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

attack, at intermediate stages of fruit development, can be highy variable and that it cannot be assumed that
attack is restricted to later periods so that, at least in the absence of a monitoring system, protection of fruit
should be recommended to begin as soon as attack can begin.
The distribution of fly infestation among trees and melon clumps was not clustered. Nested ANOVAs
compared variation in infestation between the five sampled trees (or melon clumps) in each treated half of each
field, relative to that among fruit on the same tree or clump (six fruit on each). On-tree and fallen fruit were
assessed separately. Of 44 data sets with enough data to be useable, only one (of guavas) showed a significant
difference between trees (F=2.8721[4,25]*); among the other 43, 35 F values were unity or less.
Infestation was significantly clustered among fruit. Observed distributions were compared by
Kolmogorov-Smirnov tests with Poisson distributions, with on-tree and fallen fruit assessed separately, and the
two differently-treated halves of each field pooled to obtain a spread of different infestation levels (N=60 in all
cases). In the four mango fields, none of the samples on trees significantly departed from the Poisson (between
D=0.0162 and D=0.1592) but all of the samples in fallen fruit did so (between D=0.2666*** and D=0.2780***). Of
the 18 useable data sets among the other fruits, two did not depart significantly from the Poisson model (one of
guava D=0.1082 and one of jujube D=0.0006) but the other 16 did, 11 of them at the level P