Which plants are particularly sensitive to irrigation with 2,4-D treated water?

• A. Tomatoes, peppers, grapes, and new lawns
• B. Carrots, onions, lettuce
• C. Apples and pears
• D. Corn and soybeans

Answer: (A)

The concept here is that 2,4-D acts like a synthetic growth hormone in plants, and some crops are especially vulnerable to its presence in irrigation water because they readily take up the chemical and show noticeable injury in actively growing tissues. Tomatoes and peppers are sensitive because they are herbaceous dicots with tender, fast-growing leaves that readily absorb and respond to auxin-like chemicals, leading to distorted growth, leaf curling, and stunting when exposed to even small residues. Grapes can also exhibit clear injury from 2,4-D in water, especially on new growth. New lawns are particularly at risk because establishing turf roots and shoots are highly receptive to herbicides; symptoms include leaf cupping, bronzing or bleaching, and uneven growth. In contrast, the other crops listed tend to be less consistently affected by the same residue levels in irrigation water, either because of species tolerance or growth form.