INTRODUCTION

Clover, Trifolium alexandrinum L. is a crucial fodder crop belonging to Leguminosae, and suitable to be grown at moderate and semi - arid climates of Mediterranean areas. Clover is very popular among dairy people, particularly it is a high nutritional crop, with a surplus of yield throughout its growth stages.

Unfortunately, this important fodder crops are liable to attacks of several insect pests. AbdelFattahand EL-Saadany (1978) surveyed 64 arthropod

species, from clover fields, that were classified into Diptera (36%), Hymenoptera (27%), Coleoptera (18%) and Hemiptera (8%), as well as some other orders.Tawfik et al (1980) collected, from clover fields, 93 arthropod species, belonging to 5o families and seven orders. Wagan et al (2015) surveyed aphids, lead miners, thrips, whitefly and cutworms, as harmful insects inhabiting this crop. Spodoptera littorahis, S. exigua and Aphis gossypii were surveyed from clover fields as harmful insect pests, while Coccinella undecimpunctata, Apis mellifera and Vespa orientahis were categorized as beneficial insects (Mohammad and Hafez 2023, at Kafr El- Sheikh region). Boraei et al (1993) surveyed the insect pests inhabiting clover fields, and indicated that one of important damaging insects is Hypera brunnipennis (Boheman). The latter insect pest was found present in clover fields allover the season, beginning from December up to May (Rakha 2008, and Awadalla et al 2014). H. brunnipennis was considered, by El- Husseini (2019), as a damaging insect pest to both Egyptian clover and alfalfa.

Because clover fields are rarely treated with pesticides, this gives a good opportunity to flourishing of natural enemies. On the other hand, the intensive growth of Egyptian clover and alfalfa serves as a good shelter to the natural enemies complex to manage the harmful insects particularly that both crops are used as fodder to animals.

The objectives of this investigation were to compare between clover and alfalfa as habitats for insect pests and as shelters for natural enemies. In addition, correlation coefficients were computed to find out the relationship between populations of some natural enemies and insect pests.

1. Cultural Practices

The present work was carried out at the experimental farm of Forage Research Department, Sakha Agricultural Research Station, for two successive seasons; 2020/2021 and 2021/2022. The Egyptian clover, Trifolium alexandrinum  L.(Helaly cultivar)  and  alfalfa,  Medicago sativa  L. .(Nubaria 1 cultivar) were sown  in areas of 2000 and 200 m², respectively. Both crops were sown in the last week of October in both seasons.

Normal cultural practices, as recommended by Egypt's Ministry of Agriculture, were followed throughout the season, without any pesticide applications.

2.     Insect Sampling

About one month after sowing, weekly insect samples were collected using 50 double strokes by the sweep net. The catch was introduced into 2- liter glass jars, and transferred to the laboratory for sorting and counting. Specimens of collected insects were sent to Survey and Classification Department, and Biological Control Department, Plant Protection Research Institute, Agricultural Research Center, Dokki,Cairo for identification.

3.   Meteorological Records

Records of meteorological factors were obtained from Sakha Meteorological Research Station to find out the effect of these factors on the populations of theconsidered insects.

1. 4.   Parasitism of Hypera brunnipennis

Parasitism of Hypera brunnipennis eggs was monitored through a lab- field experiment. Plastic pots, 30 cm diameter, and 30 cm depth filled with proper soil were confined in screen cages (45x45x60 cm). Egyptian clover plants, at the vegetative stage (bout 45 cm height), were pulled out from clover fields, and transplanted into the pots. Using the sweep net, adults of H. brunnipennis were collected from clover fields and released inside the cages onto clover plants, where H. brunnipennis adults lay their eggs. The following day, the pots were taken out from the cages and moved to the field and fixed among the clover plants to allow parasitoids lay their eggs (if any on H. brunnipennis eggs). Twenty-four hours later, clover plants, in the pots, were

examined, and the H. brunnipennis eggs were collected and incubated at the room temperature. These procedures were weekly practiced, beginning from December 1^st up to May 4^th in both seasons; 2020/2021 and 2021/2022. The incubated  eggs were monitored to record the number of emerging parasitoids, or H. brunnipennis hatching larvae. Thus, the parasitism percentage was  calculated.

RESUTS AND DISCUSSION

1. Insect Pest Species

The relative abundances of nine insect pest species are presented in Table (1) on Egyptian clover, Trifolium alexandrinum L. versus alfalfa, Medicago  sativa L. in 2020/2021 and 12021/2022 seasons. As averages of both seasons, Sitona lividipes and leafhoppers exhibited the highest relative abundance on Egyptian clover, with values of 57.15 and 19.14%, and on alfalfa with values of 30.92 and 34.65%, respectively. Aphids occupied the third rank of occurrence (12.40%) on Egyptian clover, but constituted a higher portion (25.25%) on alfalfa. The remaining five insect pest species were found in low relative abundance. However, the specific insect pest of clover, Hypera brunnipennis was collected in small portions; 5.16 and 4.83% on Egyptian clover and on alfalfa, respectively.

2.Insect Predator Species

Seventeen insect predator species were collected from each of Egyptian clover and alfalfa fields (Table 2). Orius spp were the most occurring in Egyptian clover and alfalfa fields, with relative abundances of

24.64 and 25.96%, respectively. Also, Coccinella undecimpunctata constituted considerable portions on both crops with values of 8.93 and 12.63%, respectively. Despite Oxytelus nitidulus was represented by 12.33% out of total catch of Egyptian clover, it represented only 2.80% in case of alfalfa. The situation was found reversed with Hippodamia convergens, H. tredecimpunctate and H. variegata which constituted only 3.20, 1.58 and 1.42% out of total predator populations in Egyptian clover compared to 13.20, 9.64 and 9.23% in alfalfa, respectively. In addition, Paederus alfierii was represented by 5.52 and 7.19% in Egyptian clover and alfalfa, respectively.

1. Parasition of Hypera brunnipennis eggs by Anaphes fusceipennis

Eggs of H. brunnipennis were almost free from parasitoids (Table 3) from December 1^st up to January 26^th, the parasitoid activity gradually increased to exhibit the first peak (33.33%) on February 16^th, and then relatively decreased, but later, the parasitoid demonstrated the highest peak (38.24%) on March 16^th. Then, the parasitism decreased and was completely absent from April 20^th till the end of the season.

Table (1): Relative abundance of insect pests attacking Egyptian clover and alfalfa at the experimental farm of Sakha Agricultural Research Station

Table (2): Relative abundance of insect predators associated with insect pests in Egyptian clover and  alfalfa at  the experimental farm of Sakha Agricultural Research Station

Table (3): Parasitism of eggs of Hypera brunnipennis inhabiting Egyptian clover fields by  Anaphes fuscipienis at the experimental farm of Sakha Agricultural Research Station

The parasitism status of H. brunnipennis eggs in 2021/ 2022 season (Table 3) was different  from that of the first season. The parasitoid was active throughout December up to January 12^th, with a parasitism ranging between

12.50 and 22.50%. Specimens of host eggs were free from parasitism from January 19^th up to February and then, the parasitoid recovered its activity, beginning from February 9^th (25.00%parasitism), and recorded the highest peak (27.50%) on February 16^th. Then, the parasitism gradually decreased to reach minimum (5.56%) on March 16^th. However, the monitoring revealed the absence of the parasitoid from March 23^rd. till the end of the season, on May 4^th. Seasonal averages of parasitism were 21.72 and 17.92% in the first and second seasons, respectively.

4.Population fluctuations of dominant  insect  pests and associated predators  in 2020/2021 season

4.1. Insect pests

Hypera brunnipennis had three peaks (Table 4) of insect adults with 32, 76 and 38 individuals/100 double strokes at Egyptian clover fields on January 18^th, March 18^th and on April 17^th, respectively. Only one peak of 72 adults was attained in alfafa fieldl on March 18^th. Total insect populations were 238 and112 adults/1500 double strokes in Egyptian clover and alfalfa, respectively.

Sitona lividipes adults were attained in two peaks of 480 and 644 adults/100 double strokes on March 18^th and April 17^th, respectively, with a total count of 2244 adults/1600 double strokes throughout the season compared to 1195 adults in case of alfalfa.

Nezara viridula nymphs and adults were collected in few numbers throughout  the season from both crops. However, the insect population was notably found during May and June, with totals of 92 and 124 nymphs and adults/1500 double strokes throughout the season on Egyptian clover and alfalfa, respectively.

Aphid nymphs and adults were more captured by the sweep net, from Egyptian clover on February 3^rd and 18^th, and on April 2^nd and 17^th. The same trend was found in alfalfa fields. Total seasonal counts revealed that alfalfa harbored more aphids than had Egyptian clover; with 892 and 498 nymphs and adults/1500 double strokes, respectively.

Leafhopper nymphs and adults mainly occurred on Egyptian clover on April 2^nd and 17^th and on June 2^nd with densities of 202, 184 and 232 Individuals/100 double strokes, respectively. On alfalfa, the major insect densities were captured on April 2^nd, May 3^rd and 18^th and June 2^nd, with 106, 150, 292 and 130 nymphs and adults, respectively. Total seasonal counts were 768 individuals on Egyptian clover compared to 912 individuals on alfalfa/1500 strokes, respectively (Table 4).

Table (4): Biweekly  numbers of the major insect  pests and associated  predators on Egyptian  clover and alfalfa at Sakha Agricultural Research Station, during 2020/2021 season

4.2. Insect Predators

Coccinellid larvae occurred intensively on both crops during the period from May 3^rd up to June 2^nd, with total populations, throughout the season, of

342 and 286 larvae/1500 double strokes on Egyptian clover and alfalfa, respectively.

Staphylinid larvae were collected in relatively high numbers, from Egyptian clover as well as from alfalfa during March, April and May. Total seasonal counts were higher (188 larvae /1500 double strokes) on Egyptian clover than on alfalfa (48 larvae) (Table4).

Chrysoperla cranea larvae were rarely collected throughout the season on both crops. The densities were relatively high on Egyptian clover by mid-April and early Jane; 14 and 10 larvae/100 double strokes, respectively. On alfalfa, high numbers were found on April 17^th and on May 3^rd, with densities of 54 and 26 larvae /100 double strokes, respectively. Thus, this chrysopid was more collected from alfalfa than from Egyptian clover.

Orius spp nymphs and adults were captured from Egyptian clover by the sweep net  mainly on June 2^nd (158) and on June 13^th (300), compared to 60 and 30 nymphs and adults/100 double strokes from alfalfa fields. Total counts were 490 and 130 nymphs and adults/1500 double strokes, from Egyptian clover and alfalfa, respectively.

5.Population fluctuations of dominant  insect  pests and associated predators  in 2020/2021 season

5.1. Insect pests

Hypera brunnipennis adults

Adults of H. brunnipennis appeared in Egyptian clover fields in three peaks; 24, 18 and 12 individuals/100 double strokes on January 5^th, February 18^th and on May 3^rd, respectively with a total number of 128 adults/1500 double strokes, throughout the season. In alfalfa fields, two peaks were attained; with 26 and 18 adults /100 double strokes on January 20^th and April 2^nd, with a total of 134 adults/1500 double strokes throughout the season.

Table (5): Biweekly numbers of the major insect pests and associated predators on Egyptian clover and alfalfa on at kafr El-Sheikh Region, during 2021/2022 season

Sitona lividipes

Adults of S. lividipes were collected from the Egyptian clover fields by the sweepnet in three peaks; 480, 78 and 200 individuals/100 double strokes on December 8^rth, March 3^rd and May 3^rd, respectively. In alfalfa fields, also, three peaks were found with 82, 68 and 56 adults/100 double strokes on December 22^nd, March 3^rd and May 18^th, respectively. The total catch, throughout the season, was too much less (539 adults/1500 strokes) than that of Egyptian clover fields (1728).

Nezara viridula nymphs and adults

In general, the population densities of N. viridula nymphs and adults were quite low throughout  2021/2022  season. In case of Egyptian clover, the insect  was only collected late in the season, ranging between 34 and 148  nymphs and adults/100 double strokes, during the period from May 18^th to June 13^th with a total of 222 individuals/1500 double strokes. In alfalfa fields, very few numbers were collected with 36 nymphs and adults/1500 double strokes throughout the season.

Aphid nymphs and adults

In the Egyptian clover, nymphs and adults of aphids constituted two peaks of occurrence; 154 and 186 individuals/100 double strokes on April 2^nd and April17^th, respectively. In alfalfa, also, two peaks were attained with 30 and 136 nymphs and adults on February 18^th and April 17^th, respectively. Over the whole season, 366 and 496 nymphs and adults were collected/ 1500 double strokes from Egyptian clover and alfalfa, respectively.

leafhopper nymphs and adults

In Egyptian  clover  fields, leafhoppers exhibited two peaks of occurrence with 110 and 264 nymphs and adults/100 double strokes on March 3^rd and April 17^th, respectively. However, three peaks were recorded in alfalfa fields with 472, 44 and 66 nymphs and adults/100 double strokes on February 3^rd, April 2^nd and May 3^rd, respectively. Total numbers, over the season, were 566 and 888 nymphs and adults/1500 double strokes in the Egyptian clover and alfalfa fields, respectively.

5.2. Insect predators

Coccinella  undecimpunctata  adults

Adults of C. undecimpunctata were mainly collected from Egyptian clover fields late in the season, by April 17^th up to June 13^th, ranging between 24 and 114 adults/100 double strokes. This predator appeared in similar numbers in alfalfa fields, with a range of 18-126 adults/100 double strokes. Over the whole period of the season, the predator populations were 262 and 252 adults/1500 double strokes in the Egyptian clover and alfalfa fields, respectively.

Staphylinid larvae

Staphylinid larvae appeared in the Egyptian clover fields with very low numbers exhibiting two small peaks on March 18^th and May 3^rd with 22 and 16 larvae/100 double strokes, respectively. The corresponding peaks in alfalfa fields were 10 and 18larvae/100 double strokes on March 3^rd and January 13^th, respectively. The total numbers for the whole season were 84 and 52 larvae/ 1500 double strokes in clover and alfalfa fields, respectively.

Chrysoperla  carnea   larvae

This predator was rarely detected with only two and four larvae, from clover and alfalfa, respectively for the whole experimental period.

Orius spp nymphs and adults

This  predator  was only collected  in May from clover  fields (102 individuals / 1500 double strokes), compared to 106 individuals/100 double strokes in alfalfa fields, where it exhibited two moderate peaks by mid-May and mid- June.

6.  Correlation coefficient values

6.1.  In clover fields

Data  presented  in Table (6) show that numbers of H. brunnipennisadults correlated  insignificantly with  each of coccinellids and Orius spp in both seasons of study. The same result was found between numbers of aphids and the two abovementioned  predators.  Sitona lividipes adults exhibited significant correlations with each of staphylinids and Chrysoperla carnes in the first season (2020/2021), and the same result was calculated between both predators and numbers of

aphids. In the second season (2021 /2022), nymphs and adults of leafhoppers correlated insignificantly with each of coccinellids and Orius spp.

6.2.  In  alfalfa  fields.

Hypera brunnipennis correlated signicantly with staphylinid population in (2020/2021) season, but correlations between S. lividipes and all considered predators were not significant, with positive values, except  staphylinids in 2021/2022  season.  Aphids had highly significant positive correlation  with Chrysoperla  carnea in the first season.  As for leafhoppers, the correlations were  highly significant  positive with coccinellids, and  significant  positive with Orius spp, both in the first season.

Table (6): Correlations between certain insect pests and associated predators in clover fields, at Sakha Agricultural Research Station.

Table (7): Correlations  between  certain insect  pests  and  associated predators  in alfalfa  fields, at  Sakha  Agricultural  Research Station.

Data in Table (8) show the correlations between weather factors and insect pests and their associated predators in clover fields. In the second season (2021/2022), there were significant positive correlations between maximum temperature and  populations of each of H. brunnipennis, coccinellids and Orius  spp. Minimum temperature correlated in the second season with significant positive values with coccinellids and Orius spp. However, maximum relative humidity exhibited negative correlations with the majority of insects and predators.

Table (8): Correlations between weather factors and populations of insect  pests and their associated  predators in clover fields, at Sakha Agricultural Research Station

7.Comparison between Egyptian clover and alfalfa as hosts for insects and predators

7.1.  predators in 2020/2021 season

Data in Table (9) show the difference between Egyptian clover and alfalfa as habitats for some insect pests and their associated predators in 2020/2021 season. Populations of H. brunnipennis, S. lividipes and Nezara viridula were

collected in significant  higher values in Egyptian clover than in alfalfa fields. The remaining insect pests and all considered predators did not differ significantly  between the two habitats in 2020/2021 season.

Date in Table 10) show that  populations  of S. lividipes  and  coccinellids, were  significantly higher in clover fields, than in alfalfa ones. The remaining insects  and  associated  predators exhibited no significant differences between the two  habitats.

Table (9): Values of "t" test for comparing the population  of insects and associated  predators between Egyptian clover and alfalfa at Sakha Agricultural  Research Station, 20201/ 2021 Season.

Table (10): Values of "t" test for comparing the population, of insect and associated predators between Egyptian clover and alfalfa, Sakha Agricultural Research Station, 20201/ 2022 Season.

In the current study, nine insect pest species were surveyed from both Egyptian clover and alfalfa. Only two species; Hypera brunnipennis and Sitona lividipes could be reported as specific to clover and alfalfa hosts. El. Kifl et al (1974) indicated that Sitona lividipes life cycle was affected by leguminous host plant as well as the soil type. In our study, S. lividipes constituted 57.54 and 30.92% out of the total population of surveyed insect pests from Egyptian clover and alfalfa, respectively. El-Dessouki and Al- Awady (1978) reported only one peak of S. lividipes per year on Egyptian Clover.The insect population in our study was very high in December and early May.

Hypera brunnipennis exhibited, in the current investigation, relatively higher  population  densities in late March up to early May. El-Mezyyen (2003) encountered two peaks for H. brunnipennis in Egypt (in January and April) and in Libya (in March and May). In a biology study on H. brunnipennis, Awadalla et  al  (214) concluded that the life cycle of the pest was shorter when reared on clover, but longer when reared on Kidney bean.

In the current investigation, we surveyed, in addition to H. brunnipennis and S. lividipes, Nezara viridula, aphids, leafhoppers, Autographa spp, Spodoptera littoralis, S. exigua and Euprepucnemis plorans. Similar results were obtained by Wagan et al (2015), in China, who recorded aphids, leafminers, thrips, whiteflies and cutworm as insect pests inhabiting Egyptian clover. In the same context, Mabrouk and Mahbob (2017) surveyed 46 arthropod species from clover and faba bean fields, at Dakhla Oasis, classified into 33 families and nine orders. These species included insect pests, natural enemies and pollinators.

Despite H. brunnipennis constituted 4.83-5.16% out of total insect pests recorded in our study, El-Sheikh (2019) indicated that this insect pest was a very important pest at El-Farafra Oasis, New valley.

It is important to understand the role of natural enemies in keeping the natural balance in the agricultural ecosystem (El-Husseini et al 2018). In this investigation, we recorded 17 insect predatory species inhabiting both Egyptian clover and alfalfa fields. Summers et al (1981) found large aestivated aggregations of H. brunnipennis inhabiting the same shelters of the insect predators; Hippodamia Convergens Guerin and Coccinella spp which means