How have the courts treated evidence in the context of an allegation of conspiracy to cultivate marijuana?

Appellant argues there was no evidence that he agreed to enter into the conspiracy to cultivate marijuana, that he cultivated marijuana, or that he intended to assist his brother in the cultivation of the marijuana. He claims there was no evidence of anything more than his mere presence in the vicinity of the marijuana gardens. The court views the evidence in the light most favorable to the prosecution to determine if any rational trier of fact could have found the essential elements of the crime beyond a reasonable doubt. United States v. Aceves-Rosales, 832 F.2d 1155 (9th Cir.1987).