The Fruit IPM Report for the week shows an upward trend with more Sharp-nosed Leafhopper (SNLH) adults maturing and moving around fields, making transmission of stunt disease to previously uninfected bushes more likely. This insect in the only regular target for post harvest sprays. Now is an appropriate time to treat.

Sharp-nosed Leafhopper Life Cycle

SNLH feeds and reproduce on blueberry, huckleberry, cranberry, and other related plants. SNLH feeding causes little direct damage but it transmits the phytoplasma that causes stunt disease in blueberries. They are small brown insects with a pointed head (Figure 1). SNLH picks up the disease while feeding on infested bushes and carries it to other plants in subsequent feedings. Usually only adults will carry the disease from plant to plant, since nymphs are wingless and can’t fly (Figure 2). This insect completes two generations in New Jersey. Adults are abundant in the woods, where many alternative hosts are present, and may move to commercial blueberry fields in the spring. Eggs overwinter inside fallen leaves and hatch in mid-May. Nymphs complete 5 instars. Nymphs from the first generation reach adult stage in mid-June, while nymphs from the second generation reach adulthood in early August. Adults move back to the woods in the fall. Monitoring these generations is critical for timing of control strategies.

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Crawler counts have increased again since last week. Growers who had infested berries during the first generation should treat this generation as soon as possible. Esteem and Diazinon are the suggested products.

Life History

Scales feed on plant sap, decreasing plant vigor and fruit yield. Adult scales are protected from insecticide sprays by a waxy covering. These insects are common in older canes when not removed, and located mostly under loose bark. In New Jersey, the Putnam scale has two generations a year. It overwinters as second-instar nymphs under loose bark. Spring activity begins in early February. Eggs from the first generation are laid in late April, and immature “crawlers” begin to appear in mid-May. Peak crawler emergences occur in late May and early June. Peak crawler emergences for the second generation occur in early to mid-August (this time of the year).

Monitoring and Management

Growers that have a scale problem need to treat post harvest for the 2nd generation of crawlers (use Diazinon or Esteem). Crawlers can be monitored by wrapping black electricians’ tape covered by double-sided sticky tape around canes. Use a hand lens to see crawlers on the sticky tape. Sprays should coincide with crawler emergence.

The blueberry leafminer is generally not considered an economic pest problem mainly because larvae experience high levels of parasitism in most blueberry fields. Larval parasitism can reach levels up to 80%. Use of broad-spectrum insecticides can have a severe effect on the natural enemy populations of the leafminer.

Because of potential contamination, the blueberry leafminer might be a problem if you are processing more blueberries than usual. Blueberry leafminer larvae may become a contaminant, especially in machine-harvested fruit, as larvae drop from the bushes together with the harvested fruit. Under this special circumstance, treatment may be justified. Otherwise, we do not see the need to treat for this insect. [Read more…]