The Economic Importance, Ecology and Integrated Management of the Variegated Grasshopper, Zonocerus variegatus (L.), (Orthoptera: Pyrgomorphidae

Abstract

The variegated grasshopper Zonocerus variegatus (L.) (orthoptera: pyrgomorphidae), which occurs in many wadis in Darfur region, has many local names but the most reputed one is " Gerad Elbawo". This study proved that, this type of grasshopper which is originated from West Africa came through the annual wadis and now spreading in Darfur wadis. The adult stage of the pest moved more distance than the nymphal instars (about 2.5 – 3.5 km/month) causing threat to crops. The species, according to this study, is expected to spread to Bahar-elarab and river Nile through the annual arrival of the valleys. The pest dispersal was increased from year to year by invading new areas helped in this by certain characteristics, i.e. different colors and unpleasant odor, which help it to hide from and repel its enemies in the field; the pest dose not fly and usually has long persistence in the sites. The density of the pest is high in the rainy season (June July) which often has a huge number of annual and perennial diverse food plants. This makes difficulties in the movement of the control teams, during this period. The study area is characterized by high rain fall and diverse plants ( field crops, gardens, weeds. forest and shrub trees), this offered suitable environment breeding and spreading of the pest. No efficient natural enemies found in the investigation except earwig as egg predators and Lizard, spiders, and army ants as predators for early stages of nymphs (1st -4th instars). The insect caused crop damage by defoliation, debarking and fruit feeding), this is reaching 80% in some cases especially in vegetables. The pest preferred plants for roosting (saaf, seida and seiseban) and not for feeding (okra, Kherwi and Aweer). The research identified that the pest has only one generation per year extended from march- April (hatching time) up to October – November (egg laying period). Eggs 5 are brown in color, elongated and found in egg pods with average length 15cm consisting about 100 eggs. The eggs hatching and the nymphs passed through five nymphal instars to reach adult which spend 1-2 months to mate and laying eggs and then die around egg laying sites. The study proved that Metarhizium + diesel suspension have high highly effect on the pest than others (diesel and diazinon), but the disadvantage of Metarhizium is delaying of the affection (4-11 days) not suitable in case of pest out breaks. Farmers in the studied area used diverse methods for controlling the pest like dusting of ache and fumigation by straws of crops, but the efficiency of these method were low. Some farmers use chemicals in a traditional way, but the results are always poor because of the misuse of chemicals. This study predict more spreading of the pest in Darfur and its borders because of certain criteria that deals with the pest like its long life in the field (8-9 months), it is polyphagus with wide host rang and less natural enemies. All these factors offered good condition for spreading. This study mitigated the proper method to control the pest by using an integrated pest management (IPM) e.g.; Agricultural methods like proper sowing date, suitable depth and time of plowing. Although using of Metarhizium as specific fungicide is recommended and using of chemicals in case of pest outbreak. By using IPM method in controlling of Z. variegatus the study attempted to improve crop protection techniques and to increase the financial capabilities of farmers through the reduction in purchasing pesticides and spraying equipments, also to minimize the environment pollution through the reduction in the use of chemicals