Abstract
In the interest of developing environmentally friendly interventions to infestations by Formosan subterranean termites, Coptotermes formosanus Shiraki, a number of carbohydrates were tested for effects on termites and symbionts. Among these, the D-galactose analog, 2-deoxy-D-galactose, myo-inositol and its fully phosphorylated derivative, phytate, showed promise as potential control chemicals. Feeding bioassays with 20 termite workers, where compounds were applied (concentrations ranged from 160.2-1281.7 µg/mm3) to 5 cm filter paper in water, indicated all three compounds significantly impact termite mortality in a dose dependent fashion over a 2 wk period. Interestingly, when myo-inositol was administered to termites in agar (40 mg/mL), in the absence of a paper food source, its toxic effect was abolished, while 2-deoxy-D-galactose toxicity remained, suggesting myo-inositol’s mechanism of toxicity may involve disruption of cellulose digestion and 2-deoxy-D-galactose may poison the termite directly. Myo-inositol feeding bioassays were also conducted with red imported fire ants, Solenopsis invicta Buren, who appeared immune to the toxic effect. Radiotracer feeding studies involving myo-inositol-[2-3H] and worker termites indicated myo-inositol is not chemically changed following its ingestion. When the hindgut protozoa of termites feeding on myo-inositol and 2-deoxy-D-galactose were quantified decreased populations were observed. Myo-inositol, phytate and 2-deoxy-D-galactose all take approximately one week to induce mortality, indicating that they may have promise as a delayed action toxins, which, if added to baits, could allow time after bait discovery for an entire colony to be affected.
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