Solarização de solo infestado com cistos do fitonematoide Cactodera cacti em sacos plásticos

Abstract

The culture of pitaya (Hylocereus costaricensis) is a culture affected by various pests and diseases caused by fungi, bacteria, nematodes, and viruses. Among the main phytonematodes that attack the crop is the cactus cyst nematode, Cactodera cacti, a heteroderid found for the first time in Brazil in the state of Ceará in 2016 and that can compromise the production of the fruit in the producing regions. As a result, an experiment was carried out with solarization of soil infested with C. cacti cysts in plastic bags to investigate the action of heat on the cysts of this nematode. The methodology used was to place 2 kg of soil infested with 50 C. cacti cysts in black plastic bags and in transparent plastic bags, which were closed with string and left for 5, 9, 13, and 17 days exposed to the sun in an experimental area of the Horticulture sector at CCA. The design used was a DIC and 04 treatments were performed in a factorial scheme (5, 9, 13, 17 days in the sun x two types of plastic bag, black and transparent) and 04 replications. Black and transparent bags containing soil and cysts were left in a shaded area of the greenhouse, as controls. Temperature measurement was performed 5 times a day, at 9 am, 11 am, 1 pm, 3 pm, and 5 pm, on alternate days, in a total of 45 readings with a digital geothermometer. At the end of each treatment, the solarized soil from 04 black bags and 04 transparent bags was poured into 2 kg pots, being used to transplant healthy rooted pitaya seedlings. The plants remained in greenhouse conditions for 40 days under irrigation. After this time, the plants were removed from the pots to evaluate the infestation in the roots, investigating the presence, number, and appearance of cysts, females, juveniles, and eggs of the phytonematode. The same procedure was performed with pitayas planted in the soil of the 04 black bags and the 04 transparent bags that remained in the shade. At the end of the evaluation of the 40 plants made in the laboratory with the examination of the roots and soil, it was found that, in comparison with the control, solarization in both types of bags was effective in reducing the population of the nematode. The harmful effect on the pathogen, however, was greater in the transparent bags, whose temperatures above 40oC occurred for a greater number of hours/day than in the black bags, resulting in a reduction of the nematode population by 87.70%, 90.98 %, 91.28% and 100% for times of 5, 9, 13 and 17 days, respectively, of exposure to the sun. In the same number of days studied, the reduction in the population of C. cacti in the black bags was 80.16%, 89.48%, 91.58%, and 97.60%, respectively.