Encyclopedia of pest orthoptera of the world

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Acanthacris ruficornis (Fabricius, 1787) (Acrididae) Christiaan Kooyman Green Pest Control Services, Nanyuki, Kenya; [email protected] Acanthacris ruficornis citrina (photo by M. Lecoq) OTHER COMMON NAMES Garden grasshopper (En), Parare-bustani (Swahili). IDENTIFICATION AND DIAGNOSIS Large species with two subspecies: A. r. ruficornis female 5-6.5 cm long; 世界直翅目害蟲百科全書2019-1_zw1.indd 3 2020/1/9 9:13:02 4 Encyclopedia of Pest Orthoptera of the World male 3.5-5 cm; A. r. citrina Female 7.5–9 cm long; Male 5.5–6.8 cm. The colour of the former subspecies is light brown with very dark brown spots on pronotum and tegmina, while the latter is very light brown to yellowish with lighter dark brown spots or hardly any. There is a tendency for individuals to be lighter coloured in drier areas and darker coloured in wetter areas. Nymphs are characteristically mottled darker and lighter green with white spots and lines on pronotum, legs and abdomen. Larger nymphs may be mottled brown. Adults of this species can be distinguished from the other Acanthacris species by the combination of brown to yellow and the deeper trilobate subgenital plate. DISTRIBUTION A. r. ruficornis occurs throughout sub-Saharan Africa from the West African forest zone south to South Africa and east to Saudi Arabia and Yemen. It also occurs on Madagascar and other Indian Ocean islands. A. r. citrina is restricted to the Sahelian and Sudanian vegetation belts from Senegal to Sudan and occurs in Morocco and Algeria as well. HOSTS Natural Hosts Feeds on a wide range of broad-leaved plants, often trees and bushes. Nothing is known about its preferences. Major Crop Hosts There are many reports of damage to crops, but in most cases, damage is minor, probably because the species is not usually known for high population densities. Where and when numbers are fairly high, damage to vegetables can be considerable. When high numbers coincide with the forming of new shoots by tree or vine crops, large numbers of shoots may be consumed, as has been reported, e.g., on grape vines in the Northern Cape Province of South Africa. Damage to coffee berries has also been reported. PLANT DAMAGE/ ECONOMIC IMPACT As mentioned above, damage can be significant when new shoots or berries are attacked. A considerable number of leaves can be damaged or even stripped, especially on fruit trees and vegetables. Though damage to crops can 世界直翅目害蟲百科全書2019-1_zw1.indd 4 2020/1/9 9:13:02 5 GARDEN LOCUST occasionally be severe, the pest status of A. ruficornis is relatively low. REPRODUCTIVE BIOLOGY In most places, A. ruficornis has only a single generation. Adults survive the dry season and lay eggs at the start of the rainy season, after which they die. Under unusual circumstances, e.g. in irrigation schemes, there may be several overlapping generations. Egg pods are 4–5 cm long and 1 cm wide, are often slightly curved and contain around 120 eggs that are each 6.5 mm × 1.5 mm. Every egg pod is covered with a froth plug of about 1.5 cm long that protects the eggs from drying out. However, the plug is not very strong in this species and is unlikely to provide much protection against predators. Each female lays up to three egg pods. Depending on the ambient temperatures, the egg stage may last 1–2 months, while hopper development takes from 2 to 4 months. Males go through 6 instars and females through 7 instars. MANAGEMENT Biological Control A product based on spores of the entomopathogenic fungus Metarhizium acridum (strain IMI 330189) is still available in several southern African countries and Madagascar, but not in the rest of Africa. However, a new product based on the strain EVCH077 is nearing registration in West Africa and will be rolled out across the rest of the continent. The spores are applied in an oil suspension. Since the product takes at least 10 days to kill large hoppers and adults (the most damaging stages), early intervention is required to minimise damage. Chemical Control Chemical insecticides are still used in most cases. Since most farmers do not closely monitor this pest species, “quick kill” is often required when infestations become manifest. The only other way to control these grasshoppers is manual removal of nymphs, which is feasible with small-scale infestations that are not too heavy. MAIN INFORMATION SOURCES COPR. 1982. The Locust and Grasshopper Agricultural Manual. Centre for 世界直翅目害蟲百科全書2019-1_zw1.indd 5 2020/1/9 9:13:02 6 Encyclopedia of Pest Orthoptera of the World Overseas Pest Research, London. Lecoq M., 1978. Biologie et dynamique d'un peuplement acridien de zone soudanienne en Afrique de l'Ouest (Orthoptera, Acrididae). Annls Soc. ent. Fr. (N.S.). 14: 603–681.

Encyclopedia of pest orthoptera of the world

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