Tomato vines struggle to set fruit when temperatures exceed 30°C. Under such hot conditions, application of hormones (growth regulators) with trade names such as Tomatotone or Tomatolan can promote fruit setting. This can lead to more fruits, larger fruits, and higher yields.

Prepare the growth regulator solution according to instructions on the label. If commercial products are not available, mix 15-75 mg of 4-chlorophenoxy acetic acid (CPA) per liter of distilled water. Use the higher rate for higher temperatures.

A cluster is sprayed when 3-5 of its flowers have opened. Direct the spray onto the green backside of the flowers (the calyx). Spraying on sunny days in the afternoon after 3 p.m. will yield best results.