Influence of Cotton Crop Types on the Variation of Phonoctonus lutescens Population Guérin Meneville and Percheron (Heteroptera: Reduvidae), a Predator of Dysdercus voëlkeri (Schmidt 1932) (Heteroptera: Pyrrochoridae) in Burkina Faso

Phonoctonus lutescens which is a predator of Dysdercus voëlkeri (Schmidt, 1932) is present in cotton fields at the same time as its prey, D. voëlkeri. The objective of this study was to see which of the biological control or chemical control programs spares and maintains the potentially beneficial insects, especially P. lutescens. This study was conducted at three sites: Farako Bâ site located in the southern Sudanian zone and has geographical coordinates between 04˚20' West and 11˚06' North. The site of Kombissiri with 12'04'' North and 1'20'' West as geographical coordinates. The site of Kouaré with the following coordinates: 11'56'' North and 0'17'' East. The design was a 2000 m 2 paired trial subdivided into 3 subplots of 640 m 2 on the three sites. The sample area is repeated 4 times in each plot. All data were subjected to analysis of variance (ANOVA) using SPSS software (version 22.0; SPSS Inc., Chicago, IL, Usa). When significance occurred, means were separated by Bonferroni test (p < 0.05). All vels of presence in Farako bâ varied from 0.17 ± 0.66 to 0.02 ± 0.1 on organic cotton than on the other treatments. At Kombissiri the levels of beneficial insects varied more on organic cotton from 0.021 ± 0.20 to 0.026 ± 0.15 than on untreated cotton and conventional cotton. These levels ranged from 0.04 ± 0.21 to 0.26 ± 0.86 on organic cotton than on the other treatments. The seed cotton yield ranged from 500.52 to 946.8 for conventional cotton, from 531.25 to 853.13 for organic cotton and from 493.75 to 763.54 for untreated cotton. P. lutescens was discreet about the types of cotton grown. Neem oil is positioned as one of the alternatives to biopesticides that can be used in organic cotton cultivation. The results suggest P. lutescens is more adapted to integrated cotton pest management program in Burkina Faso.


Introduction
Dysdercus voëlkeri (Schmidt, 1932) [1] is a boll-sucking biting insect, a bug of the family Pyrrhocoridae, and is reported to cause serious damage to cotton. It is a phytophagous insect that feeds on cotton bolls and seeds. PR-PICA, 2014 [2] reported intense outbreaks of D. voëlkeri in Benin (13.21%), Burkina Faso (29.27%), Côte d'Ivoire (4.51%) and Senegal (28.7%). The nymphs and adults of D. voëlkeri feed on the young capsules, the fruits and seeds, causing (capsules abortion and fall off [3]. There is a large reductant notably Phonoctonus lutescens Guérin de Meneville and Percheron, which live in the same environment as D. voëlkeri with similar physiognomy [4]. P. lutescens is a predator of D. voëlkeri, of the reduviidae family, which feeds preferentially on D. voëlkeri [5], which contributes to a decrease in the level of D. voëlkeri outbreaks in the field. Control measures of D. voëlkeri are dependent on chemicals, which are the most widely used in crop pest control [6]. In Burkina Faso, the chemical insecticides used in conventional cotton are organophosphates, pyrethroids, carbamates, oxadiazines and neonicotinoids. Synthetic pesticides are more dangerous than plant extracts [7], although some plant extracts such as nicotine can be toxic at certain doses to living organisms [8]. In addition to chemical control methods in conventional cotton cultivation, there is the use of biological control methods with the use of organic pesticides [9]. In addition to the use of organic compounds, there is also agronomic control, which focuses on fractioned harvesting and consists of harvesting the cotton in a staggered manner in order to prevent D. voëlkeri attacks [10]. Organic pesticides used are important in organic cotton production for integrated insect pest management in cotton ecosystem. As stated by Regnault (2007) [11], the use of organic pesticides spares and maintains natural enemies in the fields. In contrast, chemical control in ad- Agricultural Sciences dition to its dangerousness and prohibitive price, is harmful to human and animal health and the environment [12]. Several authors [13] [14] [15] [16], have shown in the laboratory and in a semi-real environment, the real insecticidal potential of organic compounds, including neem oil Azadirachta indica A. Juss neem oil, Bacillus thuringiensis (Bt), Capsicum frutescens L pepper and soap in the control of crop pests, particularly A. gossypii, D. voëlkeri, J. fascialis and B. tabaci. But beneficial insects including P. lutescens that are not targeted by insecticide and/or biological pesticide applications should maintain their populations at acceptable levels in the field. As a consequence, this study aim to evaluate the effectiveness of the protection program in organic and conventional crops on sucking biting insects: Jacobiella fascialis (jassid), A. gossypii (aphid) and B. tabaci (whitefly) and particularly D.voëlkeri on cotton, and to assess the maintenance of populations of beneficial insects including P. lutescens.

 Sites
This study was conducted in three sites. The first site was the Farako bâ research station (SOFITEX) located in the southern Sudanese zone between 04˚20' West and 11˚06' North. The second site was located in Kombissiri (FASO  The larva and adults of biting and sucking insects bite the secondary leaf veins and/or fruiting organs during formation or maturation. Heavy attacks by these biting and sucking insects are likely to stop plant development or the fall of the reproductive organs [17]. At the same time, a high presence of beneficial insects helps to limit pest attacks.

 Experimental design
The methodology presented was inspired by the work of Gnankiné (2005) [18]. The design used were a paired plot with an untreated control. The design were a 2000 m 2 couple trial subdivided into 3 subplots of 640 m 2 .
1) The first sub-plot were a conventional cotton field treated in accordance with the phytosanitary program in conventional cotton cultivation in Burkina Faso; 2) The second sub-plot, a field of organic cotton treated in accordance with the phytosanitary program for organic cotton in Burkina Faso; 3) The third sub-plot, a control that has not received any treatment. used in the study are integrated in the window approach, and could be considered as a grouping of two insecticide treatments with the same insecticide to overcome insect resistance in the field. The insecticide treatments were carried out using products validated by Cotton Research and approved by the Sahelian Pesticides Committee (CSP). Those used in the study are concentrated emulsions (CE) and applied according to the plant protection window approach. In conventional cotton cultivation, Indoxacarb 150 g/l is used in first window from treatment 1 to treatment 2 (T1 to T2). In the second window we used Lambdacyhalothrin-Profenofos 12 g/l -200 g/ha from treatement 3 to treatement 4 (T3 to T4). For the third window Lambdacyhalothrin Acetamiprid 15 g/l -16 g/ha is used from treatement 5 to treatement 6 (T5 to T6). In organic cotton cultivation, Neem oil + Pepper + liquid soap from is used from treatment 1 to treatment 4 (T1 to T4). From T5 to T8, Bacillus thuringiensis 80 WG were used. The insecticides come from SOFITEX, one of the three cotton companies in Burkina Faso. The neem oil comes from Biotrade Burkina and is concentrated at 1%. Bacillus thuringiens comes from the Société africaine de produits phytosanitaires et d'insecticides (Saphyto). The chilli is obtained from the vegetable garden. It is harvested fresh and dried in the shade before being crushed to obtain the powder. Table 1 summarises the type of cotton cultivation, the active ingredients used by type of cotton cultivation. It also indicates the rates and the frequency of use in conventional and organic cotton cultivation.  Rainfall The data was obtained from daily rainfall records taken from January to November 2019 from rain gauges installed at Farako bâ, Kombissiri and Fada in the experimental sites ( Figure 2). The choice of daily rainfall records is justified by the fact that they include the vegetative periods likely to shelter the populations of harmful and useful insects on the cotton tree. Thus, the cumulative annual rainfall recorded at Farako bâ is 1316 mm, 653 mm at Kombissiri and 469 mm at Kouaré. Heavy rainfall was recorded in May, June and July with respective heights of 87 mm in Kombissiri, 413.5 mm in Farako bâ and 104.5 mm in Fada. Thus, heavy rainfall was observed during June. During this month the rainfall

Insect Pests on Both Types of Cotton Crops
 Farako Bâ Analysis of the data on sucking pest infestations by type of cotton production in Farako Bâ indicated a significant difference between treatments ( Table 2).
Whitefly adult infestations were lower in conventional cotton with 0.42 ± 1.10 than in organic and untreated cotton at Farako Bâ. Jacobiella fascialis were more important with 0.75 ± 1.66 on organic cotton than on conventional and untreated cotton. Infestations were significantly lower with 0.01 ± 0.08 plant for aphids and significantly higher with 0.3 ± 1.76 individual for D.voëlkeri in conventional cotton than in organic and untreated cotton.  Kombissiri Analysis of the sucking insects infestation data by type of cotton production at the Kombissiri site indicated a significant difference between treatments (Table   3). Only the level of D. voëlkeri infestations was significantly lower on the untreated plot with 0.250 ± 1.38 than on the conventional and organic cotton plot.  Fada Analysis of the data on sucking pest infestation by type of cotton production at the Fada site indicated a significant difference between treatments ( Table 4).
The levels of Whitefly larva and A. gossypii infestations on the organic cotton plot and those of A. gossypii on the untreated plot were significantly higher than on the conventional cotton.

 Farako Bâ
There was high significance differences between treatments for the presence of beneficial insects in Farako bâ ( Table 5). The presence of adult ladybirds was significantly higher with 0.02 ± 0.1 for organic cotton and 0.01 ± 0.1 for untreated cotton than on conventional cotton. Religious mantises, P. lutescens, spiders and ants population were significantly higher on organic cotton than on conventional and untreated cotton. Both organic and untreated cotton had significantly higher number of spiders than conventional cotton.  Kombissiri The level of beneficial insects was significantly different between treatments at Kombissiri ( Table 6). The level of ladybird adult was higher on the organic cotton plot with 0.021 ± 0.20 individuals than on the conventional and untreated cotton which recorded 0.013 ± 0.16 and 0.01 ± 0.13 respectively. Spider populations were significantly lower with 0.002 ± 0.04 individuals in untreated cotton than in conventional and organic cotton with 0.004 ± 0.08 and 0.005 ± 0.07 respectively. Organic cotton plot registered significantly higher P. lutescens populations with 0.026 ± 0.15 individuals as compared to conventional cotton with 0.022 ± 0.15 and 0.018 ± 0.13 for untreated cotton.  Fada The level of beneficial insects in Fada varied according to the types of cotton production ( Table 7). Adult of ladybirds were more present on untreated cotton with 0.02 ± 0.16 individuals than on conventional and organic cotton. Significantly higher spiders were observed on organic cotton with 0.04 ± 0.21 individuals than on conventional and untreated cotton. Ants were significantly more present on organic and untreated cotton than on conventional cotton.  Yield performance per location The observed seed cotton yields are summarized in Figure 3. The highest yields were 763.54 kg•ha −1 in untreated plots at Farako-bâ, 853.13 kg•ha −1 in plots treated with organic pesticides at Farako-bâ and 946.88 kg•ha −1 on conventional plots with chemical insecticides at Kombissiri. A significant difference was observed between treatments at Kombissiri. In this site, the organic cotton plots obtained higher yield (89.59 kg•ha −1 ) than the untreated plot. On the other hand, plots treated with chemical insecticides produced more (93.75 kg•ha −1 ) than the organic cotton plots.

Discussion
The study on the influence of cotton crop types on P. lutescens populations showed that low levels of sucking bugs could be achieved in conventional cotton and acceptable levels of beneficial insects in organic cotton. The pest control program in conventional cotton used synthetic chemical insecticides at all three sites and resulted in lower infestations of Bemisia tabaci, jassids, D. voëlkeri and aphids. In the recommended cotton protection program, it was use Indoxacarb 25 g/ha, Lambdacyhalothrin-Profenofos 12 -200 g/ha and Lambdacyhalothrin Acetamiprid 15 -16 g/ha. However, it is noted that Lambdacyhalothrin Acetamiprid 15 -16 g/ha which is a pyrethroid is more widely used against a wide range of pests [22]. Thus the good control of adults of Bemisia tabaci, Aphis gossypii, Jacobiella fascialis and D. voëlkeri in conventional cotton plots points to the mode of action of the Lambdacyhalothrin-acetamiprid combination which acts by contact and ingestion. It penetrates the insect cuticle to disrupt nerve conduction within minutes. This result is in agreement with those of [23] and [24] who showed that contamination of a pest with the combination of Lambdacyhalothrin-acetamiprid disrupts nerve conduction within minutes, leading to cessation of feeding, loss of muscle control, paralysis and eventual death. According to Acta (2015) [25], the combination Lambdacyhalothrin-Acetamiprid is effective in reducing cotton pest infestations by keeping them at low densities.  This good control of jassids could be explained by the synergistic effect created by the mixture [30]. Azadirachtin and its derivatives in neem seeds are obtained from crushed neem seeds [31]. They have been the subject of several studies.
Some of these studies have shown that neem seed compounds contain a high amount of azadirachtin, which is a compound that regulates the dynamics of insect pests of crops and stocks, but also of insect vectors [32] [33] [34] [35] [36].
The effectiveness of neem seed juice in reducing the number of jassids was reported by [37] who showed that this substance reduced the damage of sap-and ponins and flavonoids contained in the fruits of this botanical species [6]. Concerning beneficial insects, they are represented by ladybirds, spiders, ants, praying mantises and notably P. lutescens. In general, these beneficial insects were more present in the organic cotton plot than in the conventional cotton plot and the untreated plot. The use of Lambdacyhalothrin, which is a pyrethroid, must have limited the activity of beneficial insects. This result seems to confirm that of [41] who reported that pyrethroid insecticides could significantly affect the natural enemies (Pharoscymnus ovoideus, P. numidicus and Cybocephalus palmarum) of Parlatoria blanchardi in palm groves. Adult ladybird presence levels were higher on the organic cotton plot than on the conventional cotton. Conventional cotton when treated with commonly used insecticides belonging to the pyrethroid family may limit ladybird activity. This result corroborates that of [42] who reported on the toxicity of commonly used pyrethroids on sweet corn and soybeans that this family was harmful to the Asian ladybird beetle. As for the presence of natural enemies, the observed densities were low, however they were higher in the organic cotton crop than in the conventional cotton crop. The pest surveys show that, unlike the protection program recommended for conventional cultivation, the one recommended for organic production can be environmentally friendly. This result is in line with that of [43] [45] who showed the ability of Azadirachta indica extracts for its contribution in increasing the yield obtained on treated okra plots. Similar results on yield increase were obtained by [46] who showed that plots treated with Azadirachta indica leaf extracts gave the best marketable cabbage yields. Compared to the three study sites, infestations were almost below the threshold in both the northern and southern Sudanese zones, regardless of the species. The late arrival of rain in Fada, combined with insufficient rainfall at the end of the season, did not allow for a period of intense reproduction of sucking bugs. This result differs from that of [47] who observed that the end of the season is a period of intense reproduction of A. gossypii and B. tabaci, in preparation for migration to other crops. Furthermore, in humid areas, cotton plants enter their senescence phase late, which means that nutritive support is available for the sucking bugs, but the high rainfall would explain the low level of infestation of these sucking bugs, which could be washed away by rainwater or killed by runoff. The trials were planted at the same time on all three sites and did not show any influence of sowing dates on pest populations. This is different from some authors such as [48] [49], who stated that the presence of some pests is partly related to the phenology of the plant.

Conclusion
In this study the effectiveness of chemical protection as compared to protection provided by biopesticides in organic cotton cultivation. It was found that the conventional phytosanitary practice reduced B. tabaci (whiteflies), A. gossypii and D. voëlkeri. Infestations were lower in conventional cotton and natural enemy activity was high in organic cotton, while an acceptable cotton yield was achieved in the three experimental sites. Organic cotton protection should be promoted and strengthened in the farming environment against the main cotton pests. Producers need to be made more aware to enable them to optimize the use of these biopesticides on pests before damage occurs at the end of the cotton cycle. The results suggest P. lutescens is more adapted to integrated cotton pest management program. This could help to improve producers' income and consequently, reduce poverty among farmers in Burkina Faso.