A praga, o pulgão e o fungo estão na planta.

Because a is the feminine singular definite article in Portuguese, so here it means the, not English a.

• a praga = the pest
• uma praga = a pest

This is a very common beginner confusion, because Portuguese a is often the, while English a/an is usually um/uma in Portuguese.

Portuguese often uses definite articles more than English does, especially with specific nouns in a sentence.

Here, each item in the list gets its own article:

• a praga = the pest
• o pulgão = the aphid
• o fungo = the fungus

Repeating the article sounds natural and clear in Portuguese. It marks each noun separately as part of the list.

You usually learn the noun together with its article:

• a praga
• o pulgão
• o fungo

There are some patterns:

• nouns ending in -a are often feminine
• nouns ending in -o are often masculine

But these are only tendencies, not perfect rules. For pulgão, the ending does not clearly tell you the gender, so the safest habit is to memorize the article with the word.

Because the subject is plural.

The subject is a list of three things:

• a praga
• o pulgão
• o fungo

Together, that becomes they, so the verb must also be plural:

• está = is
• estão = are

So:

• A praga está na planta. = The pest is on the plant.
• A praga, o pulgão e o fungo estão na planta. = The pest, the aphid, and the fungus are on the plant.

Na is a contraction of em + a.

• em = in, on, at
• a = the

So:

• em + a planta → na planta

This kind of contraction is extremely common in Portuguese.

Other common ones:

• no = em + o
• nos = em + os
• nas = em + as

Literally, em is broad and can cover several English prepositions such as in, on, and at. The exact translation depends on context.

With pests, insects, and fungus, English usually says on the plant, so na planta is naturally translated that way here.

So the Portuguese form stays the same, but English chooses the most natural preposition for the situation.

In a normal full sentence, that sounds less natural. Portuguese usually prefers the articles here.

• Natural: A praga, o pulgão e o fungo estão na planta.
• Less natural in this context: Praga, pulgão e fungo estão na planta.

You might see article omission in headlines, labels, notes, or very compressed style, but in ordinary speech and writing, the articles are the expected choice.

Because Portuguese, like English, normally does not use a comma before and in a simple list.

So this is the standard punctuation:

• A praga, o pulgão e o fungo...

A comma before e can appear sometimes for emphasis, parenthetical structure, or to avoid ambiguity, but not in a basic list like this.

Not exactly.

• praga is a broad word meaning pest
• pulgão is a specific kind of pest: aphid
• fungo is fungus

So the sentence is listing three things, not repeating the same idea three times. Semantically, pulgão can be one example of a praga, but grammatically the sentence simply treats them as separate listed items.

The most important thing is the ending -ão, which is nasal in Brazilian Portuguese.

Very roughly:

• pulgão sounds something like pool-GOWN, but with a nasal ending
• estão sounds something like es-TOWN, again with a nasal ending

A few useful notes:

• In many Brazilian accents, the l in pulgão sounds closer to a w sound before the next consonant.
• The ão sound is one of the most important sounds to practice in Portuguese.

So do not pronounce it like a plain English ow. Try to let the sound resonate through the nose.

They are:

• a praga → as pragas
• o pulgão → os pulgões
• o fungo → os fungos
• está → estão for plural subjects
• na planta → nas plantas if the plants are plural

So a plural version could be:

As pragas, os pulgões e os fungos estão nas plantas.

Because the sentence is talking about one plant.

• na planta = on the plant
• nas plantas = on the plants

Even though there are multiple things on it, they are all located on the same plant, so planta stays singular.