N.N. Karpun (Cand. Biol. Sci.), E.B. Yanushevskaya (Cand. Biol. Sci.)

The State Research Institution All–Russian Scientific and Research Institute of Floriculture and Subtropical Crops of the Russian Academy of Agricultural Sciences

Sochi, Russia, e-mail: nkolem@mail.ru

Monitoring modern pesticides implication

in peach agrocenosises on Russian Black Sea coast

Monitoring results of pyrethroids, strobilurins and triazoles application in peach agro censises showed no significant violations in soil sanitary condition. The content of their active substances in soil was within hygienic standards. Pyrethroids inhibited basal and substrate-induced respiration in soil microbe cenosis. Duration of the negative impact significantly depended on the functional state of soil biotic component. A single application of strobilurins did not have any adverse impacts on the indicators of general biological activity in soil microbial community. The second use of stroby and zato in peach security systems caused transient inhibition of substrate-induced respiration. Repeated use (3-4 times during the growing season) of fungicides of a triazole series shows no adverse effects.

Key words: pesticides, microbe cenosis, biological activity of soil, soil contamination.

In the last decade, a leading role in protection systems for fruit crops cultivated on the Black Sea coast, belongs to modern pesticides (pyrethroids, triazoles, strobilurins, etc.) characterized by a complex of positive properties: low toxicity, small consumption rate (less than 100 mg/ha of active substance), high biological efficacy due to the specific effect on harmful organisms [2]. Their use usually does not exceed hygienic standards of soil contamination [4]. However, the negative impact from these pesticides on soil biota is not excluded, in particular, on the metabolic activity and adaptive function of microbe cenosis, which are basic in stabilization of agro ecosystems homeostasis [1, 5].

The purpose of this research is to monitor the effects from the use of modern pesticides in peach agrocenosis.

Monitoring of negative effects from pyrethroids (karate, fastak, decis), strobilurins (stroby, zato), triazoles (scor, vectra, topaz) and dimilin and insegar were conducted from 2000 to 2013 in peach plantations (experimental plots of Russian Scientific Research Institute of Floriculture and Subtropical Crops). All experimental plots were in the same agro landscape in brown forest weakly unsaturated soils. The terms of pesticide treatments for peach are justified by the need to conduct protective measures against major pests of this crop. Sanitary conditions of the upper soil horizon (0-20 cm) were determined by the content of the residual quantities of the active ingredients of pyrethroids, triazoles and strobilurins, applying gas chromatography method [3]. In order to assess ecotoxicological impact from pesticides on soil microbe cenosis we developed and used a complex of diagnostic criteria, which are sensitive and adequately responding to pesticide load [6]. Basal respiratory activity of soil microbe cenosis was determined, which is an integral criterion, reflecting the intensity of soil metabolic processes. The level of substrate-induced respiration (substrate – 5 % glucose solution) was determined, allowing to evaluate the potential energy in intracellular processes in pesticide loads. Additional criterion for determining microbe cenosis resistance to the action of xenobiotics is the ratio of microbial respiration coefficient (MRC), calculated by the formula:

According to the long-term monitoring, it is revealed that soil contamination by residual pyrethroid active ingredients is within the sanitary standards. Their maximum content was fixed one day after the treatment and did not exceed the maximum allowable concentration (MAC of lambda-cyhalothrin – 0,05 mg/kg; MAC of alpha-cypermethrin – 0,02 mg/kg, MAC of deltamethrin – 0,01 mg/kg). The intensity of pyrethroids degradation was largely dependent on the biological activity of microbe cenosis. During the period of its highest activity (spring) full time for soil self-cleaning from this preparation’s action did not exceed 42 days. As it follows from Table 1, 28 days after peach treatment with karate, the content of lambda-cyhalothrin in soil was 25 times lower than MAC. When using this pesticide in June its main degradation occurs during the summer dry season, characterized by extremely low basal respiratory activity in microbe cenosis.

Table 1

Dynamics of lambda-cyhalothrin content in soil and basal respiratory activity in soil microbe cenosis after treatment of peach with karate

Indicators	Treatments dates	Time after treatment, 24 hours
		1	7	14	28	42	56
Content of lambda-cyhalothrin in soil (mg/kg)	22.04.2010	0,025	0,014	0,05	0,002	Not found
	15.06.2010	0,027	0,015	0,08	0,07	0,005	0,004
Basal respiratory activity, mgСО2/kg soil/24 hours	22.04.2010	105,2	115,3	119,8	125,6	132,5	124,5
	15.06.2010	121,3	105,6	98,3	71,2	68,4	65,3

The given soil conditions are, apparently, the main reason for the reduced intensity of lambda-cyhalothrin biotransformation in July-August and oppression of soil cleaning processes from its residuals. Only three months after karate application, full normalization in soil sanitary condition was fixed.

Negative consequence after contact with soil is reduction of the intensity of basal and substrate-induced respiration in microbe cenosis (Table 2).

Table 2

Impact of lambda-cyhalothrin on basal and substrate-induced soil respiration in microbe cenosis after processing peach with karate (% to the control)

Indicators	Treatments dates	Time after treatment, 24 hours
		1	7	14	21	28	42	56
Basal respiratory activity	first	78,2	81,3	86,7	95,4	102,5	104,8	98,2
	second	77,5	79,2	81,3	88,2	82,1	84,5	95,4
Substrate-induced respiration	first	75,4	79,3	87,3	101,2	105,4	99,4	102,5
	second	78,2	76,4	81,3	79,5	85,6	92,3	96,1

Thus, the MRC level, reflecting the stability of microbial community to negative influences, was within the control values. The intensity of the recovery processes was largely dependent on the biological activity of microbe cenosis. In the spring, characterized by high respiratory activity, normalization of the carried out violations lasted for insignificant periods (2-3 weeks). In the summer, as a result of deterioration of soil hydrothermal regime, the environmental sustainability of microbial communities to the action of lambda-cyhalothrin reduced, which led to an increase in the recovery period. Regularities revealed when alpha-cypermethrin and deltamethrin got into soil (active substances of fastak and decis) are similar.

According to the monitoring on application of stroby and zato in peach agro cenosis, it was determined that the the maximum level of soil contamination in a day after processing with kresoxim-methyl (active ingredient of stroby) is up to 0,3 MAC; for trifloxystrobin (active ingredient – zato) – up to 0,5 MAC. The duration of their preservation in soil is insignificant – no more than 15 days. Positive environmental factor of applying stroby and zato is in the fact that there is no negative impact from their active substances on the state of basal respiratory activity in soil microbe cenosis. Substrate-induced respiration is more sensitive to the action of strobilurin and was suppressed for a short time when stroby and zato were used for many times (2-3 times) (Table 3).

Table 3

Effect of active substances from stroby (kresoxim-methyl) and zato (trifloxystrobin) on substrate-induced respiration of soil microbe cenosis in peach plantations (% to the control)

Pesticides	Treatments dates	Time after treatment, weeks
		1	2	3	4	5	6	7
Stroby	1 — 27.04.2009	95,5	99,8	105,0	102,5	99,2	99,8	103,5
	2 — 19.05.2009	82,4	83,5	85,4	96,5	103,4	98,2	101,5
	3 — 16.06.2009	72,5	77,4	81,8	82,9	83,5	98	100,5
Zato	1 — 27.04.2009	95,5	94,2	98,4	105,2	99,7	99,4	102,8
	2 — 19.05.2009	79,5	78,5	80,4	81,2	95,8	101,4	103,8
	3 — 16.06.2009	68,2	68,5	77,1	82,4	81,5	84,6	97,8

With an increasing number of treatments, the risk of negative impact from kresoxim-methyl and trifloxystrobin which got into the soil increased, despite the same level of pollution by these substances. These changes were accompanied by a decrease in the values of MRC, however, soil recovery processes were not violated.

Similarly to fungicides of a strobilurin series, use of triazoles in peach protection systems does not lead to significant deterioration of soil sanitary conditions. One day after treatment, the amount of active ingredient scor (difenoconazole), topaz (penconazole) and vectra (bromuconazole) did not exceed 0,025 mg/kg of soil, which is four times lower than MAC. An intensive degradation of these preparations, their residual amounts in the soil were not found in 15 days after the treatments.

As a result of the research carried out for many years, there was found no negative effect from active ingredients of scor, topaz and vectra on the functional state in soil biotic component. The indicators of basal and substrate-induced respiration of soil microbe cenosis were within the control values even after repeated use of triazoles in the growing season (3-4 times). These preparations do not reduce soil environmental sustainability to ecotoxicants.

The monitoring results indicate that the use of pyrethroids, strobilurins and triazoles does not lead to a significant disruption of soil sanitary conditions in peach plantations. The residual amounts of active substances did not exceed hygienic standards.

From the standpoint of environmental safety it is appropriate to use pyrethroids in peach protection systems only single time. Single processing of peach with fungicides of stroby and zato is environmentally safe. Triazoles (scor, topaz, vectra) did not have a negative impact on the general biological activity in soil microbe cenosis even with repeated application (3-4 treatments during the growing season). Highly eficient protection systems of peach from diseases and pests is achieved by alternating these preparations during the season and in different years.

References:

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2. Karpun N.N. Methodical provisions on applying preparations of new generation in peach protection systems / N.N. Karpun, E.B. Yanushevskaya, Ye.A. Ignatova, N.N. Leonov. – Sochi: Russian Research Institute of Floriculture and Subtropical Crops, 2013. – 61 p.

3. Klisenko M.A. Methods for determination of pesticides trace amounts. – M.: Medicine, 1984. – 256 p.

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6. Yanushevskaya E.B. Methodological guidelines for determination of biological activity in soil pesticide loads. – Sochi: Russian Research Institute of Floriculture and Subtropical Crops, 2013. – 24 p.