AVENGER Organic Weed Killer, biodegradable, non-toxic &ndash; Concentrate 2.5 Gallon Avenger, organic weed killer concentrate is a non-selective, post-emergence herbicide that quickly, effectively kills weeds, grasses and broadleaves The active ingredient d-limonene (citrus oil) naturally strips away the waxy plant cuticle, causing it to dehydrate and die Approved for use in organic gardening by the u.S. Deptartment of agriculture's (usda) national organic program (nop) rule Small annual weeds: for the control of annual weeds less than 6 inches tall, use a 1:6 ratio (1 part of avenger, weed killer into 6 parts of water). Larger annual weeds: for the control annual weeds above 6 inches, use a 1:4-1/2 ratio (1 part of avenger, weed killer in 4-1/2 parts of water)