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CottonLeaf Ring Sampling for Whitefly NymphsFor whitefly nymphs, only part of the leaf must be sampled. Use a leaf ring to isolate an area the size of a quarter between the central and left-side main veins as shown below. For a leaf ring you can use a cap thread gasket (dimensions: 1-1/8 in. O.D. x 31/32 in. I.D. x 1/16 in. H) found at the plumbing department of your local hardware store. For convenience, keep this with your hand lens. Score the leaf as infested if any large nymphs (3rd and 4th instars) are present within the leaf ring. |