Management of the Quesada gigas cicada in coffee

An essential nutrient in plant development, sulfur can also help control pests such as cicada Quesada gigas in coffee trees, preferably in the form of continuous line application under the projection of the canopy and incorporated into the soil.

Cicadas are insects (Hemiptera; Auchenorryncha: Cicadidae) whose immature mobile nymph phase is lived in the soil, acting discreetly and imperceptibly on plant roots until, in the period generally between the end of August and October of each year, the presence of the adult form is noted in the aerial part.

The species of cicada Quesada gigas (Olivier, 1790) is the most commonly found on coffee trees (Coffea spp.) in Brazil. Its mobile nymphs measure 20mm to 30mm in length and attack the main root and the thickest roots of the rest of the coffee tree's root system. In the mobile nymph phase, the cicada acquires the state of pest, the adult is only for reproduction of the species.

Adult males are winged and produce a stridulatory noise (singing), through a pair of stridulatory organs, located on the ventral side of the first abdominal segment, to attract females for copulation. Each species emits characteristic, specific sounds.

Adult female cicadas, also winged, lay eggs, milky-white in color and elongated, grouped under the bark of coffee tree branches. In a few days, the mobile nymphs hatch, which, hanging by the filament they excrete, descend and penetrate the soil, locating themselves in the roots.

At the roots, the mobile nymphs, which have sucking mouthparts, begin to suck the sap, the excess of which is expelled and which also serves to soften the earth, thus making it easier for the insect to open with their front legs (fossorial or excavating legs). ), of a cavity (chamber, cell or gallery) where it remains.

A coffee plantation heavily infested by cicadas of this species Q. gigas it can present an average of 200 mobile nymphs per plant to 400 mobile nymphs per plant, an insect population that causes severe damage. The continuous sucking of sap causes depletion, which manifests itself in the aerial part of the plant through the withering, chlorosis and premature fall of the apical leaves of the branches. Symptoms are always more pronounced during times of water deficit. The final consequences of the attack result in a drop in production, and even total loss of the crop if the pest is not controlled in time.

The coffee tree can withstand, without suffering damage, an infestation of approximately 35 mobile nymphs of Q. gigas per plant, and this level must be considered when making decisions about starting control.

The use of soil-applied insecticides was the only efficient control modality to reduce the cicada population. Control must be carried out to reduce mobile nymphs in the soil, and although it does not cause the death of all of them, the population is reduced to levels that can be supported by the plants, without causing economic damage. Controlling cicada adults is unfeasible.

The most efficient insecticides have been systemic granules (GR), e.g. aldicarb, carbofuran, disulfoton, phorate, terbufos, imidacloprid, thiamethoxam, etc., which for greater efficiency must be applied to the soil during the rainy period of the year, generally November-December in most coffee growing regions of Brazil, or those in water-dispersible granule (WG) formulation, e.g. imidacloprid, thiamethoxam etc., recommended for spray application (drain) in the neck of the plant, also during the rainy period of the year. Comparatively, neonicotinoid insecticides, e.g. imidacloprid, thiamethoxam, etc., in the WG formulation have been shown to be more efficient than the same products in the GR formulation, in addition to presenting lower toxicity.

Sulfur as a nutrient is essential for plant development and fundamental in the formation of chlorophyll, as it participates in carbohydrate metabolism. Sulfur-deficient plants show decreased photosynthesis. Sulfur deficiency may not present visible symptoms in plants, and generally the deficiency that occurs in coffee plantations is only visible when it is already severe.

Elemental sulfur (S) is not directly assimilated by the plant. Microorganisms existing in the soil, bacteria of the genus Thiobacillus, oxidize sulfur transforming it into soluble sulfate (SO₄^2-) in the soil, a process that occurs throughout the plant's growth phase.

The action of the fertilizer, in contact with soil moisture, is prolonged, where the sulfur is gradually oxidized following the rate of absorption throughout the crop cycle, culminating in flowering, the stage of greatest demand.

Low levels of sulfur in Brazilian soils are almost as common as low levels of phosphorus. Deficiency symptoms and responses to S addition are known in both temporary and perennial crops. For this reason, it is common to introduce a source of S in the NPK or PK formulation.

No studies were found in the scientific literature that recommend the control of underground pests with elemental sulfur. Those found only refer to foliar use to control some pest mites and fungal diseases, as a component of mixtures in biofertilizers and phytoprotective mixtures. 

Research

An experiment to find out the effect of a 90% sulfur-based product on the control of mobile cicada nymphs Q. gigas (when applied to the soil under the canopy of coffee plants, in a continuous line without and with incorporation, at dosages of 30 kg per hectare, 60 kg per hectare and 90 kg per hectare) was installed in the municipality of Lavras, south of Minas Gerais , in a 19-year-old 'Catuaí' coffee plantation. The initial survey of the number of cicada nymphs, carried out in November, found an average of 22 mobile nymphs per plant.

Treatments with 90% sulfur (commercial product in the form of tablets) were applied to the soil in a continuous stream in the projection of the plant canopy, without and with incorporation into the soil. The doses, in kg of commercial product/ha, were 30 kg per hectare, 60 kg per hectare, 90 kg per hectare with and without incorporation into the soil.

The treatment considered standard control in the experiment was the insecticide-fungicide thiamethoxam at 300 g a.i. + cyproconazole at 300 g a.i./kg of commercial product applied via drain on the neck of the plants, in a total of 50 mL of syrup per plant and on one side, with a manual knapsack sprayer equipped with a long lance and doser. The product was chosen for use taking into account the insecticidal component of the mixture, the neonicotinoid thiamethoxam, being efficient and recommended for cicada control in coffee trees.

The product applications were carried out in November, the rainy season in the region, and the efficiency assessment was carried out in May, after 150 days of product application, through the opening of trenches in the soil, covering the entire root region, and with the count of mobile nymphs found alive in the root system of two plants from the useful part of each plot.

RESULTS

Although numerical differences were observed when comparing the highest and lowest doses of 90% sulfur in tablet form, there was no statistically significant difference between the doses evaluated, showing that even at the lowest dose the product significantly reduced the number of cicadas in the roots. . Treatment with the commercial product, at a dose of 90 kg/ha and in a continuous line format under the projection of the canopy and incorporated into the soil, showed the highest efficiency in controlling cicadas in the experiment, approximately 95%, in the month of May ( Table 1).

A negative and highly significant correlation was found between increasing the dose of the commercial product 90% sulfur in tablets, with and without incorporation into the soil, and the reduction in mobile cicada nymphs. 

FINAL CONSIDERATIONS

The commercial product 90% sulfur in tablet formulation, in doses between 30 kg/ha and 90 kg/ha (preferably in the form of continuous line application under the projection of the canopy and incorporated into the soil) is a viable option for controlling the coffee cicada Quesada gigas. Although more efficiently incorporated into the soil, tableted sulfur also presents good results when it is only applied to the soil surface and without incorporation. It is also an option for cicada control for crops that cannot receive plant protection chemicals, such as organic farming, among others. In addition to controlling the pest, it meets sulfur needs, an essential element for plant development and fundamental in the formation of chlorophyll, as it participates in carbohydrate metabolism.

Paulo Rebelles Reis EPAMIG Sul de Minas/EcoCentro

Article published in issue 210 of Cultivar Grandes Culturas.