| dc.description.abstract | At present, the global population is increasing, while soil and fresh water resources for crop production are declining. It is important to adopt sustainable practices to optimise the use
of limited natural resources without compromising the environment, and to enhance continuous
production in the long term. The rapid growth of UK strawberry industry has been achieved through
the precision use of varieties, nutrients and polythene tunnels. This intensive production has
caused significant environmental impacts especially Greenhouse Gas (GHG) emissions from the
production. Strawberry powdery mildew (Podosphaera aphanis) is a major fungal disease affecting
strawberry production worldwide particularly in polythene tunnels. The disease can result in yield
losses of up to 70% of the crop.
A ruleQbased system was used in the field trials to predict high risk days of P. aphanis
development, taking into account the optimal environmental conditions conducive to conidial
germination and disease development. The results (Chapter 3) showed that the use of this prediction
system achieved satisfactory control of P. aphanis in commercial strawberry production, with
reduced fungicide applications compared with commercial spray programme. The results were
consistent in two consecutive years and on different varieties. In addition, it was suggested that
the use of the prediction system may also lead to lower GHG emissions associated with fewer
fungicide applications, thereby benefit strawberry growers both environmentally and economically.
Results from 2014 & 2015 silicon fertigation trials showed that the use of a silicon nutrient via
the fertigation system reduced the strawberry susceptibility to P. aphanis and twoQspotted spider
mites (Tetranychus urticae Koch) in two consecutive years on different varieties (Chapter 4). In
both years, crops received the silicon nutrient only without fungicides had both lower rate of
epidemic (r) and lower value of Area Under the Disease Progress Curve (AUDPC) (r = 0.0036, AUDPC =
475 in 2014[ r = 0.001,
AUDPC = 267 in 2015) compared with the untreated control (r = 0.0042, AUDPC = 662 in 2014[ r = 0.0011, AUDPC = 281 in 2015). Silicon also delayed the epidemic buildQup in the
silicon nutrient only treatment for approximately two weeks compared with the untreated control.
Crops from the silicon nutrient plus fungicides treatment had lower susceptibility (r = 0.0012 in
2014[ r = 0.0004 in 2015) than those from the fungicides only treatment (r = 0.0017 in 2014[ r =
0.0005 in 2015) suggesting that the silicon nutrient may also enhance fungicides performance in
reducing the epidemic buildQup when used together. Moreover, the presence of T. urticae on
strawberry leaves was significantly lower (P < 0.001) in plants treated with the silicon nutrient
than those without. In addition, initial results suggested that silicon may play a positive role in
raising ºBrix of strawberry leaf petiole, improving pollen viability, and influencing the length of
flower receptacle and stamens.
Maltmas Farm has a wide range of semiQnatural habitats that provide food and nesting resources for
wild pollinators. Hoverflies, bumblebees and solitary bees were found to be the main wild
pollinators that pollinate commercial strawberries at Maltmas Farm (Chapter 5). The number of
pollinators in tunnels or open fields significantly correlated with the abundance of strawberry flowers (P < 0.05). Pollinator presence also differed between groups throughout the day and over
the seasons. Hoverflies appeared early in the day and were abundant in summer months; bumblebees
and solitary bees were present most of the day and throughout the season, whereas honeybees were
only active in sunny days. Temperatures, relative humidity and cloud coverage also affected
pollinator presence. In addition, pollinator activity was not significantly (P > 0.05) affected by
the application of the silicon nutrient via the fertigation system.
The integrated use of the prediction system (to reduce fungicide applications and subsequent GHG
emissions), the silicon nutrient (to reduce crop susceptibility to P. aphanis and T. urticae), and
sustainable farmland management (to encourage the presence of wild pollinators) could help
strawberry growers to achieve a more
sustainable production. | en_US |
