California sunshine is the perfect ingredient for healthy grape growth. Unfortunately, the hot and dry weather is also ideal for an outbreak of mites to wreak havoc on vineyards across California. This time of year, grape leaves are home to rapidly reproducing spider mites of different varieties. Fueled by the cell contents of grape leaves, these pests can lead to crop discoloration and eventually — crop loss.

Common Suspects

Pacific Spider Mite

The primary mite for grapes in the San Joaquin Valley, the Pacific spider mite hides out in the warm upper canopy of the vine. While they can show up early in the season, their prime time is in the hot, dry months of the grape-growing season. Damage begins as yellow spots that can lead to dead areas on leaves.

Willamette Spider Mite

Pale yellow to translucent, this species prefers the cooler parts of the plant and is considered an early-season mite. The light color of this particular pest is easy to remember as it corresponds to the yellowish bronze leaf damage it causes.

Two-spotted Spider Mite

True to its name, the two-spotted spider mite is easily identified by the two distinct spots behind the eyes. According to Washington State University, females can lay about 100 eggs over a span of 30 days in the summer months. The hotter the weather, the faster the eggs hatch, and an entire generation of the species can pass in 10 days.

Scout, scout, scout

Get ahead of a potential mite invasion. Frequent scouting is the best method toward pest prevention and determining your treatment threshold level. The University of California Integrated Pest Management Program recommends scouting for spider mites after the first leaves emerge, specifically the underside of the leaves.

Signs of infestation begin with light dots on the leaves, but can lead to a red or yellow discoloration before the leaves drop off the vine. A 10x or a 14x hand lens can make leaf monitoring easier and help determine when infestations reach threshold levels. 

Bring in reinforcements

Products such as VIGILANT^®, ACRAMITE^®, KANEMITE^® and OMITE^® Miticides offer protection designed specifically to ward off harmful species. Gentle towards beneficial insects and predatory mites, these miticides work together with the vineyard’s natural ecosystem to keep grape leaves pest-free.

It's best to treat for mites as soon as possible to minimize potential damage. VIGILANT and ACRAMITE Miticides provide quick knockdown and long residual protection against spider mites at all life stages. In addition, they are easy on beneficial insects and predator mites, which make them ideal for integrated pest management programs. Both VIGILANT and ACRAMITE can be applied at the first sign of pests with no need to wait until they reach threshold levels.

KANEMITE Miticide is a great option to control two-spotted spider mites and Pacific spider mites towards the end of the grape-growing season, as it has a 7-day pre-harvest interval (PHI). It delivers rapid knockdown and long-lasting control. It is easy on beneficial insects and predator mites, and its unique active ingredient has no known cross-resistance, making it an ideal choice for managing mite resistance all season long.

OMITE Miticide is another option toward the end of the season as it features three routes of entry into the spider mites — contact, residual and inhalation. The product features a unique active ingredient with fuming action that penetrates the webbing and nooks and crannies where spider mites hide. It's rainfast after drying, providing long residual control throughout the season. And it is also soft on beneficial insects and predator mites, so it won't cause secondary pest outbreaks or flare spider mites.

No matter how growers choose to control spider mite populations, it's important to catch the issue as early as possible and stay on top of it. Grower action now will help prevent damage and protect yields this year and reduce the number of overwintering female spider mites which could damage crops next season.

For a complete line of grape protection and a staff dedicated to keeping your vineyard running strong, contact your retailer or UPL sales representative for additional information, or visit www.arysta-na.com.