Greenhouse and field assessment of different organic compounds against guava-parasitic Meloidogyne enterolobii

Abstract

Guava decline is a complex disease involving Meloidogyne enterolobii and Fusarium solani and it has caused major direct losses to Brazilian growers. Although several strategies have been sought to control the nematode, the use of organic soil amendments is currently the best approach to manage this disease. To assess the best amount of meat and bone meal (MBM) to be incorporated into the soil, guava seedlings inoculated with M. enterolobii were treated with 1-5% v/v of the MBM. Ninety days later variables related to nematode reproduction and plant development were evaluated, which indicated a potential nematicidal effect of the MBM at 3%. Another experiment assessed nematode-and plant-related variables 90 days after treatment of the seedlings with MBM, chitosan, shrimp shell or neem cake at 3%, 0.05%, 2% and 0.1% v/v, respectively. The MBM ranked first, reducing nematode reproduction. This MBM rate was converted to 25 kg/tree and assessed in three application regimes (monthly, bimonthly or trimonthly), for six months, in an orchard affected by guava decline. The variables assessed were soil density of colony forming units (CFU) of bacteria and fungus, and soil and/or root density of M. enterolobii, Helicotylenchus sp., and of different nematode trophic groups. In all three application regimes the MBM reduced all plantparasitic nematodes in the soil and the fungus CFUs. It also promoted an increase in bacterial CFU and bacterivorous nematodes.Key words: Psidium guajava, Fusarium solani, neem cake, chitosan, shrimp shell, cultural control, guava decline, meat and bone meal. Avaliação em casa de vegetação e em campo de diferentes compostos orgânicos contra Meloidogyne enterolobiiResumo O declínio da goiabeira, uma doença complexa envolvendo Meloidogyne enterolobii e Fusarium solani, tem causado grandes prejuízos diretos para os produtores brasileiros. Apesar de várias estratégias terem sido discutidas para o controle do nematoide, a utilização de matéria orgânica adicionada ao solo é atualmente a melhor abordagem para conviver com essa doença. Para avaliar a dose adequada de farinha de carne e ossos (FCO) a ser incorporada ao solo, mudas de goiabeira inoculadas com M. enterolobii foram tratadas com 1-5% v/v da FCO. Noventa dias após foram avaliadas variáveis relacionadas à reprodução do nematoide e ao desenvolvimento das plantas, indicando um possível efeito nematicida da FCO a 3%. Outro experimento avaliou variáveis relacionadas ao nematoide e à planta 90 dias após o tratamento das mudas com FCO, quitosana, casca de camarão e torta de nem a 3%, 0,05%, 2% e 0,1% v/v, respectivamente. A FCO reduziu a reprodução do nematoide, destacando-se em relação aos demais tratamentos. Esta dosagem de FCO foi convertida para 25 kg planta -1 e avaliada em três regimes de aplicação (mensal, bimestral ou trimestral), por seis meses, em pomar de goiaba acometido pelo declínio. As variáveis avaliadas foram densidade no solo de unidades formadoras de colônia (UFC) de bactérias e fungos, e a densidade no solo e/ou raiz de M. en...

Interaction between Meloidogyne enterolobii and Helicotylenchus dihysteroides in guava seedlings

“…The results obtained in the work presented here corroborate those of other researchers. Although other associations were not tested here, our findings reinforce reports that guava decline only occurs in orchards infested with M. enterolobii with the associated presence of F. solani [8,21] .…”

“…In São João da Barra County, Rio de Janeiro state, this nematode has limited production of the guava crop, leading to losses of up to 100% [13] . In work carried out by Almeida et al [8] , high population densities of H. dihysteroides Siddiqi and M. enterolobii were found concomitantly in areas with dwindling productivity.…”

“…The first report in Brazil was written by Moura & Moura [1] in the state of Pernambuco. Since then, various genera and species of phytonematodes have been identified in association with the guava crop [2,3,4,5,6,7,8] . However, there are few articles that report the comparative evaluation of pathogenic actions by species of nematodes when these occur in isolated or joint infestations.…”

Relationships between M. enterolobii and F. solani: spatial and temporal dynamics in the occurrence of guava decline

“…In studies by Gomes et al [14] and Almeida et al [15] , intense decomposition was noted in the root system of guavas parasitized by M. enterolobii in association with F. solani resident in the soil. The pathogenesis was apparently aggravated by stress factors such as excess or lack of water or drastic pruning, suggesting that there is a component of physiological imbalance involved in guava decline associated with M. enterolobii.…”