Tuesday, October 28, 2008
I first hypothesized that keelbacked treehoppers, Antianthe expansa, switch from woodier solanaceous plants (like cestrum) to more succulent species like tomatoes in summer, as the tomatoes become available. Observation in 2005 + 2006 confirms egglaying on cestrum in winter, and on tomatoes in mid-summer. In 2007 I have no data because either I didn't notice any treehoppers, didn't find them interesting enough to photograph (not too likely!), or there weren't any. During 2007 I grew no tomatoes but I did have peppers; along with cestrum, several plants of the genus solanum, and nightshade, all members of the solanacea family and theoretically appropriate as food plants for the treehoppers.
So I was mildly surprised to find this one adult on the eggplant plant. It's been in the same spot for several days, likely getting ready to or already having laid eggs inside slits in the stem. In our climate, tomatoes, peppers and eggplant can be treated like tender perennials, overwintering and producing the following year after a good pruning. Perhaps the treehoppers are not discriminating as I thought in their winter sites, but the gardener chooses for them by pulling out the spent tomato plants in autumn.
As far as control of this species goes, it seems the colonies start slow with just one or a few egg-laying adults. If you can pick these off before eggs are laid (egglaying sites shown here and here), and smother any eggs with dormant oil you'd be way ahead of the mob of spiky black plant-sucking nymphs in a small planting.