be excessive nor too low for protection and production of coffee [230]. Finally, the
major influence of agroforestry system on coffee physiology is lined with limit
temperature fluctuations (by as much 4–5
C), maintaining required relative humidity, and decreases the wind speed and aerodynamic roughness of the cropped area.
Shade and yield also have controversial relationship in literature as some authors
[22, 222, 231] claimed a negative while others claimed an insignificant relationship
[210, 232, 233]. This controversy is likely due to the difference in shade type and
extent, coffee varieties, vegetative stage, ecological conditions, water and nutrients
availability, etc. [210]. The other possibilities of low yield under shade are designated to (a) less response of coffee trees to available input or due to competition, (b)
lower level of carbon assimilation, (c) greater inducement to somatic growth than
flower buds, and (d) fewer nodes per branch and flower buds at existing nodes [22,
228, 229 ]. However, Haggar and his working team showed that comparable yield to
full sun-grown coffee can be achieved via intensive organic system, i.e., by application of fertilizer and other inputs to shade-grown coffee. Shading effect was found
to be unobvious during the early vegetative growth stages and after drastic pruning
till high yielding stages [231]. Despite intensive work on shade or agro-ecosystems
in coffee, nobody still registers the mathematical relationship of yield versus sungrown coffee or yield versus shade or shade versus increased bean size. For all
additional aspects of shade other than physical cup quality of coffee, the readers are
referred to study the already available reviews on shade and coffee such as Beer
[234], Beer et al. [233], and DaMatta et al. [235].
2.7
Insect Pests and Diseases
As a perennial crop, coffee plants (both Arabica and Robusta) are considered an
attraction for a wide range of insects, pests, and diseases (IPDs). These IPDs
negatively affect the plant, plant health, plant nutrition, plant growth and development, yield, and physical and chemical quality of product. But in this section we
would like to solely relate the IPDs occurrences and resulting deteriorating physical
and chemical quality of product. This section will not cover the origin, life cycle,
epidemiology, etc., of IPDs; however, a little detail, where necessary, about agricultural or management practices may be mentioned surfacely for the cause of preserving physical and chemical quality of cherries. Most of the occurrence and intensity of
IPDs largely depends upon the kind of coffee production system [236]. Highly
diverse coffee-based agroforestry system is the habitat for many plant friendly
birds and ants important in bio-control of coffee berry borer (Hypothenemus hampei)
[237–239]. Additionally, shade prevents the various IPDs like coffee berry disease
(Colletotrichum kahawae), coffee blight (Phoma costarricencis), coffee brown eye
spot disease (Cercospora coffeicola), coffee rust, and die-back from becoming
epidemic by providing and modification of microclimatic conditions and host
physiology changes [228, 236, 240, 241]. On the opposite side, diverse agroecosystems may play a conductive role in the eruption of American leaf spot disease
(Mycena citricolor), white thread blight (Corticium koleroga), pink disease
684
A. Hameed et al.
major influence of agroforestry system on coffee physiology is lined with limit
temperature fluctuations (by as much 4–5
C), maintaining required relative humidity, and decreases the wind speed and aerodynamic roughness of the cropped area.
Shade and yield also have controversial relationship in literature as some authors
[22, 222, 231] claimed a negative while others claimed an insignificant relationship
[210, 232, 233]. This controversy is likely due to the difference in shade type and
extent, coffee varieties, vegetative stage, ecological conditions, water and nutrients
availability, etc. [210]. The other possibilities of low yield under shade are designated to (a) less response of coffee trees to available input or due to competition, (b)
lower level of carbon assimilation, (c) greater inducement to somatic growth than
flower buds, and (d) fewer nodes per branch and flower buds at existing nodes [22,
228, 229 ]. However, Haggar and his working team showed that comparable yield to
full sun-grown coffee can be achieved via intensive organic system, i.e., by application of fertilizer and other inputs to shade-grown coffee. Shading effect was found
to be unobvious during the early vegetative growth stages and after drastic pruning
till high yielding stages [231]. Despite intensive work on shade or agro-ecosystems
in coffee, nobody still registers the mathematical relationship of yield versus sungrown coffee or yield versus shade or shade versus increased bean size. For all
additional aspects of shade other than physical cup quality of coffee, the readers are
referred to study the already available reviews on shade and coffee such as Beer
[234], Beer et al. [233], and DaMatta et al. [235].
2.7
Insect Pests and Diseases
As a perennial crop, coffee plants (both Arabica and Robusta) are considered an
attraction for a wide range of insects, pests, and diseases (IPDs). These IPDs
negatively affect the plant, plant health, plant nutrition, plant growth and development, yield, and physical and chemical quality of product. But in this section we
would like to solely relate the IPDs occurrences and resulting deteriorating physical
and chemical quality of product. This section will not cover the origin, life cycle,
epidemiology, etc., of IPDs; however, a little detail, where necessary, about agricultural or management practices may be mentioned surfacely for the cause of preserving physical and chemical quality of cherries. Most of the occurrence and intensity of
IPDs largely depends upon the kind of coffee production system [236]. Highly
diverse coffee-based agroforestry system is the habitat for many plant friendly
birds and ants important in bio-control of coffee berry borer (Hypothenemus hampei)
[237–239]. Additionally, shade prevents the various IPDs like coffee berry disease
(Colletotrichum kahawae), coffee blight (Phoma costarricencis), coffee brown eye
spot disease (Cercospora coffeicola), coffee rust, and die-back from becoming
epidemic by providing and modification of microclimatic conditions and host
physiology changes [228, 236, 240, 241]. On the opposite side, diverse agroecosystems may play a conductive role in the eruption of American leaf spot disease
(Mycena citricolor), white thread blight (Corticium koleroga), pink disease
684
A. Hameed et al.