Tuesday, December 26, 2017

A New Insect That Sucks (but does little else)

About a week ago Tim Chenowith, one of our Arboretum gardeners, brought a new pest to my attention. It appeared to be some sort of sucking insect that was peppering the Senna wislezini that is part of our Southwest collection near the Rose Garden. At first I thought it was an aphid, however It did not have the two spiracles, sharp protuberances that occur on the rear of the insect, that are key identifying marks of most aphids. It was also unusual in that the ‘honeydew’ it produced was solid, and stayed on the bugs rear end until it broke off, in which case it would stick to the plant that the bug was infesting almost like sugar crystals but a little more oval in appearance. Since I hadn’t seen this pest before I did what I usually do faced with an unidentifiable pest; I sent a picture of it to Gevork Arakelian, the entomologist for Los Angeles County’s Agricultural Commissioner Weights and Measures office.
Small insect peppers this Senna with small balls of solid sugar. 
In the old days I would send the whole pest and it would be relatively involved process of sending via the county courier, the County’s own parcel post and letter delivery service. Although most times it would get to the Ag Commissioner's office intact, if I had to send the package containing the live pest on a Friday it would not get opened until Monday -sometimes resulting in an indiscernible mass of what was, just several days before, once a living pest. Now it’s pretty easy, I just position my iPhone a half an inch above the eyepiece of my microscope and take a pic. The result is then photoshopped until all the highlights, furrows, ridges, antennae and other insect parts that Gevork might need for an ID are mostly visible.

At the top is one of the insects, the thing on its rear end is a mass of solid honeydew. The white masses are surrounding the four insects in the picture are solid honeydew produced as the result of the pest excreting a sugary waste out of its rear end.  

 Gevork got back to me the the next day. He pretty much nailed it. It was a Caesalpinza psyllid, a small sucking insect that apparently causes little or no damage to its host. here is the description he sent me:

 CAESALPINZA PSYLLID, Freysuila dugesii, -(Q)-This psyllid is one of several in the genus that feed on leguminous shrubs and trees in Caesalpinia and Poinciana. The first California record comes from Palm Desert, Riverside County, where it was collected on a golf course by County Ag Biologist Richard Shaffer in January. The host was Caesalpinia cacalaco. This small shrublike plant with yellow and orange flowers is being commonly planted these days in many southern California and Arizona locations. Our specimens were confirmed by Dr. Ian Hodkinson in England. Little is known about this psyllid as it has been collected only sparingly over the years. It is most likely native to Mexico, the native home of the host. No apparent injury such as galling or malformations to the plants were noted. It is likely restricted to these hosts and whether it will cause damage to them in the future in ornamental plantings is unknown.

This also makes sense because Senna wislezini is closely related to the host, Caesalpinia cacalaco. It might infest Mexican Bird of Paradise plants (Caesalpinia pulcherrima), but if it did it would probably not damage the plants.    So thankfully this pest is probably nothing to worry about, but I'll keep an eye on it. Interestingly the coating of sticky solid honeydew balls could be a manner of camouflage for the pest, making it tough for birds to discern the sticky sugar balls from the psyllid.
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