Dear agricultural readers we continue with the series of articles related to pest insects in tropical pastures, this time an insect commonly known among agricultural producers as grass bug will be described and whose scientific name is Blissus spp . It is necessary to mention that this arthropod causes an effect similar to that of Aeneolamia in pastures, since when it is present on established forage surfaces, a kind of burning of the foliar area can be observed. Based on these premises, aspects related to ecology, biological cycle, habits, damage and insect control are addressed below.
Bioecology of the Bissus spp
The Blissustaxonomically belongs to the order Hemiptera, family Lygaeidae and genus Blissus, there are several species but some researchers have considered the insularis, as the most predominant species in tropical areas, in Venezuela the southern area of Lake Maracaibo is one of the most affected by this insect, especially in times of drought and with vulnerable grasslands belonging to the genus of the Brachiarias.
As mentioned above, the period when the infestation levels of the Blissus on foraging surfaces increase is in the low rainy period, the vulnerable grass species are:
* Brachiaria arrecta.
* would type decumbens.
* Brachiaria mutica.
* Cynodon nlemfuensis among others.
There are also tolerant species such as the Brachiaria humidicola and the Megathyrsus maximus, but despite this they could be affected if agronomic and zootechnical management of the crop is not carried out.
Biological cycle of the Blissus
The Blissus is an oviparous insect, once it is in its adult stage they place the eggs near the roots and the neck of the plants in the dry period, approximately between 6 and 15 days the eggs hatch, to give way to the nymphs, according to León (2014), when they are in the nymphal state they present five nymph instars in a span of 4 to 5 weeks, when the author talks about nymphal instars, refers to the fact that there are several stages of development when the insect is in the nymph stage, observing nymphs initially yellow with a red band on the thorax, until turning a dark brown color with a light band on the back of the abdomen, during the entire nymphal process it takes approximately between 30 to 40 days until the insect reaches its adult stage with a size between 3 to 5 cm long with a black body and white wings.
Taking into account that the biological cycle is important for the control of the same, we share the results of a research cited by Espinoza in (1994), which consisted of determining the time elapsed in the biological cycle of the insect under different temperatures as seen in the following table:
Table 1. Biological cycle of the insect under different temperatures
design of the tabla: amestyj 2020, adaptation of Espinoza (1994).
In the table it can be observed that as the temperatures decrease the biological cycle lengthens, validating this what was pointed out by many researchers and technicians when they mention that the greatest infestation is observed in the dry period, where the temperatures are higher, since the temperature influences the biological cycle shortening the time of appearance of the nymphs and greater number of adults in less time compared to the lowest temperatures.
Bibliographic references
Bracho, M. and Prieto, J. (2005).Integrated pest control in pastures. Report of the IX Seminar on pastures and forages. (p.192-194). San Cristóbal: Universidad Nacional Experimental del Táchira.
Espinoza, F. (1994). Pests of the grassland ecosystem in Venezuela. Maracay: FONAIP- Instituto de investigaciones zootechnicas.
González, B. (2010). Pests in tropical pastures. Rev. Of extension of the Faculty of agronomy of the University of Zulia Agrotecnico, (26), 50-53.
León, L. (2014). Biological pest control in tropical pastures and forages. In GIRARZ, Achievements and challenges of dual-purpose livestock farming (p.294-301). Maracaibo: University of Zulia.
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