SPOTTED CUCUMBER BEETLE or SOUTHERN CORN ROOTWORM: Diabrotica undecimpunctata howardi, Chrysomelidae
ADULT: These small (1/4 to 3/8 in. long), oval-shaped beetles have 12 black spots in rows of four on yellowish-green to green wing covers (elytra), black legs and head, and brown antennae. The third tarsal segment on all legs is laterally swollen into two lobes with the last (fourth) tarsal segment originating from between the lobes.
EGG: Small, oval shaped, pale yellow eggs are found in soil in clusters of 1 to 12. Larvae emerge in 6 to 8 d.
LARVA: The white, elongate and soft bodied larvae have three pairs of minute legs. Larvae complete their development in 15 to 22 d feeding on corn roots. Larvae are indistinguishable from those of the banded cucumber beetle.
PUPA: The white to pale green pupae are found within round cells in the soil. Adults emerge in 16 to 20 d.
GENERATION TIME: 35 to 50 d.
DAMAGE: Spotted cucumber beetles are found throughout Florida, but are most common north of Tampa. Larvae damage roots and can enter the corn stalk just above the roots where they can eat the crown and kill the buds of young plants. Bacterial wilt and other pathogens can enter the plant through these wounds. Severe root damage can result in lodging. Adults feed on leaves in and out of whorl and on silks. Adult feeding produces irregular shaped, often elongate holes in young leaf tissue within the whorls. Delayed growth, plant stunting and stand loss can result from heavy feeding damage to whorls of seedlings. Feeding damage to older leaves is evidenced by notched leaves, window paning and irregular patches with only the veins remaining. Silk pruning can result in blanks within the ears.
CONTROL: Several predacious insects and spiders prey on these insects, but migration of large numbers can quickly overwhelm the natural enemy complex. Chemical control of adults is through contact or bait insecticides. These latter type selectively treat the beetles as they eat the baits. Numerous pesticides are labeled for mostly at-plant treatment of cumber beetle larvae. Formulations, rates, and pre-harvest intervals of insecticides for spotted cucumber beetle control are listed below for sweet corn (Table 1) and field corn (Table 2).
Table 1. Chemical control of corn rootworms (including cucumber beetles, southern corn rootworms, banded cucumber beetles) in sweet corn | |||
---|---|---|---|
Insecticide, formulation | Rate/acre | Min. days to harvest | Application notes |
carbaryl (Adios, Slam) 13% | 0.25 - 0.75 lb | 0 | SCR adults |
carbaryl (Sevin, Sevin XLR Plus) 4 F, 4 EC | 1 - 2 qt | 2 ears; 48 forage; 14** | CR adults |
carbaryl (Sevin) 80 WSP | 1.25 - 2.5 lb | 2 ears; 48 fodder; 14** | CR adults |
carbofuran (Furadan) 4 F | 2.5 fl oz / 1000 row-ft | 30 feed forage | CR; banded or in-furrow at plant |
chlorpyrifos (Lorsban) 4 E *** | 6 pt | 35 fodder, grain; 14 ** | CR adults; banded or in-furrow at plant or broadcast post-emerge |
chlorpyrifos (Lorsban) 15 G | 8 oz / 1000 row-ft | 35 fodder, grain; 14 ** | SCR larvae; banded or in-furrow at plant |
cyfluthrin (Baythrioid 2) 2 EC | 1.6 - 2.8 fl oz | 0 | CR adults |
cyhalothrin (Karate, Warrior) 1 EC | 2.56 - 3.84 fl oz | 1 | SCR adults |
diazinon (D-z-n AG500) 4 EC | 0.5 - 1 pt | 7 | CR adults |
diazinon (D-z-n AG600) WBC | 6.5 - 12.75 fl oz | 7 | CR adults |
esfenvalerate (Asana XL) 0.66 EC | 5.8 - 9.6 fl oz | 1 | CR & BCB adults |
ethoprop (Mocap) 6 EC *** | 1.4 fl oz / 1000 row-ft | CR adults; banded at plant ( not in-furrow) or cultivation | |
ethoprop (Mocap) 10 G | 10.5 oz / 1000 row-ft | CR adults; banded at plant ( not in-furrow) or cultivation | |
methomyl (Lannate LV) 2.4 EC | 0.75 - 1.5 pt | 0 ears; 3 forage | CR adults |
methomyl (Lannate SP) 90 WSP | 0.25 - 0.5 lb | 0 ears; 3 forage | CR adults |
methyl parathion (Penncap-M) 2 EC | 1 - 2 pt | 3 ears; 12 forage, grazing | CR adults |
oil (Sun Spray) 7 E | 2 gal / 100 gal water | 0 | CR adults |
oxydemetonmethyl (MetaSystox-R) 2 EC | 1.5 - 2 pt | 7 - 1 app., 21 - 2 app. | CR adults |
permethrin (Ambush) 2 EC | 6.4 - 16.0 fl oz | 1 | CR adults |
permethrin (Ambush) 25 WP, WSB*** | 6.4 - 16.0 oz | 1 | CR adults |
permethrin (Pounce) 25 WP | 6.4 - 12.8 oz | 1 | CR adults |
permethrin (Pounce) 3.2 EC | 4 - 8 fl oz | 1 | CR adults |
phorate (Thimet) 20 G | 6 oz / 1000 row-ft | 30 | CR adults; banded at plant ( not in-furrow) or cultivation |
pyrethrins + piperonyl butoxide (Pyrenone) 66% L (EC) | 2 - 12 fl oz | 0 | SPCB adults |
pyrethrins + rotenone (Pyrellin) EC | 1.5 - 2 pt | 12 hr | cucumber beetle |
tefluthrin (Force) 3 G | 4 - 5 oz / 1000 row-ft | SCR; banded or in-furrow at plant or cultivation | |
terbufos (Counter) 15 G | 8.0 oz / 1000 row-ft | 30 forage, grazing | CR adults; banded or in-furrow at plant or cultivation |
terbufos (Counter CR) 20 G *** | 6.0 oz / 1000 row-ft | 60 ears; 30 forage, grazing | CR adults; banded or in-furrow at plant or cultivation |
CR = corn rootworms, SCR = southern corn rootworm, BCB = banded cucumber beetle, SPCB = spotted and 12-spotted cucumber beetle | |||
**harvest or grazing of forage or silage | |||
***check label for other application techniques and rates |
Table 2. Chemical control of corn rootworms (including cucumber beetles, southern corn rootworms) in field corn | |||
---|---|---|---|
Insecticide, formulation | Rate/acre | Min. days to harvest | Application notes |
carbaryl (Adios, Slam) 13% | 0.25 - 0.75 lb | SCR adults | |
carbaryl (Sevin, Sevin XLR Plus) 4 F, 4 EC | 1 - 2 qt | 48 fodder, grain; 14** | CR adults |
carbaryl (Sevin) 80 WSP | 1.25 - 2.5 lb | 48 fodder, grain; 14** | CR adults |
carbofuran (Furadan) 4 F | 2.5 fl oz / 1000 row - ft | 30 feed forage | CR adults; banded or in-furrow at plant or post emergence side dress |
chlorpyrifos (Lorsban) 4 E*** | 2.4 fl oz / 1000 row-ft or 1 - 2 pt | 35 fodder, grain; 14 grazing, silage | CR larvae; banded and in-furrow at plant or broadcast post-emerge |
chlorpyrifos (Lorsban) 15 G | 8 oz / 1000 row-ft | 35 fodder, grain; 14** | SCR larvae; banded or in-furrow at plant or at cultivation |
cyhalothrin (Karate, Warrior) 1 EC | 2.56 - 3.84 fl oz | 21 | SCR adults |
dimethoate (Dimate, Dimethoate 400) 4 EC | 0.67 - 1 pt | 14 | CR adults |
esfenvalerate (Asana XL) 0.66 EC | 5.8 - 9.6 fl oz | 21 | CR adults |
ethoprop (Mocap) 6 EC | 1.4 - 2.9 fl oz / 1000 row-ft | CR adults; banded at plant or at cultivation, not in-furrow | |
ethoprop (Mocap) 10 G | 10.5 - 21.5 oz /1000 row-ft | CR adults; banded at plant or at cultivation, not in-furrow | |
ethyl parathion (Parathion) 8 EC | 0.75 pt | 12 | CR adults |
methomyl (Lannate LV) 2.4 EC | 0.75 - 1.5 pt | 3 forage; 21 ears, fodder | CR adults |
methomyl (Lannate SP) 90 WSP | 0.25 - 0.5 lb | 3 forage; 21 ears, fodder | CR adults |
methyl parathion (Penncap -M) 2 EC | 1 - 2 pt | 12 | CR adults |
oil (Sun Spray) 7 E | 2 gal / 100 gal water | CR adults; early spring, summer | |
permethrin (Ambush) 2 EC | 6.4 - 12.8 fl oz | 30 harvest of fodder, grain | CR adults |
permethrin (Ambush) 25 W | 6.4 - 12.8 oz | 30 harvest of fodder, grain | CR adults |
permethrin (Pounce) 25 WP; WSB*** | 6.4 - 12.8 oz | 30 harvest of fodder, grain | CR adults |
permethrin (Pounce) 3.2 EC | 4 - 8 fl oz | 30 harvest of fodder, grain | CR adults |
phorate (Thimet) 20 G | 6 oz / 1000 row-ft | 30 | CR adults; banded at plant or cultivation, not in-furrow; not popcorn |
pyrethrins + rotenone (Pyrellin) EC | 1 - 2 pt | 12 hr | cucumber beetles |
tefluthrin (Force) 3 G | 4 - 5 oz / 1000 row-ft | SCR; banded or in-furow at planting or cultivation | |
terbufos (Counter) 15 G | 8.0 oz / 1000 row-ft | CR adults; banded or in-furrow at plant or cultivation | |
terbufos (Counter CR) 20 G | 6.0 oz / 1000 row-ft | CR adults; banded or in-furrow at plant or cultivation | |
CR = corn rootworms, SCR = southern corn rootworm | |||
**harvest or grazing of forage or silage | |||
***check label for other application techniques and rates |