Weed and Pest Control

Weeds, insects, and diseases are as inevitable with nursery crops as with any other plants. Production of a monoculture with close spacing, high fertility, and ample irrigation ensures an assortment of prolific pests. All the principles of pest control discussed in Chapters 6 and 20 are appli­cable to nursery production, but there are some differences in the ways they are applied. The differences are due to the openness of the nursery production area and the length of time the crop is under production. For example, soil pasteurization is helpful in nursery container produc­tion but far less effective than in greenhouse production. The soil, being outdoors, becomes contaminated much more quickly. Still, the quan­tity of weed seeds, insect larvae, and pathogenic inoculum is reduced initially, giving the crop a better chance of becoming established, so pasteurization can be helpful. Weeds are also much more troublesome for the nursery grower than for the greenhouse grower. Their seeds can persist in the nursery field for many years, with a fresh crop waiting to germinate each time the soil is turned over. In addition to their com­petition with the desired plants, which has been described, weeds can reduce plants’ sales appeal when they appear in the same container.

Insects and diseases are controlled by using pest-free propagative stock, by growing plants in regions of the country where their pests are not as common, by selecting resistant varieties for growth, by prevent­ing the growth of weeds that can harbor the pests, by cleaning up crop debris that can serve as sources of inoculum, and by spraying or dusting with chemical protectants and eradicants. Where chemical pesticides are required, the state’s college of agriculture can provide listings of effective products approved for use on specified crops. As noted else­where, growers should take care to mix only the quantity of pesticide that can be applied in a single spraying, and avoid spraying or dusting on windy days. If the field is sloped, run-off can also be a hazard, so the product should not be applied to the point of dripping.

Weeds can be controlled with preemergence herbicides applied in the autumn and early spring. Later in the spring, postemergence prod­ucts can keep the nursery free of broadleaved weeds. The herbicides are usually applied in granular form as a side dressing. Many of the products are specific against certain plants. They cannot be applied universally since certain crops could be harmed. The product labels list the plants that can be treated safely as well as the weeds controlled by the chemical. Some of the herbicides require mixing into the soil to become active. Others are dissolved by rainwater or artificial irrigation, and do not require cultivation. Some are reduced in effectiveness if the soil is disturbed, so mechanical cultivation must be avoided during crop production.

Some pests bother nursery crops more than floriculture crops. These include rodents, rabbits, and deer. Rodents can be controlled, though seldom eliminated, with poisoned bait placed throughout the nursery. Rabbits can be discouraged with repellants sprayed onto the base of plants or with plastic coils wrapped around the trunks of young trees. Deer are much more difficult to control, although some benefit is claimed for repellants. Fencing the nursery can prevent deer from win­ter browsing in the production fields.

Integrated pest management is possible with nursery crop pro­duction, but it is effective only if every employee who works with the crops understands and implements it in a timely manner. Scouting of the crops on a regular, frequent basis is essential to detect the pres­ence of insects, pathogens, noxious weeds, or animal injury. Immediate response to the scouting report is then mandatory if the pest is to be contained. Control procedures must be applied as soon as the scouting report is filed. In so doing, the pest can often be controlled without the need for more expensive control practices that would be required if the problem were permitted to spread.