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APHID INTERACTIONS ON ORGANIC CULTIVATED AND CHEMICAL TREATED APPLE TREES
N.P. Deligeorgidis1, P.N. Deligeorgidis1*, C.G. Ipsilandis2, D. Stavridis3 and
M. Vaiopoulou1
1: Technological Education Institute of Western Macedonia/Branch of Florina, Dpt of Crop Production. TermaKontopoulou, 53100 Florina, Greece.
(*) corresponding author.
2: Regional Administration of Central Macedonia, Dpt. of Rural Economy and Veterinary of Regional Unity of Thessaloniki, Al. Papanastasiou 61, 54453 Thessaloniki, Greece.
3: Region of Central Greece, Dpt. of Rural Economy and Veterinary of Larissa, 41222 Larissa, Greece.
ABSTRACT
The purpose of this study was to estimate insect (aphid) response to chemicals in apple tree orchards in comparison to organic cultivated orchards and additionally, to estimate possible yield losses in the two kind of orchards. Two apple-tree orchards were used for the estimation of aphids’ response during the years 2010 and 2011. At the first orchard several agrochemicals were applied to control apple tree enemies. The second one was used as a check, and no pesticides were used as it was cultivated under the organic farming specifications. Two main aphid species were recognized: Dysaphisplantaginea and Aphis pomi. 14 sampling periods followed, every 15 days, to record number of insects during biological cycle.
There were statistically significant differences between aphid species both in mean and maximum values (35.03 and 400 mean and maximum for D. plantaginea and 26.11 and 222 respectively for A. pomi). Between the two orchards differences were even greater (7.4 and 33 mean and maximum for index orchard treated with pesticides and 237.15 and 400 for check orchard respectively). Means for the two years of monitoring showed also differences (52.99 for 2010 and 69.29 for 2011). Grand mean 30.57 was depended on strong interactions including all factors. Interactions between all factors were very significant revealing that number of insects is depended on year environmental conditions, biological cycle, insect species and treatments with pesticides. Also, population fluctuations is a phenomenon recorded many times showing that biological data retrieved from pest monitoring are depended on biological cycles of different insect species and also environmental differences between years. Check orchard showed lower yields in both years. Qualitative loss reached 963 Kg in year 2011 and total loss was 4091 Kg in the same year. As a general conclusion, 28-34% loss in organic orchards must be balanced by other benefits such as greater prices or/and State support.
Key words: aphid response, population fluctuation, organic cultivation
Introduction
Apple tree arboriculture is of great importance in the prefecture of Kastoria, Western Macedonia and thus pest-host relations are now being studied for better estimations of yields under various conditions. A large number of Hemiptera species, especially aphids and bugs, may harm apple tree orchards causing significant losses in yield (Tzanakakis and Katsoyannos, 2003).
The apterous adult of the rosy apple aphid Dysaphisplantaginea (Passerini) (Hemiptera: Aphididae) is about 2.5 mm long, globe-shaped and purplish to mauve covered with a whitish pubescence. The winged adult is dark green to brown. This species is harmful only to apple tree (Malus spp.) cultivationsand is also found on plantain plants (Plantago spp.). Spreading of apterous forms on other trees is ensured by the wind. The aphid has 6-9 generations per year (4 on apple trees). On apple trees, colonies develop usually in April migrating up to late July. Winged adults return to apple trees in September. It causes curling of leaves and dropping when severe damages occur, resulting even in dropping of fruits. Migration of aphids may result in wide virus spreading.
The green apple aphid Aphis pomiDeGeer (Hemiptera: Aphididae) is a smaller species 1.5 to 2 mm long, green in colour for apterous adults and green to black for winged adults. This aphid is found in Europe, Middle East and in North America. Main host plant is apple trees, but it is found also in pears (Pyrus spp.) and other trees. It has 10-15 generations per year. A. pomi prefers the undersides of young leaves as feeding sites. The most apparent damages occur on leaves carrying colonies that may roll and curl, but will not discolour. This species occasionally feeds on immature apples, which then become malformed. Damage is more severe on nursery stock and seedlings.
Organic farming is based on absence of chemical inputs and that results in great difficulties for applied plant protection(Prophetou-Athnassiadou, 2003). Little data are available on organic apple-tree production in Greece, because those cultures are not widespread due to plant protection difficulties (ANKO, 2004; Agroepiloges, 2007). Main characteristics of such cultivations are reported to be: high initial capital, higher expenses (about 50%) at least when full production starts, lower production (about 30%) in comparison to conventional apple-tree cultivations, but finally better prices (about 30%) and lower inputs (Agroepiloges, 2007).Various techniques are practiced to support fruit production of organic tree orchards (Edwards, 1998). Especially for aphid management, predaceous species have been imported during the last two decades in combination to cultivation techniques (Staryet al., 1988; Miñarro and Dapena, 2001; Brown and Mathews, 2007). In Greece, total management or complete absence of treatments in organic orchards are the main forms of apple cultivations (ANKO, 2004).
The purpose of this study was to estimate insect (aphid) response to chemicals in apple tree orchards in comparison to organic cultivated orchards and additionally, to estimate possible yield losses in the two kind of orchards, because of severe pest infestations.
Materials and methods
In the prefecture of Kastoria, Western Macedonia (Greece), two apple-tree orchards were used for the estimation of aphids’ response during the years 2010 and 2011. The distance between the 2 orchards was about 500m and they were both about 0.4 Ha. At the first orchard (index orchard) in the place called “Karmelitsa”, several agrochemicals were applied to control apple tree enemies. The second one in the place called “Tsismulka” was used as a check, and no pesticides were used for four years as it was cultivated under the organic farming specifications. Apple trees of the variety “Red Chief” aged between 10 and 11 years old and were arranged under linear (palmeta) scheme with 4m distance between lines and 2.5 m on the line (total number of trees was 275 for each orchard). 20 sticky traps arranged in rhombus system were also applied in each orchard and renewed every 15 days. Proper pruning was practiced at the end of February and weed control was also practiced mainly by hand. Fertilizers of the type 21-7-14 (S,B) were also applied in both orchards to ensure the same level of nutrients. 14 sampling (recording) periods followed, every 15 days. Sampling (recording) started at 20 of March for year 2010 and at 18 of March for year 2011. Eight samples (replications) were formed at each orchard for every sampling period. Each sample was formed by 10 tree leaves collected in random (3 upper leaves, 3 bottom leaves, 2 on the left and 2 on the right of the apple tree). These samples were packed in a plastic bag with all the proper notes (records). Samples have been taken every 35 apple trees. In the same day samples were transferred in the lab for aphid recognition and insect number recording. Two main aphid species were recognized: Dysaphisplantaginea (Passerini) and Aphis pomiDeGeer (Hemiptera: Aphididae). In the index (application) orchard 3 pesticide applications have been made: the first at 24 of April with Calypso 480 SC (thiacloprid 48%), the second at the 4 of July with Mospilan 20 SP (acetamiprid 20%) and the last at 10 of August with Decis 2,5 EC (deltametrine 2,5%). Monthly meteorological data for temperature and rainfall were recorded for both years (Tables 1 and 2). Apple tree yields (in Kg) from the experimental orchards for both years were also measured: in Index orchard (1), in Check (2), and also apples in proper condition for the market in Check orchard (3), Qualitative loss as difference between 2 and 3 was calculated,and finally, Total loss as difference between 1 and 3.
A factorial model was used for ANOVA based on Snedecor and Cochran (1980) statistical procedures. SPSS 17.0 was used for data analysis of the factors: orchard, aphids, sampling (recording) period, for 8 replications for the 2 years. Data transformation was also used. ANOVA was based on original data, transformed data as √(X+1) and additionally as logX. Only original data are presented in tables.
Results
Figure 1 presents temperature fluctuations in both years of experimentation. Year 2011 showed lower temperatures for maximum and minimum values, especially in sampling period.
Table 3 presents factor analysis and reveals statistically significant differences for all factors (Sampling period, Aphid species, Orchard and Year). In parallel significant interactions between factors were found, for all factors used. Total interaction includes all factors and is statistically significant at p < 0.001.
Table 4 presents mean and maximum number of insects of the two aphid species (D. plantaginea and A. pomi), the two orchards (Index and Check) and the two years 2010 and 2011 of measurements. There were statistically significant differences for aphid species both in mean and maximum values (35.03 and 400 mean and maximum for D. plantaginea and 26.11 and 222 respectively for A. pomi). Data from the two orchards revealed even greater differences (7.4 and 33 mean and maximum for index orchard treated with pesticides and 237.15 and 400 for check orchard respectively). Means for the two years of monitoring showed also differences (52.99 for 2010 and 69.29 for 2011). Grand mean 30.57 was depended on strong factor interactions. Generally, data comparisons revealed statistically significant differences.
Table 5 presents yields from the two orchards in both years of monitoring. It is obvious that check orchard showed lower yields in both years. Qualitative loss reached 963 Kg in year 2011 and total loss was 4091 Kg (34%) in the same year (28% loss for 2010).
Discussion
Differences between aphid species were statistically significant and D. plantaginea showed a more dense population. It seems that, based on our data, colder year 2011 affected significantly aphid populations, indicating that higher temperatures during sampling period in 2010 (in accordance to biological cycles) may result in lower population densities. Interactions between all factors were very significant showing that number of insects is depended on year environmental conditions, biological cycle, insect species and treatments with pesticides (Deligeorgidiset al., 2007). Great interactions between factors especially between years and pest populations are often reported. Population fluctuations under various monitoring techniques is a phenomenon recorded many times revealing that biological data from monitoring are depended both on biological cycles of different insect species and environmental differences between years, (Deligeorgidiset al., 2007, 2012a, 2012b; Khadijeh and Sahragard, 2012). Especially for various Hemiptera species, this phenomenon was observed also in the neighboring prefecture of Florina, Western Macedonia, Greece (Deligeorgidiset al., 2012b). These population fluctuations may lead to uncertain productions and farmers may become unwilling to continue running organic cultivations because of the negative economic results and the manpower required (ANKO, 2004).
For the two orchards differences were even greater. Check orchard showed lower yields in both years. Qualitative loss reached 963 Kg in year 2011 and total loss was 4091 Kg in the same year. MekdaschiStuder (1994) reported strong interactions between pest (Aphis pomi De Geer) and host apple plants, where damages were severe under water stress. Environmental conditions may induce damages resulting in significant yield loss. Under these circumstances, in organic orchards, introduction of predators may be useful for the protection of fruit production (Miñarro and Dapena, 2001). As a general conclusion from our findings, 28-34% loss in organic orchards must be balanced by other benefits such as greater prices or/and State support through subsidies (ANKO, 2004). Alternatively, if in some cases apple production is no longer viable under organic cultivation, sustainability may require the introduction of a total management system in those specific apple orchards, abandoning organic farming (Reganoldet al., 2001).
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