[quote=@Senhara]
<Snipped quote by Sep>

What defines an energy weapon? In canon, none of the Covenant's weapons are defined as outright energy, unlike the Forerunners, they all fire a form of plasma, in some cases an extremely fast stream of plasma, akin to a form of particle cannon.
[/quote]

Given that Star Wars blaster weaponry is plasma-based, I would have to guess that if this is the case, Covenant weaponry will be approximately equally effective. That is, given the example of the still ongoing Republic bombardment, it can blunt the Replicators' advance, but it's still not enough to annihilate them wholesale. Ground troop/anti-personnel blasters will be borderline useless, and only ship/vehicle-mounted weaponry will have the "punch" to actually put these little freaks down. I might also argue that the Plasma Sword carried by Elites should be comparably effective to a lightsaber, which is stated to be able to do the job of killing these things reliably.