Bagrada, the unwelcome cousin
There are a number of emerging biosecurity risks that growers should have on their radar as these are exotic pests or pathogens that are proving highly invasive around the world.
WHAT IS BAGRADA BUG?
The bagrada bug Bagrada hilaris (Burmeister), also known as the painted bug, is a true bug of the order Hemiptera and in the same stink bug family (Penatomidae) as the brown marmorated stink bug (BMSB).The bagrada bug has a shield-shaped body and ranges in size from 5-7mm long and 3-4mm wide, with females slightly larger than males.
Adult bugs are black with red and yellow markings that run lengthwise down the centre and edges of its body. Bugs are most active during spring and summer and like BMSB it aggregates and overwinters in the adult stage. When environmental conditions are favourable (for example temperatures above 25°C and below 41°C) and food sources are plentiful, multiple generations can occur in a season. Females lay on average 100-200 eggs singularly or close together in linear clusters of up to 10 eggs in loose soil, on the underside of leaves and on stems.
WHY IS IT A PROBLEM?
Like BMSB, bagrada bug is expanding its distribution and is posing a threat to vegetable crops in its invaded territory. It threatens horticulture, urban environments and causes sooty mould problems on plants and hard surfaces.
It’s a phloem feeder, using its sucking mouth parts to feed and lacerating tissue during the process. The insect prefers young plant material, including new leaves and the apical meristem. Feeding damage causes circular scorching and leaf malformation that leads to wilting, desiccation and tissue death and can result in plant collapse. Bargada bugs often form large aggregations of adults and nymphs when feeding, characteristic of the species.
WHAT CROPS DOES IT ATTACK?
The main hosts of bagrada bug are brassica species including broccoli, cauliflower, kale, turnip and Asian greens. However the bug is also been known to infest grasses, potato, cotton, corn, papaya, rockmelon, wheat and legumes. It is probable that the host range could continue to expand, with bagrada bugs often seen aggregating and attempting to feed on plants that are non-hosts.
DISTRIBUTION AND SPREAD
Native to Africa, bagrada bugs are found through southern and eastern Africa, as well as Asia and parts of south Europe. Most recently in 2009, bagrada bug invaded the United States, starting from the eastern coast in California and moving into Arizona, Nevada, Utah, New Mexico and Texas. It’s often detected on plant material travelling across state borders.
RISK TO NEW ZEALAND
Bagrada bug is currently found in temperate and subtropical environments associated with a range of host plants. Unlike BMSB which overwinters in structures, bagrada bug overwinters in areas where its preferred host plants, brassicas, are present. It may be possible for bagrada bug to establish in areas of New Zealand that experience summer temperatures appropriate for the bugs lifecycle, such as Auckland and Northland.
WHAT TO DO IF YOU SEE IT
If you think you’ve seen bagrada bug, call the Ministry for Primary Industries pest and disease hotline on 0800 80 99 66.