Helicoverpa armigera and Helicoverpa zea
| Why are they important? |
Helicoverpa armigera (Old World or African bollworm) and H. zea (New World or American bollworm) Lepidoptera are listed as quarantine pests. They are absent from the UK despite being established in many countries, including those that are the origin of imported plants, flowers and vegetables. H. armigera is present in much of mainland Europe, Asia, Africa and Australasia, whereas H. zea is restricted to North, South and Central America, and the Caribbean. If introduced to protected cultivation in the UK, both species would be capable of causing significant crop losses and so are subject to legislation aimed at preventing their introduction and spread.
| How do I recognise them? |
At any stage of their life cycle, reliable differentiation of the two species requires laboratory examination, but the general description below holds for both species.
The eggs are approximately 0.5 mm in diameter and are white to brown in colour. Caterpillars pass through four developmental stages (instars) and ultimately reach 30 to 40 mm in length. The caterpillar’s body varies in colour from green, yellow, pink and red-brown, to almost black, and the head is usually pale brown. Several pale, fine, wavy, broken lines run along the body, and there is a broad cream stripe running along each side. In addition, there is often a single dark stripe along the middle of the back. Many minute spines cover the body surface and can be seen using a hand-lens; these are characteristic of these caterpillars. In addition, there are often dark, raised spots on the back, at the base of fine hairs.
Click on the image to view caterpillers in more detail |
The caterpillars pupate in the soil in a silk lined chamber. Pupae are 14-20 mm long, pale brown in colour with a tinge of green, turning darker brown as the moth develops within. The tip of the pupa bears two long (1.2-1.3 mm) straight spines.  Caterpillars of Helicoverpa sp. showing
colour variation and characteristic markings (accurate identification
to species requires laboratory examination) |
| Adult moths have a wing-span of 35 to 40 mm, and range in colour
from green-grey to orange-brown. The forewings have a network of
dark lines and a broad brown band that runs from front to back.
The hindwings are paler, with a broad, dark brown border, brown
veins, and a dark, comma-like marking in the middle. Adult Helicoverpa sp. moth (Actual body length 20-30 mm)  |
 Click on the image to view moth in more detail |
There are other, related species which may also be damaging, but they are not listed in the legislation as they are found more rarely. However, these and all other alien pests are notifiable.
| What types of crops are at risk? |
Both species have been recorded from several hundred hosts, including edible crops and ornamentals commonly grown in the UK. They are most likely to pose a risk to protected crops in the UK but their potential to feed outdoors during the UK summer is unclear and should not be discounted. Crops which may be at particular risk from H. armigera include carnations, geraniums and other ornamentals as well as fruits and vegetables such as tomatoes. Potential UK hosts for H. zea include tomatoes, aubergines, peppers, cucumbers and related crops as well as a wide range of protected ornamental and flower crops.
| What damage do they cause? |
 |
A single fertile female can lay several thousand
eggs, so numbers can build up rapidly, often resulting in severe
crop damage caused by the feeding caterpillars. At different developmental
stages, caterpillars feed on most plant structures including stems,
leaves, flower heads and fruits. They may even bore into the plants,
for example at the base of flower buds, fruits, bolls or maize-cobs.
This habit of boring into plant tissues can promote secondary infection
of the damaged tissues, and can lead to rotting and fruit or leaf
drop.Damage caused by the feeding of Helicoverpa
sp. caterpillars: note the bore holes and frass. (Click on the image to view feeding damage in more detail.) |
| What should I do? |
- Seek assurance from your suppliers that plants are free from these pests as part of any commercial contract.
- Carefully inspect new plants and produce on arrival, including any packaging material, to check for caterpillars and for signs of damage.
- Early notification of the presence of these pests, and rapid implementation of a comprehensive treatment programme will help to eradicate them quickly from your place of production. Established outbreaks are very damaging and difficult to eradicate.
|
Department for Environment,
Food and Rural Affairs 2000 PB 5189/5190 |
CENTRAL SCIENCE LABORATORY |  |
Page last modified:
20 Nov 2006
Page published: 27 May 2004