מעת עתרת משה רבינו עד עכשיו אין ארבה מפסיד בכל גבול מצרים ואם יפול בארץ ישראל ויבא ומכנס בגבול מצרים אינו אוכל מכל יבול הארץ כלום עד עכשיו וזה כבר דבר ידוע הוא לכל
In my own loose translation:
From the time of Moses's prayer [in verse 18 to remove the locusts from Egypt] until now the locust does not cause damage inside the borders of Egypt. If it lands in Israel and comes over the border into Egypt, it doesn't eat any of the produce there, to this very day. This is already a well known fact.
(This is cited in Ramban ad loc.)
This no longer seems to be a well-known fact. Albawaba Business writes:
In 2004, Egypt witnessed one of the most serious locust plagues in recent history, when farmers in 15 out of the country's 27 governorates reported infestations and extensive crop damage.
At the time, the Land Centre for Human Rights, a local NGO devoted to agriculture issues, reported that 38 per cent of the nation's crops had been damaged as a result of the phenomenon.
But perhaps the fifteen governorates afflicted are not part of the biblical-era borders of Egypt. And most reports indicate that the 2013 locust swarm did little or no crop damage in Egypt; I don't know about the various swarms before 2004.
Does anyone know whether people who study such things today agree with Rabenu Chanan'el's assessment? Or, in other words, does his statement seem to fit the facts? If not, then do any later commentaries offer an explanation? Or perhaps, contrary to my implied assumption above, R. Chanan'el never intended his statement to apply to future dates and was merely stating a fact about swarms until his time?