Abstract
3.3 Trial 2 - The effect of dosage rates of Eco-T® in cucumber bag culture (open system), on Pythium control and plant growth
3.3.3 Results
All of the results were non-significant, with high CV (%) and low F values (Table 3.3.3.A).
Mean shoot wet weights (Fig. 3.3.3.A) were mostly higher with single applications of Trichoderma compared with monthly applications, for both disease control and growth stimulation treatments. No growth stimulation was recorded, with all weights being below that of the uninoculated control.
Mean fruit weight (Fig. 3.3.3.8) shows high levels of disease control at 19/Q Eco-~
(single application) and O.5g/Q Eco-~ (monthly application). Growth stimulation in this case seems higher in plants receiving monthly applications of Eco-~.
T4 T3 T2
1::en400+ I I t - - - - I I -__-=---=:---.---I~----j 'Q)
~ 350~f---- , - -
C1l~
(5 300~---- .r::o
Cl)
c 250 euC1l
:2: 200-+---'--I---t-
control (u) P+T1 P+T3 . T1
control(i) P+T2 P+T4
Treatments
• single application
11
monthly application~450 - , - - - ,
~
Fig. 3.3.3.A Effect of Eco-TID dose rates and frequency of application on Pythium control and growth stimulation as shown by mean total shoot wet weight in cucumber. These results were not statistically significant at P= 0.05
Key to Figs. 3.3.3.A and B
Control (u) =Uninoculated control
Control (i)= Inoculated control, inoculated with Pythium
P+T1, P+T2, P+T3 and P+T4 were all inoculated with Pythium and dosed with 1, 0.5, 0.25 and 0.125 g/Q Eco-T, respectively (i.e., biocontrol).
T1,12,T3 and T4 were all uninoculated, but treated with 1,0.5,0.25 and 0.125 g/Q Eco-TID, respectively (i.e., growth stimulation).
• single application
11
monthly application 500 - , - - - ,...
.r::en
'Q) 300~f---
...~
~ 200+ . f - - - - - .Ceu
~ 100-HI!I-__-
o
+---+--+control (u) P'T1 P'T3 T1 T3
control(i) P+T2 p.T4 T2 T4
Treatments
Fig. 3.3.3.B Effect of Eco-TID dose rates and frequency of application on Pythium control and growth stimulation as shown by mean total fruit weight in cucumbers. These
Table 3.3.3.A Summary of resultsfor cucumber trial 1.
test F (treatment) CV (%)
Growth stimulation (mean total shoot weight (g)) 1.62 10.45 Growth stimulation (mean total fruit weight (g)) 0.75 49.87
Biocontrol (mean total shoot weight (g)) 0.79 52.43
Biocontrol (mean total fruit weight (g)) 0.98 19.3
3.3.4 Discussion
Statistical results (Table 5.3.3.A) showthatthis trial was unsuccessful. In all parameters measured, for both biocontrol activity and growth stimulation, no significant differences were recorded, with high CV (%) values in all cases. There are a number of reasons for this, mostly related to an initial poor understanding of the effects of Pythium on cucumber growth. During the course of the trial it was observed that the main effect of Pythium was during the two to four week stage. This resulted in a time dependent reduction in yield as growth rates were slowed during this initial stage whenPythiumwas not suitably controlled. It is thus necessary to compare the development of fruit at set nodal positions at set time periods rather than measuring fruit weight of any fruit over 20cm in each week as was done in this trial.
-Another source of error was in the choice of cultivar, which was purchased as a commercially used cultivar under the advice of the local nursery. Commercial cultivars used in tunnel growing do not produce male flowers, and are indeterminate in growth.
Ashley produced numerous male flowers and comparatively little fruit.
Plant spacing was also seen as a limiting factor. The trial was inter-cropped with a tomato trial, due to lack of space. Although tomatoes are slower growing than cucumbers and should not have interfered with cucumber growth, this did result in the cucumber plants growing closer together than optimally. Combined with this was a significant shading effect generated by the wet wall (which in this tunnel runs along the East wall) and a significant yield gradient occurred. Plants on the West side developed
on average a week faster than those on the East. The close plant spacing also made effective spraying difficult once the plants reached the overhead supports. This led to sporadic infestations of white fly and red spider mite, and a constant powdery mildew problem. All these factors combined to result in non-significant (P =0.05) data.
Despite the statistical data, if one looks at the mean results (Fig. 3.3.3.A and B), many of the general trends are the same as observed in the lettuce trial (Section 3.2). Looking at mean total plant weights (Fig. 3.3.3.A) biocontrol activity can be noted. Optimum dose rates for biocontrol appear between 1 and 0.5g1Q (P+T1 and P+T2) with single applications at planting giving better control than monthly applications. The higher optimum dose rates compared with the lettuce are, as expected, due to the differences in the system used. Some of the conidia would have been leached beyond the root zone by subsequent irrigations and would be lost to the system, unlike a recirculating system in which conidia have numerous other chances to establish in the root zone.
The lower plant weights with monthly applications of Eco-~could be due to certain phytotoxic mechanism as previously mentioned in Section 3.2.4. Pyfhium inoculation was only done at transplanting. A single application of Eco-T at the same time would have largely reduced the infection caused by this inoculation. Subsequent applications of Eco-~ would have resulted in high levels of Trichoderma in a relatively sterile medium, with little buffering capacity. Resulting low levels of nitrification bacteria would have further resulted in higher levels of ammonium in the root zone, leading to ammonia toxicity in the roots. A similar response can be seen in the growth stimulation trials where, in all cases, growth inhibition occurred.
Monthly applications of Eco-