14-spotted ladybird (Propylea quatuordecimpunctata)

14-spotted ladybird beetle (Propylea quatuordecimpunctata) is a predatory beetle belonging to the family Coccinellidae, found in parts of Europe, Asia, and Africa and North America. It was brought to the United States to combat wheat aphids and has spread quite widely there today. They can be found in gardens and parks, on grasses and herbaceous plants, in shrubs and trees. In addition, the species can be found in forest litter, on brushwood, coarse wood residues, in moss, in detritus and alluvial soil, in rotten plant residues and compost.

Appearance

Propylea is a rather small ladybird, its length reaches from 3.5 to 5 mm. Polymorphism is characteristic of this species: the colour of insects can be very diverse: there are about 100 different colour combinations of elytra and spots on them. Due to external differences, some subspecies originally belonged to separate species. Their 14 spots have an irregular almost rectangular shape and can merge with each other, forming a characteristic pattern resembling an anchor. Pronotum is whitish or pale yellow, spotted. The antennae and legs are yellowish-brown. The head is yellow with a black base, finely dotted. The male’s forehead is yellow, the female has a dark spot in the centre. There are light and dark forms.

Food

Propylea quatuordecimpunctata is a natural entomophage of various aphids: Myzodes persicae, Aphis gossypii, Aphis crassivora Koch, Acyrthosiphon pisum, etc. It also feeds on whiteflies, Coccidae, larvae and eggs of some beetles and butterflies. The main advantage of this beetle as an entomophage is that all stages of insect development, starting with the larva L1, are active predators.

Life cycle

The P-14 in natural conditions is most often found from May to August, but it can also be found in autumn. After hatching from the eggs, the larvae begin to actively feed and usually develop within 8-10 days, and then pupate within 4-5 days. Temperature strongly affects the insect’s lifespan: lower temperatures allow them to live longer. At high temperatures, their lifespan is shortened. At 17 °C, females can live for more than 120 days, while at 30 °C they only live for about 30 days.

With the onset of cold weather, the insect enters diapause and overwinters in leaf litter, tree bark or grass, typically uniting into groups of such wintering insects even if they belong to different species.

Application

Propylea quatuordecimpunctata, like many other species of ladybirds, is successfully used in greenhouses to control aphids, however, unlike, for example, the Two-spot ladybird (Adalia bipunctata), they take root quite well in greenhouse conditions and form stable colonies. Also, a characteristic feature of the species is activity even with a low pest population, while at the same time maintaining the ability to multiply rapidly when the pest becomes more. This flexibility allows the predator to be used prophylactically in the greenhouse on various crops: cucumber, pepper, aubergine, and many others.

It is best to carry out the introduction of entomophage in the spring. Then they manage to settle in the greenhouse for a longer period of time. Even in winter, when the crop rotation has already taken place, they meet again. Beetles remaining in the greenhouse are not yet active after wintering and do not lay eggs yet.

The solution is to re-introduce Propylea quatuordecimpunctata at the beginning of the year. New beetles are able to lay eggs immediately after eating aphids. The hatched larvae need a large amount of food for their development and immediately significantly reduce the amount of the pest. After a few weeks, the larvae develop into a new generation of adult beetles, which immediately attack aphids again, lay eggs, etc. This cycle can be repeated several times per season.