Weed hosts of cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae).

The exotic cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) invaded India during 2006, and caused widespread infestation across all nine cotton growing states. P. solenopsis also infested weeds that aided its faster spread and increased severity across cotton fields. Two year survey carried out to document host plants of P. solenopsis between 2008 and 2010 revealed 27, 83, 59 and 108 weeds belonging to 8, 18, 10 and 32 families serving as alternate hosts at North, Central, South and All India cotton growing zones, respectively. Plant species of four families viz., Asteraceae, Amaranthaceae, Malvaceae and Lamiaceae constituted almost 50% of the weed hosts. While 39 weed species supported P. solenopsis multiplication during the cotton season, 37 were hosts during off season. Higher number of weeds as off season hosts (17) outnumbering cotton season (13) at Central over other zones indicated the strong carryover of the pest aided by weeds between two cotton seasons. Six, two and seven weed hosts had the extreme severity of Grade 4 during cotton, off and cotton + off seasons, respectively. Higher number of weed hosts of P. solenopsis were located at roadside: South (12) > Central (8) > North (3) zones. Commonality of weed hosts was higher between C+S zones, while no weed host was common between N+S zones. Paper furnishes the wide range of weed hosts of P. solenopsis, discusses their significance, and formulated general and specific cultural management strategies for nationwide implementation to prevent its outbreaks.

Molecular typing of mealybug Phenacoccus solenopsis populations from different hosts and locations in Punjab, India.

True identity and existence of genetic variability in mealy bug from different regions holds immense significance for adopting appropriate control measures along with predicting the development of any biotypes. Mealy bug, Phenacoccus solenopsis adults were collected from four host plants i.e., Gossypium hirsutum – cotton (C), Abelmoschus esculentus – okra (O), Pennisetum glaucum – Napier Bajra (B) and a weed – Parthenium hysterophorus (P) in five cotton growing districts i.e., Abohar, Bathinda, Mansa, Muktsar and Faridkot of Punjab state. Variability among different populations was investigated through comparative analysis of four different RAPD markers. The genetic similarity dendrogram established that irrespective of the host plant and the collection site, 20 mealybug populations were distinguishable into two major clades that were related to each other by 68 %. Clade 1 included populations from Abohar district; it also included a single population each from Muktsar and Bathinda districts. The populations from all the other districts were grouped under Clade 2 with genetic similarity of 78 % Even under Clade 2, individual populations appeared to exist in location specific sub-clades. Thus, there is great possibility of development of biotypes which may differ in resistance to insecticides and host plant specificity.