High Potential for Flea Beetle Problems in Field Corn By Wayne Bailey

Mild winter temperatures during the months of December, January and February indicate the potential for high populations of flea beetle in most regions of Missouri. In our model, the potential for flea beetle damage is calculated by adding together the average daily winter temperatures for the months of December, January and February. If the average monthly temperatures for these months add to less than 900 F, then the risk of economic flea beetle infestations is low. If the total is between 900 F and 1000 F, then moderate flea beetle damage can be expected. Heavy damage is possible if the three monthly averages total 1000 F or more. Data from the 17 Commercial Ag Weather Stations located around the state are summarized by regions of the state and specific counties in the following table. Average monthly temperatures are given in degrees Fahrenheit.

County	December	January	February	Total
Atchison	32.8	25.0	36.2	94.0
Gentry	31.7	25.3	35.7	92.7
Buchanan	33.5	26.2	37.1	96.8
Linn	33.5	26.2	35.7	95.4
Chariton	33.7	28.5	37.3	99.5
Knox	32.1	27.0	35.7	94.8
Monroe	33.3	28.5	36.7	98.5
Audrain	32.4	29.9	38.1	100.4
Boone	35.2	30.9	38.8	104.9
Pettis	35.8	31.0	39.5	106.3
Morgan	37.1	32.6	40.5	110.2
Crawford	35.8	35.8	39.8	111.4
Barton	38.2	34.5	41.6	114.3
Cape Girardeau	33.8	38.1	42.1	114.0
Mississippi	36.0	40.1	43.3	119.4
Dunklin	36.3	40.3	44.0	120.6
Pemiscot	38.0	41.3	45.2	124.5
Average for all Locations	34.7	31.8	39.3	105.7

Biology/ Damage: Flea beetles are small, dark, jumping beetles which overwinter as adults. In early spring they move to seedling corn and feed on plant foliage from the time of plant emergence through about the fourth-leaf stage of growth. Adult beetles strip the chlorophyll layer (green tissue) from the surface of seedling corn leaves, resulting in the formation of "window panes" or translucent areas on leaf surfaces. Damage is often seen as translucent tracks or lines that run parallel to the veins of the corn leaf. Heavy flea beetle infestations cause plants to look tattered and wilted, similar to the type of injury caused to seedling corn when blasted by blowing sand. The most injurious flea beetle attacking corn is the corn or maize flea beetle. Typically, infestations are most severe in years where mild winters allow for increased survival of adults and cool temperatures and drought conditions during spring result in slowed growth of corn plants. Flea beetles may transmit Stewart’s wilt (a bacterial wilt) to corn, although most field corn has resistance to this plant pathogen. The economic threshold for implementation of control methods for flea beetles in field corn is an average of five or more beetles per corn seedling up through the four-leaf stage of development. To scout for flea beetles, examine corn plants for feeding damage and determine the average number of flea beetles present per corn plant. This is most readily accomplished in the early morning or late afternoon by walking slowly through the field and counting beetles as they feed. Remember, flea beetles are easily recognized by their jumping ability similar to grasshoppers.

Management Options: Although the model predicts high populations of flea beetle for most areas of the state, a couple factors may limit flea beetle numbers in the 2005 season. First, adult beetle mortality may be higher than predicted by winter temperatures due to the lack of snow cover and rapid changes from high to low temperatures experienced several times this past winter. A second factor may be that the widespread use of seed treatments for corn during the past few years may be suppressing flea beetle problems statewide, similar to what Bt corn has done to the European corn borer populations throughout the Midwest. Regardless of predictions and insecticide use, producers are encouraged to scout seedling corn for the presence of flea beetle this spring.

If an economic population is found, an effective management option for flea beetle is the use of foliar applied insecticide rescue treatments. Several insecticides are labeled for this use once the economic threshold has been reached or exceeded. Cruiser and Poncho seed treatments also provide good protection from this pest due to their systemic activity in seedling foliage. Insecticides and rates labeled for flea beetle management on field corn include the following:

Flea Beetles	Permerthrin	*Ambush	6.4 to 12.8 . oz	Over row	Treatment is justified when 5 or more beetles per plant are present or when seedling plants are being severely damage or killed and beetles are present.
	Esfenvalerate	*Asana XL	5.8 to 9.6 . oz
	Cyfluthrin	*Baythroid 2	0.6 to 1.6 . oz
	Bifenthrin	*Capture 2EC	2.1 to 6.4 . oz
	Bifenthrin	*Fanfare 2EC	2.1 to 6.4 . oz
	Methomyl	*Lannate LV	3/4 to 1 ½ pt
	Chlorpyrifos	*Lorsban 4E	1 to 2 pt
	Zeta-cypermethrin	*Mustang Max	2.72 to 4 . oz
	Chlorpyrifos	*Nufos 4E	1 to 2 pt
	Microencapsulated	*Penncap-M	2 to 3 pt
	Methyl parathion
	Permethrin	*Pounce 3.2EC	4 to 8 . oz
	Gamma-cyhalothrin	*Proaxis	2.56 to 3.84 . oz
	Carbaryl	Sevin XLR Plus	1 to 3 pt
	Lambda-cyhalothrin	*Warrior	2.56 to 3.84 . oz
Seed Treatments
	Thiamethoxam	Cruiser	See product label	On Seed
	Clothianidin	Poncho	See product label	On Seed
	Tefluthrin	Proshield with Force ST	See product label	On Seed

Wayne Bailey Entomology 573-882-2838 or 573-864-9905