Pest description and crop damage A small fly in the fruit fly family, occurring throughout the Willamette Valley in most commercial plantings. Larval infestations cause extensive damage to plant crowns and flower buds. Stand losses and reduced seed yields have been observed in heavily infested fields. Adults are about 3 mm (1/8 inch) long. Body color ranges from drab brown to gray. Eyes are red. Eggs are very small, white, and somewhat elliptical. When flower buds are present, flies insert eggs almost exclusively into these buds. During the vegetative growth stage, however, they will lay eggs in plant leaves, stems, and crowns. Eggs hatch in 7 to 10 days. Larvae are light colored and about 3 mm long at maturity.
Pest Biology A few flies can be found in meadowfoam fields when seedlings emerge in the fall. Beginning in late January, populations increase rapidly. Three or four generations peak from late January through mid-June. Water availability seems to govern adult MFF activity and population size. Few adults are seen from late June through August as fields mature and dry out. Eggs are laid singly anytime adults are active; the peak egg-laying period usually occurs from mid-January through April. The first larvae usually are detected in January in small, yellowish, distorted plants. The number of larvae increases sharply after mid-February and peaks in April. Few larvae are found in plants after bloom.
Scouting and thresholds MFF adults are monitored with unbaited yellow sticky cards. In mid-January, place traps within fields and near field borders. Use approximately one trap for every 3 acres. Inspect traps weekly from mid-January to April. Meadowfoam plants infested with MFF larvae are weak, stunted, and yellowish. A hand lens or microscope often is necessary to see the smaller larvae. Berlese funnels are used to quantify larval infestations. Apply insecticide when average daily fly counts on sticky traps increase from less than one per trap per day to four or more per trap per day. Cold, rainy, and windy weather reduces trap catches even when MFF is abundant: do not underestimate fly counts.
Control of larval infestations in individual fields and test plots does not always increase seed yield. Replicated trials seem to indicate benefit from a midwinter (late February) broadcast insecticide application on fields at risk of heavy infestations. This application reduces significant fly infestations and increases the potential for a boost in seed yield.
The following insecticide labels list meadowfoam along with other oilseed crops but does not specifically list meadowfoam fly as a pest.
- chlorantraniliprole (Coragen) at 0.045 to 0.065 lb ai/a. Make no more than 4 applications per acre per crop. Minimum interval between treatments is 5 days. Do not apply more than 15.4 fl oz Coragen or 0.2 lb ai of chlorantraniliprole-containing products per acre per year. If adjuvants are used, use only a non-ionic surfactant (NIS). PHI 21 days. REI 4 days.
- cyantraniliprole (Exirel). Do not apply a total of more than 0.4 lb ai/a of cyantraniliprole containing products per calendar year. For best performance, use an adjuvant. Retreatment interval is 7 days.
- flonicamid (Beleaf 50 SG) at 0.089 lb ai/a. Apply in sufficient water to ensure good coverage; use a minimum of 10 gal per acre when applied by ground; use a minimum of 3 gal per acre by air. Do not apply more than 8.4 oz/a per season. Do not apply more than 3 applications per season. Retreatment interval 7 days.
- solfoxaflor (Transform WG)-Do not apply within 14 days of grain, straw, for age, fodder, or hay harvest. Retreatment interval is 14 days. Do not make more than 2 applications per year nor apply more than 1.5 oz of Transform WG (0.046 lb ai of sulfoxaflor) per acre per year. Do not apply this product after petal fall.
- zeta-cypermethrin (Mustang Max) at 4.0 oz (0.025 lb/ai/a). Do not apply more than 24 oz of product or 0.15 lb ai/a per acre per season. Retreatment interval 7 days. PHI 7 days.