Abstract
<em>Deltocephalus menoni </em>is a sap-sucking insect causing severe losses to the cane sugar industry by feeding on the crop and acting as the vector of Sugarcane white leaf disease (WLD) in Sri Lanka. This study was conducted to determine the most preferred age of the sugarcane plant for optimum feeding of <em>D.</em> <em>menoni</em>. Sugarcane plants of the varieties SL 92 5588, SL 97 1442, SLC 2009 01, and SL 96 128 at six age categories from 1-6 months, were selected for the study. Female <em>D. menoni </em>adults fed on to measure the amount of feeding. Variation of the feeding of <em>D. menoni </em>on each variety with the plant age was estimated separately. The feeding of the <em>D. menoni </em>significantly varied with the age of the crop, and the highest feeding rate of 6.8 mm2, was recorded on four months old sugarcanes. The amount of secreted honeydew, measured as an indicator of the suitability of sugarcane for feeding of <em>D. menoni</em>, increased gradually from one month and reached the peak at four-month age. When the plant turned five-month-old, the amount of honeydew secretion reduced gradually, and the honeydew secretion significantly dropped at six months. A similar trend was observed in the amount of honeydew secreted by feeding on each variety, including the resistant check. The highest amount of feeding, 6.8, was recorded at four-month age, indicating four-month age of the sugarcane hybrids is the most vulnerable stage for <em>D. menoni</em> feeding, and the three to five-month period is the susceptible period for feeding.
Highlights
About 103 insect species have been found in Sri Lankan Sugarcane plantations
When the plant attained five-month age, the amount of honeydew secretion reduced gradually, and a significant drop of the amount of secreted honeydew was recorded at six-month-old plants
The highest amount of honeydew was recorded at the four-month age indicating a higher feeding at the four-month age crop
Summary
About 103 insect species have been found in Sri Lankan Sugarcane plantations. Among them, eighteen species are homopterans (Kumarasinghe, 2003). Deltocephalus menoni (Hemiptera: Cicadellidae) belongs to Subfamily Deltocephalinae is one of the sap-sucking insects causing severe losses to the cane sugar industry, feeding on the crop and by acting as the vector of white leaf disease (WLD) in Sri Lanka (Senevirathne, 2008). According to Chanchala et al (2014), there is a strong relationship between the level of WLD symptoms that appeared in the field, and the population level of the vector found four weeks before the date of recording disease level. A higher population of D. menoni was reported in fields in the grand growth stage (SRI, 2014). Female herbivore insects identify a suitable site for oviposition to maximize the development and survival of the offspring (Alyokhing et al, 2004; Weintraub, 2006 and Bonebrake et al, 2010)
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