Virus Diseases of Cacao in West Africa

Increasing the number of Pseudococcus njalensis per test plant increased the infection rate with cacao virus 1A and 1M to 95 % with twenty‐five insects. Young leaves with the red vein‐banding symptoms were better sources of virus than mature leaves, and there was evidence of virus localization in the plant. It was estimated that Ps. njalensis nymphs took about 16 min. to penetrate plant tissues with their stylets. Infection rates increased with time of test feeding up to 50 min. The virus was non‐persistent in the feeding insect, but persisted up to 36 hr. in insects starved after the infection feed. Starvation before the infection feed increased the infection rate with infection feeds up to 10 hrs., after which the infection rate with pre‐starved insects declined to the level attained by unstarved insects.