Insects can be problematic for spinach growers and pest pressures vary geographically.
“In Texas we have to deal with cucumber beetles, crown mites, some aphids and some worms,” said Stein.
Scouting the fields to determine pest population levels and spraying accordingly is the best management strategy, according to Stein.
Pests vary geographically across the country and within the same state. For example, in the Salinas Valley in California, the warmer or hotter area in the southern part of the region increases risk of pest infestation. For example, temperatures are typically higher in the southern part of the Salinas Valley than northern region throughout the year.
Generally speaking, West Coast growers are particularly worried about battle leafminers and lepidopterans pests.
“Growers typically plant these crops where the temperatures are mild and reduce the risk of severe infestation,” said Shimat V. Joseph, Ph.D., IPM advisor at the University of California Cooperative Extension.
The leafminers (Liriomyza spp.) punch the leaf surface using egg-laying apparatus and feed on the sap that flows from those injury sites.
“This injury is called stippling and it appears as yellow or white dots on the leaf surface,” Joseph said.
Sometimes these pests also lay eggs in those injured feeding sites. Eggs hatch and larvae mine between upper leaf layers causing leaf mining injury.
“Both stippling and leaf mining injuries cause economic losses to spinach growers,” he added.
Aphids such as green peach aphid can be a serious pest of spinach in any location. The pests feed on the plant juice by using a sucking mouthpart to pierce the plant. Often, the mere presence of aphids causes severe economic issues in marketing the produce.
The majority of the pest impacts are due to direct feeding injury and quality, but presence of frass (insect poop), and live or dead insects in the harvested produce will impact marketability of the produce.
The best method of control is use of insecticides. Insecticides such as cyromazine and abamectin are used for leafminer control. For lepidopteran, there are several insecticides registered: methoxyfenozide, chlorantraniliprole and spinetoram are examples that are effective. Pyrethroids such as permethrin and zeta-cypermethrin are used to control aphids and lepidopteran pests.
Pest populations vary each year and are largely dependent on the climate.
“Leafminers, lepidopterans and aphids are always present every year in the Salinas Valley,” Joseph said. “The growers and pest control advisers are always at alert to manage these insect pests all year.”
Weed and disease control
Spinach is somewhat susceptible to weed pressures. High-density planting beds make it impossible to mechanically cultivate weeds. Hand-hoeing is labor intensive and costly, which means the most effective weed management approach is prevention. Pre-emergent and post-emergent herbicides can be used to control weeds in spinach crops, but it is critical to plant the crop in fields where weeds have been properly managed. Herbicide options are limited and expensive. Stein recommended rotating planting areas, specifically wheat, leaving at least three years in-between spinach crops, and hand weeding.
Weed pressures vary geographically. In California, burning nettle, little mallow, chickweed, London rocket and shepherds purse are most problematic, whereas in Texas grasses and broadleaf weeds are of most concern. Regardless of location, methods for control are similar. Regardless of location, commit to practices that minimize disease pressures, pre-planting during growing and again post-harvest.
Pythium seedling disease and downy mildew are two diseases of most concern for growers nationwide. Diseases common to spinach crops include white rust and cucumber mosaic virus. Cultural management tactics are most important for preventing and limiting the impact of diseases.
Good fertility management is also critical. Spinach requires about 100 to 150 lbs nitrogen (N) per acre, 75 to 100 lbs of phosphorus (P) per acre and 70 to 100 lbs of potassium (K) per acre.