It's time for the second application of malathion to prevent the destruction of my plum crop by plum curculios. A plum curculio is a type of weevil (beetle) that lays it's egg just under the skin of a plum. When the egg hatches the grub eats the plum from the inside out. I a newly formed plum, the grub will actually eat the developing embryo the plum will abort. Once on the ground the grub will pupate, hatch and lay eggs on another plum two weeks later.
Generally, you spray plums every two weeks because of the timing of this process. In early spring when the fruit is small I hit them every week because I can't get the tops of the trees, meaning I can't get all the adults in one application, and because if I can minimize the amount of infested fruit the first go around, I can really lay off of spraying the last month without too many plums becoming wormy. That way I avoid having so much pesticide residue on the plums.
For the rest of it, the video is self explanatory.