Incidence, Distribution and Characteristics of Major Tomato Leaf ...
Incidence, Distribution and Characteristics of Major Tomato Leaf ...
Incidence, Distribution and Characteristics of Major Tomato Leaf ...
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<strong>Incidence</strong>, distribution <strong>and</strong> characteristics <strong>of</strong> major tomato leaf curl <strong>and</strong> mosaic virus diseases 137<br />
dimethoate were applied. Lowest infection rate <strong>of</strong> 0.032 was recorded in plots where<br />
uprooting <strong>and</strong> dimethoate were applied as indicated in table 5.7.<br />
It was established that there was no significant difference between plots with a<br />
tomato-bean intercrop with an infection rate <strong>of</strong> 0.056 <strong>and</strong> those with tomato-bean<br />
intercrop bean rows sprayed with dimethoate (n3) with an infection rate <strong>of</strong> 0.053. The<br />
latter was also similar to that <strong>of</strong> plots with only a tomato monocrop (n1), which was<br />
also the control (0.053), <strong>and</strong> were therefore not cost-effective. At the same time,<br />
uprooting alone with an infection rate <strong>of</strong> 0.049 yielded non-significant differences<br />
from the control.<br />
Table 5.6: Mean distance from initial infection to secondary infected plants<br />
throughout the cropping year (March 1999 to February 2000), calculated according to<br />
Allen (Plumb <strong>and</strong> Thresh, 1983)<br />
Treatments Ranked¹ Mean distance (cm)<br />
Monocrop x uprooting x dimethoate (n5)<br />
Monocrop x uprooting (n2)<br />
<strong>Tomato</strong> monocrop (n1)<br />
Intercrop x dimethoate on beans (n6)<br />
Monocrop x dimethoate (n4)<br />
<strong>Tomato</strong> - bean intercrop (n3)<br />
273a<br />
239ab<br />
230ab<br />
210ab<br />
173ab<br />
142b<br />
¹ Ranking is indicated by letters a <strong>and</strong> b, whereby (a), or (b) refers to means, which are significantly<br />
different, whereas (ab) refer to means that statistically have no significant difference<br />
Table 5.7: Infection rate for the different experiment plots for the period<br />
March 1999 to February 2000, calculated according to V<strong>and</strong>erplank formula (dN/dt)<br />
Treatments<br />
Monocrop x dimethoate (n4)<br />
Intercrop x dimethoate on beans (n6)<br />
<strong>Tomato</strong> - beans intercrop (n3)<br />
<strong>Tomato</strong> monocrop (n1)<br />
Monocrop x uprooting (n2)<br />
Monocrop x uprooting x dimethoate (n5)<br />
Ranked¹annual mean infection rate<br />
(dN/dt)<br />
0.074a<br />
0.056ab<br />
0.053ab<br />
0.053ab<br />
0.049ab<br />
0.032b<br />
¹ Ranking is indicated by letters a <strong>and</strong> b, whereby (a), or (b) refers to means, which are significantly<br />
different, whereas (ab) refer to means that statistically have no significant difference
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