**4. Fate of spirotetramat in the plant and environment**

It is important to note that after applying insecticides on crops or on the soil, it is possi‐ ble that the active ingredient is not absorbed permanently by the soil or that it can mobilize to bodies of water. There exist a lot of physical and chemical and microbiological factors that can determine the fate of the products used in plant protection, some are: hydrolytic degradation and photochemical, biological transformation and mineralization, absorption and movement of the active ingredient, as well as the degraded products in the soil. It is important to note that the above mentioned processes depend on the chemical structure and the physical properties of the compound used, as well as the soil, the vegetation, and the climatic conditions [22].

#### **4.1. Factors affecting the fate of spirotetramat**

are non-fertile, thus reducing the procreation and fertility of the future generations [7]. Spirotetramat has demonstrated excellent efficacy on peach, cotton, and plum aphids that are 3-4 days old. It has also been observed that on female adult whiteflies (*B tabacco*) treated with spirotetramat (40 and 200 ppm), the number of eggs produced is a function of the applied doses (major reduction 90% and 60%), including a concentration of 8 ppm, 80% of the eggs do not hatch. It was also observed that the way of contact of the insecticide influences its effectiveness on the control of the insects; it has a major effect if spirotetramat is ingested orally than if it is

Another laboratory study suggested that spirotetramat can be utilized in a safe integrated pest management program for the control of the cabbage aphid, as there is less mortality in comparison of other insecticides of the marmalade hoverfly *Episyrphus balteatus*, which is a natural aphid predator; furthermore, the fertility of the treated adult syrphids is not affected [9]. In another study to determine the collateral damage of spirotetramat on the wasp *Anagyrus*, a grapevine mealybug parasite, it was found that there was no detectable mortality on the parasite after 24 hours of application; there were no adverse effects on the development of the parasite in the pupa stage inside the mummified mealybug, nor were there any effects on the emergence of the new *Anagyrus* [10]. It must be pointed out that in an integrated pest management program where the arthropod *Galendromus occidentalis* is used for biological control*,* the use of spirotetramat is not recommended given that at concentrations of 0.228 g a.i.L-1, there was a mortality rate of 90% for the eggs, and 100% for the larvae [11]. This was also similar for the toxicity results for *Tamarixia radiata*, a parasitoid of citrus Asian psyllid (*Diaphorina citri Kuwayama*), that with an application dose of 0.8 mL L-1 with water did not

present favorable conditions for its development and it was highly toxic [12].

**Reference Dose applied Organism controlled Pest location** Moens et al., 2011 [9] 75 g a.i.ha−1 *Brevicoryne brassicae L.* Cabbage Jamieson et al., 2010 [13] 3.36 g a.i.100 L-1 *Orchamoplatus citri*). L. C. Mansour et al., 2011 [10] 120 mL h L-1 *Planococcus ficus* L. C.

Page-Weir et al., 2011 [14] 40 mL a.i.100 L-1 *Bactericera cockerelli* Tomato & potato Smiley et al., 2011 [15] 88-110 g a.i.ha-1 *Heterodera avenae* Wheat roots Duvaresch et al., 2008 [16] 120 g a.i.ha-1 *Aphis gossypii* Cotton Kay & Herron, 2010 [17] 144 g a.i.ha-1 *Frankliniella occidentalis* Peppers Fu & Del Real, 2009 [18] 60-120 g a.i.ha-1 *Planococcus ficus* Vine Marcic et al., 2012 [19] 200, 60, 18 mg a.i.L-1 *Tetranychus urticae* L. C. Frank & Lebude, 2011 [20] 1.7 oz 100 gal-1 *Adelges tsugae* Fir

*Myzus persicae Sulzer, Bemisia*

Potato (*Solanum tuberosum L)*

*tabaci Gennadius, Thrips palmi Karny*

by direct contact with the insect [1, 8].

44 Insecticides Resistance

Elizondo & Murguido, 2010 [21] 0.5 and 0.6 L ha-1

**Table 1.** Organisms controlled with spirotetramat under different conditions.

\*a.i. Active ingredient

\*L. C. Laboratory conditions

Considering that spirotetramat has no acidic properties or alkaline in aqueous solutions, it also stands out that soil pH and that of the aqueous systems have no influence on the physico‐ chemical properties of the spirotetramat. The solubility and lipophilicity of water are important because they provide us with information on the mobility and solubility of spirotetramat in water; if they are low (0.0299 g L-1), this indicates good soil absorption, resulting to very low risk of infiltrating into aquifers. With a base vapor pressure of 5.6 x 10-9 Pa and Henry's constant 6.99 x 10-8 Pa, it can be concluded that there is no possibility of spirotetramat volatizing in any significant form [22, 23]. It is important to consider the properties of the metabolite BYI08330 enol (referred as "enol" from now on); the enol form possesses properties slightly acidic (pKa=5.2). Furthermore, due to its high solubility in water (2.7 g L-1 at pH 7), it presents a risk of possible leaching into subterranean waters; same as with spirotetramat, the volatility of the enol form possesses no significant role [22].

#### **4.2. Plant metabolism of spirotetramat**

Before the creation of spirotetramat, there were only systemic insecticides that were only capable of moving in one way, those that enter the plant then move to different locations within the plant; however, this travel was only one way going up the xylem. The advantage of spirotetramat is that once it penetrates under the leaf of a plant, it is transformed by a hydrolytic split to spirotetramat-enol that due to its physiochemical properties is capable of moving up and down through the phloem, which allows it to reach and access pests that are difficult to reach, such as the grape mealy bug (*Planococcus ficus*) [18]. In contrast with systemic insecticides that travel only one way, such as the case with imidacoprid, spirotetramat-enol being a systemic metabolite with double lanes can protect new leaves generated after the application and it can even protects the roots [1, 18].

Reference [24] determined the metabolism of spirotetramat in apple, cotton, lettuce, and potato (Table 2). In the cultivars analyzed, the main residues found were the father (BYI08330) and three dominant metabolites, BYI08330 enol, BYI08330 enol-glucoside, and BYI08330 cetohy‐ droxy, which is in accordance with those reported by [25] (Figure 3). However, in apples, they detected a fourth metabolite, BYI08330 monohydroxy, with a considerable percentage (around 15.6%); meanwhile in the potato tuber, the main metabolite was BYI08330-enol, along with the absence of the father compound. To conduct those studies, a foliar application of spirotetramat OD-100 was applied, where the dose administered was 167 g a.i.ha-1 for lettuce, which was equivalent to the maximum recommended by the manufacturer; the same was administered for apple, potato, and cotton, with rates of 576, 308, and 264 g a.i.ha-1, respectively, which were equivalent to 2.5, 1.1 at 1.8 and 0.85 times the dose recommended per each season.

It is important to consider that even using higher doses than the recommended, none of the residual concentrations found will surpass the maximum residual limit (MRL) established by the Environmental Protection Agency (EPA) and the Codex Alimentarius of the FAO/OMS [25]. It was observed that the residual concentration of insecticide on apple leaves, potato leaves, and lettuce was superior to the apple fruit, potato (tuber), and the cotton seed. In the three leaves analyzed (lettuce, apple, and potato leaves) the father compound was found to be above 49% of the total residues, which may indicate that the major part of the compound recovered as residue remains in the leaves without being metabolized.


Source: [24], modified

**Table 2.** Proportions and principal metabolites of spirotetramat in apple, cotton, lettuce, and potato.

#### **4.3. Fate of spirotetramat in the soil**

It is necessary to investigate the degradation of the active compounds in the soil since it is possible that part of the insecticide will reach the soil directly or indirectly after being applied to a crop. The most important process to consider in the soil is the degradation by microor‐ ganisms under aerobic conditions. However, there are other factors that could contribute, such as the abiotic chemical degradation expressed as photolysis on the soil surface and also hydrolysis; other physical processes involved such as leaching, a translocation that can make it more profound in the soil; volatility; and the evaporation from the plant or from the soil Spirotetramat — An Alternative for the Control of Parasitic Sucking Insects and its Fate in the Environment http://dx.doi.org/10.5772/61322 47

*Source*: [24], modified

15.6%); meanwhile in the potato tuber, the main metabolite was BYI08330-enol, along with the absence of the father compound. To conduct those studies, a foliar application of spirotetramat OD-100 was applied, where the dose administered was 167 g a.i.ha-1 for lettuce, which was equivalent to the maximum recommended by the manufacturer; the same was administered for apple, potato, and cotton, with rates of 576, 308, and 264 g a.i.ha-1, respectively, which were

It is important to consider that even using higher doses than the recommended, none of the residual concentrations found will surpass the maximum residual limit (MRL) established by the Environmental Protection Agency (EPA) and the Codex Alimentarius of the FAO/OMS [25]. It was observed that the residual concentration of insecticide on apple leaves, potato leaves, and lettuce was superior to the apple fruit, potato (tuber), and the cotton seed. In the three leaves analyzed (lettuce, apple, and potato leaves) the father compound was found to be above 49% of the total residues, which may indicate that the major part of the compound

equivalent to 2.5, 1.1 at 1.8 and 0.85 times the dose recommended per each season.

**(leaves)**

**Table 2.** Proportions and principal metabolites of spirotetramat in apple, cotton, lettuce, and potato.

It is necessary to investigate the degradation of the active compounds in the soil since it is possible that part of the insecticide will reach the soil directly or indirectly after being applied to a crop. The most important process to consider in the soil is the degradation by microor‐ ganisms under aerobic conditions. However, there are other factors that could contribute, such as the abiotic chemical degradation expressed as photolysis on the soil surface and also hydrolysis; other physical processes involved such as leaching, a translocation that can make it more profound in the soil; volatility; and the evaporation from the plant or from the soil

Spirotetramat (BYI08330) 0.32 26.37 1.75 <0.001 - 5.455 BYI08330-enol 0.01 4.26 0.56 0.047 0.168 0.870 BYI08330-enol glc 0.03 - 0.36 0.004 0.006 0.395 BYI08330-cetohydroxy 0.05 1.09 0.20 0.011 0.018 2.745 BYI08330-monohydroxy 0.10 - - - - -

Total residues 0.61 36.63 3.13 0.119 0.225 11.057 MRLa 0.7 - 8 0.3 1.6 - MRLb 0.7 - 7 - 0.8 -

**Lettuce**

**Cotton (seed)**

**Potato (tuber)**

**Potato (leaves)**

recovered as residue remains in the leaves without being metabolized.

**(mg kg-1) Apple Apple**

**Compound**

46 Insecticides Resistance

a MRL, [26]

b MRL, [25]

Source: [24], modified

**4.3. Fate of spirotetramat in the soil**

**Figure 3.** Principal reactions and metabolite of spirotetramat in plants: a) Hydrolytic split, b) Oxidation of the Pyrrole group, c) Conjugation of the hydroxyl group BYI08330-enol with glucose, and d) Reduction.

surface [22]. However, these same researchers [22] observed that spirotetramat under aerobic soil conditions will degrade rapidly after 1-2 days, dissipating more than 90%. At the same time, during the testing period the two major metabolites generated were BYI08330-enol (maximum 24.3%) and BYI08330-cetohydroxy (maximum 16.3%), two of the dimers enol BYI08330-MA-amida (maximum 6.4%), and lastly two minor metabolites, BYI08330-desmeth‐ yl-enol (maximum 3.7%) and BYI08330-oxo-enol (maximum 1.2%) [23, 27].

In the study designed for 127 days, under aerobic conditions, spirotetramat was degraded rapidly; a day after the application, only 53.6% and 72.2% of the substance was detected. There were two principal metabolites identified, BYI08330-cetohydroxy (maximum 25.3%) and BYI08330-enol (maximum 7.8%); there were also three minor metabolites detected, these were confirmed using the previous method established in laboratory studies. It was also observed that for the aerobic soil metabolism, under acidic extraction, the metabolite BYI08330-enol was partially unstable, and that like spirotetramat it dissipated using a two-phase kinetic [22].

As was mentioned earlier, the velocity of degradation of spirotetramat in the soil under aerobic conditions was very rapid. Under laboratory conditions, the degradation time (DT50), was from 0.14 days (geometric average); for the majority of the scenarios it was 0.21 days. In situations with trails under outside climatic conditions, spirotetramat also degraded rapidly, with a DT50 average of approximately 2 days. The velocity of degradation for BYI08330-enol in the soil under aerobic conditions was 0.08 days (DT50); this information allows us to conclude that this metabolite is the one that will degrade rapidly [22].

The soil degradation studies under field conditions with spirotetramat demonstrate that the dissipation velocity DT50 was between 0.3 and 1.0 days; the dissipation of 90% (DT90) was between 1.1 and 3.5 days. In the case of the combined residues of spirotetramat (BYI08330 enol, BYI08330-cetohydroxy), the DT50 was between 5.0 and 23.4 days, the DT90 had a range of 16.7 to 77.8 days. The residues of spirotetramat were not found to be below the shallow layer (0-15 cm), due to the possibility of the presence of leaching in subterranean waters was not probable. Considering that within 14 days after the application of spirotetramat it degraded to concentrations below 0.5 μg kg-1, the possibility of the accumulation of residues in the soil one year later after the first application is low [22, 27].

The photo-transformation of spirotetramat on the soil surface does not represent a process of degradation relevant to conditions of solar radiation. The trials undertaken to evaluate phototransformation on the soil surface reveal that there are no different products derived from this effect after the application of spirotetramat [22, 23].

On the other hand, the anaerobic degradation in the soil follow almost the same route as under aerobic conditions, that is to say that no different metabolites are formed than those observed under aerobic conditions and it is concluded that it degrades rapidly [22, 23, 27].

Based on the literature discussed previously, the main route of spirotetramat dissipation in soil is the degradation to enol-BYI08330 and BYI08330-cetohydroxy; these followed by a degradation to non-extractable residues and mineralization to CO2. Concerning the mobility of the spirotetramat, the results showed that this pesticide can be classified as low mobility in soil. In the case of the BYI08330-enol, the strongly retained portion is considered stationary, while the weak form, as well as the BYI08330-cetohydroxy bound fraction possesses an intermediate leaching potential through the soil [22, 27].

#### **4.4. Fate of spirotetramat in the aquatic environment**

The research trials conducted demonstrate that spirotetramat is susceptible to degradation under biotic and abiotic processes in darkness as well as solar light. With reference to the abiotic degradation, the hydrolytic degradation becomes a relevant mechanism for the degradation of spirotetramat in the environment, especially under neutral and alkaline conditions. The halflife under hydrolytic conditions (20°C) at pH 7 is from 13 days, and at pH 9 it is less than half a day. On the other hand, hydrolysis does not represent a relevant degradation mechanism with regards to BYI08330-enol in the environment, the half-life at the pH range of 4 to 9, at 25°C is expected to be about a year [22].

The results of the photo-transformation in water demonstrate that this mechanism contributes in a significant way to the elimination of spirotetramat in natural water. In systems with water/ sediment, spirotetramat is degraded rapidly through the metabolites BYI08330-enol and BYI08330-cetohydroxy. In the same system under anaerobic conditions, spirotetramat de‐ grades rapidly, mainly into the metabolite BYI08330-enol. From the previous information and the evaluation of drinking water exposure, the use of spirotetramat does not represent a risk to human health [22, 23].

According to the results of toxicological studies isolated in *Ceriodaphnia dubia*, it was observed that mixing spirotetramat with an agricultural adjuvant (Destiny) caused more damage together than each one separately; this does not indicate synergy, but that each compound causes a certain level of mortality, and together the effect of the mixture is additive. This suggests that no further study is needed to determine which mixes of insecticides and adjuvants are causing damage to aquatic organisms [28].

#### **4.5. Interaction of spirotetramat with the air**

As was mentioned earlier, the velocity of degradation of spirotetramat in the soil under aerobic conditions was very rapid. Under laboratory conditions, the degradation time (DT50), was from 0.14 days (geometric average); for the majority of the scenarios it was 0.21 days. In situations with trails under outside climatic conditions, spirotetramat also degraded rapidly, with a DT50 average of approximately 2 days. The velocity of degradation for BYI08330-enol in the soil under aerobic conditions was 0.08 days (DT50); this information allows us to conclude that

The soil degradation studies under field conditions with spirotetramat demonstrate that the dissipation velocity DT50 was between 0.3 and 1.0 days; the dissipation of 90% (DT90) was between 1.1 and 3.5 days. In the case of the combined residues of spirotetramat (BYI08330 enol, BYI08330-cetohydroxy), the DT50 was between 5.0 and 23.4 days, the DT90 had a range of 16.7 to 77.8 days. The residues of spirotetramat were not found to be below the shallow layer (0-15 cm), due to the possibility of the presence of leaching in subterranean waters was not probable. Considering that within 14 days after the application of spirotetramat it degraded to concentrations below 0.5 μg kg-1, the possibility of the accumulation of residues in the soil

The photo-transformation of spirotetramat on the soil surface does not represent a process of degradation relevant to conditions of solar radiation. The trials undertaken to evaluate phototransformation on the soil surface reveal that there are no different products derived from this

On the other hand, the anaerobic degradation in the soil follow almost the same route as under aerobic conditions, that is to say that no different metabolites are formed than those observed

Based on the literature discussed previously, the main route of spirotetramat dissipation in soil is the degradation to enol-BYI08330 and BYI08330-cetohydroxy; these followed by a degradation to non-extractable residues and mineralization to CO2. Concerning the mobility of the spirotetramat, the results showed that this pesticide can be classified as low mobility in soil. In the case of the BYI08330-enol, the strongly retained portion is considered stationary, while the weak form, as well as the BYI08330-cetohydroxy bound fraction possesses an

The research trials conducted demonstrate that spirotetramat is susceptible to degradation under biotic and abiotic processes in darkness as well as solar light. With reference to the abiotic degradation, the hydrolytic degradation becomes a relevant mechanism for the degradation of spirotetramat in the environment, especially under neutral and alkaline conditions. The halflife under hydrolytic conditions (20°C) at pH 7 is from 13 days, and at pH 9 it is less than half a day. On the other hand, hydrolysis does not represent a relevant degradation mechanism with regards to BYI08330-enol in the environment, the half-life at the pH range of 4 to 9, at

under aerobic conditions and it is concluded that it degrades rapidly [22, 23, 27].

this metabolite is the one that will degrade rapidly [22].

48 Insecticides Resistance

one year later after the first application is low [22, 27].

effect after the application of spirotetramat [22, 23].

intermediate leaching potential through the soil [22, 27].

**4.4. Fate of spirotetramat in the aquatic environment**

25°C is expected to be about a year [22].

With a base vapor pressure of 5.6 x 10-9 Pa for spirotetramat and 1.2 x 10-10 Pa for l BYI08330 enol, it is expected that none of the two compounds will volatize when applied to the leaves or to the soil surface. Furthermore, considering the estimated life of these compounds in the air (maximum 3 hours); they are not expected to be able to travel in a gaseous state over large distances and as a result they cannot accumulate in the air [22, 27].
