Pests and Diseases of Sweet Basil after Methyl Bromide Phase Out: the Northern Italian Experience

Sweet basil (Ocimum basilicum) is an economically important herb crop in several countries including Italy. Several soilborne diseases affect this soil grown crop including vascular wilts and basal and root rots. In addition, soilborne root knot nematodes (Meloidogyne sp.) may often cause severe yield losses together with the foliar nematode (Aphelenchoides ritzemabosi). In the past, the control of soilborne pest and disease complex was easily obtained by the use of methyl bromide or steam due to the wide spectrum of activity against pests, diseases and weeds of both methods. As a consequence of the phase out of methyl bromide under open field conditions soil disinfestation is generally carried out with methyl isothiocyanate generators or throughout the soil injection of chloropicrin and 1,3 dichloropropene mixtures. Nevertheless, since open field crops are directly sowed at the beginning of May in soil fumigated at least 21 days earlier, cold soil temperature often strongly limits the soil treatment. Under protected crop, several basil growers shifted from soil to soilless crop in order to skip the risk of economical disruption, particularly after MB phase out. Open soilless system is the most common growing method and plastic trays filled with potting mix substrate, are the most common substrate containers. After MB phase out some pests and diseases increased in protected and open air basil fields. In open field crops the presence of Meloidogyne arenaria race 2 was detected, particularly in fields where the fumigation was only occasionally carried out. Moreover due to the shift from soil to soilless growing methods a leaf bacterial disease (Pseudomonas viridiflava) and the leaf nematode (A. ritzemabosi) caused severe damages. The present contribution illustrates the pests and the diseases recently found on basil crops and the relationship of the shift from traditional to new growing systems due to MB phase out.