Looking after roses is difficult because they often get eaten by insects and so need to be sprayed regularly with insecticide
It is difficult to care for roses because they are often attacked by insects and so need spraying regularly
Roses are difficult to grow because they attract insects and so often need spraying.
「バラは虫に食われやすいから消毒が大変」＝ Looking after roses is difficult because they often get eaten by insects and so need to be sprayed regularly with insecticide / It is difficult to care for roses because they are often attacked by insects and so need spraying regularly / Roses are difficult to grow because they attract insects and so often need spraying.
ボキャブラリー
バラ ＝ rose
虫 ＝ insects
食われやすい ＝ often get eaten by / often attacked by
消毒 ＝ insecticide （＝虫を殺す液体）
look after / care for / grow ＝ （植物を）育てる
difficult ＝ 難しい、大変
regularly ＝ 定期的に
spray ＝ しぶきを飛ばす
attack ＝ 狙う
Roses are susceptible to pests, so it's hard to keep them free from insects.
「バラは虫に食われやすいから消毒が大変」という表現は英語で "Roses are susceptible to pests, so it's hard to keep them free from insects." と言えます。「susceptible to pests」は「虫に食われやすい」を意味し、「it's hard to keep them free from insects」は「虫がつかないようにするのが大変」という意味です。
例えば、具体的な状況を説明する場合は以下のように言えます： "Roses attract a lot of pests, which makes it difficult to maintain them." 「バラは多くの害虫を引き寄せるので、維持が大変です。」
イギリス 
アメリカ合衆国 
