(D9)
ORANGE: Citrus sinensis L., cv. ‘Hamlin’
MANAGEMENT OF ADULT DIAPREPES ROOT WEEVIL ON CITRUS WITH FOLIAR
SPRAYS OF ZETA-CYPERMETHRIN, 2004
Clayton W. McCoy
University of Florida, IFAS
Citrus Research and Education Center
700 Experiment Station Road
Lake Alfred, FL 33850
Entomology and Nematology Department
Phone: (863) 956-1151
Fax: (863) 956-4631
E-mail: [email protected]
Robin J. Stuart
Michael E. Rogers
Herbert N. Nigg
William S. Castle
Diaprepes Root Weevil (DRW): Diaprepes abbreviatus (L.)
The residual and contact activity of Mustang Max 0.83EC at a rate 4 fl oz product/acre was compared to
an untreated check for adult control of DRW in a seasonal management program on citrus. The
experimental site was located 6 miles east of Poinciana, FL (Osceola County) in a heavily infested 2.5-yrold, two-row bedded grove of ‘Hamlin’ orange on mixed rootstocks. Chemical treatments were applied to
five consecutive trees in row, in 10-tree plots replicated 30 times in a RSP design. The remaining five
tree/plot served as untreated checks. The first foliar spray was applied on 11 Jun when trees were
beginning to flush summer leaves, and the number of adult DRW were increasing on the tree
(approximately 5 DRW/tree). The application was applied using a high-pressure handgun sprayer at a
volume of 125 gpa at 300 psi. A second application of Mustang Max at 4 fl oz product/acre + , Micromite
80WG at 6.25 oz product/acre + FC 435-66 oil at 5 gal/acre was applied on 2 Jul when the trees were at
full summer leaf flush and adult DRW were at peak density on the tree (approximately 15 DRW/tree).
Pre- and post-treatment survival of adult DRW in the treated and untreated plots was determined using
three sampling methods. The “shake” method was used to determine contact toxicity of Mustang Max to
adults infesting the tree canopy. The number of surviving adult DRW per tree was estimated weekly by
counting dislodged live weevils accumulating on the soil surface beneath the tree canopy after vigorously
shaking the small tree at the main trunk and branches for 3 sec with a hooked pole. A total of 150 trees
per treatment were sampled weekly.
The residual toxicity of Mustang Max to adult DRW was determined subsequent to spray application
using the “bag” method. Within 4 h after the first application, three laboratory-reared adults were placed
in each of 24 screen bags (12 × 16 inches). Twelve chemically treated and 12 untreated terminal flushes,
one terminal per tree, were placed into a bag exposing the flushes to feeding by the adults. Limb bags
were then tied firmly to the terminal to prevent weevil escape. After 1 wk post-treatment, the limb bags
were removed from the terminal and adult survival recorded from each bag. Frequently, weevils escaped
from a given bag. When this occurred, lost adults were treated as missing data. At week 2 and 3, this
procedure was repeated using a new cohort of “bagged” adults and new terminals with and without the
original chemical treatment. In recording our results, surviving adults were characterized as free moving
and able to return to an upright position when placed on their back. To estimate larval entry into the soil
subsequent to controlling adults in the tree canopy, 140 funnel traps per treatment were placed beneath
the tree canopy near the tree trunk to catch neonates dropping to the soil surface. Traps consisted of an
8.0-inch-diameter plastic funnel attached to a 1.2 × 20 inch length of PVC pipe support elevated about 12
inches above the ground. A screw top conical tube (50 ml) containing 5 ml of glycerol was attached to the
funnel tip to serve as a collection unit. The identification and counting of neonates within tubes was
performed microscopically in the treated and untreated check weekly. All data were square root
transformed prior to analysis. Data on adult survival from the bag method were compared using
contingency table analysis and Fisher’s exact test (P ≤ 0.05). Data generated from the shake method on
adult survival and from funnel traps on neonate abundance were compared by 3-factor analysis of
variance and LSMEANS mean separation (P ≤ 0.05).
When applied to a building population of DRW in early Jun, Mustang Max significantly (P ≤ 0.05)
reduced adults on the tree below that of the untreated check (Table 1); however, adult populations
rebounded within 7 days suggesting that the compound has very little residual effect. At 3 wk posttreatment, the adult population in the trees was significantly higher in the treatment compared to control.
The second application of Mustang Max was applied to a peak population (17.9 adults per tree) of DRW.
Contact toxicity of Mustang Max was outstanding, significantly reducing adults per tree to an
undetectable level (Table 1). Throughout Jul and Aug, DRW populations remained low in both the
chemically treated and untreated plots. As shown in Table 2, according to the bag method, adult survival
in chemically treated compared to untreated plots was not significantly different after exposure to leaf
terminals for 5, 13, and 20 days post-treatment. Overall survival ranged from 75.0 to 100%. The initial
application of Mustang Max on Jun 11 that reduced a building population of adult DRW in the tree by Jun
16 (Table l), appeared to result in the subsequent reduction in neonates entering the soil during the month
of Jun (Table 3). For the period of Jun 29 - Jul 6, a significantly higher number of neonates were trapped
weekly in the untreated check compared to the chemical treatment.
Table 1.
Mean no. of live adults/tree
Treatment/
formulationa
Rate amt
product/acre
Mustang Max +
4.0 fl oz
Micromite 80WG + 6.25 oz
FC 435-66
5.0 gal
Untreated check
---
27 May 3 Jun 10 Jun 16 Jun
23 Jun
1 Jul
8 Jul 15 Jul 22 Jul 29 Jul 4 Aug 12 Aug 26 Aug
2.5a
1.2a
5.1a
0.6a
8.9a
17.9a
0.0a
0.2a
0.9a
0.9a
1.7a
1.3a
1.2a
1.6b
1.1a
4.6a
9.0b
16.1b
9.8b
3.8b
2.2b
2.9b
1.9b
1.6a
1.5a
1.3a
Means within columns followed by the same letter are not significantly different based on a 3-factor analysis of variance and LSMEANS mean
separation (P > 0.05).
a
Treatments applied on 11 Jun (Mustang Max 0.83EC alone) and 2 Jul (Mustang Max + Micromite + FC 345-66 oil).
Treatments replicated 30 times.
Table 2.
% adult survival; DAT
5
Treatment/
formulationa
13
Rate amt
product/acre
n
%
4.0 fl oz
---
26
24
80.8a
87.5a
Mustang Max +
Untreated check
n
20
%
n
8 75.0a
25 100.0a
%
9 88.9a
30 100.0a
Percentages within columns followed by the same letter are not
significantly different based on a 3-factor analysis of variance and
LSMEANS mean separation (P > 0.05).
a
Each treatment replicated 12 times.
Table 3.
Treatment/
b
formulation
Mustang Max +
Micromite 80WG +
FC 435-66
Untreated check
Mean no. of neonates captured in funnel traps weeklya
Rate amt
product/acre
4.0 fl oz
6.25 oz
5.0 gal
---
25 May
1 Jun
8 Jun 15 Jun 22 Jun 29 Jun
6 Jul
13 Jul 20 Jul 27 Jul 3 Aug
10 Aug
0.3a
0.5a
0.4a
0.1a
0.0a
0.0a
0.0a
0.6a
0.0a
0.3a
0.0a
0.0a
0.4a
1.0b
0.2a
0.1a
0.2a
0.4b
0.5b
0.5a
0.2b
0.4a
0.0a
0.2b
Means within columns followed by the same letter are not significantly different based on a contingency table analysis and Fisher’s exact
test (P > 0.05).
a
Means neonates trapped in 140 funnel traps/treatment.
b
Treatments applied on 11 Jun (Mustang Max 0.83EC alone) and 2 Jul (Mustang Max + Micromite + FC 345-66 oil).