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

Table IV.C.1. Fruit infestation assessment methods scored by criteria of advantage
(1=low; 2=intermediate; 3=high).
Criterion Sample Sample Farmer
inspection larva harvest
rearing estimate
Sample size 1 1 3
Proximity to harvest 1 1 3
Objectivity 2 3 1
Species identification 0 3 0
Robustness 2 1 3
Results
Throughout, data are summarised as unadjusted means and standard deviations (S.D.); statistical
analysis was generally by related t test or analysis of variance (ANOVA), after data normalisation by the arcsine
transformation in the case of data as frequencies or percentages (Sokal and Rohlf, 1995).
Table IV.C.2 gives infestation levels in unprotected plots, including some where no experimental results
were obtained and are not discussed below, together with the overall estimates of Stonehouse et al. (1998), with
which they seem to be in overall broad agreement. No parasitoid was found in any fruit or trap. Trimedlure traps
deployed near Islamabad airport and the main road to the NWFP and Khyber Pass caught no Ceratitis capitata
or other insect.
Table IV.C.2. Mean percentage infestation of fruit by flies in various zones (by pupal emergence unless
specified) in the absence of controls. Species were unknown where larvae emerged but not adults. Also included
(as “Survey”) are the comparable overall Pakistan loss estimates by Stonehouse et al. (1998).
Crop Location Year Species Infestation (%)
Melon DI Khan 1999 Bactrocera cucurbitae 50
Melon RY Khan 1999 Bactrocera cucurbitae 23
Melon Faisalabad 1999 None 0
Melon Kulachi 1999 Bactrocera cucurbitae 1 37 2
Melon Survey Several All 35
Guava (summer) DI Khan 1998 Bactrocera zonata 80
Guava (summer) RY Khan 1998 Bactrocera zonata 11
Guava (summer) Mardan 1998 Bactrocera zonata 14
Guava (winter 3 ) RY Khan 1998 None 0
Guava (overall 4 ) Survey Several All 35
Jujube DI Khan 1998 Unknown 3
Jujube DI Khan 1999 Carpomyia vesuviana 45
Jujube Faisalabad 1999 None 0
Jujube Survey Several All 15
Mango RY Khan 1999 Bactrocera zonata 9
Mango Survey Several All 15
Persimmon Mardan 1998 Bactrocera zonata 11
Persimmon Survey Several All 40
Luffa RY Khan 1998 Unknown >15
Plum Peshawar 1999 Bactrocera dorsalis 1 23 5
Plum Peshawar Survey All 35
1 Identification inferred from trap catches although no adults were reared.
2 Difference in mean yield weight between treated and untreated plots (Table IV.C.5, below) - not a strict record of infestation.
3 Result from a single winter fruit sample to check the common view that the winter guava crop is largely unattacked.
4 Stonehouse et al. (1998) did not distinguish summer and winter guava crops.
5 Figure from another study in this project (Hai, 2001); fruit were not collected, but identified as attacked on the tree.
Sequential samples taken after the development of ripe fruit allowed the assessment of the development
of infestation rates through the harvesting period, and the observation of how infestation, as the average of
treated and untreated plots, may build up. In two melon plots, when ripening fruit frequency was 46 and 52% of
final, infestation was 76% and 186% of final. In four guava plots, when ripening fruit frequency was between 27
and 73% of final, infestation was between 12% and 1467% of final. In two jujube plots, when ripeness was 62 and
68% of final, infestation was 50 and 113% of final. In one mango field, when ripeness was 83% of final, infestation
was 50% of final. These data were inadequate for statistical analysis, but are sufficient to show that levels of
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