Evaluation of a prototype of soil thermal solarizer for control of gall nematode in the production of coffee seedlings

Abstract

In coffee crops at Rondônia State of Brazil, there is an increase in phytonematode epidemics.Since most local coffe nurseries at Rondônia use soil as substrate for seedling production, this work aimed to test the minimum exposure time at 60 ºC to control of root-knot nematodes Meloidogyne incognita in soil by means of solar heating, using a solarizer, in an adapted version for better heating perfomance. The used solarizer prototype was built of a wooden box covered with metal sheets, thermal blankets, painted black, with aluminum pipes of 0.5 cm in diameter at the bottom of the box that circulates the water heated by the collector box. The soil was inoculated with a suspension of 1000 eggs + J2 of M. incognita per liter and placed in equipment with a capacity of 150 liters. Exposure times at a minimum temperature of 60 °C were evaluated, with 14 treatments: C1 (non-inoculated and not autoclaved), C2 (inoculated), C3 (non-inoculated and autoclaved) T0’, T15’, T30’, T45’, T60’, T180’, T360’, T720’, T1440’, T2880’ and T4320’ . The temperature was measured every 15 minutes using a skewer-type digital thermometer. The soil was removed according to the exposure time, and placed in 8-liter pots, in which clone 125 and BRS 2357 coffee seedlings, susceptible to M. incognita , were transplanted and growing in a greenhouse for 180 days. The experimental design used was DIC, with 6 replications, each seedling as na experimental unit. Reproduction factor (FR), number of eggs per plant (NOGR) and number of galls per gram of root (NGGR) were evaluated. The FR, NOGR and NGGR variables reduced with exposure time. All treatments showed an effect to control the population of M. incognita in infected soils, with 100% efficacy of pathogen eradication from the T45’ treatment, 60 minutes of exposure is recommended for the production of Coffea canephora seedlings. Taken together, thir work showed the high potential of thr solorizer to contribute in the root-knot nematode control to seedling production.