Abhijit Ghosal

By Abhijit Ghosal

Whitefly started to infest cotton soon after planting in favourable weather condition. During November planting mean whitefly population were highest (6.9 whiteflies per 3 leaves) and slowly declined in successive planting dates. It was found that number of population were above ETL during the month of December, January and February. Maximum population were recorded in the month of February depending on the growth stage of the crop. Maximum temperature beyond 35°C, minimum temperature below 8°C and moderate to high rainfall was very much detrimental to successful population build up. The most favourable temperature was ranged in respect of min. temperature and max. temperature was ranged 12–30°C. Simple regression value reflects whitefly population were influenced to the tune of 70.8%, 69.5%, 35.3% and 75.4% in November, December, January and February month respectively. Whitefly population were negatively correlated with temperature (max. and min.), rainfall and relative humidity (max. and min.); while, positively correlated with sunshine hours, but during November planting relative humidity (max. and min.) was positively correlated and sunshine hours were negatively correlated. Thus adjustment of planting dates may be adjusted or suitable plant protection measure may be introduced according to the weather forecast.

Part of the book: Cotton

By Abhijit Ghosal

Sap feeders have typically piercing sucking mouthparts through which they suck sap from the plant, and due to this feeding, the plant produces specific symptoms. Their role as transmitting plant viruses is well known and considered a very important factor in achieving a desirable yield. Their small size, ability to develop quick resistance and biotypes make them very difficult to manage. Insecticide is considered the most potent weapon to cope with the sap feeders because of its quick knockdown effect and ease of application. At the same time, its indiscriminate use makes the situation harsh, leading towards the disruption of several ecological phenomena. We have seen a significant increase in honey bee colony collapse disorder in recent years, owing to extensive crop coverage with neonicotinoids. Similarly, the emergence of whitefly and jassids in Bt cotton as the dreadest pests is a result of not following the conservation of refuge strategy. As the crop ecosystem is a centre of multiple interactions between several biotic organisms along with abiotic factors, holistic approaches need to be developed combining cultural, mechanical, physical, biological, biopesticidal, and chemical management incorporating the host plant resistance.

Part of the book: Insecticides in Pest Control - Impact, Challenges and Strategies [Working title]