Diseases of Basil and Their Management.

Abstract

weet basil (Ocimum basilicum L.) is an economically important herb crop in several Mediterranean countries. Approximately 80 ha are grown annually in Italy, 30 ha in France (C. Poncet, I.N.R.A., Antibes, France, personal communication), and 20 ha in Israel (T. Katan, ARO Volcani Center, Bet Dagan, Israel, personal communication). Basil is also an important fresh and processed (frozen and pesto sauce) crop in U.S. markets (7,38; A. P. Keinath, Clemson University, Charleston, SC, personal communication). It is used fresh, dried, and processed for flavoring and fragrances and in traditional medicines (5,55). The crop value in Italy can reach $500,000 per ha per year. Recently, increased interest in so-called “Mediterranean cuisine” has led to a significant increase in basil consumption worldwide. Basil has become associated with the consumption of pasta and with healthy eating habits. It ranks first among the herbs most commonly used by California restaurants (4). In its processed form (pesto), it is known worldwide, thus strongly contributing to the image of Italian cuisine. In Italy, most production takes place in the Riviera Ligure (59) (Fig. 1), where 53 specialized farms with average areas of 1 ha, and about 100 nonspecialized farms with average areas of 0.15 to 0.20 ha, grow basil. All the Ligurian farms are typically family-managed properties. Basil’s high value makes it suitable for farmers with small operations in other countries such as Israel (T. Katan, personal communication) and the United States (57). O. basilicum apparently is native to India (26) and naturalized in Africa and the Pacific Islands (53). However, recent findings show that this species was known in Egypt at the time of the pharaohs (39). Basil has been cultivated in Italy for more than 100 years. It is a member of Labiatae (Ocimoideae) and is related to other herbs, such as mint (Mentha spp.), oregano (Origanum vulgare), marjoram (Origanum majorana), sage (Salvia officinalis), lemon balm (Melissa officinalis), rosemary (Rosmarinus officinalis), and thyme (Thymus serpyllum). In Italy, Genovese Gigante is the basil cultivar most appreciated for fresh consumption. It is the only cultivar used for industrial production of pesto and covers 90% of the total growing area (49). Basil is grown year-round in Italy in the Riviera Ligure, but it is a fall, winter, or spring crop in other locations and latitudes. In Italy, basil typically is grown as a directseeded crop by using 10 to 12 g (1 g = 600 to 800 seeds) of seeds per m2, with planting and management strategies dictated by the market destination (fresh consumption or pesto sauce). The number of plants per m2 can reach 5,000 to 6,000. In Italy, basil is often overseeded after the first two to three harvests of the previous crop and is repeat-harvested after regrowth. In Israel and the United States, basil is transplanted. Most fresh-market basil is hand-harvested and sold as bunches of 10 to 15 plants. Basil for processing often is harvested mechanically. As with most agricultural commodities, diseases impose significant production constraints, affecting both yield and overall quality of basil. Many diseases afflict basil. This article focuses on the most important diseases of basil in Italy, with reference to work carried out by several authors in other regions where basil is grown.