What is in this article?:
- New Mexico pecan growers and consultants are on high alert after a new leafminer pest species was found last year along with the reappearance of the hickory shuckworm insect.
- The pecan serpentine leafminer creates winding tunnels inside pecan leaflets which can result in tattered foliage when the mines dry and break apart in the wind.
- Pecan serpentine leafminer will likely be a very minor pest in New Mexico pecans.
- Nuts affected by the hickory shuckworm look like hailstorm damage occurred.
Suggested HSW management includes looking for shuck abnormalities during scouting. Female HSWs leave small chalky markings on shuck surfaces when laying the eggs. The marks may resemble bird droppings.
“Mark the nuts and come back in a week to see if anything has hatched,” Sutherland suggested. “Open the husk and check for caterpillars or maggots with a hand lens.”
HSW caterpillars are white with well-defined, tan-head capsules and have three pairs of short thoracic legs and five pairs of short, fleshy prolegs on the abdomen. In contrast, the walnut husk fly, an occasional pecan pest, does not leave chalky markings when laying eggs. Immature husk fly larvae are legless, conical shaped, dirty-white maggots with tiny mouth hooks.
Mike Hall, Louisiana State University research and extension entomologist in Shreveport, La., also discussed HSW at the conference. Hall says HSW has one distinguishing characteristic that separates the insect from the similar pecan nut casebearer.
“The hickory shuckworm moth has a series of stripes running along the outside edge of the front wings,” Hall said. “The pecan nut casebearer is silvery gray with a ridge of scales across the back.”
Hall has conducted insecticide trails for HSW in commercial pecans in Louisiana. He says insecticides are the best method to control the insect. All tested products provided good control.
Hall offers these suggestions before applying insecticide sprays for HSW.
First, make sure the insect is present – there is not a good way to monitor its activity. Pheromone traps do not catch HSW during the hot active months of July through September. Black light traps are the most practical way to monitor insect activity.
Second, look for damage. Orchard sanitation helps control the insect. For a small pecan planting with HSW, destroy the old shucks and dropped nuts to reduce the infestation.
Third, select the appropriate insecticide keeping the pest complex in mind. If the stink bug is also found, use a product mixture or a pyrethroid effective again the stink bug and HSW. Make sure the spray equipment is working and calibrated properly.
And last, use water with a 5.5 to 6.5 pH level in the spray mix for maximum product efficacy. Insecticides are ineffective with water at 8 to 9 pH, Hall says.
Pecan serpentine leafminer and HSW are found throughout the Texas pecan belt, but not in Arizona and California pecan orchards, according to university Extension specialists in the respective states.