Full Length Research Paper

Alternate host plants of Phenacoccus manihoti) Matile - Ferrero (Homoptera : Pseudococcidae), the cassava mealybug

Essien, Rosemary Anietie1*, Odebiyi, Johnson Adebayo2 and Ekanem, Mfon Sunday3

Abstract

Thirteen alternate host plants of Phenacoccus manihoti were identified during a field survey of cassava plots in Ibadan, Nigeria. The host plants were screened in the laboratory to determine their attractiveness to P. manihot. More eggs were laid by P. manihoti on two host plants Talinum triangulare (Portulacaceae) and Ageratum conyzoides (Compositae). These two host plants were found to support all life stages of the pest. Further laboratory studies to compare P. manihoti preference to T. triangulare (water leaf), A. conyzoides (goat weed) and the primary host plant, Manihoti esculenta (cassava) showed that while pre and post-oviposition periods were similar and shorter in P. manhoti fed with T. triangulare and M. esculenta, the periods were significantly longer (P<0.05) with A. conyzoides. The larval sizes of P. manhoti on A. conyzoides were significantly smaller and developmental period significantly (P<0.05) longer than those fed with T. triangulare and M. esculenta. The total life span of P. manihoti on A. conyzoides was significantly shorter, and its mortality rate higher than those fed with T. triangulare and M. esculenta. There was similarity between the growth rates on T. triangulare (5.40) and M. esculenta (5.10) while on A. conyzoides there was a significantly lower rate (3.10). Egg laying was significantly (P<0.05) lower on A. conyzoides (140 eggs) than on T. triangulare (393) and M. esculenta (370). Of the two alternate hosts, T. triangulare is the most attractive alternate host of P. manihoti in the Ibadan area. This study shows that some weeds could harbour the pest, pending when the primary host is available. Therefore, weeds and some vegetables especially T.triangulare should not be allowed in cassava farms.

Key words: Alternate host, goatweed, Larvae, M. esculenta P. manitoti, waterleaf.

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