Management of Euxesta Spp. in Sweet Corn with Mcphail Traps
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Neotrop Entomol (2020) 49:139–146 https://doi.org/10.1007/s13744-019-00733-1 PEST MANAGEMENT Management of Euxesta spp. in Sweet Corn with McPhail Traps SR LOPES,ICRUZ Embrapa Milho e Sorgo, Sete Lagoas, MG, Brasil Keywords Abstract Bio Anastrepha®, food attractant, maize ear Pests attacking the ear of sweet corn, such as Helicoverpa and Euxesta fly, natural control, traps species, cause economic losses for the producer and the processing indus- Correspondence try. Feeding on the style-stigmata preventing fertilization and on the de- ICruz,Embrapa Milho e Sorgo, Sete Lagoas, veloping grain and the association with pathogens are the main causes of 35701-970, MG, Brasil; ivan.cruz@embrapa. br product depreciation. The traditional control such as spraying with chem- icals is not effective, even with several applications directed to the corn Edited by Rafael M Pitta – Embrapa ear. Bacillus thuringiensis (Bt) corn also does not reach the fly. McPhail Received 5 June 2019 and accepted 22 traps that have been used to monitor the pest can be a control strategy. October 2019 This work evaluated the efficiency of food attractants placed inside Published online: 8December 2019 McPhail traps to remove adult insects, in order to reduce ear damage. Twelve McPhail-type traps were installed in a randomized complete block * Sociedade Entomológica do Brasil 2019 design containing Bio Anastrepha® alone or combined with different doses of insecticide. Every 10 days, all the captured insects were counted and separated by species and sex. Only Euxesta eluta and Euxesta mazorca were found. The occurrence of insects was greater in the period between silk emergence and grain filling. The number of females was higher, prob- ably due to the need to feed before oviposition. The number of E. mazorca females caught in the treatment containing only Bio Anastrepha® was higher compared with that of others. The mean ear damage was very low, and there was no interaction between the production parameters and the distance between the trap and the harvested plant. In short, the use of McPhail trap containing food attractants may be a viable alternative to control corn silk flies. Introduction directly to the grains. Injuries caused to the tip of the ear may not cause so much damage to the industry as they can Sweet corn is a “special crop” in Brazil, and all production is be mechanically eliminated in processing. However, when destined to canned food companies. This market has been damage occurs along the ear, caused by Lepidoptera and growing in recent years, especially when it comes to exports ear fly larvae, the loss in this case is total for the industry. (Figueiredo et al 2015). The same insect species that attack The sweet corn pests with the greatest potential to conventional grain corn can be found in sweet corn. cause injury and, consequently, to cause losses to both However, sweet corn is known to be more susceptible to the agricultural and industrial sectors are those that affect phytophagous insects. According to Cruz et al (1999), maize specifically the ear, such as the Lepidoptera larvae yield reductions due to Spodoptera frugiperda (J.E. Smith) S. frugiperda and Helicoverpa complex, which also cause leaf damage were 57.6, 28.9, and 21%, for insect feeding on leaf damage, and Euxesta spp. (Diptera) (Cruz et al 2016). a sweet maize BR 400, a white high-quality protein maize BR Insects feeding on corn ears are usually sheltered from con- 451, and a conventional yellow maize BR 201, respectively. ventional pest control technologies such as chemical appli- Reduction on the quality of the ear due to requirements cation. There is also the possibility of unacceptable residues of the processing industry may occur by insect damage in the harvest product. Even the use of transgenic maize 140 Lopes & Cruz (Bacillus thuringiensis [Bt] maize) has not been an alterna- by a wood pole 1.2 m above the ground and spaced 30 and tive, due to non-acceptance by consumers. Therefore, there 22 m apart (vertical and horizontal directions, respectively), is a need for new low-cost, efficient control technologies to covering an area of 666.7 m2 (Fig 1). The experiment was increase field and industrial yield. For Lepidoptera species, carried out in a randomized block design with four treat- biological control has been successfully performed by re- ments, each with three replicates. The treatments were as leasing egg parasitoids such as Trichogramma spp. follows: (I) food attractant Bio Anastrepha®; (II) Bio (Figueiredo et al 2015,Cruzet al 2016). Unfortunately, there Anastrepha® + 1.5 mL Karate 50 CS (lambda-cyhalothrin; is still no technology to control efficiently the corn silk fly Syngenta); (III) Bio Anastrepha® + 2.25 mL Karate 50 CS; while providing residue-free grain. (IV) Bio Anastrepha® + 3.0 mL Karate 50 CS. The commercial The damage caused by the fly is a consequence of the product is efficient, low cost and toxicological class III (mod- injury caused by the larvae initially feeding on the silk (thus erately toxic), and legally registered for use on maize spray- reducing pollination and consequently fertilization) and then ing especially for Lepidoptera control. According to Nuessly attacking the grains in the milk stage, reducing the quality and Hentz (2004), relatively low doses of pyrethroids, al- and yield of the crop (Frias 1981;Painter1985; Branco et al though causing a low initial mortality rate, had enough sub- 1994). The problem is exacerbated by the attempt to control lethal effect to almost completely immobilized adult insects with chemical insecticides, since the high number of applica- after just 1 h of exposure; however, causing 95% mortality tions leads to an increase in the concentration of chemical with 2 h of exposure. Subsequently, Owens et al (2016b) residues in the final product. Pesticide residues above the demonstrated that both Chaetopsis massyla Walker and maximum residue limits allowed by the law constitute a bar- Euxesta stigmatias recover soon after applying different py- rier to processed food exports (Figueiredo et al 2015). rethroid treatments. In one of the first Brazilian works in the field, Cruz et al All traps received the food attractant Bio Anastrepha®, (2011) demonstrated the efficiency of different food attrac- whose efficiency has already been verified (Cruz et al 2011). tants associated with McPhail traps to monitor Euxesta spp. The commercial product was first diluted in water to a final in maize areas, which would allow its use for pest manage- concentration of 5%; then, aliquots of 1.2 L were taken out. ment. In the same work, the authors reported for the first For treatments II, III, and IV, we added 1.5, 2.25, and 3.0 mL, time in the country the presence of Euxesta mazorca in ears respectively, of the commercial insecticide with lambda- of corn. cyhalothrin (50 g L−1). Afterwards, 400 mL of each aliquot Considering the lack of adequate control methods, the was transferred to three separate vials (plastic bottles), and main objective of this work was to evaluate the use of the liquid solution without the addition of any preservatives McPhail traps containing food attractants to remove corn silk was placed inside at the base of the McPhail trap and soon flies in sweet corn fields, in order to reduce kernel damage after covered by a clear plastic lid; this way, the air intake was and yield losses caused by the pest in field conditions; ensure only through the bottom of the traps. product quality, and therefore, increase processing yield; and Nine evaluations of the presence of captured insects oc- minimize the environmental impacts and residues in food curred, with a 10-day interval, starting 10 days after placing caused by chemical pesticides, making use of clean technol- the traps, that is, 45 days after plant emergence. Similar ogy and Good Agricultural Practices. ranges had already been used (Cruz et al 2011), and in this experiment, no significant physical loss of the flies was veri- fied either; therefore, no preservatives were used. After each Materials and Methods evaluation, the traps were washed and refilled with new 400 ml of the solution; although, in this period, there was The work was conducted at a sweet corn seed production area no drying of the diluted BioAnastrepha solution. In each eval- of the Brazilian National Maize and Sorghum Research Center, uation, the captured insects were placed in 500-mL bottles, located in the municipality of Sete Lagoas, Minas Gerais State, taken to the laboratory, and immediately counted after be- Brazil (coordinates 19°28′45″S and 44°10′08″W). The planting of ing separated by species and by sex. The task of insect count- sweet corn seeds took place in February 25, in an area of 0.8 ha ing and sex separation was relatively easy to perform since under the central pivot irrigation system. Pest control in the the insects remained well preserved within the McPhail trap area is carried out mainly for Lepidoptera species, notably as the solution drying was very low. Morphological character- Spodoptera frugiperda (Smith) and Helicoverpa zea (Boddie) istics, such as wing color and the presence of ovipositor in by releasing the egg parasitoid Trichogramma pretiosum Riley females (Steyskal 1968, 1974;Huepeet al 1986), were the (Figueiredo et al 2015). identification tool parameters to separate sex and species To capture Euxesta spp., we installed 12 McPhail traps in of Euxesta. At the end of the evaluation, the insects were April 7, when plants were in the vegetative stage 7 (V7) deposited at the Embrapa Entomology Museum in Sete according to Ciampitti et al (2011). The traps were hung Lagoas, Brazil. Management of Euxesta spp.