“These are freshly cut flowers from the Netherlands infected with western California flower thrips,” the chief sanitary inspector for Rosselkhoznadzor, Yekaterina Slakova, said in a televised appearance as workers burned boxes of roses.

The tit for tat has been so obvious that even pro-Kremlin commentators have dropped the pretense, saying the flower burning is intended as a warning to the Netherlands over risks to trade if the investigation proceeds unfavorably for Russia.

“This is connected to the Malaysian Boeing,” Sergei A. Markov, a former member of Parliament in the pro-government United Russia party, said in a telephone interview. “Russia is certain that the Dutch government is falsifying this investigation,” he said, but cannot say so directly.

The stepped-up flower inspections, he said, are the Kremlin’s means of communicating displeasure with the inquiry.

“It is an attempt to talk in not such an obvious way, softly, a bit byzantine,” Mr. Markov said of the message of the flower burning. “I generally like byzantine. But this is not a great quality in this case. Our diplomats should have just called things by their names.”

Dutch floral industry officials agree that the flower inspections have been mostly for show, so far.

With its greenhouses, auction houses, and trucks and trains running like clockwork, the Netherlands provides an estimated 40 percent of all fresh-cut flowers and houseplants sold in Russia, last year worth about 283 million euros, or about $314 million at the current exchange rate.