Description of the Pest
Tomato pinworm occurs throughout southern California and sporadically in some areas of the San Joaquin Valley and coastal growing areas.
Eggs, seldom noticed because of their small size, are usually laid singly on lower surfaces of leaves. Early instars are light colored and appear smooth even when observed with a hand lens; they lack the obvious tubercles and bristles of newly hatched tomato fruitworms or tobacco budworms. Later instars are most often found in fruit; they usually are gray or yellowish with an irregular band of red or purple across each segment. Larvae either pupate in leaf shelters or drop to the ground to pupate. The slender, brown pupa is usually enclosed in a loose silk cocoon with adhering soil or plant debris. Adult moths are small, about 1/4 inch (6–8 mm) long, and light gray, peppered with small black flecks.
There can be as many as seven or eight overlapping generations per year.
This caterpillar feeds on leaves and creates blotch-type mines, but causes most of its damage when it attacks the fruit. Where abundant, the tomato pinworm may seriously damage foliage and infest nearly 100% of the fruit. Larvae normally enter fruit through the calyx, but when populations are high they may enter at any point on the fruit's surface. They make dry burrows and do not penetrate very far into the fruit. When infested fruit is picked, caterpillars may be difficult to detect unless they have been feeding long enough to create small piles of brown, granular frass at the edge of the calyx. Because the pinworm has many generations per season, it becomes more serious as the season advances. The greatest damage occurs where tomatoes are grown from early in the season to late in the fall or in areas where the seasons for early and late tomatoes overlap.
Successful management requires keeping pinworm infestations below damaging levels in the current season, and reducing the overwintering population that will attack later crops. Important management tools are host-free periods, mating disruptants, insecticides, destroying plant residues after harvest, and destroying other solanaceous host plants in the field's vicinity. Careful monitoring can improve management. In the central San Joaquin Valley, tomatoes planted in late winter rarely require treatment for tomato pinworm.
Parasites, including Apanteles spp., Sympiesis stigmatipennis, and Parahormius pallidipes, can be important in controlling pinworm in unsprayed or lightly sprayed fields. Hold infested foliage in cages or bags at room temperature for 2 to 3 weeks. Note the number of parasites that emerge to pupate to determine the percentage of parasitism.
A host-free period is essential for reducing pinworm populations; the longer the period the better. Destroy residues by burning (where permitted) or plowing-under to help reduce overwintering populations of pinworm. Avoid growing both an early and late-season crop if pinworm is a persistent pest in your area. Shred and disc crop residues immediately after harvest completion, if substantial tomato pinworm populations are present during the first planting and a second crop has been planted in an adjacent field. Crop rotation is not an efficacious management tool unless practiced on an area-wide basis and must also include the removal of solanaceous weeds.
Transplants have been implicated as a potential source of infestation. Check transplants for evidence of pinworm larvae and avoid infested plants.
Organically Acceptable Methods
Biological and cultural control and the use of mating disruptants are acceptable on organically certified produce.
Monitoring and Treatment Decisions
Set out pheromone traps at planting. Use one trap for each 10 acres but no fewer than two traps per field. Distribute traps throughout the field. Check traps and remove any trapped moths twice a week from planting to harvest. When you begin trapping pinworm adults, start monitoring foliage for larvae. If a mating disruption program is being used, pheromone traps will not catch moths.
To survey the foliage, carefully check for mines and folded leaf shelters on all foliage in several sections of row, each 6 feet long, chosen at random throughout the field; record the average number of larvae per row section. Conduct the first survey as soon as seedlings are well established; continue checking weekly until it is necessary to begin treatments. A provisional guideline is to treat when you count an average of 1 to 2 larvae per row section. Also monitor parasitism percentages.
If pinworm populations reach damaging levels, the narrow-spectrum insecticide abamectin can be used. If broad-spectrum insecticide materials are used, it usually is necessary to continue treating throughout the season until final harvest. The time between treatments depends on population levels. Several materials used to control tomato pinworm kill parasites of Liriomyza leafminers, so repeated applications often cause leafminer outbreaks.
Pheromone mating disruption can be effective in isolated fields and where all tomato fields in an area are treated. In fields surrounded by untreated fields, females may mate in the untreated fields and migrate into treated fields to lay eggs. Where successful, pheromone confusion suppresses pinworm populations without affecting natural controls of pest species. Combine pheromone confusion with a comprehensive program of visual monitoring (pheromone mating disruption will disrupt moths from being attracted to pheromone traps) so you can tell if numbers reach treatment thresholds.
|Common name||Amount per acre**||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(No Mate TPW Spirals)||200–400 spirals/acre
|(Checkmate TPW)#||200 dispensers/acre
|COMMENTS: Apply according to label instructions with good general distribution throughout field. Check with your certifier to determine which mating disruptant products are acceptable for use on an organically certified crop.|
|(Agri-Mek SC)||3.5 fl oz||12||7|
|MODE-OF-ACTION GROUP NUMBER1: 6|
|COMMENTS: Also effective against leafminers and russet mites; does not harm natural enemies.|
|(Intrepid 2F)||10–16 fl oz||4||1|
|MODE-OF-ACTION GROUP NUMBER1: 18|
|COMMENTS: Low toxicity to natural enemies.|
|(Coragen)||3.5–5 fl oz||4||1|
|MODE-OF-ACTION GROUP NUMBER1: 28|
|COMMENTS: Can be applied as either a foliar application or in drip chemigation.|
|MODE-OF-ACTION GROUP NUMBER1: 6|
|MODE-OF-ACTION GROUP NUMBER1: 22A|
|COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Asana XL)||5.8–9.6 fl oz||12||1|
|MODE-OF-ACTION GROUP NUMBER1: 3A|
|COMMENTS: Do not feed or graze livestock on treated vines. Some bleaching or spotting may occur on the foliage of young plants. This does not affect yield or fruit quality. May cause outbreaks of mites on fresh market tomatoes. Do not use this product if leafminers are present because it is destructive of their parasites. Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Lannate SP)||0.5–1 lb||48||1|
|(Lannate LV)||1.5–3 pt||48||1|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Will also control fruitworm, armyworm, and cabbage looper. Some resistance has been documented. Do not use if psyllids are in the field as carbamates tend to promote development of their populations; also if leafminers are present, it may cause outbreaks by destroying their natural enemies. Use only late season or if other management options have been exhausted.|
|**||See label for dilution rates.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment until harvest can take place. In some cases the REI exceeds the PHI. The longer of these two intervals is the minimum time that must elapse before harvest may take place.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|#||Acceptable for use on organically grown produce.|
|1||Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|