This works best on acorns and walnuts, as these are heavy enough to throw or sling, but others may work. However, if used in a sling, apply -1 to damage as compared to a proper stone, since they aren't designed to be used a sling stones.

Affliction [18] 
    Advantages [+39%] 
        Innate Attack (Burning) 1d+1 [3.9] 
            Follow-Up (Weapon Strike) [+0%] 
            Must Be Wielded (Anyone can use) [-30%] 
            Magical [-10%] 
    Malediction (As Regular Spell) [+100%] 
    Based on Activation Roll [+5%] 
    Area Effect (2 yard radius) [+50%] 
        Need this to affect multiple seeds 
    Only Works on Seeds/Nuts [-60%] 
    Only Works on a Handful of Seeds/Nuts [-30%] 
        As many as can be held in one hand 
    Magical [-10%] 
    Spell Components [-20%] 
        Must say "seed" in Latin 
        Must gesture with hands