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

Infestation
(%)
ANOVA F
Tree Mean 3.9 16.1 30.6 44.4
S.D. ±4.2 ±25.1 ±24.3 ±36.6
Ground Mean 8.9 17.8 33.9 41.7
S.D. ±10.2 ±16.8 ±24.3 ±24.7
Treatments 81.6134[1,2]* 0.3281[1,2]ns
Locations 21.4615[1,2]* 7.2344[1,2]ns
Sites 364.8379[2,2]** 7.5350[2,2]***
Table IV.C.12. Infestation of mango fruit from four sites, as in Table IV.C.10. No interactions were significant.
The inferred reduction in infestation by MAT was 100%.
Indicator: Pupae Marks
Output Protection: MAT None MAT None
Infestation Tree Mean 0.0 10.0 5.0 17.5
(%)
S.D. ±0.0 ±7.2 ±1.9 ±11.0
Ground Mean 4.2 24.2 68.3 73.3
S.D. ±1.7 ±6.3 ±6.4 ±9.4
ANOVA F Treatments 211.0847[1,3]*** 36.9901[1,3]**
Locations 92.1408[1,3]** 1047.3419[1,3]***
Sites 6.9911[3,3]ns 15.2315[3,3]*
Estimates of fruit infestation at harvest (method iii, above) were adequate for analysis only in melons
and mangoes. The results are given in Table IV.C.13.
Table IV.C.13. Farmer estimates of percentage loss frequencies among harvests on four mango farms and five
melon farms. Spoiled mangoes were identified as “fly-attacked”, melons as“fly-attacked” and “spoiled but not
visibly fly-attacked”. The inferred reduction in all spoiled melons by BAT was 63.6%; that by MAT in attacked
mangoes was 96%.
Fruit: Mango Melon
Symptom: Attacked Attacked Spoiled
Protection MAT None BAT None BAT None
Mean (%) 0.3 8.9 0.7 5.3 2.9 4.9
S.D. ±0.1 ±5.0 ±0.4 ±1.8 ±1.5 ±2.4
Related t 5.0533[3]* 6.2755[4]** 6.0701[4]**
Conclusions
The methodology developed was able to distinguish many important variables. Visible marks were
recorded on sampled fruits, as a back-up to the more accurate but less robust (in case of larval mortality before
emergence) record of emerged pupae. Visible mark records were inferior to pupal rearing in the detection of
infestation differences, but provided some meaningful information, and may be recommended as a back-up when
there is a risk of loss of pupal emergence data. Estimates of fruit numbers on trees and on the ground were able to
distinguish different levels of production.
The number of sites used was only barely adequate. The greater clarity of conclusions from guava and
melon (on five sites) than from mango and jujube (on respectively four and three) strongly suggests that
replication levels of at least six plots should be sought in studies of this sort.
Flies were not clustered among trees or bushes within fields, but were clustered among fruit, although
the number of larvae per infested fruit was not constant, and not significantly less variable than the infestation
rate.
Losses in general were most apparent as infestation levels on trees. There was evidence, however, that
fruit with heavier fly attack were likely to be less numerous, possibly because more likely to fall from the tree.
This would make loss estimates derived from infestation rates alone too low, by removing from the sample some
fruit which are attacked.
Bait sprays were effective in controlling fruit flies on guava, jujube and melon, and are preferable to
cover sprays for reasons of cost, safety and environmental contamination. All farmers who hosted trials made
favourable comments about BAT regarding its effectiveness and its low demands for water and work.
MAT was able effectively to control fruit flies in mangoes. However, losses may anyway sometimes be
too low to justify controls. Both BAT and MAT attained control even on small and medium-sized farm plots (0.2
to 2.0ha).
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