A team of researchers in China finds that the sweet-taste inhibitor lactisole reduces sugar feeding in aphids. However, in some cases, lactisole also reduces plant growth, meaning further research is needed to turn it into an effective tool for aphid pest management. The green peach aphid (Myzus persicae) was one of two aphid species included in the study. (Photo by David Cappaert, Bugwood.org)

By Andrew Porterfield

Andrew Porterfield

Aphids can cause damage to a variety of plants due to their sap-sucking feeding behavior, which can cause discoloration, leaf curling, yellowing, and stunted growth. Sucrose in the plant sap, or phloem, helps guide the insects to plant juices and acts as a feeding stimulant.

Sucrose triggers the aphid feeding response through receptors that perceive sugar and transmit this information to the aphid’s nervous system. Studies on the receptors have revealed their genomics, evolution, and expression patterns. But is it possible to manipulate sucrose perception to help control aphid populations?

A team of researchers in China studied the role of sucrose receptors in aphids, and experimented with a commercial sweet-taste inhibitor, lactisole, to see if the chemical could alter aphid feeding behavior. The researchers found that lactisole does reduce sugar feeding in aphids, reporting their findings in an article published in February in the Journal of Economic Entomology.

Lactisole, which was originally derived from roasted coffee beans, is used to reduce intense sweet flavors in some products. It can bind to sugar receptors, thereby reducing the impression of sweetness. This study is the first known to look at lactisole as a pest management tool.

The scientists examined lactisole’s role in feeding behavior by adding it to an artificial diet and by root drenching and spraying on plant leaves. They also used an electropenetrograph to monitor feeding behavior on wheat seedlings coated with lactisole. Colonies of green peach aphid (Myzus persicae) and English grain aphid (Sitobion avenae)were collected and reared from cabbage and wheat seedlings.

For the artificial diet experiment, the scientists prepared stock solutions of amino acids, vitamins, and trace minerals as well as a 20 percent sucrose solution. Fifteen adult M. persicae or S. avenae were introduced to feeding chambers made from paraffin layers over a petri dish. The number of aphids settling was recorded between 10 minutes and 24 hours. The diets contained different concentrations of lactisole to determine its dosage effects on aphid behavior.

For feeding preference and aphid growth, seedlings were sprayed with lactisole. Then, 15 adult aphids were introduced and numbers on each seedling recorded. For aphid performance assays, the scientists root drenched wheat or Chinese cabbage seedlings with either a water control or lactisole. After three days, aphids were introduced to each plant and removed after one day, leaving six to eight nymphs on the leaves. All aphids were collected and weighed after six days.

Finally, feeding behavior of adult S. avenae on root-drenched seedlings was monitored using an electropenetrograph. Gold wire was attached to the back of each adult S. avenae, and each was placed on a wheat leaf. Signals were recorded for eight hours during daytime.

The researchers found a significant reduction in the number of aphids and number of nymphs after a lactisole-supplement artificial diet, a reduction to one or two aphids or nymphs, compared to two to five after 24 hours. Higher doses of lactisole also reduced aphid growth, and root-drench lactisole reduced aphid and nymph numbers significantly. Phloem ingestion and salivation events were higher when feeding on wheat seedling roots drenched by lactisole.

“Both M. persicae and S. avenae exhibited a reduced preference for the artificial diet containing lactisole, probably because lactisole bonded to their sweet taste receptors and thus inhibited aphids’ perception of sucrose,” the researchers write.

However, lactisole’s capacity as a pest control mechanism has a challenge—it also inhibits plant growth when applied as a root drench. “Future research should enhance the efficacy of sweet taste inhibitors on insects while mitigating their adverse effects on plant growth, possibly through the synthesis of lactisole derivatives or the development of novel sweet taste inhibitors,” they add.

Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He is based in Camarillo, California. Follow him on Twitter at @AMPorterfield or visit his Facebook page.