A. Aphids:
Scientific Name: i) Rhophalosiphum maidis F. ii) Aphis sacchari Z
Class & Order: Aphididae: Hemiptera
B. Delphacids:
Scientific Name: Peregrinus maidis A.
Class & Order: Delphacidae: Hemiptera.
Economic Importance: They are the most important pests of Jowar. The infestation is usually high on rabi crop. The yield is adversely affected and the fodder quality also deteriorates.
Marks of Identification: Aphids-Adults are minute, soft bodied, oblong, light green or pale yellow Cornicles: They are characterized by the presence of 2 tubes like structures on the dorsal side of abdomen. They are generally wingless but winged forms are often noticed usually in the beginning and towards end of season for migration to other crops.
Nymphs: Smaller and greenish. Aphids are found in large numbers on lower surface of leaves and leaf whorls and do not move unless disturbed.
Delphacids: Adults: Wedge, pale yellow, walk diagonally. Nymphs -like adults but wingless. Delphacids found mostly in the whorl of the plant.
Host plants: Jowar, bajara, other cereals and sugarcane.
Life history: Aphids – only females are noticed in Maharashtra. Reproduction parthenogetically on an average each female produce about 42 young ones within period of 5 days. Nymphs moults 4 times in a period of 5 days. A generation is completed in about 2 weeks.
Delphacids: Eggs – about 150 eggs are laid in tissues incubation period 7-8days nymphal period 15-19 days (moults 5 times) Life cycle completed in about a month time.
Nature of damage: Both nymphs and adults suck the sap from plant especially from the leaves. As a result the leaves turn yellow and in case of heavy infestation the plants remain stunted. Their injury causes oozing of sap which crystallizes on evaporation forming sugary material called “Chikta” OR “”Sugary Disease”. Due to sugary material oozing out of the plant and honey due excreted by the insects, the sooty mould develops and the leaves turn blackish. The yield is adversely affected and the fodder quality also deteriorates.
Management Practices: Spraying with dimethoate / quinalphos at 0.03% or formothion / monocrotophos /methyl demeton at 0.02%OR dusting the crop with endosulfan 4D / quindphos 1.5 D @20kg’lia. Spraying is more effective than dusting.
