Fumigant alternatives for perennial crop nursery production
Several perennial nursery trials conducted in the early 2000’s had direct bearing on the development of the Pacific Area-wide Program for Integrated Methyl Bromide Alternatives.
In 2001, a trial was initiated to evaluate several several tarped and untarped preplant applications of 1,3-dichloropropene, chloropicrin, and methyl iodide (iodomethane) in comparison to methyl bromide (Table 1). Crop safety and nematode infestation were evaluated on ten fruit and nut tree, nine grapevine, and five berry types or cultivars. Root knot nematode populations were evaluated at planting and again at nursery stock harvest. Weed control and crop vigor was also evaluated.
Results and More Information
In general, tarped applications performed slightly better than untarped applications with regards to weed and rootknot nematode control (Table 2). The combination of 1,3-D:Pic and chloropicrin alone also failed to completely control nematodes at some depths. This experiment also demonstrated the marked difference in grape nursery stock susceptibility to nematode infestation at harvest fifteen months after fumigation (Table 3, similar results for tree and berry stock not shown).
The results of these trials demonstrated some of the differences in control of non-quarantine pests, especially soil borne fungal pests and weeds, among the methyl bromide alternatives (Table 5). Drip-applied fumigants tended to provide less reliable control of pests at greater depths in the soil which may prove unacceptable to producers of deep-rooted nursery stock (Table 6). Overall, these trials highlighted the need for consistent control of quarantine and non-quarantine pests with technologically and economically feasible alternatives before widespread adoption can be expected.
Table 1. Fumigation treatments in a perennial fruit and nut plant open-field nursery trial established in 2001 near Visalia, CA.
Table 2. Relative weed index immediately prior to planting and root-knot nematode populations at planting in a perennial fruit and nut plant open-field nursery trial near Visalia, CA. Fumigation treatments were applied in Oct. 2001 and weed evaluations and nursery crop planting occurred in Mar. and Apr. 2002.
Table 3. Root-knot nematode population on roots of nursery grapevines harvested nine months after planting in an open-field perennial crop nursery trial near Visalia, CA. Fumigation treatments were applied in Oct. 2001; vines were planted in Mar. 2002, and harvested in Dec. 2002.
Table 4. Shank- and drip-applied fumigant treatments in 2001 garden rose and 2004 nut tree open field nursery trials.
Table 5. Pythium populations, weed control, and plant vigor in a commercial rose nursery trial near Wasco, CA in 2001 to 2003.
Table 6. Nematode control in a nut tree nursery fumigation trial near Yuba City, CA in 2004 to 2006. Bags containing citrus nematode (Tylenchulus semipenetrans) contaminated soil were buried at four depths in each plot prior to fumigation and recovered one month later. Native nematode populations in the top 30 cm soil were determined nine months after planting.
The results of these studies were published as:
Various aspects of these and related projects were reported on at the International Research Conference on Methyl Bromide Alternatives and Emission Reductions (MBAO.org) including: