Authors:
L.V. Bustamante-Espinosa, A. Castaneda-Ovando, J. Hernandez-Avila, M. Reyes-Lopez, P. Montes-Garcia and V.G.Jimenez-Quero ,Mexico |
Abstract:
The encapsulation of Entomopathogenic Nematodes (EPNs) in pellets is a promising alternative to use as a biological control method. However, it is necessary that the nematodes survive as long as possible inside the pellet before its release in field. In this research were to evaluate (at two periods of time)the survival rates(SRs)of EPNs contained inside of pellets. The pellets were made with the combination of three materials powders: bentonite clay(B), diatomaceous earth (D) and sugarcane bagasse ash (SCBA). In order to adequately manufacture the pellets (quasi-spherical shaped) and avoid their early disintegration, the decision was made to combine 95%B+5%D and consider this combination as a control mixture (C). Three ternary mixtures were prepared, a mixture with 90%B+5%D+5%SCBA (T5), a mixture with 85%B+5%D+10%SCBA (T10) and a mixture with 90%B+5%D+5%SCBA (T15). Eight pellets of each mixture were made (not including nematodes in their interior) and its capillary absorption was evaluated at 21 and 30 days after its elaboration. Subsequently, ten pellets per mixture with nematodes inside were elaborated and stored at room temperature. The evaluation of the survival level of the nematodes was carried out after 21 and 30 days of storage, respectively. The results show that at 21 days the pellets made with the four mixtures followed the same trend in their absorption capacity. From 0 to 240 seconds was the period of time in which there was a higher percentage of absorption (about 70%of the total) and from 240 seconds, the percentage of absorption was lower. The pellets made with the T15 mixture had the longest time to saturate (2300 seconds). At 30 days the pellets made with mixture C had the highest absorption capacity and saturated in the minor time (1200 seconds). The pellets made with the T10 and T15 mixes had a similar absorption capacity, however, the pellets made with the T15 mix had the longest saturation time of 2400 seconds. With respect to survival rateat 21 days the following was obtained:the nematodes encapsulated inside the pellets manufactured with the T10 mixture had the highest survival rate (62%) and the nematodes encapsulated inside the pellets made with the control mix (C) had the lowest survival rate (11%). The SRs of the encapsulated nematodes in the pellets manufactured with the T5 and T15 mixtures was 33% and 35% respectively.At 30 days the SRs of the EPNs encapsulated in the pellets of all the mixtures were slightly lower than those obtained at 21 days.The addition of 10%SCBA to the mixture of powdered materials for the manufacture of pellets, improved the absorption and water retention capacity in them, which was beneficial in increasing the survival rate of EPNs.Using amounts of SCBA greater than 10% causes greater water absorption, expansion and disintegration of the pellets; therefore, the death of more nematodes. |
