**6. Chemical control of Russian wheat aphid and other cereal aphids**

All commercially available wheat varieties in Kenya are susceptible to Russian wheat aphid and other cereal aphids and chemical control of cereal aphids has been the only option for many growers [25]. Research has focused on screening for more effective insecticides, applica‐ tion methods and development of recommendations for wheat growers on economical control measures. Control of cereal aphids can be achieved with systemic insecticides applied as seed dressings or foliar spray and contact insecticides applied with aerial or ground equipment. The seed dressing insecticides controls the colonizing migrant aphids and prevents primary infestation. The foliar applied insecticides controls primary spread.

Control recommendations in Kenya include the use of systemic insecticides as shown in **Table 5** [33]. The rolling of leaves as a result of the feeding habit of RWA causes the leaves to roll around *D. noxia* aphid colonies thus protecting the aphids from being reached by the contact insecticides. A characteristic behavior of RWA is to feed and develop inside the rolled leaf whorl confining insecticide options to active ingredients with systemic action able to penetrate the rolled leaf [23]. Systemic insecticides presented in **Table 5** have proven to be effective against Russian wheat aphid and other cereal aphid species in rainfed wheat crops with resultant high grain yields [33].


**Table 5.** Recommended insecticides for control of cereal aphids in rainfed wheat in Kenya.

Seed dressing is an insurance against infestation by early seedling pests such as the Russian wheat aphid. The use of seed dressers ensures a better crop establishment, more uniform and healthier crops with increased yields and quality. Cereal aphids occurring during other growth stages of wheat are controlled using foliar applied insecticides (**Table 5**). Applications of Gaucho 350FS followed by applications of systemic foliar insecticides achieved very good control of the Russian wheat aphid [26, 29, 33]. Contact insecticides are not effective against Russian wheat aphid but they are effective against *R. maidis*, *S. graminum*, *Sitobion* spp., *M. dirhodum* and *R. padi*. Satisfactory control of RWA using foliar applied aphicides depends on early detection of infestation through periodic scouting. This approach will therefore offer a cheaper strategy for cereal aphid and BYD control. Farmers are advised to scout their fields weekly in order to make an accurate decision on whether or not treatment is required. It is important for wheat growers to know that not all insects are pests. One should know the insects, which are beneficial to mankind. Ladybird beetles, hoverflies, lacewings, spiders, dragonflies and praying mantis feed on other insects. Using insecticides indiscriminately can cause harm to the beneficial insects too. Farmers should monitor and consider beneficial insects when making control decisions and after treatment application, continue monitoring to assess pest populations and their control.

BYDV is a virus disease vectored by cereal aphids during feeding. The best control is of this disease is by use of resistant varieties. However, majority of the current wheat varieties are susceptible to the disease and control is by use of insecticides to control the cereal aphid vector. Seed dressings control early cereal aphids' infestations and later infestations are controlled by use of foliar applied insecticides. Seed treatment is a good insurance against infection by seed borne, soil borne and early seedling pests. Seed dressings with insecticides also controlled early seedling pests such as barley bulb fly, cutworms, chaffer grubs and cereal aphids that also transmit BYDV [7]. The seed treatments provided early protection against cereal aphids, while the foliar applied aphicides provided good control for management of later infestations on wheat crops. Therefore, utilization of both seed dressing and foliar applied aphicides could be used in integrated pest management programs for controlling the cereal aphids.

However, controlling cereal aphids with insecticides has many risks, including destruction of natural enemies and accelerated development of insecticide resistance in cereal aphid spe‐ cies. In addition, chemical control of cereal aphids has proven expensive and there is need for development of resistant varieties.
