Phylloxera in the Archive: Missing Records and Conflicting Dates

The claim is plausible but not established by the described sources. Catalogues show that resistant rootstocks were advertised from 1888; they do not show quantities sold, destinations, or whether the stock was infested or clean. Railway ledgers from one company record tonnage without destination or vine health, so they cannot trace movement to outbreak sites. The missing 1883–1887 bulletins remove the period when the trade may have expanded, and the undated letters are ambiguous. Counting catalogue mentions as a proxy for trade volume assumes that advertising tracks sales, which is an untested assumption and vulnerable to survival bias. Before accepting the claim, I would want nursery sales ledgers or invoices, import and export records, railway waybills with destinations, correspondence linking specific shipments to subsequent outbreaks, and a comparison with a province where nursery trade was absent or restricted. I would also distinguish the spread of infested plant material from the spread of the insect by natural means. The strongest defensible statement may be that nurseries were a plausible vector and that the timing is consistent, not that they accelerated the epidemic.

Treat the gap as missing data, not as zero and not as a smooth trend. First, document exactly what is missing: which variables, which months, whether any duplicate copies exist in another archive, and whether the missing years can be reconstructed from secondary sources. Second, use the railway ledgers and neighbouring provinces' bulletins as independent series, but do not merge them into a single index without checking definitions. Third, run a sensitivity analysis: present results with the gap excluded, with the gap treated as a range of plausible values, and with the pre- and post-gap periods analysed separately. Do not interpolate a line through the gap and then test it as if observed. Fourth, use qualitative evidence from the letters to describe what actors believed, clearly labelled as interpretation. Finally, state in the methods that the gap limits any claim about timing in the mid-1880s. If the argument depends on the missing years, the honest conclusion is that the evidence is insufficient.

Establish the catalogue's purpose: it is an advertisement, not a ledger. Ask who produced it, for which market, and whether it survives because a few large nurseries kept archives. Compare catalogue titles and prices across years to see whether the range expanded, but do not assume that a listed item was sold in quantity. Cross-check with trade directories, newspaper advertisements, agricultural society reports, import records and, where available, invoices or correspondence. Look for corroboration between a catalogue claim and an independent record of shipment or planting. Consider the 'rhetoric of novelty': resistant rootstocks may be promoted before they are widely available. Also check the date of the catalogue against the outbreak chronology; a catalogue printed after an outbreak cannot explain its onset. Present catalogue evidence as evidence of availability and marketing, not of volume. If quantitative claims are needed, state the proxy and its limitations, and avoid converting mentions into tonnages.