Weather patterns drive cotton moth migration

19 October, 2005

___Warmer inland temperatures, favourable prevailing winds, and an abundance of wildflowers in central Australia have stimulated ideal breeding conditions and higher levels of Helicoverpa and tipworm populations at this early stage of the cotton growing season, according to CSIRO entomologist, Colin Tann._

Commenting on the weekly CSD Web on Wednesday video, Mr Tann said that judging by rainfall events, this year has obviously been a successful breeding year in the inland, with wildflowers there excellent hosts for Helicoverpa punctigera and other species.

“As these hosts start to dry out in the inland regions and the temperature warms up, they take to the wind and they end up over here (in cotton growing regions). You get fairly poor survival but when the conditions are good you get a lot of months coming across.

“At the moment we’re doing surveys of spring crops such as chickpea, faba bean, sunflower, canola and also roadside weeds. We are picking up populations on those at the moment.

“If anyone examines wildflowers on the side of the road, they will probably find grubs on them. This is the first generation. With regular rainfall events and constant moisture to have good host availability as we go into warmer months, so the conditions are really good for breeding, and it’s shaping up that we’re probably going to find quite a few moths early in the season.”

__He noted that cooler conditions could slow the development of grubs on the plant, and slow the emergence from pupation.

“From October on we start seeing a few Helicoverpa armigera starting to get into the system and H. puntigera moving into their second generation, so the conditions should be very favourable for moth activity this year.

“November is usually a pretty good month when you get a lot of moths around and they’re going to be mixed species. People have probably been finding a lot of months around lights on buildings and they’re mixed species; they’re not all H. punctigera, so there’s no need to panic.

“There’s another native species (Heliothis punctifera) and people might have been alerted to that. This insect is not that significant. It can be a pest, but it usually disappears pretty quickly. It’s been migrating across and it usually beats the H. puctigera as it develops a bit quicker.”

He also commented that with a lot of marshmallow plants growing along roadsides, this suggests that there’s going to be tip worm around this year, with prospects for Army worms as well.

__“It’s a good season and people have got to expect it to be a higher pest year. On the other hand, the beneficial populations are enormous, and a lot of the stuff we’re collecting out of crops and other hosts is heavily parasitized, so pest mortality is very high, but I’m sure we’ll find H. punctigera in the system fairly frequently this year,” Mr Tann said.

_Further Information:
_"Robert Eveleigh, John Marshall, Craig McDonald, David Kelly or James Quinn":showstaff.asp?staff=1