Mulching by spreading organic matter around plants is an effective
method to manage some pest insects as well as weeds (Brown &
Tworkoski 2004; Johnson et al. 2004). Mulches provide shelter for
predatory insects (Pullaro et al. 2006). Soil solarization, a
hydrothermal method of managing nematodes, diseases, insects, and weeds,
is accomplished by passive heating of moist soil covered with
transparent plastic sheeting (McGovern & McSorley 1997). Because of
the lethal effects from high soil temperature, solarization must be
conducted before crops are planted. The objective of the present study
was to evaluate the integrated effects of solarization and organic mulch
on the soil surface insect community, including non-target and
Field experiments were conducted in fall 2008 at the University of
Florida Plant Science Research and Education Unit (lat.
29[degrees]24’N, long. 82[degrees]9W), near Citra, FL. The soil was
Arredondo sand (95% sand, 2% silt, 3% clay) with 1.5% organic matter.
The field was rototilled in Jul, and beds were formed (20 cm high, 76 cm
wide, with 1.8 m between bed centers). Individual plots were single
beds, 9.14 m in length. Average soil moisture measured gravimetrically
before bed formation was 8.7%.
Four treatments were arranged in a randomized complete block design
with 5 replications. The treatments compared were: solarization (S) =
plastic pre-plant, nothing post-plant; mulch (M) = mulch pre-plant,
mulch post-plant; mulch + solar (MS) = plastic pre-plant, mulch
post-plant; and control (C) = nothing pre-plant, mulch post-plant. For
the mulch treatment, a pre-plant mulch of sunn hemp (Crotalaria juncea
L.), 3 cm thick (8.16 kg total weight/plot), was applied over the bed
surface on Aug 13. In the solarization treatment, beds were covered with
Polydak[R] (1.3-milthick, UV- stabilized, transparent film, Ginegar
Plastics Products, Ginegar, Israel) plastic film for 6 weeks beginning
on Aug 12 as described by Gill et al. (2009). After 6 weeks, plastic was
removed, and all beds were planted with ‘Potomac Pink’
snapdragons (Antirrhinum majus L.). Mulch was again applied on Oct 2, as
a main mulch application, to M, C, and MS treatments. Note that is not
possible to have mulch and solarization plastic present on a plot at the
Soil surface insects were sampled with plastic sandwich containers
(14 cm x 14 cm x 4 cm deep) used as pitfall traps as described by Borror
et al. (1989). Each pitfall trap was placed in the center of the plot
and buried so that the upper edge was flush with the soil surface. Traps
were filled three-quarters full with tap water, and 3 to 4 drops of dish
detergent (Ultra Joy[R], Procter & Gamble, Cincinnati, OH) added to
break surface tension, and ensure that the insects remain in the trap.
Traps were set out in the morning and collected before noon the next day
(recorded as the sampling date). Traps were placed in cold storage
(10[degrees]C), contents transferred and stored in 70% ethanol, and
insects were identified to order and family and counted.
Data were subjected to one-way analysis of variance (ANOVA) with
the Statistical Analysis System (version 9.1; SAS Institute, Cary, NC).
Treatment means were separated based on the least significant difference
(LSD) range test, at P [less than or equal to] 0.05.
Preplant mulching or solarization was useful in reducing weeds in
the plots. The main weeds were nutsedges (Cyperus spp.), grasses,
Florida pusley (Richardia scabra L.), purslane (Portulaca oleracea L.),
and hairy indigo (Indigofera hirsuta L.). The percentage of the plot
surface area occupied by weeds averaged 3 to 5% in MS, ca 90% in C, 20
to 25% in S, and 35 to 40% in M plots, respectively.
On most sampling dates, Collembola populations were higher in the M
treatment than in the S treatment (Table 1). Collembola are associated
with decomposing organic matter (Colemen & Crossley 1996), which was
provided by sunn hemp in the M treatment. Collembola were not as
abundant in S plots, possibly because mulch was absent. In addition, the
solarization process itself may have reduced populations that were
present in soil.
Many groups of arthropods, including spiders, ants, grasshoppers,
crickets, elaterids, and staphylinids were unaffected by the treatments
(data not shown), but interesting trends were observed in some others.
Cicadellids were more abundant (P [less than or equal to] 0.10) in C
plots (12.0 [+ or -] 2.59/ trap) than in MS plots (5.8 [+ or -]
2.42/trap) on Nov 9. On Oct 28, highest numbers (P < 0.10) of
carabids (0.8 [+ or -] 0.37/ trap) and flea beetles (0.4 [+ or -]
0.24/trap) were observed in S plots. Highest numbers (P < 0.10) of
dolichopodids (8.0 [+ or -] 2.43/trap) were observed in S plots on Dec
8. Solarized plots were free of mulch and had relatively low weed
levels, both of which might influence insect movement. Environmental
heterogeneity is known to interfere with movement and host finding of
flea beetles and other insects (Root 1973; Smith & McSor ley 2000).
On Oct 28 and Nov 9, other plant feeders (whiteflies, thrips, and
aphids) were significantly higher (P < 0.05) in the C treatment
compared with the other 3 treatments (Table 1). It is possible that
whiteflies, thrips, aphids, and maybe leafhoppers were present and fed
on the abundant weeds in the control treatment. Treatments that limit
weeds may be helpful in limiting these plant-feeding insects as well.
Integrating solarization and mulching did not have much overall impact
on the insect community, compared to solarization alone, but it did lead
to recovery of Collembola populations later in the season to similar
levels found in mulched plots.
Integration of solarization and organic mulch did not affect the
insect community as much as solarization alone. Solarization and
mulching influenced Collembola population levels and occasionally
affected other insect groups, depending on their behavior. Plots without
solarization or mulching developed heavy weed levels and increased
levels of plant-feeding insects.
BORROR, D. J., TRIPLEHORN, C. A., and JOHNSON, N. F. 1989. An
Introduction to the Study of Insects, pp. 751-753. 6th ed., Saunders
College Publishing, Chicago, IL.
BROWN, M. W., and TWORKOSKI, T. 2004. Pest management benefits of
compost mulch in apple orchards. Agric., Ecosyst. Environ. 103: 465-472.
COLEMAN, D. C., and CROSSLEY, JR., D. A. 1996. Secondary
production: Activities of heterotrophic organisms–the soil fauna, pp.
51-106 In Fundamentals of Soil Ecology. Academic Press, San Diego, CA.
GILL H. K., MCSORLEY, R., and TREADWELL, D. D. 2009. Comparative
performance of different plastic films for soil solarization and weed
suppression. Hort Tech. 19: 769-774.
JOHNSON, J. M., HOUGH-GOLDSTEIN, J. A., and VANGESSEL, M. J. 2004.
Effects of straw mulch on pest insects, predators, and weeds in
watermelons and potatoes. Environ. Entomol. 33: 1632-1643.
MCGOVERN, R. J., and MCSORLEY, R. 1997. Physical methods of soil
sterilization for disease management including soil solarization, pp.
283-313 In N. A. Rechcigl and J. E. Rechcigl [eds.], Environmentally
Safe Approaches to Crop Disease Control. CRC, Lewis Publishers, Boca
PULLARO, T. C., MARINO, P. C., JACKSON, D. M., HARRISON, H. F., and
KEINATH, A. P. 2006. Effects of killed cover crop mulch on weeds, weed
seed, and herbivores. Agric., Ecosyst. Environ. 115: 97-104.
ROOT, R. 1973. Organization of a plant-arthropod association in
simple and diverse habitats. The fauna of collards (Brassica oleracea).
Ecol. Monogr. 34: 95-124.
SMITH, H. A., and MCSORLEY, R. 2000. Intercropping and pest
management: A review of major concepts. American Entomol. 46: 154-161.
HARSIMRAN K. GILL and ROBERT MCSORLEY
Entomology and Nematology Department, University of Florida,
Gainesville, FL 32611-20
Table 1. Effect of treatments on insect taxa (numbers/pitfall
trap) on selected sampling
Treatment (1) Collembola feeders (2)
MS 10.2 b [+ or -] 3.34 1.6 a [+ or -] 0.51
C 21.8 ab [+ or -] 5.46 4.4 a [+ or -] 1.54
S 14.6 b [+ or -] 5.33 3.8 a [+ or -] 0.97
M 32.2 a [+ or -] 6.63 6.8 a [+ or -] 3.34
F value 3.26 1.24
P value 0.0492 0.3268
MS 13.8 b [+ or -] 4.93 1.0 b [+ or -] 0.45
C 15.0 b [+ or -] 1.76 7.6 a [+ or -] 2.87
S 12.0 b [+ or -] 1.52 2.4 b [+ or -] 1.03
M 32.8 a [+ or -] 3.51 0.6 b [+ or -] 0.40
F value 8.9 4.3
P value 0.0011 0.0209
MS 46.6 a [+ or -] 8.25 0.8 b [+ or -] 0.37
C 34.4 b [+ or -] 6.45 6.4 a [+ or -] 2.38
S 14.0 b [+ or -] 3.73 1.6 b [+ or -] 0.81
M 32.6 a [+ or -] 5.35 1.6 b [+ or -] 0.51
F value 4.76 3.9
P value 0.0148 0.0287
MS 21.8 ab (4) [+ or -] 3.80 3.0 a [+ or -] 0.71
C 34.4 a [+ or -] 7.56 1.6 a [+ or -] 0.93
S 16.0 b [+ or -] 2.61 2.6 a [+ or -] 0.75
M 24.2 ab [+ or -] 2.24 2.0 a [+ or -] 0.84
F value 2.83 0.59
P value 0.0717 0.6302
(1) Solarization (S) = plastic pre-plant, nothing post- plant;
mulch (M) = mulch pre-plant, mulch post-plant; mulch + solar
(MS) = plastic pre-plant, mulch post-plant; and control (C) =
nothing pre-plant, mulch post-plant.
(2) Other plant feeders include whiteflies, aphids, and thrips.
3Statistics from analysis of variance (ANOVA).
Data are means [+ or -] standard error of 5 replications. Means
followed by the same letters do not differ significantly based on
LSD test (P [less than or equal to] 0.05)
(4) Mean separation at P [less than or equal to] 0.10