Insetos fitófagos associados à soqueira de algodoeiro durante o período de vazio sanitário

Abstract

The cotton plant (Gossypium hirsutum L.) is one of the Brazilian main cultures, however it has faced phytosanitary barriers lately, as the attack of a great diversity of pests. The need of chemical interventions increasingly constant and the maintenance of the level of insects infestation under control show us a great challenge for the production increase and productivity. For this reason, it is not necessary to elaborate a control plan, based on a single method, but it is necessary to consider the need of measures that, harmoniously combined, result in the effective control of these organisms. The cotton stalk destruction is one of the methods of Integrated Pest Management that has to be adopted as a prophylactic measure aiming the pest control. This is a very important sanitary measure, required by Federal Law (Ordinances of the Ministry of Agriculture, n° 75 of June 16th 1993, n° 77 of June 23rd, 1993 and n° 116 of June 16th from 1994) and regulated at Mato Grosso do Sul state by the Resolution SEPRODES/MS n° 355 (Mato Grosso do Sul, 1999) which refers to the measures of control of A. grandis pest and takes providences. This study aimed to analyze the composition of insects-pests that occur during the period of fallowing in cultural remains of cotton plantation in the state of Mato Grosso do Sul - MS. It was divided into two regions (North and South of the state), according to the proposed division for the fallowing calendars in MS. The North cities studied were Alcinópolis, Chapadão do Sul and Costa Rica, and South ones were Dourados and Sidrolândia. A standard sampling design was determined for the municipalities of Alcinópolis, Chapadão do Sul, Costa Rica and Sidrolândia, being two sample units per municipality. Each sampling unit was composed of a hundred random points, and we chose the same region for the evaluation period. At each random point the insects-pests that occurred in the cotton plants were inspected and counted. The evaluations were carried out in areas that had stalks, re-regrouth and post-harvest plant of cotton, and each evaluation was performed every 13 days. In the South region, the evaluation period was between June 1st 2015 to September 31st 2015. In the North region, the period was from September 15th 2015 to November 30th 2015, these dates are regulated by law respectively as the beginning and end of the cotton fallowing period in the state of Mato Grosso do Sul. The analysis of the rarefaction number was carried out aiming to detect if the sampling effort was sufficient, and demonstrated a satisfactory number of samples to detect possible new species. During the period of fallowing were sampled 23 species of insectpests distributed into five orders and fifteen families. When we analyzed the composition of species, we observed an interspecific competition between species Bemisia tabaci biotype B (Hemiptera: Aleyrodidae), Aphis gossypii (Hemiptera: Aphididae) and Frankliniella schultzei (Thysanoptera: Thripidae). The regions of the state also differed, and the insect predominant in the North region were B. tabaci, F. schultzei, Anthonomus grandis (Coleoptera: Curculionidae), Dysdercus spp (Hemiptera: Pyrrhocoridae), Agallia sp. (Hemiptera: Cicadellida) and Lagria villosa (Coleoptera: Tenebrionidae), Euchistus heros (Hemiptera: Pentatomidae), Planococcus minor (Hemiptera: Pseudococcidae), Edessa metidabunda (Hemiptera: Pentatomidae), Liriomyza sp. (Diptera: Agromyzidae), Dichelops melacanthus (Hemiptera: Pentatomidae), Horciasoides nobilellus (Hemiptera: Miridae) ,Chinavia sp. (Hemiptera: Pentatomidae), Helicoverpa spp. (Lepidoptera: Noctuidae), Alabama argillacea (Lepidoptera: Noctuidae), Pectinophora gossypiella (Lepidoptera: Gelechiidae) and Spodoptera frugiperda (Lepidoptera: Noctuidae), while in the South region, the predominant species were: Aphis gossypii (Hemiptera: Aphididae), Diabrotica speciosa (Coleoptera: Chrysomelidae), Astylus variegatus (Coleoptera: Dasytidae), Conotrachelus denieri (Coleoptera: Curculionidae), Chrysodeixis includens (Lepidoptera: Noctuidae) and Cerotoma arcuatus (Coleoptera: Chrysomelidae). With respect to the pest occurrence and the evaluation periods, we had the most cases of B. tabaci, Dysdercus spp., A. gossypii and F. schultzei at the beginning of the fallowing until the 29° Day After the Beginning of Fallowing (DABF); the A. gossypii didn’t show a significant population during the beginning of the fallowing whereas this population was verified during all the evaluation time until the end of the fallowing in every city; A. grandis didn’t show difference in relation to the period of evaluation, being found from the beginning of evaluation to the end of the fallowing in each city studied. The bug complex (E. heros, E. metidabunda and D. melacanthus) and the caterpillars (C. includens, S. frugiperda, Helicoverpa spp.) that appeared in cotton plant and also appeared in soybean culture, were predominant from 43rd (DABF), also present in cotton cultural remains, in the middle of soybean culture. The other phytophagous species related in this paper (Agallia sp., D, speciosa, L. villosa, Liriomyza sp., H. nobilellus, Chinavia sp., A. variegatus, C. denieri, A. argillacea, P. gossypiella and C. arcuatus) didn’t show a pattern behavior during the research, which means that more researches related to theirs occurrence period during the cotton fallowing are needed. We concluded that there is a need of a fast and right stalk destruction, aiming the death of pests in cotton culture remains in order to minimize the infestation of the next crops.