتية = also definite, feminine, singular

That matching shows it is a noun + adjective phrase, not an iḍāfa.

Because Arabic adjectives must agree with the noun in definiteness.

Since الآفة is definite, the adjective describing it must also be definite:

• الآفة النباتية = the ... plant-related / botanical ...

If the noun were indefinite, the adjective would also be indefinite:

• آفة نباتية

So the double الـ is normal here.

Because it is describing الآفة, and آفة is a feminine noun.

In Arabic, adjectives must agree with the noun they describe in gender. So a feminine noun takes a feminine adjective.

That is why you get:

• الآفة النباتية

not a masculine form.

Also, النباتية is the feminine form of the adjective related to plant / vegetal / botanical.

Yes. In Arabic, a present-tense sentence often has no written or spoken verb meaning is/are.

So:

• الآفة النباتية قرب البرعم

can function as a complete nominal sentence meaning that the plant-related pest/disease is near the bud.

Grammatically, you can think of it as:

• الآفة النباتية = the topic / subject
• قرب البرعم = the predicate, telling where it is

Arabic often leaves out the present-tense is where English requires it.

قرب means near or close to here.

For learners, it is easiest to think of it as a word that works a lot like a preposition in this sentence:

• قرب البرعم = near the bud

More precisely, in traditional grammar it is often treated as a noun of place / ظرف used in an adverbial way, rather than a simple preposition. But at your level, the most useful idea is:

• قرب + noun = near + noun

So in this sentence it tells the location.

Because it comes after قرب in the expression قرب البرعم.

In full vocalization, you would typically see:

• الآفَةُ النَّباتِيَّةُ قُرْبَ البُرْعُمِ

Notice the ending:

• البُرْعُمِ with -i sound

That is because البرعم is grammatically dependent on قرب.

So if you are reading unvowelled Arabic, you do not see the case ending, but in fully vocalized Arabic it would normally be genitive here.

A careful pronunciation is:

al-ʔāfatu n-nabātiyyatu qurba l-burʿumi

A more readable breakdown:

• الآفة = al-ʔāfa(h)
• النباتية = an-nabātiyya(h)
• قرب = qurb(a)
• البرعم = al-burʿum

Two useful pronunciation notes:

1. In النباتية, the ل of الـ is not pronounced separately, because ن is a sun letter. So it sounds like an-nabātiyya, not al-nabātiyya.

2. In البرعم, the ب is a moon letter, so the ل is pronounced: al-burʿum.

Because Arabic is very often written without short vowels and case endings in normal texts.

So the sentence appears as:

• الآفة النباتية قرب البرعم

But in fully vocalized form, it would usually be something like:

• الآفَةُ النَّباتِيَّةُ قُرْبَ البُرْعُمِ

Those endings help show the grammar, but they are usually omitted in everyday writing, newspapers, signs, and many textbooks outside of grammar-focused sections.

Yes, it could be written without الـ, but the meaning would become more indefinite.

Compare:

• الآفة النباتية قرب البرعم = the specific plant-related pest/disease is near the bud
• آفة نباتية قرب برعم = a plant-related pest/disease near a bud

So الـ makes the noun phrase definite. In Arabic, definiteness is an important part of how the sentence is interpreted.