Evaluation of the Egg Predator Blattisocius tarsalis (Mesostigmata: Blattisociidae) for the Biological Control of the Potato Tuber Moth Tecia solanivora under Storage Conditions

Round 1

Reviewer 1 Report

Comments are given in the PDF file attached. 

The findings of the manuscripts is quite interesting. As the experiment assessed the effect of temperature on predation ability.

However, the effect of the temperature range on the pest is not provided in the experiment. Similarly the wide range of temperature also had some effect on the pest activity. This data will provide information to the readers about the temperature management for potato mite.

Comments for author File: Comments.pdf

Author Response

Dear reviewers,

Your comments and contributions clearly increase the quality of our work and we want show you our sincerely gratefully. Thank you very much for the time spent to the revision.

Response to Reviewer 1:

• Under storage conditions in the title and non- refrigeration conditions in the abstract is quite confusing?

The authors accept the suggestion and rewrite lines 14-15 of abstract:

“The results show B. tarsalis is a very good candidate as a control agent in storage conditions and even in mixed infestations of T. solanivora and P. Operculella.”

• What are the percentage of losses caused by this pest if left unmanaged?

The loss percentage could not find in the bibliography research.

• Pictorial display seems more understanding for the readers. Need to add the eggs picture both predated, partially and not predated.

The authors consider it is a very good suggestion and add a new figure 1 to show health egg, partially consumed egg a total consumed egg. Also rewrite (new lines 119-120) to clarification:

“At the end of the predation period, the female mites were extracted, and all eggs were examined under a stereo microscope (10×) to register the number of eggs predated (no present or less than 25%) and/or partially consumed by the mites’ feeding activity (Figure 1).”

• The findings of the manuscripts are quite interesting. As the experiment assessed the effect of temperature on predation ability. However, the effect of the temperature range on the pest is not provided in the experiment. Similarly, the wide range of temperature also had some effect on the pest activity. This data will provide information to the readers about the temperature management for potato mite.

The authors accept the suggestion and add information in introduction, new lines 54-55 and 62-65.

“and theses low temperatures promote the laying reaching 311 eggs at 15ºC [16 ][17 ].”

“The temperature affects the pest as the natural enemies, specifically the developed time T. solanivora decrease to 208 days at 10ºC to 37 days at 27ºC [ 7]. Moreover, the development 63 time of B. tarsalis decrease to 22 days at 15ºC to 6 days at 27ºC, also it was observed 64 the predatory activity of mite rise in temperature [21][ 22 ].”

• 10-27 c is big range as the results showed that the efficacy is quite reduced in this particular rage. As the results showed deference was 33-75 efficacy. So how to justify that the predators would be useful between range of temperature 10-27 c? As most of insect sized there activities below 20 C. The optimal range for egg, larval and egg-to-adult development was between 26 and 30 °C.

The authors rewrite conclusions partially.  It is indicated in this range B. tarsalis would not be enough effective, only would be useful in non-refrigerated conditions. Lines 386-387:

“By contrast, the results show low and insufficient efficacy to B. tarsalis at 10ºC, for this 386 reason it could not effective under the usual refrigerated conditions (5-10ºC).”

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript reports the predation rates of Blattisocius tarsal on the potato pests Tecia solanivora and Phtorimaea operculella. The results presented showed that the predator has the potential for use in the biological control of both pests. However, the authors need to address two concerns in the statistical analysis and supplied crucial details of the manuscript.

(i) There is no reasoning for the number of eggs used in the experiment, and how it could potentially lead to prey depletion during the experiments. Experiments were also performed in a different number of hours of exposition, which need also be justified by the authors. In the choice experiment, there is no choice for the prey since the eggs of both species were placed in the same tube. And in the discussion, the main argument of the authors comparing the current study with the earlier is that egg size plays a role in predator behavior, but the results here (no difference) show the opposite.

(ii) The authors used the Wald test to compare means in their analysis, but the test checks the significance of variables in a model, rather than comparing means. Plus, the results section writes down an Omnibus test that was not previously informed in the material and methods section. Two experiments were performed in a factorial way, but the authors do not take them into account in the analysis. In turn, later, the results seem to try for such interaction without statistical support.

I acknowledge the paper’s findings and its importance for future studies on semi-field and field conditions. However, in its current form, the manuscript needs a main review

Lines 3-4 and 11-12: The aim does not match with the experiment reported in lines 11-12. It may need to be rewritten.

Introduction: The authors may consider supplying information about egg-laying (number of eggs per female) because it is the central part of the methods, but no information was provided.

Line 88: The authors looked at predation rates, there is no behavior analysis in the manuscript.

Line 107: Why do the authors use five eggs? Does it stand for real conditions? Is it proper to avoid prey depletion?

Line 112-113: What do the authors mean by partially consumed?

Lines 117-120: There is two-factors mite presence x temperature. Thereafter, the authors evaluated this interaction by a subset of analysis, which can be incorporated into one model only. Plus, the Wald test checks the significance of variables in a model. I don’t see how the authors apply this test to test means differences. Please verify carefully.

Lines 107 and 134: The authors did not inform the eggs’ age in the first experiment. Please provide this info for correctness.

Line 107: What was the female age in the experiment? Did the females were in a starvation period before the experiment?

Line 141: Dose is not a suitable term as it means the amount of something taken (weight/weight). I recommend the use of densities.

Line 140-144: And nothing was provided to the mites for 45 days? Which data were the authors based on to choose for this long time, since the earlier experiment was done in 48 hours?

Lines 145-146: What is the biological meaning to evaluate these stages once the predator only feeds on eggs? Yet again, the authors are only considering one factor, when they have two (eggs density x mite density).

Lines 157-160: How does the predator have a choice when both eggs are mixed in a tube? Particularly, a generalist predator?

Lines 204-213 and 120-123: The authors report a different test than those informed in the material and methods. Please check cautiously.

Line 214: It was or not? P = 0.05?

Lines 224-229: I don’t understand again why the authors did not use a multi-comparison (e.g., Tukey) test rather than compare it in pairs to conclude. Please justify.

Discussion: I would recommend to the authors summarizing the main findings in the first paragraph. It provides to the reader which arguments will the authors count on in the light of the findings. Arguments are divergent and seem to explain one result but are inconsistent with others. In lines 290-295 the authors mention egg size as a factor that appears to determine the predation rates. However, in lines 333-334 they said that prey studies among tuber moths have been found. It turns the egg size argument invalid.

Line 279: Only temperature was evaluated here. The authors may change to postharvest temperature conditions to be concise.

Lines 376-377: It was not assessed and may perhaps be quite speculative.

Table 1 and 2, Figure 1: Replace the comma with the dot in SE values reported and y-axis.

Author Response

Dear reviewers,

Your comments and contributions clearly increase the quality of our work and we want show you our sincerely gratefully. Thank you very much for the time spent to the revision.

Response to Reviewer 2:

• Lines 3-4 and 11-12: The aim does not match with the experiment reported in lines 11-12. It may need to be rewritten.

The authors rewrote these lines:

"The choice-assay showed no preference of B. tarsalis between T. solanivora and Pthorimaea operculella suggesting this mite could be useful in mixed infestations of potato moths"

• Introduction: The authors may consider supplying information about egg-laying (number of eggs per female) because it is the central part of the methods, but no information was provided. The authors think it is good consideration and add the information in new lines new lines 54-55

“and theses low temperatures promote the laying reaching 311 eggs at 15ºC [16] [17].”

• Line 88 (new line 94): There is no behaviour analysis in the manuscript.

The authors accept the suggestion and change the text:

“Therefore, in the present work, the predation of B. tarsalis on TCS have been studied under different storage conditions in order to assess its viability as a biological control

agent in warehouses.”

• Lines 107 and 134 (new lines 109-137): The authors did not inform the eggs’ age in the first experiment. Please provide this info for correctness:

The authors add the information: “five TCS eggs laid 1-24 h before”.

• Line 107 (new line 109): What was the female age in the experiment? Did the females were in a starvation period before the experiment?

Due to the rearing system followed in the laboratory populations, it was not possible to ascertain the age of the adult females used. For this reason, it adds in text:

“…female adult mite with 24h of starvation (no attempt was made to determine their age not to synchronize).”

• Line 107 (new line 113): Why do the authors use five eggs? Does it stand for real conditions? Is it proper to avoid prey depletion?

Previous bibliography references establish these time and number of preys enough for this type of tests with prey eggs in two species of Blattisocius:

Gallego et al., 2020a, DOI: 10.1007 / s11540-019-09438-9.

Gallego et al., 2020b, DOI 10.3390/insects11030196.

Gavara et al., 2021 DOI: 10.3390 / agronomy11020288.

• Line 112-113 (new lines 119-120): What do the authors mean by partially consumed?

The authors add a new figure 1 to show health egg, partially consumed egg a total consumed egg. Also rewrite lines 118-120 to clarification:

“At the end of the predation period, the female mites were extracted, and all eggs were examined under a stereo microscope (10×) to register the number of eggs predated (no present or less than 25%) and/or partially consumed by the mites’ feeding activity (Figure 1).”

• Lines 117-120 (new lines 124-127): There is two-factors mite presence x temperature. Thereafter, the authors evaluated this interaction by a subset of analysis, which can be incorporated into one model only. Plus, the Wald test checks the significance of variables in a model. I don’t see how the authors apply this test to means differences. Please verify carefully.

Indeed, you are partly right. We have verified it. But the analysis using Generalized Linear Models has been carried out by SPSS software, considering two factors and maximum likelihood. The only option that this software allows for the comparison of means is the Wald test.

• Lines 224-229: I don’t understand again why the authors did not use a multi-comparison (e.g., Tukey) test rather than compare it in pairs to conclude. Please justify.

Please, see answer in previous point.

• Line 141: Dose is not a suitable term as it means the amount of something taken (weight/weight). I recommend the use of densities.

The recommendation has been applied in all text.

• Line 140-144 (new lines 151-155):
• And nothing was provided to the mites for 45 days?

The mites weren’t provided, because we wanted observe the efficacy of mite only in one TCS generation, we didn’t' allow new lays of TCS.

2. Which data were the authors based on to choose for this long time, since the earlier experiment was done in 48 hours?

It wouldn't have been possible to handle the potatoes without destroying part of unconsumed eggs and the results would have been altered. In previous assay (48h) we could observe the eggs through the test tubs. In addition, we wanted obtain preliminary evaluation the efficacy of the mites at different densities in long time (more real than 48h)

We base on the life cycle of TCS (Torres et al. 1997), after 45 days at 25ºC most of the individuals are in the pupa or adult stage (Torres et al. 1997)   and which are easier find and count, because the previous larval stage are inside the potato.

Torres WF, Notz A & Valencia L (1997) [Life cycle and other aspects of the biology of Tecia solanivora in Tachira state, Venezuela.] Boletín de Entomologia Venezolana 12, 95– 106. doi/10.1111/j.1365-2338.2005.00859.x

• Lines 145-146 (new lines 152-153): What is the biological meaning to evaluate these stages once the predator only feeds on eggs? Yet again, the authors are only considering one factor, when they have two (eggs density x mite density).

Really, we don't count these particular stages, we are counting the survive, please read previous respond. How it’s confusing we rewrite the text to clarification it:

“After this period, the surviving individuals, larvae, pupae and adult moths of each treatment were counted.”

• Lines 157-160 (new lines 164-167): How does the predator have a choice when both eggs are mixed in a tube? Particularly, a generalist predator?

The process of prey selection by a predator, although it is generalist, is complex; There is ample literature on the subject of choosing prey in the case of many species of Phytoseiids. We do not understand how there may or may not be preferences in a generalist predator.

• Lines 204-213 (new lines 209-220) and 120-123 (new lines 123-133): The authors report a different test than those informed in the material and methods. Please check cautiously.

We check it. There was a confusion, we correct it rewriting lines 123-133:

The number of surviving larvae and the kill TCS eggs were statistically analysed using a Generalized Linear Model (GLM) with a Poisson distribution and logarithm link function. In turn, the mean values were compared in pairs using the Wald test at P = 0.05. Also, the percentage of partially consumed TCS eggs at every tested temperature were compared using nonparametric Kruskal–Wallis one-way analysis with a level of significance of P = 0.05. All the analyses were carried out with IBM SPSS version 25 statistical software.”

• Line 214 (new line 221): It was or not? P = 0.05?

We correct it: P < 0.05.

• In lines 290-295 (new lines 297-303) the authors mention egg size as a factor that appears to determine the predation rates. However, in lines 333-334(new lines 341-342) they said that prey studies among tuber moths have been found. It turns the egg size argument invalid.

The prey selection process for predators depends on the size of the prey, however other factors may be involved such as olfactory chemical tracks (Kairomones) and even chemicals (food test) that causes it to reject the prey. Also, although they are very close species, the egg chorion (which has not been measured) may be larger and / or more mechanically resistant, as well as other factors.

we added this clarification in lines 299-301:

“...the earlier the mite would be satisfied and the greater the survival possibilities of the prey eggs, although other chemical and mechanical factors may be involved [ 34 ,36 ]”

• Line 279: Only temperature was evaluated here. The authors may change to postharvest temperature conditions to be concise.

The authors accept the recommendation.

• Lines 376-377: It was not assessed and may perhaps be quite speculative.

We rewrite conclusions partially, considering your suggestion (new lines 386-387):

“…the results show low and insufficient efficacy to B. tarsalis at 10ºC, for this reason it could not effective under the usual refrigerated conditions (5-10ºC).”

• Table 1 and 2, Figure 1: Replace the comma with the dot in SE values reported and y-axis.

The authors have corrected the mistakes.

Author Response File: Author Response.pdf