Migdolus fryanus is an aggressive pest that causes severe damage to sugarcane cultivation in the main producing regions of Brazil. The management integrated to “coexist” with this insect requires a logical and rational. Due to its complex behavioral biology, population reduction must be planned over the long term.
Species of the genre Migdolus have caused severe damage to the culture of sugarcane, in the main producing regions of Brazil, and may attack other cultivated plants (e.g. blackberries, coffee, eucalyptus, cassava, pastures), or native (e.g. assa-peixe, native vines), being M. fryanus the predominant species in sugarcane cultivation.
You Damage is caused by the insect larvae, which have an underground habit and they feed on the root system, destroying it. In 1992, it existed in the state of São Paulo, an area affected by the insect of approximately 50 thousand hectares, with losses of around 45 million dollars, which indicated a 25% drop in production in the affected areas. In 1995, including all producing regions of state of São Paulo, it was estimated that the areas affected by Migdolus spp. exceeded 100 thousand hectares of sugar cane. Currently, the estimated area more than 280 thousand hectares under attack by Migdolus spp., in different sugarcane producing states - Goiás, Mato Grosso, Mato Grosso do Sul, Paraná and São Paulo - causing annual losses exceeding 252 million dollars.
Due Despite the limited bioecological information about this pest, there is still no established the economic level of damage, nor efficient actions for its control. Losses caused by this insect can vary from 25 tons of sugarcane per hectare to 30 tons of sugarcane per hectare until the crop is completely destroyed, resulting in early retirement, even in first-cut sugarcane fields.
A great difficulty encountered in studying the biology of this insect, in natural conditions, is the fact that the larvae, when moving through the soil, can reach up to 3 meters deep to 4 meters deep, with cycle very long biological period, which can exceed more than 12 months in duration.
You Eggs are cylindrical in shape and milky white in color, measuring approximately 4,5 mm of lenght. They are deposited individually in the soil, at a depth which varies between 1,6m and 4,0m, probably between the months of October to March, occurrence dependent on its region of incidence.
To the larvae have a cerambiciform shape, milky white in color, with legs atrophied, with a larger anterior region of the body. In the segments abdominals, there are dorsal expansions in the form of lumps, more or less oblong, transverse and those in the ventro-lateral region facing the rear of the body, in an arch with the shape of a half moon. These projections of abdominal segments function as pseudopods to assist in displacement of the larvae inside the galleries, in the soil. In the final stage of development the larva can reach approximately 50mm in length.
A Metamorphosis takes place in the soil, where the larva builds a pupal chamber. The pupa It has a yellowish white color and lives in this stage for a short period of time. Newly formed adults remain inside pupal chambers, in dormancy for a period and, for unknown reasons, awaken collectively and comes to the surface for the flock.
You adults show marked sexual dimorphism. Males have antennae larger and black in color (most), and are more abundant. Females, for their part, less frequent, have smaller size, smaller antennae, color reddish-brown or dark brown, very rudimentary hindwings narrow, being unsuitable for flight. The male, after the start of flights, lives on average from 4 days to 7 days. Females can live from 7 days to 38 days and after oviposit copulation of 14 eggs to 45 eggs, which have an incubation period variable from 17 days to 23 days.
O reproductive behavior of M. fryanus It is complex and characteristic. Its complete development - egg to adult - is gives into the soil, rising to the surface, males and females, only for the mating, which is preceded by flocks, which occur on days with high temperature and humidity, usually after rainy periods. The adults in surface overcome the physical barrier of the soil through, in part, galleries opened and left by the larvae in their wanderings before the process of construction of the pupal chamber and subsequent metamorphosis for pupation. In the flight males come to the surface of the soil, while females try to expose themselves less. Sometimes they simply release the pheromone still inside the channel that the brought, without abandoning it completely or walking on the ground, as they are incapable of to take flight. Males emerge to the surface before females, and remain patiently on the ground or in parts of plants, until the appearance of females. They are attracted to the strong sex pheromone released by females, they fly at low altitude or walk quickly to the vicinity and from there they try to locate her. With the help of their jaws, they clamp the partner, and carry out copulation.
A Mating disputes usually involve several males and multiple copulations occur in a short space of time. After this ritual, the female returns to the ground, generally, through the same hole that brought it to the surface. The posture will occur at different depths.
Fundamental for mating, the flocks last for varying lengths, generally 07 days or more and always occur at the same time during the day. This one Hours vary depending on the region, generally starting around 7am with the appearance of the first males and ends around 15pm. The time of The peak, in which males and females are more active, occurs between 10 am and 11 am.
A population dynamics of M. fryanus It is complex, as the larvae show great vertical movement in the soil when throughout the year. The largest populations of larvae on the surface - up to 30cm - consequently attacking roots and the base of the clumps coincide with the months coldest and driest of the year, that is, between April and September. After this period, with the appearance of the first rains, there is a drastic decrease in the population in this depth. Flights take place between October and February. From March / April, there is again an increase in the larvae population, partly influenced by the posture of females after mating. This behavior varies depending with the region and annual climatic conditions. However, as there may be overlap of generations, many larvae are also found during flocking periods. Considering the annual occurrence of flocks in a given location, this event may be the indicative of the existence of different generations occurring simultaneously there, as the complete biological cycle of the pest is estimated to last approximately two or three years.
O Monitoring is carried out through systematic surveys of the population of the pest using pheromone traps. The commercial name of this pheromone is “Migdo”, distributed in the plantation along the carriers (01 trap per every 50 ha). The traps should be inspected weekly, and it is advisable to change the pellets or tablets every 30 days. Various types of containers have been adapted as traps, and the use of bottles is currently very common “Pet” type plastics, used in packaging soft drinks and mineral water, however, the traditional trap is known as “Pitfall”. A device concave (funnel type) is screwed into the mouth of the bottle containing the pellets or tablet, being buried close to or slightly below the surface of the soil. Weekly, During the flock period, captured insects must be removed.
Due the complex behavioral biology of M. fryanus, its population reduction must be planned in the long term, for generally involve overlapping generations. In this way, integrated management To “coexist” with this pest, a logical and rational sequence must be followed, taking into account the investments necessary for this.
That method involves the need to reform the sugarcane field and the great inconvenience of imply huge economic expenses to carry it out. Although, is undoubtedly what contributes most to significantly reducing the pest population. Its objective, in addition to the death of larvae through the action of implement, their exposure to predators. To do this, two considerations must be taken into account. important points: the time of execution of the work and the implement to be used.
Studies from the floating of larvae M. fryanus have shown that the time of year the largest number of larvae is found in the first 20 cm of the soil at 40 cm from the soil, coincides with the coldest and driest months of the year (March to September). With In relation to the implement to be used, the Soqueira Mechanical Destroyer can reduce the larvae population by more than 80% when compared to grids plows. Complementing this practice with crop rotation is essential after this process, with the aim of leaving the area for as long as possible without its main source of food, sugar cane. The big secret to success in controlling this pest is to maintain the soil, relatively frequently, being constantly manipulated in its layer closest to the surface (20cm to 40cm) in order to systematically eliminate the larvae that approach there to feeding or even depriving her of it. Hence, depending on the severity of the problem, the need to keep the place free from contamination for a longer period of time. long-cycle crops, such as sugar cane, returning after this period to planting the crop.
Chemical Barrier - operation that precedes the planting, the chemical barrier aims to completely distribute insecticide in sub-surface, the depth varies from 50cm to 60cm. It is recommended for this operation, subsoiler duly adapted for correct distribution of syrup (blade triangular subsoiler attached to the lower end of the shaft) or mouldboard plow. These Equipment must be equipped with an autonomous sprayer assembly. O set can optionally be driven by power take-off or engine hydraulic, spray tips with fan jet and air induction, installed behind each “shoe” of the subsoiler or mouldboard plow, to deposit the insecticide in a continuous, homogeneous layer across the entire width work, forming a chemical barrier. The volume of syrup, in addition to the choice correct use of insecticide for this modality, is essential for the success of operation, where 800 liters is recommended of syrup per hectare to 1000 liters of syrup per hectare. Its main disadvantages are the high cost of execution, soil contamination and destruction of other non-target organisms in the process.
Planting Furrow - With a flow rate of 250 liters of syrup per hectare, in the bottom and walls of the planting furrow, when covering the billets of sugarcane or simultaneously with the distribution or mechanical planting process.
Traditional ratoon cutter - In ratoon sugarcane areas (post-harvest), the chosen insecticide must be applied with an implement specific, which injects 100% of the syrup into the sugarcane line, at a depth varies from 15cm to 20cm. For this method it is recommended spraying with a variable water volume from 250 liters to 500 liters per hectare, depending on the season of the year and type of soil.
In reason of biology, not yet fully known, and the peculiar behavior M. fryanus constitutes a challenge to coexistence, implying the adoption of unusual methods for its control. These actions imply large expenses, burdening production in areas under attack of the plague. However, its low dispersion capacity is a factor favorable, restricting attacks to areas where they traditionally occur. Other positive aspect consists of its long life cycle, which limits the number of generations in time. In this way, mechanical control actions and/or through Mass collections of adults (males) tend to contribute significantly to reduce their populations and damage. Another measure, the fallowing of the affected area free of host plants for an extended period, from two to three years, helps in solving the problem. During this period the area can be explored with crops of short cycle, with the soil being frequently worked, through plowing and harrowing at times when there is an accumulation of larvae on the surface with the aim of eliminate them. Such a measure constitutes an alternative to, perhaps, resolve the problem definitively, due to the significant reduction in its population or eradicate it. To do so, the farmer has to give up, during this period, explore the area with sugar cane and later return to the activity.
Article published in issue 223 of Cultivar Grandes Culturas, December 2017/January 2018.
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Present in all Brazilian states, studies on biological aspects of the development of this insect in different crops, such as soybeans, cotton, corn and wheat, are of fundamental importance for successful management.
