Hackberry nipplewhat?

This week has been the week of the hackberry nipplegall maker, Pachypsylla celtidismamma. I should have known when, during the Entomological Society of America's annual conference in Austin last week, I opened my 23rd floor hotel room blinds and saw the outside window covered with these insects.

Pachypsylla adults (about 1/8-inch long) are
commonly found at this time of year indoors, around windows

Sure enough upon return to my office, calls and messages were awaiting me about little "gnats"  covering window screens, outside walls, and cars. The small size of these insects allows them to enter buildings with ease, even squeezing through window screens.  Though these insects are present annually, the invasion seems to be unusually heavy and widespread this year with complaints from Austin to east Texas and the Dallas area.

Pachypsylla is a genus of tiny insects that grow up inside galls that form on hackberry leaves. Also called psyllids (SILL ids), they are not gnats or flies, but belong to the same order as the leafhoppers and cicadas. Like other gall making insects, Pachypsylla adults lay their eggs on leaves, which then start to swell around the egg or developing larva, forming a gall. After feeding on the gall tissue all summer, Pachypsylla adults emerge in the fall. Unfortunately for your customers, these adults commonly enter structures at this time in their search for a warm place to hang out and, perhaps, catch some football or prime time TV during the winter.

The nipple-like swellings on hackberry leaves give this little
insect its name.

Despite being a nuisance, hackberry nipple-gall insects are pretty harmless.  They do not bite, do not eat clothes and do not hog the remote. Apart from needing to be vacuumed up from windowsills occasionally, there is little you can do about these insects. In most cases, poor seals around windows and doors provide entry points, but truth is they can get indoors through any crack or gap in the building envelope.

Those who have tried spraying window screens with an insecticide noted that the main result is smeared windows.  If you do offer to spray, keep your sprays limited to window and door frames, and obvious gaps and cracks in outdoor siding.  I do not advise treating indoors, as these insects should die relatively quickly anyway. And no, you can't treat the trees. A vacuum is the best control tool, in my estimation.

For customers who find the invasion to be an annual occurrence, removing nearby hackberry trees and replacing them with another well-adapted tree is one possible solution.  Keep in mind, however, that these little guys can fly.  They were, after all on my 23rd floor windows  last week. So if other hackberries are nearby, cutting down the tree may not help a lot,  especially during a banner year like this.

I have no explanation for the great numbers of nipplegall makers this year.  This obscure group of insects has not been as well scrutinized as other, more important pests.  However we do know there was something they liked about 2013, rain at the right times, the temperature, or few natural enemies.

Hackberry psyllids in homes

These nipple-like galls on hackberry leaves protect a small
insect called Pachypsylla. In the fall the insects emerge and
may invade nearby structures.

Insect species that specialise in invading homes in the fall are almost as predictable as the cooler weather itself. A number of insect species, like paper wasps, multicolored Asian lady beetles, box elder bugs and cluster flies are already pretty well known to the pest control industry. But nature is full of surprises, and there's always an obscure insect or two that can surprise you.

Pachypsylla adults (about 1/8-inch long) are commonly
found at this time of year indoors, around windows.

This year seems to have been a good year for one tiny invader, at least in the north Texas area. It's the hackberry nipplegall maker, Pachypsylla celtidismamma.  If you've ever noticed nipple-like swellings on hackberry leaves, you already know a little about this insect. Pachypsylla is a genus of homopterous insects in a family referred to as psyllids (SILL ids).  The specialised Pachypsylla grows up only inside galls that form on hackberry leaves.  Like other gall makers, Pachypsylla adults lay their eggs on leaves, which then start to swell around the egg or developing larva, forming a gall. After feeding on the gall tissue all summer, Pachypsylla adults emerge in the fall.

Unfortunately for fastidious homemakers, or the unprepared PMP, these adults commonly enter structures at this time in their search for a warm place to hang out (and, perhaps, catch some football or prime time TV).  This week I've had multiple reports of Pachypsylla home invasions here in north Texas.  Most calls are accompanied by deep concern by homeowners that these tiny insects might be harmful.

You can tell your customers that hackberry nipple-gall insects are pretty harmless.  They do not bite and do not eat clothes (and don't hog the remote!). Apart from needing to be vacuumed up from windowsills occasionally, these insects shouldn't pose too much of a problem; however I suggest an application of a pyrethroid insecticide to the outside frames of windows and doors.

These insects are small. Adults are 2-3 mm-long (about 1/8-inch) and just a little over 0.5 mm wide. With the average window screen mesh about 1.5 mm apart, these guys can easily slip through screens. Recommend to your client to check the tightness of seals around windows and doorways, the most common points of entry.

If Pachypsylla invasions are a regular occurrence at an account, suggest that the property owner remove nearby hackberries and replace them with another well-adapted tree.

According to the Encyclopedia of Insects, the exact mechanism by which insects induce plants to form galls is still poorly understood, but it involves chemicals applied to or injected into the plant that influences plant growth hormones.  In the case of Pachypsylla, the plant responds to its springtime egg laying by forming  round, nipple-like galls on the undersides of developing leaves.  Each gall surrounds a growing Pachypsylla nymph.  In the fall mature adults emerge from these galls and search for a protected site to spend the winter. There is only one generation per year.

Stink bug sighting

Last July I wrote about the brown marmorated stink bug (BMSB).  This insect is a new invasive pest from Asian and has been spreading pretty rapidly across the eastern states.  Last month I got a report from John Rourk, ACE with Certified Termite and Pest Control in Corpus Christi, about what may be the first confirmed report of this pest in Texas.

Fall aggregation of BMSB and other stink bugs under light outside a home.
Photo by Leske, 2010.  (not from Texas)

According to Rourk, he received a call from a resident about a large number of bugs in their travel trailer after a recent visit to Pennsylvania. When he got to the residence he saw two stink bugs flying from the RV flying towards the residence. He also found and collected three specimens from the RV and was told by the owner that they had already killed “more than we can count.” He he was unable to find any more evidence of activity or live specimens in the RV or on the premises.

Rourk knew what he was doing when he collected specimens. The only way to confirm an unusual or exotic pest is to collect it. A photograph is better than nothing but is still not as good as a specimen (dead or alive). According to Dr. Roy Parker, Extension entomologist at the Texas AgriLife Center at Corpus Christi, the identity of Rourk's specimens has been confirmed by the Texas A&M University entomology museum, and has been reported to USDA.

In a 2010 report by USDA's Plant Epidemiology and Risk Analysis Laboratory (APHIS/PPQ), BMSB is projected to be agriculturally important in east Texas and the panhandle regions. According to the report, once BMSB invades a new area it is very difficult to control because of its high mobility and large number of host plants.

Called by some the "Interstate bug" because of its habit of hitching rides on trucks, RVs and vans, the BMSB will often be found clustered in engine compartments or other warm protected areas of vehicles.  Besides being an agricultural pest, once it becomes established it also becomes a household pest as a fall invader (see picture).

Just because the BMSB was found in an RV in Texas does not mean it is likely to have become established here. Several hurdles have to be leaped before an invasive pest can establish a viable breeding population. Dispersing bugs may not be able to find one another for mating and reproduction in a new area.  There may not be a critical density of acceptable host plants at the point of introduction, and weather conditions must be favorable at time of import.  According to USDA, we still don't know the minimum population level needed for successful establishment of BMSB into a new area, although the insect has been successfully introduced to at least seventeen states. Since 2003, however, BMSB has been intercepted or trapped in at least seven states (Florida, Illinois, Maine, Mississippi, Missouri, Rhode Island, and South Carolina) where they do not appear to have established breeding populations.

Remember, as a PMP you are on the cutting edge of surveillance for new pests. Observations made by the pest control industry are, and will continue to be, an important part of urban entomology research and knowledge about insects.