**1. Introduction**

Grain cereals contribute significantly to food security in Kenya. Bread wheat (*Triticum aestivum* L.) is the second most important cereal crop in Kenya, after maize. It was grown on 147,210 ha producing 328,637 tons of grain with a yield of 2232 kg/ha [13]. However, there

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is still a gap between production and consumption of wheat in Kenya [44]. Increased popula‐ tion growth, urbanization and change in eating habits have led to increased wheat demand. The national demand is estimated at more than 990,000 tons per year while production is as low as 360,000 leading to importation to meet the difference [52]. It is mainly grown in Nakuru, Trans Mara, Uasin Gishu, Nyandarua, Narok, Meru Central, Trans Nzoia, Keiyo and Laikipia counties. The crop is grown in diverse agro‐ecological zones at altitudes ranging from 1500 to 2900 m.a.s.l. in areas with 700–1000 mm rain per year.

The country in its strategic plan is struggling to become self‐sufficient in wheat produc‐ tion either by increasing yields per unit area or by expanding the area under production in the marginal areas. This is possible when the gap between potential yield of wheat varieties (6–7 t/ha) and the actual yields (2.3 t/ha) realized by wheat growers in Kenya is filled. This gap is attributed to the lack of good quality seed, lack of appropriate technology and attack by diseases and pests, which have presented a continuous challenge to wheat productivity in Kenya. Cereal aphids are considered as one of most serious insect pests attacking rainfed wheat [8, 60]. Cereal aphid outbreaks are frequent in Kenya and are responsible for most of the control interventions on wheat. They are capable of completely devastating the crop by mak‐ ing it a total failure during years of severe infestation [59]. Aphids damage the cereals by direct feeding and transmitting barley yellow dwarf virus (BYDV) diseases, both causing losses in yield [22, 57]. Outbreaks of cereal aphids that are vectors of barley yellow dwarf are frequent in Kenya and often result in extensive use of insecticides [39, 58]. Their relative importance as pests/vectors varies considerably from one area with losses in the range of 1–100% [28]. Yield losses of 47% due to BYDV have been reported in wheat [57]. It is transmitted by cereal aphids in a persistent, circulative but nonpropagative manner. Five strains occur in Kenya and their principal vectors are RPV (*Rhopalosiphum padi*), RMV (*R. maidis*), MAV (*Sitobion avenae*), SGV (*Schizaphis graminum*) and PAV (*R. padi*, *S. avenae* and others) [25]. In the field, symptoms appear as yellow or red patches of stunted plants. In general, PAV causes severe symptoms, MAV moderately severe and RPV, RMV and SGV produce mild symptoms [16]. This chapter reports on cereal aphids affecting wheat in Kenya with emphasis on Russian wheat aphid *Diuraphis noxia*, their problem and possible integrated pest management strategies.
