ZA EcoBb tomato whitefly 2007 .pdf


Nom original: ZA_EcoBb_tomato_whitefly_2007.pdf
Titre: ZA_EcoBb_tomato_whitefly_2007
Auteur: fleischli.simon

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Trial to determine the efficacy of Eco-Bb in controlling whitefly in field
grown tomatoes
Trial commenced: January 2007
Conducted by: Dr. B. Neumann
Location: Ukulinga, University of KwaZulu-Natal (Pietermaritzburg) research farm
Materials and Methods:
Tomato seedlings (cultivar Rodade) were grown in the Plant Pathology greenhouse for 5
weeks prior to transplant. Seedlings were then transplanted into blocks consisting of two rows
of 7 plants each (14 plants per block). Rows were 1m apart and inter-row spacings were 50cm
between plants. Two meter wide paths were left between treatment blocks in an attempt to
minimize interplot interference. The following 4 treatments were used:
1 = untreated control
2 = chemical standard control (Methomix)
3 = Eco-Bb @ 1g/l
4 = Eco-Bb @ 2g/l
Seedlings were given 1 week after transplanting to establish and whitefly were then
introduced to the trial area as in previous trials. Whitefly were given a further 3 weeks for
populations to establish. Whitefly infestation never became severe possibly due to the
presence of natural predators or unsuitable weather conditions. Counts of larvae per leaf
resulted in insufficient data due to the low severity of infestation. For this reason it was
decided to work rather with adult whitefly incidence. Two leaves were sampled from the 10
central plants in each block. Whitefly adults were recorded as either present or absent. The
percentage leaves infested with adult whitefly were then used for statistical comparison
between treatments. Analysis was done using SAS (Windows edition).
Results and Discussion:
All treatments resulted in significant control of whitefly compared to the untreated controls.
Eco-Bb at 1g/l appears to be a suitable dose for field applications despite slightly poorer
performance in week 3. The difference between 1g/l and the other treatments in week 3 was
however not significant and the efficacy improved again in week 4. It is most likely that
application error or interplot interference accounted for this slight reduction in efficacy in
week 3. No signs of phytotoxicity were observed in any of the treatments. Given the nature of
the product and its formulation ingredients it is extremely unlikely that any phytotoxicity
could ever result.

whitefly incidence (average of 20
leaves sampled)

90
80
70
60

untreated

50

chemical

40

1g/l
2g/l

30
20
10
0
week1

week2

week3

week4

Figure 1: Graph showing efficacy of Eco-Bb in controlling whitefly in field grown tomatoes

Table 1: Table of means for different treatments (Treatments in the same column that share
the same letter do not differ significantly from each other at the 95% confidence level)
treatment Week1
Week2
Week3
Week4
Avg
Untreated 60 (A)
63.3 (A)
80 (A)
83.3 (A)
71.7 (A)
contol
Chemical 53.3 (A)
13.3 (B)
11.7 (B)
13.3 (B)
22.9 (B)
control
Eco-Bb
46.7(A)
20 (B)
25 (B)
8.3 (B)
25 (B)
@ 1g/l
Eco-Bb
50 (A)
21.7 (B)
13.3 (B)
16.7 (B)
25.4 (B)
@ 2g/l
F = 0.83
F = 16.61 F = 46.71 F = 82.23 F = 56.46
P = 0.05
P = 0.05
P = 0.05
P = 0.05
P = 0.05


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