EFFECT OF PLASTIC MULCH, FLOATING ROW COVER AND MICROTUNNELS
ON INSECT POPULATIONS AND YIELD OF MUSKMELON
J. Farias-Larios, M. Orazco-Santos1 and J. Perez
Facultad de Ciencias Biológicas y Agropecuarias. Universidad de Colima
Apartado postal 36.28100 Tecomal, Colima, Mexico. E mail jferias@volcaaucolmx
Abstract This woik was conducted to evaluate the effect of clear (CP) and black polyethylene (BP)
middies, floatingrowcover (FRC) and perforated plastic aixl IXJ perforated microtunnels on growth and yield of muskmelon; and
to determine the effect of diese üeatments on population densities of aphids, sweetpotato whitefly and soil temperature. Treatments
were: 1) CP+FRC, 2) CP+ polyethylene perforated microtunnel (MPP), 3) CP+ polyethylene not perforated microtunnel
(MNPP), 4) BP+FRC, 5) CP alone, 6) BP alone, and 7) bare soil as the control. Pests were completely excluded by FRC in die
plots covered Protected plants had 0 and 1 nymphs/cnr at 34 and 41 days after sowing,respectively,whereas the control showed
3 and 29 nymphs/an2 at the same dates. CP + FRC increased soil temperature, number of maiketablefruits(452 and 44.8%
higher) withrespectto BP + FRC aixl bare soil. Polyethylene microtunnels were found notrecommendedby its costs for
cantaloupe production. It is proposed diat floatingrowcover should be selected for their effects on insects in addition to their effects
on soil temperature and melon yield
Keywords: Cucumis meló L, aphids, sweetpotato whitefly, soil temperature, yield
Introduction
Cucurbits comprise the largest acreage of cash crops grown in western Mexico, and are also a major crop in the Mexico
countiy. Of the cucurbits, the most important ciop is muskmelon, followed by watermelon and cucumber. Muskmelons and
related melons sell for a high price, but many farmers arereluctantto grow them because of pest problems which frequently result
in poor yields. The most important insect pest are: sweetpotato withefly (Bemisia (abaci Gennadius) and the aphids Aphis
spiraecola (Patch), Uroleucon ambrosiae (Tilomas), Myzus persicae (Sulzer), A. gossypii (Glover) and Rhopalosiphum
nrfiabdomimlis (Sasaki) (17). Both insect groups cause damage by feeding directly and indirectly through the excretion of
lioneydew: They are vector of one or more viiuses affecting cucurbit crops (12,2).
Mich of theresearchdocumenting the effects of mulching systems on the colonization of selected insect pests has been
conducted withreflectivemulches. Such muidles liave been evaluated on cucurbit crops, particularly inrelationto virus vectors (8,
6,4.7). However, die use and adoption of polyethylene orreflectivemulches is limited by some of its disadvantages. Primarily,
reflective mulches arerelativelyexpensive compared with clear or black plastic mulch; and secondly, theyresultisreducedsoil
temperatures which canreducetheir potential for use during winter muskmelon production
The use of clear and black plastic mulches has become a standard practiceformany vegetable crops in western Mexico
where it lias been demonstrated that it speeds crap development and enhances earliness (9,17). These polyethylene mulches are
used by some fannersforweed control in melon, and it is suggested tliat these might also affected insect population. Finthennore,
inrecentyears, die use of floatingrowcoverslias been practiced with variableresultsonreducinginsect pest populations, delaying
virus diseases, increasing earliness and total yield of muskmelon (18).
1
INIFAP. Campo Experimental Tecomán. Apartado postal 88. 28100 Tecomán, Colima, México. E mail
orozco@bciencias.ucol.mx
76
Polyethylene mulch in combination withfloatingrow covers show promise as a method for excluding insects, reducing
viats diseases and increasing yield of cucurbit ciops (14,1,13,22,16). However, there is poor information on the development of
the muskmelon crop grown underfloatingrowcover and polyethylene microtunnels in tropical conditions. The objectives of this
study were 1) to determine the effectiveness of clear and black polyethylene middies, used alone or combined withfloatingrow
cover and perforated plastic or no perforated microtunnels, on growth and yield of muskmelon; and 2) to determine the effect of
these treatments on population densities of aphids, sweetpotato whitefly and effect on soil temperatures.
Methods and Materials
Thefieldexperiment was conducted at die Tecoman Expeiimental Station, located at Tecoman valley, western Mexico
(18°51' N, 103°50' W) and 40 m above sea level, during die winter 19%. The soil at the site was clay with a pH of 6.5 and 3%
organic matter. Soil was disked and bedded, then, plastic mulch (0.025 mm thick, 12 m wide, clear and black embossed) and drip
irrigation tubing (020 mm thick, emission spacing 30 cm, flowrateof 1.5 liters/min. per 30 m ofrowat 55 kPa (Hi Tech Irrigation,
Tecoman, Mexico) were applied usingrecommendedcommercial practices. Syntheticfertilizertreatments (113.5 N - 207 P and
225 Kgtia) were applied to the plots before mulching using urea, superphosphate of calcium triple and potassium nitrate. On 7
January, melon (Cucumis melo L Cv. Cniiser) was direct seeded at 25 cm intervals in the center of 1.78 m wide, and plots were
watered with a drip irrigation system to piomote geimination. Each bed had an emitter tube with emission spacing of 0.50 m, and
flowrateof2.3 litech.
Seven treatments were evaluated: (1) clear polyediylene mulch (CP), (2) black polyethylene mulch (BP), (3) CP + floating
row cover (FRC, spounbonded polypropylenefiberAGRJBON (weight 17 gem2), Bonlam S. A de C. V., Guadalajara, Mexico)
removed at the vegetative stage (12 Maich, before staminatedflowersappeared in die plants), (4) BP + FRC, (5) CP + microtunnel
with perforated polyethylene (MPP), (6) BPM + miaotunnels with non-perforated polyethylene (MNPP), and (7) bare soil as
control. Each treatment consisted ofthiee 7.0 m-long bedsreplicatedfour times in arandomizedcomplete block design Data were
collected from the centrerow.After seeding FRC, MPP and MNPP were set on the beds with both edges and ends of covers
secured with soil. Weeds wereremovedmanually. All plots, except in FRC and MNPP, standard applications of insecticides
(endosul&i, imidacloprid, methamidoplios, diazinon and permethrin) were made at 5- to 7- day intervals. Fungi diseases were
controlled byfosetyl-Al,mancozeb and methalaxyl applications. Supplementalfertilizationwas made with 163.3 N, 00 P and 89.6
K applied through die drip system Soil water status was measured with tensiometers at 15- and 30-cm depths, and water was
applied when water potential at 15 cmreached-024kPa
Yellow pan plastic traps for aphids (28x22x 12 cm) containing a mixture of water and detergent were placed in die middle
of each plot and die number of aphids trapped were lecoided twice weekly to determine die effectiveness of each treatment in
delaying aphid infestation. The nmiber of whitefly adults was detennined twice weekly on 20randomlyselected plants of each
treatment (two leaves/plant). Early morning (07:00 - 08:00 h), beforeflightactivity, the leaves were gently turned and adults
visually counted (5). On 10 and 17 February (34 and 41 days after sowing,respectively),die number of whitefly nymphs on five
leaflets oftwotowerleaves were countedfrom10randomlyselected plants with the aid ofa lOx dissecting microscope.
During the entire experimental period, soil temperature at 10 cm deep was measured in each treatment Soil thermometers
were installed next to plantrootsand temperature leadings were taken three times a week during the morning (08:00 h), midday
(12:00 h), and evening (18:00 h). Plots were harvested by hand on 20,28 April and 01 May. Weight and number offruitwere
lecoided and marketable fruit (according to exportingregulationspecifications) was sized into 9,12,15,18, and 23 melon/carton,
weighing 18.0 - 18.5 kg on average for each box. Data were analyzed with analysis of variance and means of different treatments
were compared with a Duncan's multiplerangetest procedure.
77
Results and Discussion
3.1. Aphid populations
Aphids were excluded completelyfromde melon plants growing under MPP and MPNP until the plastic was removed
during perfectflowering.Also, the plots with FRC had similarresults(Fig 1). Winged aphids were not caughted in the treatments
withrowcover during thefirstfiveweeks after sowing Howeverfromthe six to tenth weeks when the covers wereremoved,a
reduced number of aphids (less than 50 aphids'trap) were trapped in the yellow pan plastic traps. Over the whole experimental
period, plots with CP and BP mulches had lesser number of caughted aphids withrelationto the bare soil plots (between 100 to
200 aphids/trap). On the bare soil plots the highest aphid populations were caught during thefirstsix weeks after sowing.
WEEKS
Fig. 1. Winged aphids caughted in ysllowtraps at several times on melon crop.
32. Whitefly populations
Colonization of whitefly nymphs on the plant foliage wasreducedby all treatments, compared to the control (Table 1).
During thefirst34 days alter sowing, populations of nymphs were excluded from the melon plants growing under FRC and
microtunnels. Also, plastic mulches (black and clear)reducedthe number ofwhitefly nymphs compared with bare soil beds. At 41
days after sowing, treatments that had FRC and microtunnels showed less nymphs populations,recordingbetween 0.6 to 22
nymphsfcm2, while plots with clear and black mulches had 33 and 4.1 nymphs,respectively.In contrast, plants growing on bare
soil plots had significantly greater numbers of whitefly nymphs at 34 days (2.4 nymphs) and 45 days (292 nymphs-fern2) after
sowing
33. Soil temperature
Soil temperatures at 10 cm depth on different hours of day, on selected dates, are shown in Fig. 2. Soil temperatures were
consistently highest under clear polyethylene mulch plus floatingrowcover treatment and lowest under bare soil at 8:00,12:00 and
18:00 h during all period
78
23
_
s
1Q
3
P
32
0 30
D
28
2 2«
0
a
£
<1>
O
CO
22
20
30
-
37
35
-
33
—
31
-
29
-
27
-
25
A
5
Weeks
Fig. 2. Effect ofdifferent plastics andfloatingrowcoveison soil temperature registred at 8:00 (A), 13:00 (B) and 18:00 h (Q.
3.4. Marketablefruityield
Clear polyethylene mulch plusfloatingrowcover significantly increased (PO.Ol) export fruit number and export number
of cartons in plots of 28 nr in comparison of all treatments (Table 2 and 3). Nationalfruitnumber and national number of cartons
production were similar (P>0.05) between clear polyethylene mulch plus microtunnel perforated plastic and CP + FRC (Table 2
and 3). Fewer muskmelon for export production was found in clear polyethylene mulch plus microtunnel with non perforated
polyethylene.
79
Table 1. Average number ofwhitefly nymphs counted on different treatments and times.
Number ofnymphs/an2
Mulch type
Clear polyethylene
Black polyethylene
Clear+floatingrowcover
Black +floatingrowcover
Clear+microtunnel perforated
Clear+microtunnel no perforated
Bare soil
34DAS2
41 DAS
0.4 bP
0.4 b
0.0 b
0.0 b
0.1b
0.0 b
2.4 a
33 b
4.1b
0.6 c
22 be
0.8 c
2.0 be
292 a
7
DAS=days after sowing of muskmelon.
=Mean separation within columns by Duncan's Multiple Range Test, P < 0.05
y
Table 2. Effect ofdifferent plastic mulches onfruitnumber with commercial quality in plots of28 m2.
Fruits number
•
Mulch type
Clear polyethylene
Black polyethylene
Clear+floatingrowcover
Black+floatingrowcover
Clear+microtunnel perforated
Clear+microtunnel no perforated
Bare soil
Export
National
Total
1925 bcy
11.00 bed
47.50 a
21.50b
7.75 cd
0.00 d
025 d
5025 b
49.75 b
65.50 ab
51.50b
8725 a
41.50 b
425 c
70
61
113
73
95
41
5
y
" Mean separation within columns by Duncan's Multiple Range Test, P £ 0.05
Theresultsextend findings by ourselves (9,17) and others that plastic mulches used alone (7) andfloatingrow covers can
improve productivity of muskmelon (3,19,18), tomato (20) or bell peppers sowing at high population densities (11,10,15). Yield
was significantly increased by die mulch treatment, while dierowcover treatments 5 yielded the least Average of number of
cartons was also significantly increased by CP + PRC, over the bare soil and BP + FRC or clear and black polyethylene mulch
used alone. Ourresultsshow that mulching muskmelon with CP + FRC has enhanced yield andreduceinsect pest incidence
during thefirstweeks of cultivation This is not consistent withresultsof otherresearcherssuch as Rubeiz and Freiwat (21) who
found diat early production in tomato is enhanced by black plastic mulch, while therowcover used alone had a negative effect on
yield. Also Jollife and Gaye (15) working with bell peppers found that die row covets depressed the efficiency of leaves in
generating shoot diy matter, as expressed by unit leafarea
80
Table 3. Mean number ofcommercial picks of muskmelon and total number grown on different
mulch type androwcover in plots of28 m2.
Number ofcartons
Mulch type
Clear polyethylene
Black polyethylene
Clear +floatingrowcover
Black+floatingrowcover
Clear+microtunnel perforated
Clear+microtunnel no perforated
Bare soil
Export
National
Total
1.03 bcy
0.53 bed
2.45 a
1.10b
0.37 cd
0.00 d
0.01 d
231 be
221 be
2.96 ab
2.47 b
3.73 a
1.15cd
0.16d
3.34
2.74
5.41
3.57
4.10
1.15
0.17
y
=Mean separation within columns by Duncan's Multiple Range Test, P < 0.05.
Our data show that air temperatures at 18:00 h under therowcover exceeded 35°Con many days. Rubeiz and Freiwat (21)
found that such temperatines would become detrimental for tomato yield as it would lead to insufficient pollination blossom drop
or fruit abortion Similar effects were obseived in our study in muskmelon plants grown under clear polyethylene mulch plus no
perforated microtunnels.
Total yield was significantly increased by use of clear mulch alone and CP + FRC, while the BP + FRC, microtunnels,
plastic mulch used alone and control treatments yielded least. However, average fruit weight of the total yield was similar among
these treatments.
Conclusions
This work indicates that large muskmelonfruityields can be attained with management practices, such as mulching and
floatingrowcovers, thatresultin vigorous growth and less harm due to pests. Also, this study indicates that clear polyethylene
mulch plusfloatingrowcover had a potential economic value for muskmelon production as they advanced muskmelon fiuit
production and increased yield with less insecticide applications. Whereas, die polyethylene perforated and no perforated
micratunnels had a detrimental effect on muskmelon pioduction when are used in die western Mexico. In muskmelon crop,
floatingrowcovers should beremovedafterfloweringstarts and before day temperature exceeds 35°C, to prevent excess lieat
build-up which would affect pollination andfruitsetting Furtherresearchis needed to determine the appropiatetimeofremovalof
thefloatingrowcover and microtunnels, when used in conjunction with clear polyethylene mulch.
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