Relationship Between Kilifia acuminata (Signoret) and Chlorophyll
Percentage Loss on Mango Leaves
Feeding injury caused by mango shield scale, Kilifia acuminata (Signoret)
(Hemiptera: Coccidae) reduced leaves chlorophyll content significantly between
infested and uninfested leaves. Quantification of chlorophyll loss caused by
K. acuminata feeding on mango leaves is vital importance for photosensitize
and later on crop yield. The uninfested leaves had higher levels of chlorophyll
in comparison with infested ones. The study was conducted in Plant Protection
Research Institute, ARC, Egypt from April to June 2012 on mango shield scale,
K. acuminata to calculate chlorophyll percentage loss on mango leaves
variety Shmama. Simple correlation and partial regression were done between
numbers of insect and chlorophyll loss percentage in infested and uninfested
unites (inch2). Positive highly significant effect was recorded between
numbers of insect and percentage of chlorophyll loss. Chi-square (χ2)
was used to calculate economic threshold and economic injury levels for K.
acuminata that causes economically damage in disk chlorophyll content. Economic
threshold and economic injury levels were 3 and 8 individuals per disk, respectively.
Received: December 14, 2012;
Accepted: January 28, 2013;
Published: April 27, 2013
Soft scale insects (Hemiptera: Coccidae) are one of the largest families of
scale insects classified together with armored scales and mealybugs. There are
one thousand species distributed all over the world and these comprise one hundred
genera (Hamon and Williams, 1984). Soft scale insects
occur all over the world in all geographic regions (Ben-Dov,
1993). In Egypt Soft scale insects comprise about 23 species included 10
genera (Abd-Rabou, 2003). Scale insects can be done
their damage sucking the plant sap that give low photosynthesis and respiration
which leads to curling, yellowing, dropping to leaves, so malformations, dwarfing
and decreasing fruit production (quality and quantity) (Moffit,
Kilifia acuminata (Signoret) (Hemiptera: Coccidae) considered as one
of the most important soft scale insects in Egypt. It attacks mango, Mangifera
indica L., Psidium guajava L., Pyrus communis L., Citrus
spp. and other hosts of fruit trees and ornamental plants (Ezzat
and Hussein, 1967; Hamon and Williams, 1984; El-Dash,
1997; El-Dash et al., 2002; Soliman
et al., 2007). According to its economic importance in Egypt especially
on mango trees, the present study was aimed to determine the concentrations
of photosynthetic pigment (chlorophyll a and b) in uninfested and infested mango
leaves to calculate economic threshold and economic injury levels for K.
acuminata on mango leaves. Economic threshold and economic injury level
numbers were very important numbers because between those chemical control must
be took place. Few studies have been conducted to assess the effect of feeding
insects on chlorophyll levels such as aphids (Golawska
et al., 2010). Whoever, till now no similar studies have been conducted
to assess the effect of feeding by K. acuminata on chlorophyll levels,
this research represents an initial effort to characterize the effect of K.
acuminata on chlorophyll a and b loss in mango leaves.
MATERIALS AND METHODS
Insects and plant materials: Studies were carried out on mango leaves, Mangifera indica L. (Varity Shmama) to determine the loss of chlorophyll content in mango leaves by infestation with K. acuminata.
The study was carried out from April to June 2012, in an area of about one feddan of mango variety Shmama. For sampling, mature leaves were picked up randomly and put in black polyethylene bags and transferred into the laboratory (Plant Protection Research Institute, Sharkia Branch). The leaves were divided into disks (inch2) were examined in the same day by the aid of stereomicroscope. The adult females of K. acuminata were counted and recorded.
Chlorophyll determination: The chlorophyll content average (chlorophyll
a and chlorophyll b) in 50 disks (inch2) of mango leaves for every
level of infestation and uninfested disks as control was extract and determine
spectrophotometrically according to Moran (1982) as following:
The immersion leaflet disks in 5 mL of N, N-Dimethylformamide at least 48 hrs. Concentration of chlorophyll a and b were determined spectrophotometrically from absorbance at 647 and 664 nm, respectively. The pigment concentrations were calculated using the following equations:
Chlorophyll a (mg/inch2) = 12.64xE664-2.99xE647
Chlorophyll b (mg/inch2) = 23.26xE647-5.6xE664
Total chlorophyll (mg/inch2) = Chlorophyll a+Chlorophyll
Chlorophyll loss percentages were calculated by using the following
Statistical analysis: Simple correlation (r) between number of insects
per disk and percentage of chlorophyll loss was studied using COSTAT
According to Hendy (1969), Hosny
et al. (1972), Little and Hills (1972), Salem
and Zaki (1985) and Hassan (1998), the partial regression
formula "C-multipliers" independent variance (X) represented the scale insects
per disk, the dependent variance (Y) represented percentage of chlorophyll loss
per disk. Simple correlation (r) and simple regression (b) were calculated.
The slope (b) of the straight regression line was carried out to obtain the
corrected values for the percentage of chlorophyll loss.
Chi-square (χ2) was used to calculate economic threshold and
economic injury levels for K. acuminata that causes economically damage
in disk chlorophyll content.
RESULTS AND DISCUSSION
Data given in Table 1 revealed that percentage of chlorophyll content loss per unit was declined significantly with increasing of insect numbers. Scale infestation significantly reduced the level of chlorophyll a and b of the disks the reduction average from 6.41 to 62.24% as the infestation occurred from 1 to 30 insects per disk, respectively.
There was positive highly significant difference between number of insects per disk and percentage of chlorophyll loss where (r) value was 0.967**.
Simple correlation and partial regression and chi square were used to calculate economic threshold and economic injury levels, Chi-square analysis was applied for mathematic determination of the point at which the increase of insect number caused a significant effect on chlorophyll loss percentage. Results revealed that economic threshold and economic injury levels were 3 and 8 insects per disk, respectively.
Results showed that there was positive highly significant between number of
females and percentage of chlorophyll loss. This result was agreed with Fanizza
et al. (1991) who reported a drop in chlorophyll content under a
different stress treatment. Leaves of stressed plants apparently synthesized
less chlorophyll pigment. Other studies also show that responses differ. Rafi
et al. (1996) found that Diuraphis noxia (Mordvilko) (Hemiptera:
Aphididae) reduced chlorophyll levels in resistant cereals. Heng-Moss
et al. (2003) reported that total chlorophyll and carotenoid concentrations
differed among Betta wheat isolines in response to D. noxia feeding.
Infested Betta-Dn2 plants had higher levels of chlorophylls and carotenoids
than uninfested plants, but infested Betta-Dn1 plants had the same chlorophyll
and carotenoid levels as uninfested plants.
Burd and Elliott (1996) found a significant decline
in chlorophyll concentration in infested leaf tissue of D. noxia susceptible
wheat and barley, whereas total chlorophyll concentration was not significantly
affected by D. noxia in resistant wheat or barley. Golawska
et al. (2010), determined the chlorophyll a and b levels in uninfested
leaves and in leaves after 7 and 17 days of aphid infestation in four Fabaceae
species (Pisum sativum L., Vicia faba L., Trifolium pretense
L., Medicago sativa L.). Feeding by pea aphids Acyrthosiphon pisum
Harris (Hemiptera: Aphididae) caused significant loss of chlorophyll a and b
in the infested plants. Uninfested leaves on both short and long-infestation
plants had significantly higher chlorophyll a and b than infested leaves. In
this study the amount of chlorophyll differed between infested and uninfested
mango leaves. The chlorophyll a+b concentration in uninfested leaves was significantly
higher than infested ones.
|| Numbers of insect, Kilifia acuminata (Signoret) and
percentage of chlorophyll loss on mango leaves per disk and chi square values
|r = 0.967**, Y = 13.71 +1.83 x, YOb: Observed values of chlorophyll
percentage loss, YEx: Expected values of chlorophyll percentage loss
Overall results indicated that economic threshold and economic injury levels
were 3 and 8 insects per square inch, respectively. Hassan
(1998) also reported that economic threshold and economic injury levels
for olive parlatoria scale, Parlatoria oleae (Colvée) on olive
trees in Egypt were 8.5 and 12.06 individuals/twig.
There was positive highly significant difference between number of insects per disk and percentage of chlorophyll loss. Simple correlation and partial regression and chi square were used to calculate economic threshold and economic injury levels. Chi-square analysis was applied for mathematic determination of the point at which the increase of insect number caused a significant effect on chlorophyll loss percentage. Results revealed that economic threshold and economic injury levels were 3 and 8 insects/inch2, respectively.
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