Topics in Subtropics

The early history of the parent navel orange was presented in the last issue of Topics in Subtropics as The Parent Washington navel orange tree - Its first years.

In January, 1995 during my second consultancy visit to Thailand, I was asked to lecture to the staff of KasetsartUniversity located in Bangkok. The lecture was on the problems of the greening disease in their country where trees die between 4 and 8 years and rarely reach 12 years of age.

To maximize profits in the early navel orange market, growers need to have large fruit size and sufficient yellow-orange color and a high enough sugar-acid ratio to meet or exceed the legal minimum harvesting standards.

In many ways our pest and disease management of fruit tree crops are exacerbated by our cultural practices. Avocado and citrus offer some very clear demonstrations of how we manage our trees can lead to reduced pesticide use.

In the last two decades, many distinctive citrus selections have become available at retail markets in the US. These include cultivars such as 'Cara Cara' navel orange, 'Cocktail' pummelo-mandarin hybrid, 'Variegated Pink' lemon, 'Seedless Kishu' mandarin and 'Buddha's Hand' citron.