In recent years terrestrial gastropods have increased considerably in economic importance in Egypt. Thereby field and laboratory experiments had been carried out to study the effect of certain chemical, biological and cultural control methods on land snails infesting major crops in Qalubia Governorate. The obtained results could be summarized as follows:
1. Laboratory experiments.
Certain trails were executed under laboratory conditions to study the effect of some chemical and biological compounds on different two species of land snails M. obstructa and E. vermiculata. As well as some tests were performed to explant the effect of unchemical control methods on above mentioned land snails.
1.1. Food attractant traps for land snails:-
This part of work was performed under laboratory conditions to show the succeptibility of land snails M. obstructa and E. vermiculata to unpoisonous baits. Two carrier materials were used (wheat bran and rice hulls), after mixing with molasses. Four different treatments were applied as Follows (baits without molasses, baits with 3.5 and 8% of molasses). Study was carried out also to exhibit, the effect of the stored baits on attraction of land snails. Each type of baits with each concentration of molasses was applaied at different four forms of period storage (baits after prepared directly and after 24, 48 and 72 hours of storage). Results cleared that the individuals of M. obstructa and E. vermiculata snails preferred the baits of wheat bran and rice hulls which were mixed with high concentration of molasses. Average rate of collected snails was 6.7 and 5.7 snails on wheat bran, and it was 7 and 6.1 snail on rice hulls baits respectively.
Also the issues offered that M. obstructa and E. vermiculata snails were preferred the baits of wheat bran or rice hulls which were stored for 72 hours with any concentration of molasses.
1.2. Biological control:
The bacteria of Sccharopolyspora spinosa was used against M. obstructa and E. vermiculata land snails under laboratory conditions to study the effect of this bacterium type on the moratality percentages of land snails . Four concentrations were used 0.5, 1.0, 2.0 and 3.0% to make bacterial baits. Four different formes of baits were executed under each concentration as follows (baits applied directly after preparing and baits after one, three and seven days of storage). Data displaied that the impression of poison baits was increased as the period of storage was increased to three days for two species of snails, LC50and LC90 were (0.546 and 1.79%) and (0.878 and 3.40%) for M. obstructa and E. vermiculata, respectively. Although when the store period was increased to seven days, the effect of baits was decreased on two species of snails. As well as results explained that M. obstructa was more affected with poisonous bacterial baits than E. vermiculats.
1.3. Chemical control methods:
This part of the present work was conducted to explant the effect of chemical compounds metaldehyde and methomyl (90%) on the two mentioned land snails under laboratory conditions.
1.3.1. Effect of metaldehyde on M. obstructa and E. vermiculata:-
1.3.1.a. Effect of metaldehyde on the weight reduction:
The using of molluscicide compound metaldehyde was very effective on reducing the weight of M. obstructa and E. vermiculata snails under laboratory conditions. Four ages of each snail were used in this trail. These ages were (3, 6 and 9 months and adult snails). Weight of different four stages was impressed with metaldehyde. Weight reduction was giving fluctuating results, the highest reduction of weight was recorded for adult stage (0.25±0.008 g) and the lowest reduction (0.07±0.08 g) was recorded by 3 months stage for M. obstructa snail. Also the reduce of weight of E. vermiculata snail was the least by 3 months stage (0.14± 0.04 g) and while the highest reduce of weight was registered by adult stage (2.18± 0.04)g. Weight reduction was significant with 3 months stage and the other stages of M. obstructa snail. As well as there was no significance between 3 and 6 months ages while the significance was high between adult and the other ages of E. vermiculata snail.
1.3.1.b. Effect of metaldehyde on the dealth period:
Metaldehyde compound was very effective on death period of M. obstructa and E. vermiculata snails under laboratory conditions, with different four ages (3.6 and 9 months and adult) ages. The lowest period of death was recorded with 3 months age of M. obstructa and E. vermiculata, it was (1.10±0.07)and (1.45±0.10) days, respectively. While this period was the longest for 9 months stage (1.85±0.07 day) of M. obstructa and for 9 months and adult stages of E. vermiculata it was (2.45±0.10) and (2.50±0.10) day respectively. Death period was significant with 3 months stage and the other stages of different Species of tested snails.
Generally M. obstructa snail was more susceptible to methatdehyde than E. vermiculata snail.
1.3.1.c. The lost amount of metaldehyde by M. obstructa and E. vermiculata:
Nine months age of M. obstructa snail was exhausted the highest amount of metaldehyde baits (0.064±0.02) and (0.053±0.2)g followed by adult and 6 months ages, while the least amount was spended by 3 months stage (0.45±0.008) and (0.38±0.009)g. On the other hand the consumed amount of metaldehyde by 3.6 and 9 months and adult stages was highly significant with the first day and remainder days. Moreover adult stage of E. vermiculata snail was spended the most amount of metaldehyde, it was (1.26±0.03) and (0.96±0.02)g. followed by 9 and 6 months stages, while the lowest amount was taken by 3 month stage it was (0.67± 0.02) and (0.63 ± 0.01)g and the most amount was wasted during the fird day of test by different four stages of snail.
1.3.2. Effect of methomyl compound on M. obstructa, and E. vermiculata.
This study was carried out in the laboratory to indicate the effect of the insecticide methomyl (90%) on M. obstructa and E. vermiculata land snails. The two species of Snails were exposed to baits of lannate with different four concentrations (0.5, 1.0, 2.0 and 3.0%), and under each concentration baits were applied at different four cases as following, baits applied directly after preparing and after one, three and seven days after storage. Results provide that the baits of lannate was deadly more and more on the two mentioned snails, where it had been stored for three days after prepared, LC50 and LC90 were (0.661 and 2.334%) and (0.859 and 5.734%) for M. obstructa and E. vermiculata respectively. While the least impression of lannate baits on the two species of snails was recorded when it had stored for a week. Generally M. obstructa was more affected than E. vermiculata by this compound.
2. Field control methods:
This part of study was executed under field conditions to expose the impression of some chemical, biologica and mechanical control methods on percent of reduction of land snails infested navel orange trees and swallow plant in Kalubia Governorate.
2.1. Cultural control methods:-
This methods were undertaken in the field conditions against the land snail species were infested neval orange orchard at Moshtohor locality, Toukh district, Kalubia Governorate, to explain the efficiency of it on reducing population density of land snails without poising hazard for man or the environment.
2.1.1. Effect of hand collection method
Hand collection method was carried out in four treatments (plots without collection and hand collection for once, twice and three times)to control Monacha spp., S. putris and E. vermiculata, during January, February and March months. Data cleared that the highest reduction of population density was recorded in the treatment of hand collection for three times during January, February and March compared with other treatments, and the highest reduction of population density was occurred with E. vermiculata followed by S. putris and Monacha spp. While the lowest rates of numbers during April month was recorded for plots which exposed to hand collection process for three times.
2.1.2. Effect of removing herbs process:
Number of land snail Monacha spp., S. putris and E. vermiculata were reduced by using the process of removing herbs under the trees. This process was used for once, twice and three times also and plots without treatment as control, the percentages of reduction of land snails were increased when this process was used for several times during January, February and March months successively, and the lowest rates of mentioned land snails were occurred during April month in the case of treatment for three times.
2.1.3. Effect of corrupting and ploughing soil method
Impression of corrupting and ploughing soil on reducing numbers of Monacha spp., S.putris and E. vermiculata, was more effective and more when it used three times during Junaury, February and March months, respectively, while the lowest effect of this process was by using it one time during January month only.
2.2. Biological control methods:
The bacteria of Saccharopolyspora spinosa was applaied as mortal baits under field conditions with four concentions (0.5, 1.0 , 2.0 and 3.0%) and four cases under each concentration (baits after preparing and baits after one, three and seven days of storage), to control the land snails Monacha spp., S. putris and E. vermiculata infesting neval orange and swallow plant. Data showed that the highest effect of this bacterial baits was recorded in the case of baits treated after three days of storage especially at the high concentration 3%. Percent of reduction were (87.7, 82 and 59.5) and (84.2, 70.9 and 53.4)% for all species of land snails in navel orange and swallow respectively. But the impression of this bacteria was very low while the storing of the baits continued for seven days. As well as Monacha spp. was more sensitive to this baits than the other species of land snails, and the effect was increased in the high concentrations.
2.3. Chemical control methods:-
2.3.1. Effect of metaldehyde on reduction percentages of land snails
Three rates of molluscicide metaldehyde were used (5, 10 and 15 kg/feddan) that is to say these rates were (30. 60 and 90 g/tree or plant). Resultes elucidated that reduction percentages of land snails Monacha spp., S. putris and E. vermiculata were increased as metaldehyde rate was increased under trees of navel orange or swallow plants, the highest percent of reduction was registered by using 90 g of test compound, it was (78.1 and 83.7), (74,1 and 71) and (61.5 and 59.5) for different species of land snails respectively. Data showed that also E.vermiculata snail was the most resistant to metaldehyde compound. On contrary Monacha spp. was the most sensitive to this compound.
2.3.2. Effect of methomyl on reduction percentages of land snails:
Methomyl compound was applied as virulent baits with different four concentrations (0.5, 1.0, 2.0 and 3.0%), and four treatments under each concentration were carried out as fellows (fresh baits and baits treat after one, three and seven days). Results illustrated that methomyl baits were effective on the percent of reduction of land snails Monacha spp., S. putris and E. vermiculata when it were used after preparing directly on neval orange tree and swallow plant. Howsoever this effect was increased when baits was stored for one day, but the high effect was recorded when baits stored for three days specially at high concentration3%, reduction percentages were (83,71.7 and 60) and (86.1, 73.5 and 54.3)% for three species of snails in neval orange and swallow respectively. Although the effect was decreased when baits had stored for a week under field conditions. As well as the impression of lannate was increased as the concentration was increased in all treatments. Also it is cleared from results that Monacha spp. was the most sensibility for this baits compound under field conditions.
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