The beet fly (Pegomya betae Curtis, 1847) is a dipterus belonging to the Anthomyiidae family.
From a systematic point of view it belongs to:
P. betae species.
The terms are synonymous:
– Anthomyia betae Curtis, 1847;
– Anthomyza dissimilipes Zetterstedt, 1849;
– Anthomyia femoralis Brischke, 1881.
Geographic Distribution and Habitat –
Pegomya betae is a species of fly present in the Palearctic area and distributed over much of Europe, Central Asia, Siberia, Japan and North America.
This species is oligophagous that lives especially at the expense of the Chenopodiaceae and is considered a parasite of beet and sometimes spinach crops.
The beet fly is a small diptera, 7 mm long, which has a grayish thorax and a gray-yellowish abdomen with a darker longitudinal band.
The body is covered with short dark bristles with reddish yellow legs with black legs.
The larva measures 6 – 8 mm, greenish white in color. It is also recognized by the pointed front part which reveals 2 dark buccal hooks. It has anterior stigmata with 6 or 8 digits.
The pupa measures 8 mm and is brown-red in color.
The eggs measure 1 mm, very elongated, pure white, decorated with a thin net; these are deposited on the lower layer of the leaf in groups of 3 or 6.
Attitude and Life Cycle –
Pegomya betae overwinters as a pupa in the ground.
In the spring period, towards the month of April, the first generation adults appear and lay eggs on the underside of the leaves.
The female lays in successive cycles with a duration ranging from 8 to 10 days and lays her eggs in groups of 3 to 8 for a total fecundity of 70 to 80 eggs.
The newborn larvae lead an endophytic life in the mesophyll by undermining the leaf tissue.
The larva crosses the chorion of the egg at the point of contact with the leaf, thus penetrating it. Dig a narrow tunnel between the two skin. The galleries of the larvae hatched from the same egg group come together. The nymph forms in the soil at a variable depth depending on the humidity.
These reached maturity pupate in the ground and originate a second generation.
The adults of the second generation appear in the month of July; these ovipose and originate a second larval generation which, in optimal conditions, will be able to generate a third generation in the period of late summer or early autumn.
The pupa enters diapause in September.
In countries with warm and humid temperatures, there may still be one or two generations.
In Italy and the Mediterranean, it usually turns 2-3 generations a year.
Ecological Role –
For Pegomya betae, population fluctuations are enormous and vary according to climatic conditions and bioethical agents. This fly is most harmful if the month of May is cold and rainy. In summer, drought and high temperatures are limiting factors (lethal to larvae and eggs).
The adult, on the other hand, feeds on the nectar, and on the sap that gushes from the wounds caused to the plant.
The damage, which is caused by the larvae, occurs on the leaves; in the event of a consistent attack, the leaves may undergo rotting and drying with serious damage to the photo-synthetic efficiency.
These manifestations are particularly evident on young plants and seedlings, and are due to the larvae digging tunnels in the leaf blades, causing the plant to weaken or even die.
At the level of the destroyed tissues, there are appearances of translucent spots that dry up and darken.
When the Beetroot has passed the 6th stage (authentic leaves), its sensitivity decreases considerably and interventions are no longer necessary.
The fight against Pegomya betae must be biological or, at best, integrated. In the guided and integrated struggle, samples are taken, carried out on the real leaves, to determine the number of eggs laid and present. The intervention threshold is from 4 to 20 eggs per plant, respectively on plants with 3-4 true leaves up to over 6-7 true leaves.
The treatment must be performed with endotherapeutic products.
The choice of the product must also take into consideration the possibility of using an active principle with a common activity against other pests, should the need arise for combined interventions.
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.