Late sun

I was almost tricked into thinking that it was high summer today even though the evidence was against it. The sun has now sunk down in the sky casting a warm filtered light. Bees are outnumbered by yellow jackets busing themselves with investigations of each freshly dug heap of soil in a slow zig-zag meandering flight. Enjoying the unseasonably warm day I edged and weeded the beds - pulling out long stolens of the subterranian roots of couch grass as it wound its way through the beetroot and chard. Though growth is slowing the plot is still producing well and showing promise for the winter: the cabbages are hearting up, the sprouts are beginning to bud and the purple sprouting broccoli is starting to stand tall, although covered with those pesky whitefly. Does anyone know of an organic way to treat them?