A greater understanding of why the pest Helicoverpa armigera is passionate about pigeon pea flowers is helping researchers in breeding efforts and pest management strategies.

Moths are highly attracted to flowering pigeon peas, laying most of their eggs on the pulse’s flowers. As caterpillars develop, the larger ones will start feeding on pigeon pea pods, where they do the most economic damage.

With GRDC support, Queensland Department of Agriculture and Fisheries (DAF) research scientist Trevor Volp is building a greater understanding of this behaviour and identifying potential crop defence traits.

The first step has been exploring why pigeon peas are so susceptible in the first place. “We have been taking an approach to understand why. We have now developed a pretty good idea of what makes pigeon pea so susceptible to H. armigera and will continue to work on solving the problem,” Mr Volp says.

The aim is to use this knowledge to develop ways of reducing damage in commercial pigeon pea crops, making it a viable summer pulse crop. This will move it away from being seen as just a refuge crop in cotton-growing areas.

This involves identifying a chink in the pest’s armour, Mr Volp says. This is similar to how sorghum researchers developed host-plant resistance by finding that female sorghum midge cannot lay eggs on certain genotypes.

We have been searching for a break in H. armigera’s armour. We think we have potentially found a couple; now the key will be trying to identify plant traits that exploit those weaknesses.

The research involves laboratory, glasshouse and field-based experiments. “As agricultural researchers, it is critically important to show any results we find in the lab or glasshouse will ‘scale up’. So far, the results we see in the lab and glasshouse do.”

Mr Volp was recently awarded a Crawford Fund grant to travel to the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and work under the supervision of head entomologist Dr Jaba Jagdish.

Based in India, ICRISAT is the global headquarters of pigeon pea research and holds an enormous collection of pigeon pea germplasm, including wild varieties that have well-documented resistance to H. armigera.

“Only time will tell, but I am really interested to see what our Australia–India collaboration can deliver. The prospect of pest-resistant pigeon pea varieties for Australian and Indian farmers is very exciting.”

Although knowledge is still developing, the DAF research team is taking on board H. armigera’s preference for flowers. This includes selecting varieties for synchronised flowering and shorter flowering windows.

“At the moment, some varieties flower incrementally. For example, a few plants will start flowering one week, then a few more the next week and so on. As a result, the flowering period is spread out over an extended period. If we can select varieties that flower over a shorter period, it would make pest management easier,” Mr Volp says.

Reducing insect damage is important for making pigeon peas a better summer crop option.

“The amount of yield lost and the damage to grain quality depends on the level of caterpillar infestation. But I have seen experimental plots with large caterpillar infestations where plants had all their reproductive structures completely removed because of pest feeding.”

More information: Trevor Volp,  trevor.volp@daf.qld.gov.au