Diaphania hyalinata  (Linnaeus)

and Diaphania indica (Saunders)

Melon moth 

General

• Tropical insect attacking many cultivated or wild Cucurbitaceae. Belongs to the order Lepidoptera and the family Crambidae.
• Insect present in Central America, South America and the West Indies.
• Observed in the open field as well as under shelters.
• Considered to be one of the most important pests of the Cucurbitaceae botanical family in Guyana.

• Sensitive botanical family (s)

• Affected production areas :

* Presence of D. indica

• Organs attacked

Symptoms, damage

• Symptoms :
  • Leaves devoured by larvae. The blade is irregularly cut, some veins are not consumed.
  • Rare external and internal fragments of the fruits if the foliage is lacking.

• Signs : Presence of larvae on plants and in the culture (Figures 2 and 3).

• Possible confusion : With other moths such as D. nitidalis.

Biology 

• Development cycle : The female larva lays eggs on the leaf organs.
  • The larvae hatch, the first larval stage is transparent and then takes on a yellow-green tint as it develops. The fifth and final instar has two conspicuous dorsal white bands and is 1.6 cm long.
  • Pupa giving birth to an adult butterfly 9 days later. The wings of this one have a wingspan of about 2.5 cm, are partly transparent, tinged with brown on the periphery.
• The duration of the complete cycle of this insect is probably less than 30 days in the hot and humid conditions of Guyana.

Protection

• Weed the crop and its surroundings.
• Produce the seedlings in an nursery insect-proof .
• Check the sanitary quality of the plants before and during their introduction into the crop or shelter.
• Install  canvases  insect-proof in the nursery, on the rows in the open field when planting, and at the openings of shelters when weather conditions allow. During flowering, the nets will be removed to allow pollination of the flowers except for the parthenocarpic cucumber varieties. Pollinators can optionally be introduced under the nets to allow good fruiting while protecting the crop throughout its cycle.
• Install pheromone traps outside the shelter. (1)
• Favor natural enemies in field crops or under open shelters (2).
• Use biopesticides (3).
• Reason the  chemical protection that is possible for this use ( e-phy site ). Remember to respect the conditions of use of phytosanitary products.

(1) In order to detect the presence of adults in the culture early, pheromone traps can be placed in the culture. However, the pheromones tested in Guyana did not reveal good trapping efficiency. Since giraumons and squash are very sensitive to melon moths, they can serve as indicator plants for the presence of moths.

(2) Natural predators such as Hymenoptera Vespidae and hoverfly larvae can attack the early larval stages of the melon moth. These naturally occurring auxiliaries can be favored by limiting insecticide treatments and by planting nectar-bearing plants near the plot. Ants of the Formicidae family are also excellent predators of the eggs of Diaphania sp. For more information on crop auxiliaries, consult the Biosavane guides .

(3) If the larvae are visible on the foliage, a preparation based on Bacillus thuringiensis var. kurstaki can be applied to the crop.