The economic viability of most northeastern apple orchards depends upon the production of a high proportion of large, well-colored fruit of high quality. Adjustment of fruit load, or thinning, is an integral part of achieving this production goal. Although the effects of feeding damage caused by leafhoppers is controversial, many orchardists believe that this damage, particularly early in the season, is detrimental to production, and they apply insecticide treatments to maintain infestations below a threshold level. Carbaryl has been long recognized as a fruit-thinning agent, as well as a broad-spectrum insecticide. Field experiments were conducted during 1995 and 1996 to examine the horticultural benefits of carbaryl when used in combination with the plant growth regulators naphthaleneacetic acid and 6-benzyl adenine, and to assess the efficacy of carbaryl against an indigenous leafhopper complex when applied during a typical thinning window. In a majority of cases, the addition of carbaryl to naphthaleneacetic acid or 6-benzyl adenine significantly enhanced fruit thinning and increased fruit size. Two thinning rates of carbaryl with or without naphthaleneacetic acid significantly reduced early-season infestations of leafhopper nymphs. The highest rate suppressed nymphs and adults for the entire season and allowed lower leaf damage ratings. Results show that carbaryl in combination with other chemical thinners is beneficial in the management of crop load, and at the same time effects suppression of the leafhopper complex. In orchards that do not rely upon natural control of phytophagous mites, this unique horticultural chemical fits well into integrated crop management programs on apple.