“Key Informant Survey” of Production, Value, Losses and ... - DfID

trap set” so that it may economically be extended in future, if need be, to a larger number of sites (and
be less prone to theft). Lure traps may be made of PET drinks bottles or plastic sachets (Verghese
and Jayanthi, 2001), food traps of such bottles or plastic ice cream tubs (Nakagawa et al., 1975;
Rhode and Sanchez, 1982) and visual traps by painting sticky adherent to coloured plastic toy balls; the
construction of these traps, however (receptacles used, number and size of holes etc.) will require
standardisation, possibly with reference to international studies. It may be necessary to begin with
some comparative studies to evaluate candidate traps for relative power, as is being done in India for
cotton pink bollworm traps (Tamhankar et al., 2001). In a selection of sites it is proposed also to use
specialised, imported traps such as McPhail traps, to allow the relative catching power of home-made
and imported versions to be calculated for calibration.
Each survey zone will include two trap set replicates in the same district, separated by at least
1km. In each trap set the lay-out will be as a circle 10m in diameter, with advantages of direction given
to the less powerful - coloured sticky balls facing west and south, parapheromone lures facing north
and food lures facing south and east. Traps will be monitored weekly year-round. Additional records
will include the simplest ways of recording the known important extrinsic factors dictating abundance -
host availability and temperature were found by many studies to be the major determinants of
abundance (eg Shukla and Prasad 1985) although it may be desirable to include relative humidity,
though costlier to record. Records will comprise the following:-
1: Annual Record Sheets will record each trap site’s map reference, altitude, ground
vegetation and building cover and the approximate percentage land surface coverage by the eight most
important crops over (a) the surrounding 1km 2 and (b) the surrounding 100km 2 . This will be done by
simple ordinal scores of estimates, for example of vegetation cover as 0=none (0%); 1=small patches
or isolated individuals (1-10%); 2=medium patches or several individuals (11-30%); 3=large areas or
many individuals (31-60%); 4=dominant, near-continuous (61-100%).
2: Weekly Record Sheets will record:-
a - All Tephritid catches by trap, species and sex
b - Weekly near environment, as the developmental stage of each crop, with estimates of fruit
production, the week’s weather and other local events such as irrigation and pesticide sprays. This
information, though often largely subjective and impressionistic, will enable allowance to be made for
peculiar local factors such as chemical sprays or large flushes of particular host fruit, which may
influence local trap catches
c - Temperature by maximum-minimum recording thermometers. Cheaper and simpler than equipment
to record average temperature, which requires continuous temperature monitoring, these allow the
recording of day degrees or thermal units (Aliniazee, 1976) given as the average of maximum and
minimum temperatures minus 5 degrees, which was found by Shukla and Prasad (1985) to be a close
predictor of fruit fly abundance.
3: All catches from food and visual traps (cleaned and prepared as necessary) and a sample of
at least 30 flies from each lure trap, will be pinned out, remaining lure catches will be preserved in jars
of alcohol; all will be cross-referenced to their data sheet records.
Trap Survey: Material Requirements
- Trap suite as above, with baits, lures and killing strips.
- Water, alcohol and acetone for cleaning of flies from bait and sticky traps
- Dry mounting materials - plastezote sheets, pins, labels, mounting cases, desiccant and preservative
chemicals
- Wet preservation materials - alcohol and jars
1.2.2: Rearing Out
Susceptible fruit of important types will be collected for the rearing-out of fly pests and natural
enemies. As very demanding of resources if done on a large scale, this part of the survey will be
largely ad hoc rather than systematic or comprehensive, to clarify and enlighten points raised by the
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