**3. Results and discussion**

#### **3.1. Efficacy of diazinon formulations**

Major knockdown effect and longer residual period to control *D. perniciosus* (**Figure 1**, **Table 1**) and *P. viburni* (**Figure 2**, **Table 2**) was achieved by using emulsion in water (EW) than wettable powder (WP). In addition, higher levels of mortality of both pests were achieved with the use of EW formulation. One work performed with diazinon against the attack of San Jose scale crawlers showed that diazinon provided 12–13 days of protection [45], which can be considered similar to results obtained on this chapter for WP formulation, but apparently it is underestimated for EW formulation. On both parameters (mean of infested fruits by scales or mealybugs and mean of living scales or mealybugs on fruits), EW seems to be effective even until the last evaluation carried out at 25 DAA.

On the other hand, about *C. pomonella* control (**Figure 3**), both formulations showed and optimal and similar control until 10 DAA, and then, better results—but not optimal—were obtained with EW formulation. One work conducted in 1965 proposed that for diazinon, optimal insecticide activity against *C. pomonella* would have an approximate duration of 6 days [46]; in the present work, demanding for 90% minimum of larvae mortality, both formulations deliver 10 days of control. On 14 DAA evaluations, EW formulation showed a mortality level close to 80%, which is considered insufficient from the economic point of view for the

**Figure 1.** Mean of infested fruit by living San Jose scale according to the treatment of diazinon formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

farmer. Therefore, although both formulations show significant differences in the control of *C. pomonella*, commercially (demanding a mortality of at least 85%), both only control efficiently for up to 10 days.

the surface tension of the solution and hence droplet formation and deposition of diazinon residue. Diazinon is a water-soluble insecticide with high affinity for lipids [47]; then, solvent and emulsifier used on emulsion in water formulations can play a crucial role on the deposition pattern. Emulsion in water dissolved in water forms an emulsion, which does not need constant agitation to maintain it; instead, the wettable powder formulation forms a suspension, which requires constant agitation to keep its fine particles suspended in the water. These differences in the physical-chemical behavior of both formulations were reflected in differences in their initial deposition and persistence of its residues, but this does not seem to be a constant to all types of formulations and insecticides. One work comparing residue levels generated by three formulations of chlorpyrifos (emulsifiable concentrate (EC), wettable granules (WG),

**Mean of living obscure mealybugs on fruits according to diazinon formulation by evaluation moment (DAA) Treatment Prespraying 3DAA 7DAA 10DAA 14DAA 21DAA 25DAA** Control 33.50a 42.75a 48.00a 55.00a 57.00a 61.50a 62.25a Emulsion in water 31.25a 3.00c 6.00c 5.75c 5.50c 7.25c 12.50c Wettable powder 32.75a 18.75b 21.25b 24.75b 24.50b 26.50b 32.25b *F* **0.55 80.36 175.45 279.37 129.88 178.28 142.53** *p* **value 0.597 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001**

Means followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**Table 2.** Mean of living obscure mealybugs on fruits according to the treatment of diazinon formulations.

**Figure 2.** Mean of infested fruit by living obscure mealybugs according to the treatment of diazinon formulations. Values

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followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

#### **3.2. Residues of diazinon formulations**

Emulsion in water generates higher initial and final diazinon residues than wettable powder (**Figure 4**). These results are probably due to differences between formulations that affect


**Table 1.** Mean of living San Jose scale on fruits according to the treatment of diazinon formulations.

**Figure 2.** Mean of infested fruit by living obscure mealybugs according to the treatment of diazinon formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

farmer. Therefore, although both formulations show significant differences in the control of *C. pomonella*, commercially (demanding a mortality of at least 85%), both only control effi-

**Figure 1.** Mean of infested fruit by living San Jose scale according to the treatment of diazinon formulations. Values

followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

Emulsion in water generates higher initial and final diazinon residues than wettable powder (**Figure 4**). These results are probably due to differences between formulations that affect

**Mean of living scales (***D. perniciosus***) on fruits according to diazinon formulation by evaluation moment** 

Means followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**Table 1.** Mean of living San Jose scale on fruits according to the treatment of diazinon formulations.

**Treatment Prespraying 3DAA 7DAA 10DAA 14DAA 21DAA 25DAA** Control 31.00a 36.00a 39.25a 40.00a 43.75a 47.75a 51.75a Emulsion in water 29.25a 7.25c 4.75c 3.25c 6.75c 7.75c 8.25c Wettable powder 27.50a 11.75b 14.75b 12.75b 12.00b 17.50b 19.25b *F* **1.08 200.45 78.63 72.98 172.79 155.83 137.18** *p* **value 0.379 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001**

ciently for up to 10 days.

48 Insecticides - Agriculture and Toxicology

**(DAA)**

**3.2. Residues of diazinon formulations**

the surface tension of the solution and hence droplet formation and deposition of diazinon residue. Diazinon is a water-soluble insecticide with high affinity for lipids [47]; then, solvent and emulsifier used on emulsion in water formulations can play a crucial role on the deposition pattern. Emulsion in water dissolved in water forms an emulsion, which does not need constant agitation to maintain it; instead, the wettable powder formulation forms a suspension, which requires constant agitation to keep its fine particles suspended in the water. These differences in the physical-chemical behavior of both formulations were reflected in differences in their initial deposition and persistence of its residues, but this does not seem to be a constant to all types of formulations and insecticides. One work comparing residue levels generated by three formulations of chlorpyrifos (emulsifiable concentrate (EC), wettable granules (WG),


**Table 2.** Mean of living obscure mealybugs on fruits according to the treatment of diazinon formulations.

with WP formulation showed differences in the droplet-size spectra and deposit levels, attrib-

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Differences on efficacy only after 21 DAA were observed with acetamiprid formulations on codling moth (**Figure 5**). Major knockdown effects on San Jose scale (**Figure 6**; **Table 3**) and obscure mealybug (**Figure 7**; **Table 4**) were obtained using wettable powder (WP); nevertheless a longer protection period was obtained using soluble powder (SP). On *C. pomonella*, both treatments showed appropriate control until 21 DAA, and then, only soluble powder main-

Acetamiprid has shown good control activity against *C. pomonella* [51]. It is systemic and intended to control sucking insects like aphids, mealybugs [52], and San Jose scale [53]. In this study, differences on the behavior on control could be explained by differences on chemicalphysical property between both formulations. Although they have many similarities, when mixed on water, WP generates a suspension, and when applied, formulation particles remain on the treated surface [54]; instead, SP generates a homogenous solution which is easily incorporated by the plant. In addition, between both formulations, the concentration of active ingredient and the proportion and type of coformulants vary. Then, it is possible that these differences are reflected in different rates of absorption by the plant and/or insects [55]. There is some consensus that biological performance of a pesticide is frequently affected by the choice of formulation type [56, 57], for example, a formulation which delivers the chemical in

**Figure 5.** Mortality (% Abbott) of *C. pomonella* larvae according to the treatment of acetamiprid formulations. Values

followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

uted to the influence of additives present in different formulations [50].

tained a percentage of control with over 85% larvae mortality until 25 DAA.

**3.3. Efficacy of acetamiprid formulations**

**Figure 3.** Mortality (% Abbott) of *C. pomonella* larvae according to the treatment of diazinon formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

and microencapsulates (ME)) applied to oranges shows that the decline curve and the residue levels in fruits, leaves, and soil could change remarkably if the same active ingredient is used in different formulations [48]; on contrary, the study performed with fenitrothion applied to oranges and clementines with emulsifiable concentrate and microencapsulate formulations did not find differences on rate of decline residue of the active ingredient for both kinds of commercial formulations [49]. For the insecticide azadirachtin, EC formulations compared

**Figure 4.** Initial and final residues of diazinon quantified for each formulation. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA).

with WP formulation showed differences in the droplet-size spectra and deposit levels, attributed to the influence of additives present in different formulations [50].

#### **3.3. Efficacy of acetamiprid formulations**

and microencapsulates (ME)) applied to oranges shows that the decline curve and the residue levels in fruits, leaves, and soil could change remarkably if the same active ingredient is used in different formulations [48]; on contrary, the study performed with fenitrothion applied to oranges and clementines with emulsifiable concentrate and microencapsulate formulations did not find differences on rate of decline residue of the active ingredient for both kinds of commercial formulations [49]. For the insecticide azadirachtin, EC formulations compared

**Figure 4.** Initial and final residues of diazinon quantified for each formulation. Values followed by different letters

indicate significant differences with *p* < 0.05 (ANOVA).

50 Insecticides - Agriculture and Toxicology

**Figure 3.** Mortality (% Abbott) of *C. pomonella* larvae according to the treatment of diazinon formulations. Values

followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

Differences on efficacy only after 21 DAA were observed with acetamiprid formulations on codling moth (**Figure 5**). Major knockdown effects on San Jose scale (**Figure 6**; **Table 3**) and obscure mealybug (**Figure 7**; **Table 4**) were obtained using wettable powder (WP); nevertheless a longer protection period was obtained using soluble powder (SP). On *C. pomonella*, both treatments showed appropriate control until 21 DAA, and then, only soluble powder maintained a percentage of control with over 85% larvae mortality until 25 DAA.

Acetamiprid has shown good control activity against *C. pomonella* [51]. It is systemic and intended to control sucking insects like aphids, mealybugs [52], and San Jose scale [53]. In this study, differences on the behavior on control could be explained by differences on chemicalphysical property between both formulations. Although they have many similarities, when mixed on water, WP generates a suspension, and when applied, formulation particles remain on the treated surface [54]; instead, SP generates a homogenous solution which is easily incorporated by the plant. In addition, between both formulations, the concentration of active ingredient and the proportion and type of coformulants vary. Then, it is possible that these differences are reflected in different rates of absorption by the plant and/or insects [55]. There is some consensus that biological performance of a pesticide is frequently affected by the choice of formulation type [56, 57], for example, a formulation which delivers the chemical in

**Figure 5.** Mortality (% Abbott) of *C. pomonella* larvae according to the treatment of acetamiprid formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**Figure 6.** Mean of infested fruit by living San Jose scale according to the treatment of acetamiprid formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

a solution, as in SL, EC, or SP formulations, is commonly considered more biologically active than WP or SC formulations, but also, it has a greater risk of being phytotoxic [58].

three different apple growth stages [59]. Even when both SP and SL form solutions, these formulations differ on its coformulants and the concentration of active ingredient contained proportionally therein. Thus, even if in this work an equal amount of active ingredient per hectoliter per hectare has been dosed, the proportion and type of surfactants, carriers, or oth-

**Figure 7.** Mean of infested fruit by obscure mealybugs according to the treatment of acetamiprid formulations. Values

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followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

In general terms, results from the literature are not conclusive with respect to the effect of different formulations in residue deposits and behavior of pesticides, perhaps because of the difficulty of isolating other factors that also affect the degradation of residues such as species and varieties; use of adjuvants; types and concentration of coformulants; fruit growth;

**Mean of living obscure mealybugs on fruits according to acetamiprid formulation by evaluation moment** 

Means followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**Table 4.** Mean of living obscure mealybugs on fruits according to the treatment of acetamiprid formulations.

**Treatment Prespraying 3DAA 7DAA 10DAA 14DAA 21DAA 25DAA** Control 33.50a 42.75a 48.00a 55.00a 57.00a 61.50a 62.25a Soluble powder 29.00a 15.75b 7.00b 5.50c 7.75c 9.00c 10.75c Wettable powder 28.00a 7.25c 11.25b 15.25b 17.00b 18.75b 22.25b *F* **2.60 79.16 282.59 282.08 168.09 234.43 238.61** *p* **value 0.13 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01**

ers will not be equivalent.

**(DAA)**

#### **3.4. Residues of acetamiprid formulations**

Wettable powder formulation generated higher initial deposition of acetamiprid than observed for the soluble powder formulation (**Figure 8**). These results contradict what was proposed for a comparison between decline curves of acetamiprid on apple (cv. Pink Lady) performed with SL and WP formulations. In that work, no significant differences were found on the initial and final depositions of acetamiprid between both formulations, applied on


**Mean of living scales (***D. perniciosus***) on fruits according to acetamiprid formulation by evaluation moment** 

**Table 3.** Mean of living San Jose scale on fruits according to the treatment of acetamiprid formulations.

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**Figure 7.** Mean of infested fruit by obscure mealybugs according to the treatment of acetamiprid formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

a solution, as in SL, EC, or SP formulations, is commonly considered more biologically active

**Figure 6.** Mean of infested fruit by living San Jose scale according to the treatment of acetamiprid formulations. Values

Wettable powder formulation generated higher initial deposition of acetamiprid than observed for the soluble powder formulation (**Figure 8**). These results contradict what was proposed for a comparison between decline curves of acetamiprid on apple (cv. Pink Lady) performed with SL and WP formulations. In that work, no significant differences were found on the initial and final depositions of acetamiprid between both formulations, applied on

**Mean of living scales (***D. perniciosus***) on fruits according to acetamiprid formulation by evaluation moment** 

**Treatment Prespraying 3DAA 7DAA 10DAA 14DAA 21DAA 25DAA** Control 31.00a 36.00a 39.25a 40.00a 43.75a 47.75a 51.75a Soluble powder 28.25a 11.50b 6.50c 2.25c 4.50c 6.00c 9.25c Wettable powder 30.25a 6.00c 13.50b 8.25b 12.50b 24.25b 27.75b *F* **1.22 204.07 79.46 169.31 178.52 127.69 102.01** *p* **value 0.34 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01**

Means followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**Table 3.** Mean of living San Jose scale on fruits according to the treatment of acetamiprid formulations.

than WP or SC formulations, but also, it has a greater risk of being phytotoxic [58].

followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**3.4. Residues of acetamiprid formulations**

52 Insecticides - Agriculture and Toxicology

**(DAA)**

three different apple growth stages [59]. Even when both SP and SL form solutions, these formulations differ on its coformulants and the concentration of active ingredient contained proportionally therein. Thus, even if in this work an equal amount of active ingredient per hectoliter per hectare has been dosed, the proportion and type of surfactants, carriers, or others will not be equivalent.

In general terms, results from the literature are not conclusive with respect to the effect of different formulations in residue deposits and behavior of pesticides, perhaps because of the difficulty of isolating other factors that also affect the degradation of residues such as species and varieties; use of adjuvants; types and concentration of coformulants; fruit growth;


**Mean of living obscure mealybugs on fruits according to acetamiprid formulation by evaluation moment** 

**Table 4.** Mean of living obscure mealybugs on fruits according to the treatment of acetamiprid formulations.

(CS) formulation showed better efficacy, with the longer stable control period. Key difference between Zeon technology and EC formulation is that the first one encapsulates the active ingredient in small capsules with thin walls; instead, the second one comprises the active ingredient, a solvent, and emulsifiers. This enables for Zeon formulation quick "knockdown" of insects coupled with long-term persistence [63, 64], properties that were observed in this study. Even when they observed differences between efficacy parameters of both formulations, some authors propose that other parameters as application rate should be considered [65], which, in the present study, is a constant factor for the comparison of both formulations allowing us to conclude without other variables. One work conducted to evaluate efficacy against *Cydia molesta* founded that in the laboratory and in the field, the toxicity to *C. molesta* larvae of microencapsulated (CS) l-cyhalothrin was similar to that of the emulsifiable concentrate (EC) formulation. However, the same work proposed that different toxicity responses were obtained when evaluating its effect on the predator *Typhlodromus pyri* Scheuten, where CS formulation results significantly more

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Apparently, the different release rates of the active ingredient are not significantly different at their start (1 DAA) and at 25 days from the application (**Figure 10**), possibly because the microencapsulated formulations do not necessarily vary the deposition of the active ingredi-

Control of *P. viburni* showed by soluble liquid (SL) and suspension concentrate formulations was similar to wettable powder (WP) formulation until 10 DAA, reflected in both the average

**Figure 10.** Initial and final residues of l-cyhalothrin quantified for each formulation. Values followed by different letters

ent residue, but their biological availability and, as it was observed, its effectiveness.

toxic than EC formulation in pyrethroid-susceptible predator population [66].

**3.6. Residues of l-cyhalothrin formulations**

**3.7. Efficacy of imidacloprid formulations**

indicate significant differences with *p* < 0.05 (ANOVA).

**Figure 8.** Initial and final residues of acetamiprid quantified for each formulation. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA).

climatic conditions; spraying method; measuring technique; and pesticide physicochemical properties between others [60–62].

#### **3.5. Efficacy of l-cyhalothrin formulations**

Although both formulations showed insecticidal activity against *C. pomonella*, significant differences between both formulations were observed since the first evaluation (**Figure 9**). Zeon

**Figure 9.** Mortality (% Abbott) of *C. pomonella* larvae according to the treatment of l-cyhalothrin formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

(CS) formulation showed better efficacy, with the longer stable control period. Key difference between Zeon technology and EC formulation is that the first one encapsulates the active ingredient in small capsules with thin walls; instead, the second one comprises the active ingredient, a solvent, and emulsifiers. This enables for Zeon formulation quick "knockdown" of insects coupled with long-term persistence [63, 64], properties that were observed in this study. Even when they observed differences between efficacy parameters of both formulations, some authors propose that other parameters as application rate should be considered [65], which, in the present study, is a constant factor for the comparison of both formulations allowing us to conclude without other variables. One work conducted to evaluate efficacy against *Cydia molesta* founded that in the laboratory and in the field, the toxicity to *C. molesta* larvae of microencapsulated (CS) l-cyhalothrin was similar to that of the emulsifiable concentrate (EC) formulation. However, the same work proposed that different toxicity responses were obtained when evaluating its effect on the predator *Typhlodromus pyri* Scheuten, where CS formulation results significantly more toxic than EC formulation in pyrethroid-susceptible predator population [66].

#### **3.6. Residues of l-cyhalothrin formulations**

Apparently, the different release rates of the active ingredient are not significantly different at their start (1 DAA) and at 25 days from the application (**Figure 10**), possibly because the microencapsulated formulations do not necessarily vary the deposition of the active ingredient residue, but their biological availability and, as it was observed, its effectiveness.

#### **3.7. Efficacy of imidacloprid formulations**

climatic conditions; spraying method; measuring technique; and pesticide physicochemical

**Figure 8.** Initial and final residues of acetamiprid quantified for each formulation. Values followed by different letters

Although both formulations showed insecticidal activity against *C. pomonella*, significant differences between both formulations were observed since the first evaluation (**Figure 9**). Zeon

**Figure 9.** Mortality (% Abbott) of *C. pomonella* larvae according to the treatment of l-cyhalothrin formulations. Values

followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

properties between others [60–62].

54 Insecticides - Agriculture and Toxicology

**3.5. Efficacy of l-cyhalothrin formulations**

indicate significant differences with *p* < 0.05 (ANOVA).

Control of *P. viburni* showed by soluble liquid (SL) and suspension concentrate formulations was similar to wettable powder (WP) formulation until 10 DAA, reflected in both the average

**Figure 10.** Initial and final residues of l-cyhalothrin quantified for each formulation. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA).

number of fruits infested by the pest (**Figure 11**) and the mean of living mealybugs on fruits (**Table 5**); then, longer efficient period of control was obtained using SL formulation.

Imidacloprid is highly effective against mealybugs [67] and others hemipteran pest [68, 69]. It is available in different formulations (WP, SL, SC, OD, WG) registered generally according to their use intention (foliar sprays, seed treatments, and via soil application) [70]; but for the same target of control and way of use, more than one formulation can be available. The choice of one formulation or another may vary the metabolism and persistence behavior of imidacloprid [71, 72]. In our work, even though the three formulations differ in the characteristics of their coformulants, WP and SC formulations have in common that both form suspensions on water; instead, SL forms a solution. This difference could generate different responses in the mobility and translocation of the active ingredient, and therefore its availability to control the pest.

#### **3.8. Residues of imidacloprid formulations**

Both initial and final deposits of imidacloprid were higher in SL, compared with WP and SC (**Figure 12**). Even though this work presents only two points or moments of evaluation within a possible residue decline curve, we can infer that the degradation of imidacloprid residue was affected by the formulation, resulting more persistently the residue of imidacloprid generated by the formulation SL than that of the other formulations WP and SC.

In all the cases studied on this research (except both formulations of l-cyhalothrin), concentration of active ingredient contained in 1 l or kg of each commercial product varied with their respective comparison. Thus, even though all treatments were performed to look for the same dose of active ingredient per hectare, there was always a variation in the content of adjuvants, surfactants, inerts, or other contents according to the formulation. In the case of l-cyhalothrin, the variations passed through the type of coformulants in addition to the differentiating characteristics of the rate of release of the active ingredient, but not in the concentration of active ingredient. For Food and Agriculture Organization (FAO), two pesticides may not be classified as equivalent even when they have the same concentration of active ingredient, as their similarity depends on the type of formulations. Nor does it apply nominally similar products from other manufacturers or at all those where the active ingredient is produced

**Figure 12.** Initial and final residues of imidacloprid quantified for each formulation. Values followed by different letters

indicate significant differences with *p* < 0.05 (ANOVA).

Means followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

**Table 5.** Mean of living obscure mealybugs on fruits according to the treatment of imidacloprid formulations.

**Mean of living obscure mealybugs on fruits according to imidacloprid formulation by evaluation moment** 

**Treatment Prespraying 3DAA 7DAA 10DAA 14DAA 21DAA 25DAA** Control 33.50a 42.75a 48.00a 55.00a 57.00a 61.50a 62.25a Suspension concentrate 36.50a 5.25b 4.75b 6.25b 12.75b 16.00b 19.75b Soluble liquid 36.00a 6.25b 5.00b 5.00b 1.75c 3.50c 6.75c Wettable powder 35.75a 4.25b 3.75b 4.75b 14.5b 17.00b 24.50b *F* **0.51 10.12 29.31 33.09 20.82 23.49 17.13** *p* **Value 0.68 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001**

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**(DAA)**

On the other hand, the formulations WP and SC had similar behaviors with each other, which is coincident with what was observed in the construction of metalaxyl decline curves in grapes for WP and SC formulations of this pesticide [73].

**Figure 11.** Mean of infested fruit by obscure mealybugs according to the treatment of imidacloprid formulations. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).


**Mean of living obscure mealybugs on fruits according to imidacloprid formulation by evaluation moment** 

number of fruits infested by the pest (**Figure 11**) and the mean of living mealybugs on fruits

Imidacloprid is highly effective against mealybugs [67] and others hemipteran pest [68, 69]. It is available in different formulations (WP, SL, SC, OD, WG) registered generally according to their use intention (foliar sprays, seed treatments, and via soil application) [70]; but for the same target of control and way of use, more than one formulation can be available. The choice of one formulation or another may vary the metabolism and persistence behavior of imidacloprid [71, 72]. In our work, even though the three formulations differ in the characteristics of their coformulants, WP and SC formulations have in common that both form suspensions on water; instead, SL forms a solution. This difference could generate different responses in the mobility and translocation of the active ingredient, and therefore its availability to control the pest.

Both initial and final deposits of imidacloprid were higher in SL, compared with WP and SC (**Figure 12**). Even though this work presents only two points or moments of evaluation within a possible residue decline curve, we can infer that the degradation of imidacloprid residue was affected by the formulation, resulting more persistently the residue of imidacloprid gen-

On the other hand, the formulations WP and SC had similar behaviors with each other, which is coincident with what was observed in the construction of metalaxyl decline curves in grapes

**Figure 11.** Mean of infested fruit by obscure mealybugs according to the treatment of imidacloprid formulations. Values

followed by different letters indicate significant differences with *p* < 0.05 (ANOVA, Tukey's test).

erated by the formulation SL than that of the other formulations WP and SC.

(**Table 5**); then, longer efficient period of control was obtained using SL formulation.

**3.8. Residues of imidacloprid formulations**

56 Insecticides - Agriculture and Toxicology

for WP and SC formulations of this pesticide [73].

**Table 5.** Mean of living obscure mealybugs on fruits according to the treatment of imidacloprid formulations.

In all the cases studied on this research (except both formulations of l-cyhalothrin), concentration of active ingredient contained in 1 l or kg of each commercial product varied with their respective comparison. Thus, even though all treatments were performed to look for the same dose of active ingredient per hectare, there was always a variation in the content of adjuvants, surfactants, inerts, or other contents according to the formulation. In the case of l-cyhalothrin, the variations passed through the type of coformulants in addition to the differentiating characteristics of the rate of release of the active ingredient, but not in the concentration of active ingredient. For Food and Agriculture Organization (FAO), two pesticides may not be classified as equivalent even when they have the same concentration of active ingredient, as their similarity depends on the type of formulations. Nor does it apply nominally similar products from other manufacturers or at all those where the active ingredient is produced

**Figure 12.** Initial and final residues of imidacloprid quantified for each formulation. Values followed by different letters indicate significant differences with *p* < 0.05 (ANOVA).

by other synthesis methods [74]; inferring that, it is expected that there are certain variations in its practical behavior, whether in its pattern of residues, biological behavior, or efficacy. Accordingly, in the pesticide registry and its establishment of maximum residue limits, it is suggested that information is submitted for the formulation to be registered, and, if a new formulation is to be introduced, it is suggested to carry out collaborative trials (even between different manufacturers) that previously demonstrate that the variations made in the new formulation will not change the pattern of residues [41]. The information generated in these studies is not public.

**Author details**

Karina Buzzetti

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While the chemical industry posits that some formulations do not imply significant variations between them [74], there is a lot of confidential information that is not known to the end user, which prevents easily discriminating when variations are expected or when not. For the same reason, and because the effectiveness or protection periods may be severely affected by variations between formulations, further comparative inquiries are required to discriminate between product profiles for pest control.
