Thatch in a lawn attacked by chinch bug. This photographs illustrates two layers within the thatch: a lighter, upper layer at 38 to 45 mm on the ruler, and a darker, lower layer at approx 31-38 mm. Fermanian et al. 2003[L30] comment: "Thatch is not uniform…Generally, the upper layers of thatch represent the most recently contributed plant materials, often with visible plant parts that are highly distinguishable. Lower levels of thatch are generally a dark colored, spongy, humus materiual with no distinguishable plant parts. This lower portion of the thatch, generally called mat, can be troublesome." -