It is best to feed around the rhizomes, not on them. Do consult your local growers on what works best in your soil and climate. Alfalfa has shown some promising preliminary results as a growth stimulant. It contains several trace vitamins and minerals and triacontanol, thought to stimulate growth. Do get plain alfalfa, not feed that contains additives such as corn or salt.
Borers are a problem especially in the northeastern quadrant of the USA and nearby points.
The single most important step to take in avoiding borer problems is to do a very thorough cleanup well before the expected last frost, removing all withered foliage and debris. These were likely where eggs were laid last fall and overwintered, and taking it away before they hatch goes a long way toward eliminating problems. Beneficial nematodes have been suggested as a biological control mechanism. They need to be applied and active when the eggs hatch and the larvae are making their way to target leaves, triggered by the day that the temperature first goes above 70-72 degrees, often soon after the last expected frost date. The most effective active measure that can be taken is to spray with a systemic insecticide like Cygon-2E, a powerful chemical.