Insects become pests in crop production when their numbers and/or damage have surpassed the level at which they begin to threaten farmers' return on investment (Ortega, 1987). As stated previously, yield losses of field corn can be as great as 20-50% due to insect pests, especially corn rootworm. For this reason, many field corn growers use a soil-applied insecticide to control this and other insect pest problems.
Table 17 shows the percent of total acres planted to field corn grown for grain that were treated with insecticides in New York State in 1994. Fifty- one percent of the grain acreage in this survey was treated with insecticides, ranging from 27.3% in the Southern Tier, to 92.0% in the Hudson River area. Only 27.9% of the total acres planted to field corn for silage were treated with insecticides in 1994 (Table 18). No insecticides were used in the Hudson River or North Country areas, while 54.4% was treated in the Catskills/Capitol area.
Table 19 shows a summary of insecticides used by New York State growers on corn grown for grain in 1994. Only 35 growers applied insecticide to their grain corn crop. Tefluthrin (Force) was used on the greatest number of acres (37.8% of insecticide treated acreage), and the greatest amount of active ingredient applied (2,546.9 lbs.) was chlorpyrifos. There was a total of 5,533.4 lbs. insecticide active ingredient applied to 6,151.4 acres of corn for grain, making an average of 0.9 lbs. ai applied per acre in 1994. The greatest amount of ai/acre was applied in the Southern Tier (1.19 lbs/acre), followed by the Upstate area (0.92 lbs/acre, Figure 9).
Table 20 shows who applied the insecticides, the application equipment used, the timing and method of application, and the basis for application of insecticides applied to field corn grown for grain in New York in 1994. One hundred percent of insecticides were applied by the grower. A planter box was used almost exclusively for applying insecticides. They were applied at planting (89.1% of fields, 85.3% of treated acreage), and were banded (71.9% of fields, 70.3% of treated acreage). The most common reasons that insecticides were applied were "routine application" (50.0% of fields, 70.3% of treated acreage) and "presence of pest on the basis of scouting" (48.4% of fields, 51.7% of treated acreage).
Table 21 shows a summary of insecticides used by New York State growers on corn grown for silage in 1994. Twenty-three growers applied insecticide to their silage corn crop. As with corn for grain, tefluthrin (Force) was applied to the greatest number of acres (54.7% of treated acreage), but unlike corn for grain, the greatest amount of active ingredient applied (787.3 lbs) was terbufos. There was a total of 1,182.6 lbs insecticide active ingredient applied to 1,734.5 acres of corn for silage, making an average of 0.68 lbs ai applied per acre in 1994. The greatest amount was applied in the Upstate area (1.06 lbs ai/acre, Figure 10).
Table 22 shows who applied the insecticides, the application equipment used, the timing and method of application, and the basis for application of insecticides applied to field corn grown for silage in New York in 1994. Ninety-seven percent of the fields, and 99.3% of the treated acreage were sprayed by the grower using a planter box. The insecticides were applied at planting (93.5% of fields, 95.4% of treated acreage), and were banded (67.7% of fields, 77.9% of treated acreage). The most common reason insecticides were applied to a particular field was "presence of pest on the basis of scouting" (54.8%). A cost comparison of insecticides used in field corn production is shown in Table 23.
Table 24 shows a comparison of rotation on the percent of field corn acres treated with insecticides in New York in 1994. One would expect that the need for insecticide treatments would be less in first and second year corn versus third and continuous corn. This is the pattern for corn grown for silage, but in corn grown for grain, 37.2% of the total 1st year corn acreage was treated with insecticides versus only 29.4% of 3rd year corn acreage. This same pattern appears when comparing pounds of insecticide active ingredient applied per acre (Figure 11). Pounds active ingredient per acre for third year corn for grain is much higher than the others (2.62 lbs/acre), but the amount applied to continuous corn (0.76 lbs/acre) is less than both first and second year corn (1.06 and 1.0 lbs/acre, respectively). The same is true for corn for silage, but the difference is greater. One half pound, and one-quarter pound less active ingredient per acre was applied to continuous corn versus first and second year corn, respectively.
Table 25 shows a comparison of type of tillage used on the percent of field corn acreage that was treated with insecticides. Corn grown for grain and for silage show the same pattern in regard to percent of acres treated based on tillage. Growers using no-till systems treated little to no acreage with insecticides, while growers using conservation tillage systems treated 12 to 24% more acreage than those with conventional tillage systems. The amount of active ingredient applied to corn grown for grain appears to be inversely related to the percent of acreage treated. That is, no-till corn for grain had 1.76 lbs ai/acre applied, versus 0.57 lbs ai/acre applied to corn grown with conservation tillage (Figure 12). Amount of active ingredient applied to corn for silage was about the same regardless of the tillage system used.
Table 26 shows the types of insects for which New York State growers treated corn for grain in 1994. Corn rootworm larval stage, was the major insect for which growers treated. More than half of the acreage was treated in order to control corn rootworm. This was true for all active ingredients used except carbofuran and carbaryl. The same pattern applies to corn for silage (Table 27), where greater than three-quarters of the treated acreage was treated to control corn rootworm, except with the active ingredient chlorpyrifos, where cutworms were the major insect pest.
Figure 13 illustrates the percent of acreage treated with insecticides for specific insect pests by area of the State. Maize billbugs, nematodes, and slugs were only a problem in the Southern Tier in corn grown for grain, while they were not even indicated as a pest in corn grown for silage. Upstate New York (for both grain and silage) only had a major problem with corn rootworms, while the other areas had more insect pests for which they applied insecticides.
The effect of rotation on types of insect pests is illustrated in Figure 14 for both types of corn. As expected, corn rootworms (larval stage) appear to be a bigger problem in third year and continuous corn versus first and second year corn.
The effect of type of tillage on insect pests appears to be that corn grown in conventional tillage systems are treated for more types of insect pests than conservation or no-till systems (Figure 15). The large number of missing answers for the question of what insects the insecticides were applied for indicates that growers probably did not know which insects were a problem. The fact that the majority of insecticide applications were made as "routine applications" confirms this.