Black bean aphid – Aphis fabae
Black bean aphids overwinter on the spindle tree, migrating to bean and sugar beet crops in the summer. Egg counts may be conducted to assess the risk of infection each year. Damage is mainly caused by aphid populations which colonise plants prior to flowering. These colonies result from the primary migration from overwintering hosts in mid May to mid June. Aphid populations initiated after flowering cause little damage. These are often secondary migrants, usually from sugar beet crops. Spraying is considered to be economic if 5 % of stems are infected by primary migrant on the south west headland of the field by mid June.
Late sown crops are generally at greater risk as the aphid migration is more likely to coincide with an earlier developmental stage of the crop. Control is achieved with pirimicarb ('Aphox'). Low rates of pirimicarb are almost as effective as the full recommended rate (Figure 1), especially if aphid predators are present in large numbers. The presence of mummified aphids is a good indicator of predator presence and can be used as an incentive to reduce rates.