The Occurrence of Cereal Aphids in Rainfed Wheat in Kenya: The Problem and Possible Integrated Pest Management Strategies

Abstract

Cereal aphids cause direct damage to rainfed wheat through sucking of plants sap and cause losses of up to 90%, particularly in dry years in Kenya. The Russian wheat aphid (RWA) is the most destructive and may account for up to 50% yield loss or more depending on the severity and length of infestation. Current control strategies mainly rely on the use of insecticides to control cereal aphids' infestations. Chemicals improve yields in the short term, but adversely afect the environment, hence the need for development of efective IPM strategies. Early planted crops escape heavy aphid atacks and give good yields. A combination of seed rate of 100 kg and 100 kg N/ha provided the best cultural management of RWA. Ladybird beetles Adonia variegata, lacewings (Chrysoppa spp.) and parasitic wasp Aphidius sp. were the most important natural enemies. Control of cereal aphids can be achieved with systemic insecticides applied as seed dressings or foliar applied insecticides. Four lines of wheat were found to show RWA resistance and crosses with Kenyan wheat made and populations are being evaluated for resistance to cereal aphids.

Incidence and distribution of insect pests in rain-fed wheat in eastern Africa

“…The leaf rolling effect also allows other cereal aphids (M. dirhodum, R. maidis, and R. padi) to stay longer on the crop. In addition, leaf rolling of some wheat varieties, in response to drought conditions, provides shelter for some of the cereal aphids, thereby allowing them to stay longer on the crop (Macharia et al, 2002).…”

“…The seed dressing insecticides control the colonising migrant aphids, and prevents primary infestation. The foliar applied insecticides control the primary spread of cereal aphids ( (Macharia et al, 2002).…”

Past, Current and Future of Wheat Diseases in Kenya

“…Apart from fungal diseases, another disease that threatens wheat production in Kenya is the Barley Yellow Dwarf Virus (BYDV), which is an important virus disease of cereals globally and has a wide host range that includes wheat, barley, oats, triticale, and over 150 grass species [51]. The disease was first reported in Kenya in 1984 and causes serious damage in barley, wheat, and oats and estimated losses range from 16.5−54.7% [62,63]. Cereal aphids are vectors of the barley yellow dwarf and five strains have been known to occur in Kenya: RPV (Rhopalosiphumpadi), RMV (R. maidis), MAV (Sitobionavenae), SGV (Schizaphis graminum), and PAV (R. padi, S. avenae [63].…”

“…The disease was first reported in Kenya in 1984 and causes serious damage in barley, wheat, and oats and estimated losses range from 16.5−54.7% [62,63]. Cereal aphids are vectors of the barley yellow dwarf and five strains have been known to occur in Kenya: RPV (Rhopalosiphumpadi), RMV (R. maidis), MAV (Sitobionavenae), SGV (Schizaphis graminum), and PAV (R. padi, S. avenae [63]. Outbreaks are frequent, and management practices require use of seed dressing insecticides: Gaucho 350FS (Imidacloprid), Cruiser 350FS (Thiamethoxam), Redigo Deter 350FS (Clothianidin + prothioconazole), Celest Top 312FS (Thiamethoxam + fludioxonil +difenoconozole, and (ii) foliar-applied insecticides (Karate Zeon (Lambdacyhalothrin), Bulldock star 262.5EC (Betacyfluthrin + Chlorpyrifos), Thunder OD 145 (Imidacloprid + Betacyfluthrin), Keshet 2.5EC (Deltamethrin),Twigathoate 40EC (Dimethoate), Nurelle D 50/505 EC (Cypermethrin + Chlorpyrifos), Alphadime (Alphacypermethrin + Dimethoate), Cyclone 505EC (Cypermethrin + Chlorpyrifos), and Pirimor 50WG (Pirimicarb) [6,64,65].…”