Finally we have some warm, sunny weather, and that means fruit are growing quickly. Generally, fruit are 10–20 mm depending on where in the state you’re located. Many of our common post bloom thinners such as NAA, Sevin and Maxcell work very well when fruit are around 12mm and temperatures are in the 70s. Once fruit are in the 15-20mm range, the only materials likely to be effective are Sevin and ethephon. While ethephon can be an effective thinner, it can have variable effects (more than other thinners) and is too risky for most growers to consider unless they are really in a tight spot. So when fruit are in this size range (15-20mm) the thinning window is starting to close very fast, and Sevin is probably the best choice for growers.