Helicoverpa punctigera, the native budworm, Australian bollworm or Chloridea marmada, is a species of moth in the family Noctuidae. This species is native to Australia. H. punctigera are capable of long-distance migration from their inland Australian habitat towards coastal regionsGregg PC (1993) Pollen as a marker for migration of Helicoverpa armigera and H. punctigera (Lepidoptera: Noctuidae) from western Queensland. Australian Journal of Ecology, 18, 209-219. and are an occasional migrant to New Zealand.
This species is a generalist, with larvae observed feeding on at least 100 plant species, and are considered a pest for tobacco, flax, peas, sunflower, cotton, maize, tomatoes and other crops.Zalucki MP, Daglish G, Firempong S and Twine P (1986) The biology and ecology of Heliothis armigera (Hubner) and H. punctigera Wallengren (Lepidoptera: Noctuidae) in Australia: what do we know? Australian Journal of Zoology 34, 779-844. Outside of agricultural settings, primary host plants include some Australian native daisies, in particular flat billy buttons Leiocarpa brevicompta,Walter GH and Benfield MD (1994) Temporal host plant use in three polyphagous Heliothinae, with special reference to Helicoverpa punctigera (Wallengren) (Noctuidae: Lepidoptera). Austral Ecology, 19, 458-465. annual yellow tops Senecio gregorii, poached egg daisy Polycamma stuartii,Zalucki M, Murray D, Gregg P, Fitt G, Twine P and Jones, C. (1994) Ecology of Helicoverpa-Armigera (Hubner) and Heliothis-Punctigera (Wallengren) in the Inland of Australia - Larval Sampling and Host-Plant Relationships During Winter and Spring. Australian Journal of Zoology, 42, 329-346. and also the native legume Cullen cinereum.Gregg PC, Henderson GS, Del Socorro A, Le Motte K and Birchall C (2016) Polyphagy in an uncertain environment: Helicoverpa punctigera in inland Australia. Austral Ecology, 41, 819-828. Helicoverpa punctigera is often compared to its cousin species H. armigera who unlike H. punctigera has developed resistance to certain insecticides and other genetically modified cotton crops. The two species can occasionally be confused with one another as they look similar. However, the two species can be differentiated by characteristic differences in their hindwings. H. punctigera is often confused with two other moth species of the family Noctuidae – the Armyworm Moth (Mythimna unipuncta) and the Looper Moth – due to the medium-sized nature of the three species.
Taxonomy
Helicoverpa punctigera was first described in 1860 by Wallengren. The subject of classification has changed over the years. Originally classified into the Heliothis genus, this moth species was later re-classified into the Helicoverpa genus. The earliest record of H. punctigera in South Australia was in 1910 when it was referred to as "Grubby Tomatoes".
Description
Eggs
Helicoverpa punctigera egg are spherical in shape and in diameter. While its colours vary based on the stage of larval development. The eggs are initially white, before turning brown and finally black shortly before hatching.
Larvae
Newly hatched larvae are observed to be in length and will grow up to in length. Observed to be various shades of brown, green and orange, the larvae's colour darkens as it matures and the dark spots on it become more apparent. The H. punctigera larva's body is covered in small bumps, long stiff back hairs and bristles that cover its body and there are black hairs around the head.
Pupae
Helicoverpa punctigera pupae range from dark brown to shiny brown in colour.
Adult
Compared to other moths, the adult H. punctigera is average in size, having a wingspan of . While the male H. punctigera generally have dull green or yellow forewings, the female H. punctigera have brown or reddish-brown forewings. The adult H. punctigera strongly resembles the adult H. armigera except for its hindwing pattern: H. punctigera have a uniformly dark section in the hindwing, whereas H. armigera have a small pale patch here.
Life cycle
Eggs
H. punctigera eggs observe four stages in their development. The stages can be identified based on the colour of the egg. Freshly laid eggs are white and over time. In warmer climates, the eggs take approximately three days to hatch, while in colder climates, they take between six and ten days to hatch.
Larvae
H. punctigera larvae pass through six stages of growth before reaching the pupa stage. With a warmer temperature, they will reach the final stage within two to three weeks, while under colder temperature, they take about four to six weeks. The caterpillars have been shown experimentally to distinguish between host plant species when moving across the ground, and readily move between nearby plants.Jones, L.C., Rafter, M.A. and Walter, G.H. (2021), Showier plants host more larvae: distribution and movement of generalist caterpillars among plants in the field. Ecol Entomol, 46: 514-524. https://doi.org/10.1111/een.12994
Pupae
Prepupae larvae (larvae after the 6th growth stage) tunnel up to under the soil to the base of the plant. The pupal chamber constructed will allow the H. punctigera to resurface when in adult stage. The pupal tunnels constructed are smoothed, well-packed soil with a thin layer of silk. The prepupae larvae avoid selecting soil locations where the temperature is higher than 38 degrees and have compacted soil. The emergence of the adult is highly favoured by dry conditions. Rain and other external conditions that might collapse the tunnel reduces the survival rate of the adult H. punctigera due to the disruption of emergence.
The pupation process relies on the external temperature. In warmer temperatures, the pupation process takes approximately two weeks. While in colder temperatures, up to six weeks. During colder seasons, 70% to 90% of the pupae enter diapause. Pupae Diapause is the process in which the pupae development to the adult stage is suspended due to inhibiting or unfavourable environmental conditions.
Adult The adult Helicoverpa punctigera moth feeds on nectar after emerging from the pupae. Their adult lifespan is limited to ten days where they mate and lay their eggs before dying. The female typically lay their eggs either in clusters or singly on various developing fruit and flower buds. Each adult female lays approximately 1000 eggs during its lifecycle. Adult Helicoverpa punctigera moths typically live between two and four weeks. As they are nocturnal, they rest during the day and are active at night
Reproduction Belonging to the insecta class of animals, the H. punctigera follows an oviposition behaviour where it expulses its eggs by a vertebrate. Oviposition is the expulsion of eggs from the female insecta's oviduct to an external environment. While the Oviposition behaviour is unrelated to the feeding habits of the female H. punctigera, the female H. punctigera tends to lay its eggs in areas with more flowering crops than in other areas. This is mainly due to the female H. punctigera feeding habits as the food chain is crucial in the reproductive cycle of the H. punctigera. Any factors affecting the food supply during their reproduction period (usually in summer) would determine the reproductive potential of the H. punctigera specials. Despite the H. punctigera feeding habits however, the female H. punctigera is able to lay its eggs anywhere and at any time of day.
The selection of area is also crucial to the survival of the eggs and larvae of the H. punctigera. Selecting an area in the open will lead to the eggs and larvae being susceptible to various predatory insects and animals. Furthermore, selecting an area without sufficient food would mean that the larvae would not have enough to feed on as well.
Migration
Helicoverpa punctigera is capable of long-range migration at high altitudes () over host crops () in addition to entire regions (). With long-distance flight being possible for the H. punctigera, their habitats are generally observed to be temporary once the H. punctigera reaches the adult stage of the life cycle. It is noted that the H. punctigera are found in abundance in the far inland and around the coast of Australia during the summer period. This is heavily due to the climate being favourable for the reproduction in summer.
there was research regarding the migration of the H. punctigera, but it was difficult to test for the back-migration of H. punctigera. That was primarily due to there being a gradual migration of the population and there being no appropriate markers to track individual H. punctigera. tracking had been greatly improved by advances in radar, population genetics markers, and dispersal modeling.
Ecology
Mutualism
As a member of the Noctuidae family, H. punctigera plays a part in the pollination process of plants.
Food guilds
H. punctigera particularly feed on high value crops such as cotton, soybean, maize, and tomato and various other horticultural hosts.
In the early larvae stages, the H. punctigera feed on seeds and damage plant pods while in the mid to late stages of development, the larger H. punctigera larvae are able to consume entire plant pods and their contents.
Defence
When disturbed, the H. punctigera lifts its head and curls it below the front of itself. If disturbed further, it lets go of the leaf it resides on and drops while curling itself up into a spiral shape.
Economics
Agricultural impact While in the larval stage, H. punctigera cause farmers to lose millions of dollars' worth of crops due to their polyphagous eating habits. They prefer eating mostly broadleaf species of plants such as cotton, chickpea and various native herbs in addition to a broad selection of other various pastures. The further the H. punctigera larvae are in the growth stage, the more the larvae consume. When in the 5th and 6th instars, the H. punctigera larvae consume 90% of the grain consumption the H. punctigera consumes in its life cycle.
When the H. punctigera consumes crops, chewing damage and holes can be observed on the plant pods and seed heads.
Control measures
Pheromone traps Various pest control measures have been implemented. Including the use of pheromone traps. Pheromone traps use synthetic pheromone lures (similar to the sex pheromones that females emit while mating) to lure the male punctigera into the trap. In addition to trapping the adult H. punctigera, pheromone traps are often used to monitor the activity of and predict the infestation rate of H. punctigera and other moths.
Genetically Modified Crops
Unlike the closely related H. armigera, H. punctigera has not developed any resistance to majority of the chemical control measures created. Genetically modified Cotton plants such as the Bollgard II® and the Bollarrd 3® are genetically modified plants that are used to deal with the H. punctigera larvae. These genetically modified plants produce their own Bacillus thuringiensis toxin that are toxic to the H. punctigera larvae.
Insecticides
Research has shown that at the different instar (stages of development) stages of the H. punctigera, various insecticides have different levels of effectiveness with significant differences being observed through the various instar stages. (Source) Endosulfan used to be one of the components used in H. punctigera insecticides before its ban in 2011. In addition to chemical pesticides, various Biopesticides have been created to manage H. punctigera in vegetation and field crops.