The Mango mealybug, Drosicha mangiferae (Green), belongs to the family Margarodidae (or Monophlebidae, giant coccoids/giant mealybugs), Order Hemiptera. Unlike typical mealybugs which belong to Pseudococcidae, Drosicha is placed in Margarodidae due to distinct morphological features including prominent abdominal spiracles and lack of ostioles.

Correct matching is (A)-(II), (B)-(I), (C)-(IV), (D)-(III):

• Powdery mildew of mango: Oidium mangiferae (II) (fungal pathogen infecting inflorescence and young leaves).
• Bacterial wilt of cucurbits: Erwinia tracheiphila (I) (vectored by striped/spotted cucumber beetles, Acalymma/Diabrotica).
• Bacterial wilt of corn (Stewart's wilt): Pantoea stewartii (IV) (vectored by the corn flea beetle, Chaetocnema pulicaria).
• Fire blight of pear and apple: Erwinia amylovora (III) (historic bacterial disease spread by bees and sucking insects).

Host plant association and damage by cucurbit gall midges:

• Lasioptera falcata (Diptera: Cecidomyiidae) is an emerging gall fly pest causing severe shoot and stem galls in Bitter gourd (Momordica charantia).
• The female oviposits on tender growing shoot tips and nodes. Larval feeding stimulates abnormal swelling, resulting in elongated spindle-shaped woody galls that arrest vine elongation, cause leaf curling, and drastically reduce fruit yield.

Plant virus transmission by insect vectors:

• Tomato yellow leaf curl virus (TYLCV) is a devastating begomovirus (Family Geminiviridae) causing severe curling, chlorosis, and stunting in tomato crops.
• It is transmitted in a persistent, circulative, non-propagative manner exclusively by the sweetpotato whitefly, Bemisia tabaci (Order Hemiptera: Family Aleyrodidae).