QuestionI still have some fruit on the naval & grapefruit & getting leaf curl & leaf miner. Can I spray with say Volck & how long before I can pick the remaing fruit?
AnswerVolck is used to discourage leaf miners--spray new growth every few days until the leaves mature. It is not the best and works only on young leaves to keep adults from laying eggs. The insecticide listed below are safe and can and will be washed off when the fruit is picked. Due to the leaf miner is already in the leaves it is hard to treat and does not overall damage the trees production. I would check with your local Agricultural Extension Service for their recommendations is your area. Here is some more information on Citrus leaf miner.
Citrus leafminer larvae feed by creating shallow tunnels, or mines, in young leaves of citrus trees. The pest is most commonly found on citrus (oranges, mandarins, lemons, limes, grapefruit, and other varieties) and closely related plants (kumquat and calamondin). Other mining-type pests (including a citrus peelminer that attacks the fruit and stems of citrus) attack weeds, ornamentals, and crop plants, but citrus leafminer is the only mining insect that commonly attacks citrus leaves.
Citrus leafminer is a very small, light-colored moth, less than 1/4 inch long. It has silvery and white iridescent forewings with brown and white markings and a distinct black spot on each wing tip. The hind wings and body are white, with long fringe scales extending from the hindwing margins. The larval stage is found only inside mines of citrus leaves and other closely related plants. As it feeds and develops, the larva leaves a frass (feces) trail, observed as a thin dark line, inside the meandering serpentine mine just under the surface of the leaf. This visual characteristic is used to help identify the pest. In its last stage the larva emerges from the mine and moves to the edge of the leaf. It rolls the leaf around itself and pupates in preparation for adulthood, creating a rolled and distorted leaf.
Citrus leafminer has four life stages: egg, larva, pupa, and the adult moth. Adults do not damage plants and live only 1 to 2 weeks. Adult moths are most active in the morning and the evening and spend the day resting on the undersides of leaves, but are rarely seen. Soon after emerging from the pupal case, the female moth emits a sex pheromone that attracts males. After mating, the female lays single eggs on the underside of host leaves. On the tree, the newly emerged leaflets of flush growth, particularly along the midvein, are the preferred egg-laying (oviposition) sites. Eggs hatch about 1 week after being laid. The newly emerged larvae immediately begin feeding in the leaf and initially produce tiny, nearly invisible, mines. As the larva grows, its serpentine path of mines becomes more noticeable. The larvae molt 4 times over a 2 to 3 week period as they develop. The larva emerges from the mine as a prepupa and rolls the edge of the leaf over causing a curling of the leaf. Inside that curled leaf edge the leafminer becomes a pupa. The pupal stage lasts from 1 to 3 weeks. The entire life cycle of the insect takes 3 to 7 weeks to complete. Citrus leafminer develops best at temperatures between 70?to 85篎 and greater than 60% relative humidity,
Citrus leafminer can survive as a larva only in the tender, young, shiny leaf flush of citrus and closely related species. Older leaves that have hardened off are not susceptible unless extremely high populations are present. The larvae mine inside the lower or upper surface of newly emerging leaves, causing them to curl and look distorted. Mature trees (more than 4 years old) that have a dense canopy of older foliage to sustain them can tolerate damage on new leaves during part of the growing season with negligible effect on tree growth and fruit yield. Very young trees do not have much mature foliage and they produce more flush year-round, thereby supporting larger citrus leafminer populations. Young trees may experience a reduction in growth. However, even young trees with heavy leafminer populations are unlikely to die. The flush growth of citrus trees attacked by leafminer will look unsightly, but the best course of action is to leave it alone and let the natural enemies of the citrus leafminer feed on and parasitize the larvae in the mines, rather than trying to control this pest with insecticides.
MANAGEMENT
On mature backyard citrus trees, citrus leafminer rarely causes serious damage and management is normally limited to practices that limit succulent growth and protect natural enemies. Very young trees are more vulnerable to injury and insecticide treatment may occasionally be justified. However, available insecticides for backyard trees are not very effective and many products leave residues that kill natural enemies, compounding problems. Pheromone traps are available for detecting leafminer moths.
Biological Control
Citrus leafminers are killed by various parasites and predators, including tiny nonstinging, naturally occurring wasps such as Cirrospilus and Pnigalio species. The parasites lay their eggs inside the mine, inside or on top of the leafminer larva. When the parasite egg hatches the parasite larva consumes the leafminer larva. These parasites are very important for reducing citrus leafminer levels. Do not spray citrus with broad-spectrum insecticides and avoid other practices that disrupt natural enemies whenever possible. Using physical controls and preventive cultural methods will also encourage the activities of native natural enemies. You do not need to release parasites, because many native parasite species that attack other leafminer species will also find your citrus trees and attack citrus leafminer.
Cultural Control
Citrus leafminer moths are attracted to the new flush of citrus trees. Avoid pruning live branches more than once a year, so that the cycles of flushing are uniform and short. Once the leaves harden, the pest will not be able to mine the leaves. Do not prune off leaves damaged by citrus leafminer since undamaged areas of leaves continue to produce food for the tree. Do not apply nitrogen fertilizer at times of the year when leafminer populations are high and flush growth will be severely damaged, such as in the summer and fall.
Physical Control
Vigorous shoots known as water sprouts often develop on branches and above the graft union on the trunk of mature trees. These shoots grow rapidly and produce new leaves for a prolonged period of time. Where citrus leafminer is a problem, remove water sprouts that might act as a site for the moths to lay eggs (oviposition). Suckers, the vigorous shoots which grow from the trunk below the graft union, should always be removed since they originate from the root stock and do not usually produce desirable fruit.
Chemical Control
Many insecticides that are registered for residential use do not effectively control citrus leafminer because they have difficulty reaching the larvae inside the mines. Leafminer infestations on mature trees rarely require insecticide treatment. If very young, or high-value, trees are infested, insecticides can be applied to the foliage when egg-laying moths are active, as determined by pheromone trapping, to reduce future infestations. Insecticide products that contain the natural insecticides neem (azadirachtin) or spinosad show some efficacy against larvae. However, the residues do not last very long and these insecticides may need to be reapplied every 7 to 14 days. Application of Green Light Spinosad is limited to six times per season. Imidacloprid (Bayer Advanced 12-Month Tree and Shrub Insect Control concentrate) applied to the ground for young trees or to the soil of potted citrus provides the longest period of control (1-3 months). Imidacloprid applications should be timed to protect periods of flushing, such as in the summer and fall. Frequent use of broad-spectrum insecticides such as malathion, carbaryl and pyrethroids will kill beneficial insects and are not recommended and can result in a build up of whiteflies, scale insects, and other citrus pests.
