5 For, before the harvest, when the blossom is gone and the flower becomes a ripening grape, he will cut off the shoots with pruning knives, and cut down and take away the spreading branches.

Read Isaiah 18:5 Using Other Translations

For afore the harvest, when the bud is perfect, and the sour grape is ripening in the flower, he shall both cut off the sprigs with pruning hooks, and take away and cut down the branches.
For before the harvest, when the blossom is over, and the flower becomes a ripening grape, he cuts off the shoots with pruning hooks, and the spreading branches he lops off and clears away.
Even before you begin your attack, while your plans are ripening like grapes, the LORD will cut off your new growth with pruning shears. He will snip off and discard your spreading branches.