Bruchid species are important storage pests, causing serious storage losses among smallholder farmers. In the absence of any control measures, farmers indicated that more than 50% of their stored beans could be lost by bruchids. Lack of control of insect populations can lead to important economic and environmental losses [1]. There is increasing emphasis on diversifying and intensifying legume production in the developing countries as a useful option towards improving protein intake in the human diet and augmenting food supplies [2]. Every country is making concerted efforts to augment its agricultural production to meet the demand of an ever-increasing population. Loss of 13 million tons due to insects alone and a total of 100 million tons due to improper storage were encountered during the last few years [3]. Pulses ranked second after cereal crops, nicely complementing them, in feeding the people in the developing world. Leguminaceae include approximately 600 genera, with about 1300 species, out of which only about10-12 are of economic importance [4]. Pulse species, besides groundnuts and soybeans, that are of major importance include members of the genera, Vigna, Phaseolus, Cajanus, Cicer, Pisium, Vicia, Lens and Dolichos. These legumes are considered to be an important source of protein to most people in the tropics. Legumes are symbionts of nitrogen-fixing bacteria that form root nodules and indirectly increase the level of soil nitrogen. Hence, they are important components of any balanced crop rotation, particularly in the traditional agricultural sector. Also, they provide much-needed Vitamins, minerals, and fiber to humans. Some genera of legumes are, also, sources of drugs, and gum E.g Acacia. Legumes are the meat substitute for the poor, in the third world and the medicine for the over-carnivorous in the first and second world [5].

The country’s forest covers about 67 million hectares or approximately 28 percent of total land cover. The savanna zones suffer from large-scale tree clearance, repeated floods during the rainy seasons, erosion, seasonal fires, and sometimes conflict between nomadic herders and farmers. Little information is available about insects and disease impact on forests in Sudan. One report, however, estimated that 102874 km² of forested areas in four states-Darfur, Kordofan, Eastern and Central were affected by insect pest and disease [6]. Seeds affected in this way will germinate very badly or not at all. Species of the genus Callosobruchus and Caryedon are very damaging pests of stored and forest leguminous seeds in Kordofan areas. Data on the extent of infestation, damage, loss, and control under different storage conditions are rather scanty. No information is, however, available on the field status of these pests, especially on leguminous cropsin terms of percentage pod/seed infestation, quantitative losses, its carryover to stores and the effect on seed germination. This study attempts to analyze these aspects of bruchid beetles’ infestation on leguminous crops, in terms of distribution all over Kordofan state as well as the performance of some species of bruchids on legume seeds. This study aimed to assess loss and damage in some forest tree species seeds due to infestation of C.chinensis and to list the group of insects in the family Bruchidae in different sites of study areas that is associated with forest tree seeds. It also aimed to produce a structure map for the relative distribution of the species in Kordofan.

2. MATERIALS AND METHODS

2.1 Research sites

South Kordofan site was represented by, Talodi, (10 38N°), Kadugli (11 00N°), Lagawa (11 24N°), Abu-Gubeiha (11 27N°) and Elfolla (11 42N°). The Middle Kordofan site was represented by Gibeish, (12 08N°) and Um Ruwaba (12 53N°). North Kordofan site was represented by Bara, (13 41N°) and Sodary, (14 24N°). The average rainfall of Talodi, Kadugli, Lagawa, Abu Gubeiha and Elfolla were 792.4, 764, 631.2, 675.8, and 479.3 mm/annum, respectively. The rainfall of Gibeish and Um Ruwaba were 352 and 298, respectively.  While the rainfall of Bara and Sodary was 270, and 39 mm/annum, respectively (Table 3.1).

2.2 Field work and survey

A survey for insects associated with legume seeds in the three sites was carried out during February to June 2009. For each site legume seeds were collected. The source for the seeds were trees, the local market, and / or local stores. Seeds were kept in cloth bag (25 ×30 cm) and transferred to the laboratory. At the laboratory, bruchid insects were separated and preserved in Alcohol /Glycerol mixture (9:1). Insects were identified at the insect museum, ARC, Wad-Medani, Sudan. The findings, were expressed in a structural map and key for the separation of the encountered bruchid species.

2.3 Laboratory work

2.3.1 Preparation of the stock cultures

The study was carried out in the laboratory of Crop Protection, Faculty of Natural Resources and Environmental Studies, University of Kordofan. The mean temperature and relative humidity were 32.5± 2.5 C° and 37.5± 2.5%, respectively. The cowpea beetles Callosobruchus chinensis and Callosobruchus maculatus were collected from a chickpea lot obtained from Elobeid local market during the season 2008/2009. The variety “black eyed cowpea” was used as a media for rearing C. chinensis and C. maculatus. Seeds were purified manually to get rid of impurities, shriveled, damaged and broken seeds, and the sound seeds were kept in an oven set at 60 C° for ten minutes to disinfest them and then stored at room temperature for seven days for reconditioning before being used to establish a new culture [7].  Seeds were placed in cloth bags (30×35 cm) and then inoculated with a number of adults, where several generations were produced. Cloth bags were periodically checked and fresh sterile cowpea seeds were added to serve more adults, and to avoid overcrowding and the development of moulds.

2.4 Assessment of loss and damage due to Callosobruchus chinensis 

2.4.1 Preparation of legumes 

Lots of 4 kg of different legumes of season 2008/2009 were manually purified to give sound seeds. Grains were put in an oven, set at 60C°for ten minutes to disinfest them. The lots were stored for seven days for reconditioning as stated above in 3.2.1. Then grains were put into lots of two hundred and fifty grams. Each lot was contained in a pot. The pots were disposable and used for soft drink. From each pot 100 seeds were weighed as a reference and then taken back to the same pot. The legumes included cowpea, pigeonpea, chickpea, hashab and mesquite.

2.4.2 Preparation of insects

A sample of grains from stock culture was taken. Adults’ insect was separated using a seive (3 mm size). The adult free lot was kept for 24 hrs. Then newly emerged adults (≤ 24 hours) were collected for experimentation, using an Aspirator.

2.5 Execution of the Experiments

Pots were inoculatedby 10, 15 or 20 pairs of newely emerged adults of C. chinensis. In addition, a control (insect free) was used. Each pot was covered with a piece of cloth which was tied with a rubber band. Treatments were replicated four times. The experiments were kept under laboratory condition for 16 weeks.

Temperature and relative humidity

Temperature and relative humitidy were recorded daily at afternoon time, using a digital multifunctual measuring device, (digital, hygro-thermometer) model Human Gmph, brand Human, made in Germany.

Quantitative data

As stated above, 100 seeds were taken from each pot, then weighed and put back to the same pot. This procedure was done every four weeks during the experimental period. The balance used was a sensitive balance. Model DHAUS, brand Adventure, made in China.

Qualitative data

Number of holes

The one hundred seeds, stated above, were checked for damageindicated by exit holes. The number of holes per 100 seeds were counted and recorded seeds were taken back to its original pot.

Germination test

At the end of the experiments (16 weeks) a germination test was executed. From each treatment, 4 petri dishes furnished with moist filter paper (9 cm) were prepared. Each petri dish was inoculated with 10 seeds and kept 3-10 days, depending on type of legume seeds. Then germination percentages were recorded.

2.6 Statistical analysis

The data were analyzed using, analysis of variance using the computer program MSTAT and Duncan’s multiple range tests was used for means separation.

3. RESULTS

3.1 Field survey

3.1.1 South Kordofan Latitude 10 38 – 11 42

Table (4.1b) shows infestation of bruchid on Acacia spp in different surveyede areas.  C. serratus was reported on seed of Hashab in all areas. But the insects were not found, except in Kadugli and Abu Gubeiha. C. serratus also, infested Sunut seed in all areas, but the insects were not found. Talh seed, was infested in all areas with C. serratus except in Lagawa. Kitr  seed were infested in all areas, except in Kadugli, and the insects were found in Abu Gubeiha. Kakamout seed was infested in all areas. Laot seeds were infested in Kadugli, Lagawa and Abu Gubeiha, but the insect were not found in other areas. Saljum seeds were infested in Kadugli and Elfolla, but insects were not found in all areas. Table (4.1c)Bruchid species associated with some trees species seeds in various locations in Southern part of the Kordofan region, shows the Tamarind seed was infested

with C. serratus  in all areas, and the adults were found in all areas, except in Kadugli. C.maculatus infested the seed of Kaddad in all areas, but the adults were not found except in Lagawa. Arad in Kadugli Babanous seed in Abu Gubeiha and Elfolla, were infested but the insects were not found. Kulkl seed in Talodi was infested by bruchid, but the insects were not found.  Goldmore seed in Kadugli, Abu Suruj and Gughan seed in Elfolla were not infested.

3.1.2 Middle Kordofan

C.chinensis and C.maculatus, were found associated with their host in all areas under survey of Middle Kordofan (Table 4.2a). The two insect species were reported on cowpea seed in Gibeish and Um Ruwaba. While C. serratus was reported on groundnut, in Gibeish. However, adults were not found in Um Ruwaba. C.chinensis and C.maculatus, also, were also reported on chickpea seed in all areas. Broad bean seed was infested with bruchid in all areas, but the insects were not found. C. chinensis and C. maculatus, were also reported on Pigeonpea seed in Gibeish. However, adults were not found in Um Ruwaba. Phaseolus seeds were infested in Gibeish and it was insect-free in Um Ruwaba. However, adults were not found in Gibeish.  C. serratus was reported on seed of Hashab in all areas (Table 4.2b.). But the insects were not found in Um Ruwaba. C. serratus also infested Sunut seed in all areas, but the insects were not found in Gibeish. Dign elbasha in Um Ruwaba, was infested with bruchid, but the insects were not found.  Kitr  seed were infested in all areas and the insects were found in Um Ruwaba.  Aradeib seed was infested in all areas, but the adults of C. serratus were found only in Gibeish. Haraz

3.1.3 North Kordofan

C.chinensis and C.maculatus, were found associated with their host in all areas under survey of North Kordofan (Table 4.3a). The two insects and their damage were reported on cowpea seed. While C. serratus was reported on groundnut in the Bara. C.chinensis and C.maculatus, were not reported on chickpea seed in the two areas. Broad bean seed was infested with bruchid in all areas, but the insects were not found. C.chinensis and C.maculatus also were reported on pigeonpea seed in Sodary. However, adults were not found in Bara. Phaseolus seed were insect-free. C. serratus. was reported on seed of Hashab in all areas (Table 4.3b.). But the insects were not found. C. serratus also infested Sunut seed in a ll areas, but the insects were not found in Bara. Bruchus baudoni was found to be associated with it in Sodary. Seyal seeds in Sodary were infested, but insects were not found. Kitr  seed in Sodary were infested with C.serratus, but the insects were not found in Bara. Aradeib seeds were infested in all areas, but the insects were not found in Sodary. Laot seeds, were infested in Sodary, but the insects were not found. Haraz seeds were infested in all areas, but the insects were not found.

Insect identification

The bruchid species were found associated with their host in all areas under survey. It revealed an extremely high infestation.Figure (4.1) showed the distribution of some bruchid species in the Kordofan region, which as was follows:

1. Callosobruchus chinensis (L.).

2.  Callosobruchus   maculatus (Fabricius).

3.  Caryedon serratus (Olivier).

4. Bruchus baudoni (Caild).

3.2 Laboratory work

3.2.1 Loss in weight/100 seeds of Hashab and Mesquite due to infestation by C. chinensis

3.2.1.1Loss in weight/100 seeds of Hashab (in grams)

Table (4.7) showed that there was no significant difference (P=0.05) in the weight of seeds among different treatments in the first count, after 4 weeks and in the subsequent counts, until the end of the experimental period, 16 weeks. The mean percentage total weight loss was 0.0%. Hashab showed no significant difference in infestation at different level of infestation and at different time of infestation.

3.2.1.2 Loss in weight /100 seeds of Mesquite (in grams)

The results obtained indicated that there was no significant difference in weight among different treatments in the all counts, at 4 weeks intervals for a period of 16 weeks. The mean percentage of total weight loss was 0.0%.

3.3 Qualitative data

3.3.1 Number of holes/100 seeds of Hashab

Table (4.11) showed that there were no significant differences (P=0.05) in number of holes among different level of infestation especially at the end of the experment, starting (after 4 weeks) and in the subsequent counts, until the end of the expermintal period (16 weeks). There were no significant differences in number of holes at different lenghth of time in all levels of infestation and number of holes increased when more time was given to infestation. The subsequent counts, until the end of the experimental period (16 weeks). Also, no increase in infestation was reported on Hashab with time.

3.3.2 Number of holes/100 seeds of Mesquite

The results obtained indicated that there was no hole in the different  

treatments starting from the first count (after 4 weeks) until the end

of theexpermintal period (16 weeks).

3.3.3 Germination test

 showed the mean germination percentage Hashab seeds. When treated with different level of C. chinensis. It was 60% in the untreated control.

DISCUSSION

4.1 Field surveys

Hashab, Sunut, Taleh, Kitr  Kakamout, Laot, Saljam, Seyal, Tamarindus, Kaddad, Arad, Haraz, Babanouse, Dign elbasha, and Kulkul were infested with bruchids (whereas prevailed). These results were in line with other studies on Acacia senegal and Albizia lebbek [8,9]. Tamarind pods as a main host for the bruchid and it develops more quickly when bred on its pods than on unshelled groundnuts [10]. He further added that C. serratus does not breed on cotton seeds or cowpeas. The other report include: several species of wild tree legumes, four species of Acacia, four species of Bauhinia, three spp of Cassia, Piliostigma spp, and Tamarindus indica [11, 9].The most suitable host for multiplication of C. serratus was found to be Tamarind, followed by groundnut [12].

The infestation of Mesquite seed with C. serratus began when the pod began to ripen and continued until seeds matured. A similar view was also expressed [13] who reported that Caryedon longuidus larvae fed on P. cineraria seed.  While Goldmore, Abusruj and Gughan seeds were found to be incapable to infestation by any Bruchid, this is solely due to:

(i) Antibiosis: The presence of compounds that inhibit oviposition and the development of insects [14].

(ii) Physical structure (1): seed testa made difficulties encountered by the hatching larvae and by the emerging adult in penetrating through the seed coat. This result was in line with [15] who reported that the thickness of the seed-coat seems to be only limiting factor significantly reducing infestation by C.chinensis during storage.(2): Tightness of the glumes in unmilled Rice [16, 17] which serve as a physical barrier working against penetration by insects. Hardness of seeds [18] was thought to make insect penetration more difficult thus, providing protection. (3) seed size [19] had also been shown to influence infestation by insect pests as large grain legumes provide more surface area for oviposition and larval development than small–sized grains; (4) the texture and hairiness of the coats of Cowpea seed; may have negative influence on the oviposition of the Cowpea weevil [20]. (5): the quantity and quality of nutritional constituents have been described to have an influence on the fecundity of the females, the developmental period of the pre-imaginal instars and the rate of adult emergence [21].

4.2 Laboratory work

4.2.1 Loss in weight/100 seeds of Hashab and Mesquite due to infestation of C.chinensis (in grams)  

In Hashab and Mesquite, there was no significant difference (P=0.05) in weight of seeds among different treatments in the first count. This was probably due to the time needed by C.chinensis to develop. At the beginning, the population size was slow and by the time it progressed so rapidly. It is worth to mention that Lack of control of insect populations can lead to important economic and environmental losses [1]. Hashab seed showed very low susceptibility, and Mesquite seed showed resistance to this beetle for developing in the laboratory. There were no significant differences in the weight among different treatments in the first count and in the subsequent counts. This probably may be due Hashab and Mesquite seeds are not preferred to C. chinensis to develop. The mean percentage total weight loss in all treatments was 0.0%. But the eggs were laid on the seeds. A similar view was also expressed [18] who examined a large number of non-host leguminaceae and found that the hardness and chemistry of the seed coat may be important as a barrier to entry of C. maculatus. The inability of the insect to develop on Hashab and Mesquite seeds may be because their seed coat could not be penetrated by the larvae. Similar view was also expressed by [15] who claimed that the relative resistance of some varieties of Broad beans (Vicia faba) to C. chinensis, is solely due to difficulties encountered by hatching larvae and by the emerging adult in penetrating through the seed-coat. The thickness of the seed coat seems to be a limiting factor. Also, the testa may contain toxins and failure of the larvae to survive. The toxicity of the testa provides an effective barrier to protect the seed.

4.2.2 Qualitative data

4.2.2.1 Number of holes /100 seeds of Hashab and Mesquite due to infestation of C.chinensis 

The inability of the insect to develop on Hashab seed may be because their seed coat could not be penetrated by the larvae, or the test may be so thick that the newly hatched larva dies before it reaches cotyledon, or the cotyledon may be too hard to penetrate or poisonous. A similar view was also expressed [18]. The mean total numbers of holes/100 Mesquite seeds infested by C.chinensis in all treatments showed no variation, constituted zero holes/100 seeds, The inability of the insect to develop on Mesquite seed may be because as stated in 5.2.1.1.1.  The result indicates that the Mesquite seed were not host to C. chinensis in the laboratory.

4.2.2.2 Germination test

In Hashab seed, the treatments of 15, and 20 pairs gave the best result with 70%. The remaining treatments which had a germination percentage of 60 and 50%. This result indicated that the few holes made by bruchids increase absorption of water, and accelerate germination. High infestation by bruchid beetles could present a serious problem for seed germination.

CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions

  The results of this study showed that the loss and damage in Hashab due to the infestation of C. chinensis was significant. C.chinensis, C.maculatus, B. boudoni and C.serratus were found in different sites of the Kordofan region, in forest and legumes.

5.2 Recommendation

This study recommended significant care toward these pests due to their economic effect with regards to hashab trees and other forest tree species.

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