Blissus spp. pest of tropical pastures

amestyj (69)Memberin HeartSTEM • 3 years ago

Dear readers, this publication is a continuation of the series of articles related to insect pests in tropical pastures, in this opportunity we will describe an insect commonly known among agricultural producers as the grass bug, whose scientific name is Blissus spp. It is necessary to mention that this arthropod causes in pastures an effect similar to that of Aeneolamia, since when it is present in the established forage surfaces, a kind of burning of the leaf area can be observed. Based on these premises, aspects related to the ecology, biological cycle, habits, damage and control of the insect are discussed below.

_{Design by @amestyj, with image with no known copyright restrictions.}

*Bioecology of Bissus spp*

The Blissus taxonomically belongs to the order Hemiptera, family Lygaeidae and the genus Blissus, there are several species but some researchers have considered the insularis, as the most predominant species in tropical areas, in Venezuela the area south of Lake Maracaibo is one of the most affected by this insect, especially in times of drought and vulnerable grasslands belonging to the genus Brachiarias.

As previously stated, the period where Blissus infestation levels increase in forage surfaces is in the low rainfall period, the vulnerable grass species are:

* Brachiaria arrecta.
* Digitaria decumbens..
* Brachiaria mutica..
* Cynodon nlemfuensis among others..

There are also tolerant species such as Brachiaria humidicola and Megathyrsus maximus, but despite this, they could be affected if agronomic and zootechnical management of the crop is not carried out.

*Blissus life cycle*

The Blissus is an oviparous insect, once in its adult stage they lay eggs near the roots and the neck of the plants in the dry period, approximately between 6 and 15 days the eggs hatch, According to León (2014), when they are in the nymph stage they present five nymphal instars in a period of 4 to 5 weeks, when the author speaks of 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 they become dark brown with a light band on the back of the abdomen, during the entire nymphal process, approximately 30 to 40 days elapse until the insect reaches its adult stage with a size between 3 to 5 cm long with a black body and white wings.

_{Design by @amestyj, with image with no known copyright restrictions.}

Bearing in mind that the biological cycle is important for their control, we share the results of a research cited by Espinoza in (1994), which consisted in determining the time elapsed in the biological cycle of the insect under different temperatures as shown in the following table:

_{Table 1. Insect life cycle under different temperatures}

_{Table design: amestyj 2020, adapted from Espinoza (1994).}

The table shows that as temperatures decrease, the biological cycle lengthens, validating what many researchers and technicians have pointed out when they mention that the greatest infestation is observed during the dry period, when temperatures are higher, since temperature influences the biological cycle, shortening the time for the appearance of nymphs and a greater number of adults in less time compared to lower temperatures.

*Habits and damage caused by Blissus in grassland ecosystems*

It is already known that this insect is adapted to dry climates and in its adult stage they usually climb to the top of the foliage and feed on the plant near the nodes, insects have been found in the leaf ligule. As for the damage caused, the Blissus in its nymph and adult stage feeds on the sap of the roots and leaf area and inject toxins generating drastic damage throughout the vegetative zone, a yellowing of the leaves and stems is generated as a burnt effect, at first glance it could be confused with the attack of candelilla as the symptoms are similar, the difference lies in the rainy or rainy periods.

_{Design by @amestyj, with image with no known copyright restrictions.}

*Diagnosis and control*

To corroborate if the pastures are being affected by Blissus, it is necessary to carry out inspections in the paddocks, since generally small spaces are observed in the paddocks with burned or dry grass leaves, on the other hand it is recommended to carry out inspections in sunny hours from 10:00 am to 04:00 pm at the base of the stems or in the area near the ligule to verify if there are nymphs.

As for control, in the first place it is recommended to implement preventive management with the application of fertilizers and thus keep the plants vigorous, in addition to carrying out an adequate zootechnical management avoiding overgrazing of the crop, among other alternatives that allow having a plant capable of tolerating the first attacks of the insect, Similarly, another preventive method would be biological control with the application of entomopathogenic fungi at the end of the rainy season, as it has been shown from some research that the eggs of some species are susceptible to Metarhizium anisiopliae.

On the other hand, if there are compacted soils and stoloniferous pastures, the harrow can be passed through the soil to aerate it and decompact it a little, if there is an irrigation system on the farm, it can be watered periodically to maintain low levels of the pest and finally, if there is a high threshold of infestation, it is advisable to apply insecticides such as Lorsban, On certain occasions, rains facilitate pest control, since heavy rains cause the insects to climb up to the areas, leaving them exposed for the application of insecticides. On the other hand, it is necessary to remember that the indiscriminate use of pesticides can cause imbalances in the ecosystem.

Dear readers, it has become evident with the last publications that establishing a forage crop is something complex, since the pasture is a crop and needs agronomic management such as pest control, controlling a pest in forage surfaces requires taking into account when the animal can enter the pasture again, especially if agrotoxins are used, so we avoid that the animal has contact with certain substances that can create imbalances in its organism and that the products such as meat and milk present residues of the substance used.

From agrotecnia we reiterate our gratitude to the HeartSTEM community for valuing our agricultural content, this commits us to continue sharing quality information. On the other hand, the images that are without copyright restrictions in the publication, belong to the University of Minnesota Agricultural Experiment Station and University of Kansas Department of Entomology.

*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 zootécnicas.

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 control of pests in tropical grasses and forages. In GIRARZ, Achievements and challenges of dual purpose livestock (p.294-301). Maracaibo: Universidad del Zulia.