Native budworm

Agronomist, Terry Edis (Elders), has reported native budworm (Helicoverpa punctigera) caterpillars in several canola paddocks west of Temora, in the South West Slopes district of New South Wales. Terry says caterpillar numbers have increased significantly over the last 7-10 days, and have now reached densities above established threshold levels. In some paddocks, between 10 and 20 caterpillars have been collected in 5 sweeps. The majority of caterpillars are still quite small, ranging from 3-7 mm in length (indicating they are mostly 1^st and 2^nd instar larvae).

Agronomist, David Jarrott (IK Caldwell), reports native budworm caterpillars within irrigated canola crops near Deniliquin, in the Riverina district of New South Wales. The majority of caterpillars being found in sweep nets are about 5 mm in length. David said pheromone trapping had indicated a significant flight of native budworm moths occurred around Deniliquin in the last two weeks. District agronomist, Philip Bowden (NSW DPI), says native budworm have recently been reported near Griffith, also in the Riverina district of New South Wales.

Consulting agronomist, Ross Watson (Ross Watson Agriculture), has also reported native budworm activity around Scone, in the Hunter district of New South Wales. Ross has observed native budworm moths flying around lights at night in the last few weeks. Crops in the area will need to be monitored for levels of caterpillars. Eggs laid by moths now will take at least 2 weeks before they hatch and grow to a size of approximately 5 mm where the caterpillars can be detected whilst sweep netting crops. It typically takes about 7 weeks from the time of egg laying until caterpillars are fully-grown.

Native budworm caterpillars feed on buds, flowers, fruiting parts and seeds of various crops, including field peas, faba beans, lentils, chickpeas, lupins, canola, as well as lucerne, annual medic and clover. A sweep net or beat sheet should be used to monitor caterpillar activity in crops. Monitor field pea, faba bean, lentil and chickpea crops from budding and flowering development through to maturity. Monitor narrow leaf lupin and canola crops at pod development to maturity. Pod inspections are also essential in order to detect small caterpillars and accurately determine numbers. When caterpillars are detected, it is important to sample representative parts of the entire crop prior to making a control decision.

The decision to spray native budworm in crops that are close to harvest/windrowing is challenging. Native budworm caterpillars eat increasing quantities of plant material as they grow. The last two growths stages (5^th and 6^th instars, which are >25 mm in length) are responsible for eating over 90% of their total food consumption. Late season caterpillar hatchings are often too late to cause significant feeding damage even if numbers are close to threshold levels. This is because the caterpillars will be early instar larvae and therefore not had an opportunity to consume large amounts of plant material prior to pods becoming dry and hard. However, in canola crops, high numbers of small caterpillars can cause economic damage late in the season, especially if rain prolongs crop maturity or delays swathing.

For further information about native budworm, refer to PestFacts Issue No. 8.