Brownheaded leafroller - Natural enemies and diseases

The natural enemies of the brownheaded leafroller species have not been studied as much as those of lightbrown apple moth in apple orchards. However, they have many natural enemies in common and much of the description and pictures provided for the natural enemies of lightbrown apple moth are also applicable to brownheaded leafrollers. The following information is based on that for lightbrown apple moth but contains adjustments where differences have been shown from specific studies on brownheaded leafrollers. Brownheaded leafrollers in New Zealand are attacked by a range of parasites and by predators and diseases, which make a major contribution to control, particularly if broad-spectrum insecticides are avoided. With the introduction of selective insect growth regulator chemicals and organic production methods for leafroller control, these natural enemies are now playing a greater part in leafroller management in orchards. Biological control by the introduction of natural enemies from overseas has never been specifically undertaken for brownheaded leafrollers. However, some parasitoids introduced from Australia for the control of lightbrown apple moth have also attacked brownheaded leafrollers and are now found in their populations.

The greatest mortality occurs to young larvae hatching from egg batches and before they have settled (spun shelters) on the leaves. These losses are probably due to a number of predators, including spiders and predatory bugs, as occurs in lightbrown apple moth.

Natural enemies and diseases include (this is not an exhaustive list):

Ancistrocerus gazella - this predatory eumenid wasp paralyses and collects caterpillars of brownheaded leafrollers. The caterpillars are stored in the nest cells as food for the wasp larvae.

Anystis baccarum (L.) - a bright red or orange predatory mite (whirligig mite) which feeds on eggs and young leafroller larvae.

Birds - a number of bird species feed on the larval, pupal, and adult stages of leafrollers, including the silvereye, Zosterops lateralis.

Brachymeria phya (Walker) and Brachymeria teuta (Walker) - chalcid wasps introduced from Australia. These pupal parasitoids are encountered only occasionally.

Diadegma sp. - ichneumonid wasps which attack a small percentage of the leafroller caterpillars.

Dolichogenidea tasmanica - this braconid parasitic wasp (about 2-3 mm long) attacks young (1st and 2nd stage) brownheaded leafroller caterpillars. There are at least four closely related species of Dolichogenidea obtained from leafrollers in New Zealand, including Dolichogenidea carposinae and Dolichogenidea sp. 3, formerly referred to as Apanteles sicarius. This last species has been recorded commonly from brownheaded leafrollers.

Eulophid wasps - two genera of these parasitoids (Sympiesis sp. and Zealachertus sp.) attack a small percentage of the caterpillars of leafrollers. Several wasps are produced from each caterpillar.

Eupsenella sp. - bethylid wasps which attack the 3rd and 4th stage caterpillars of a range of leafroller species.

Forficula auricularia L. - the common earwig that feeds on young caterpillars is considered an important predator of lightbrown apple moth in Australia. It probably feeds on caterpillars of brownheaded leafrollers.

Goniozus jacintae, a bethylid wasp introduced from Australia. This commonly attacks the 3rd and 4th stage leafroller caterpillars, including brownheaded leafrollers. Goniozus sp. was introduced in the period 1967-1969 and examination of the voucher specimens has shown that this included G. jacintae which was already present in the country. G. jacintae was probably introduced in 1922 and may have been self-introduced with lightbrown apple moth from Australia.

Glabridorsum stokesii (Cameron) - an Australian species introduced to New Zealand in the 1970s. It is now well established in the North and South Islands. This ichneumonid wasp parasitises the pupal stage of brownheaded leafrollers.

Glyptapanteles demeter (Wilkinson) - a braconid wasp (about 2 mm long) which frequently parasitises 1st and 2nd stage caterpillars.

Orius vicinus (Ribault) - a predatory bug which feeds on eggs and young larvae of many insects.

Pales funesta (Hutton) and Pales feredayi (Hutton) - minor parasitic tachinid flies which attack caterpillars of brownheaded leafrollers, and emerge later from the pupal stage.

Pentatomid bugs - including Oechalia schellenbergii (Guerin Meneville) and Cermatulus nasalis (Westwood). These predatory bugs feed on leafroller caterpillars, including brownheaded leafrollers.

Sejanus albisignata (Knight) - a predatory bug which feeds on eggs and young larvae. The nymphs of the bug are brick red in colour while the adult is black with two characteristic white flecks, one each side of the wings midway down the back.

Spiders - a range of species feed on the caterpillar stages and adults. Spiders are considered imporrtant predators of lightbrown apple moth in Australia, especially the theridiid Achaearanea veruculata, which also occurs in New Zealand. Serological tests with spiders in Australia have shown that 53% of Thomisidae, 46% of Theridiidae, and 41% of Salticidae preyed on lightbrown apple moth larvae. All these families of spiders are well represented in New Zealand. Spiders encountered in Auckland apple orchards include Achaearanea veruculata, Ixeuticus martius (Amaurobiidae), Trite planiceps and Trite sp. (Salticidae), several Diaea spp. (Thomisidae) and Clubiona sp. (Clubionidae). Laboratory tests demonstrated that all these spiders would feed on leafroller caterpillars, including brownheaded leafroller.

Trichogrammatids - minute parasitic wasps which attack the eggs causing them to turn black. Three species have been identified: Trichogramma sp., Trichogramma (Trichogrammanza) funiculatum and Trichogrammatoidea bactrae fumata.

Trigonospila brevifacies (Hardy) - a parasitic tachninid fly introduced from Australia in the 1970s. This fly is well established in New Zealand throughout the North Island and has been recovered in the north of the South Island. It has been recorded parasitising brownheaded leafrollers.

Vespula spp. - the common and german wasps have been recorded as predators of leafroller caterpillars.

Xanthopimpla rhopaloceros Kreiger - an ichneumonid wasp introduced from Australia in the 1970s and widespread throughout the North Island. It has also been recovered in Nelson. It parasitises brownheaded leafroller pupae.