Common Pumpkin Pests, Diseases, and Weed control

Numerous pests, diseases and weed pressure can reduce the yield of pumpkin plants if left uncontrolled. In most cases, the effectiveness of a control measure depends on the time of the application-intervention. Early applications and preventive measures can protect crops and reduce such problems. Some of the most important preventive measures for pumpkin pests and diseases are crop rotation and using healthy, certified propagation material (seeds or seedlings). Some of the most common problems of pumpkins are:

Important Pests in Pumpkin fields

Aphids (Aphis gossypii and Myzus persica are the most common)

Aphids are small, soft-bodied insects that can grow in large populations quickly. They can usually be found on the underside of the leaves and can cause direct and indirect damage to the plants infested. The direct damage is caused by the feeding activity of the insect from the plant tissues (sucking of plant sap), leading to curling of the leaves, chlorosis, decreased fruit quality and plant development, and in severe infestations, wilt. The honeydew released by the insect can cover the plant canopy and favor secondary fungal infections, reducing fruit yield and quality even more. Furthermore, aphids need to be kept under control mainly due to their ability to transmit important plant viruses (see below). To effectively control the insect, many pumpkin farmers spray with insecticides (mercaptothion, mevinphos, fenthion, or dimethoate) (apply when 10% of the plants are infested). However, since there are plenty of aphids’ natural enemies, it is essential to protect them in the farm ecosystem by reducing the applications of insecticides. Crop rotation with no Cucurbita species is necessary.

Cucumber beetle

There are 2 types of cucumber beetles that affect pumpkin plants.

The striped cucumber beetle, Acalymma vittata (is yellow and has 3 black strips on its back), and
The spotted cucumber beetle Diabrotica undecimpunctata howardi (is yellow with 12 black spots on its back).

They appear very often in the United States and Southern Canada. The adult beetles chew and feed on the foliage, flowers, vines, and fruit of pumpkins, causing severe damage. The larvae can also harm the stems and roots, leading to plant defoliation, wilt, and death. Striped cucumber beetles can also feed on flowers and pollen, reducing yields. However, the damages these beetles cause are not only tissue injuries from chewing. They also transmit a dangerous pathogenic bacterium called Erwinia tracheiphila that can cause Bacterial wilt disease in pumpkins and other Cucurbita species. Furthermore, the beetles are vectors and can transmit the squash mosaic virus. Some pumpkin farmers use yellow sticky cup traps, spray with kaolin clay or combine these methods with the technique of “trap crops” like dark green zucchini or blue hubbard squash (they are more attractive to the insect than pumpkins).

The most important Pumpkin Diseases

Alternaria leaf blight (Alternaria cucumerina)

Alternaria leaf blight is a fungal disease caused by Alternaria spp (species) such as Alternaria cucumerina. The infection is favored by warm, wet weather with high humidity levels for an extended period. At first, the farmer may observe the characteristic small, brown spots on the oldest leaves. These spots will become necrotic lesions on leaves as the disease progresses. During the last stages, the entire leaf will eventually die. The disease can lead to severe problems in a pumpkin field if uncontrolled. Since no resistant pumpkin cultivars are available, most farmers invest in preventing measures (e.g., increasing aeration within the crop, drip irrigation, etc.), or in the case the local authorities recommend (or symptoms are observed) they can spray with suitable fungicides (chlorothalonil is the most effective substance).

Powdery Mildew (Podosphaera xanthii or Sphaerotheca fuliginea)

Powdery mildew is generally a more common disease than Downy mildew and is caused by many different species of fungi, with the Erysiphe cichoracacearum and Podosphaera xanthii (or Sphaerotheca fuliginea) being the most dominant. We can actually see a white powdery deposit on the leaf surface. As the fungus moves through the vessels, leaves become brown and fall (defoliation), and the plants seem weak and stunned. In severe infection cases, the plant canopy may wither and die. The pumpkin farmers are advised to disinfect all tools after coming in contact with an infected plant to decrease the spread of the disease. Adapting higher planting distances to facilitate airflow inside the crop can also reduce the risk of infection. Additionally, preventive fungicide applications combined with the cultivation of tolerant pumpkin varieties are the most effective protection and control measures for powdery mildew.

Anthracnose (Colletotrichum lagenarium)

Anthracnose is a fungal disease that causes severe damage mostly on leaves and other above-ground plant organs of pumpkin and other Cucurbita plants. Cool (70-80°F or 21-26°C) and rainy weather favors the disease’s spread and the fungus’s growth. On the contrary, dry and hot weather conditions stop the disease cycle, which will continue when weather conditions are optimal again. The symptoms that are brown necrotic spots (the center of the spot may fall, leaving the leaves a “shot hall” appearance) appear primarily on the older leaves. We may also observe these damages on stems, flowers, and fruits (round sunken lesions). Anthracnose control begins with proper prevention measures. Farmers are advised to use healthy, disease-free certified seed, apply crop rotation and deep cultivation, and spray with protectant fungicides when needed.

Mosaic viruses – Curcubita viruses

There are 4 important mosaic viruses that can cause problems in pumpkin crops: papaya ringspot virus or watermelon mosaic virus, watermelon mosaic virus 2, cucumber mosaic virus, and zucchini yellow mosaic virus. Most of these viruses are usually transmitted by aphids. Symptoms include curling of the foliage and the formation of a characteristic yellow mosaic on the leaves. We may also observe underdeveloped leaves and green and distorted petals. If the infection happens in early developmental stages, these plants may produce low or no fruit yield. In later stages, symptoms may also appear on the fruits (smaller fruits with spots, discoloration, or a mosaic pattern. The disease severity or risk of infection is usually higher in late summer when the carriers-vectors (aphids) are more abundant and numerous. Management includes the control of the aphids population on the field and hygiene measures such as tools disinfection, removal of infected plants from the field, and using healthy propagation material. Like for other crop diseases and pests, it is essential to avoid planting Cucurbita species consecutively in the same field. There are only a few tolerant pumpkin varieties to specific of these viruses.

Weed control in a pumpkin field

First of all, you must always consult your local licensed agronomist in order to form a weed control policy that respects biodiversity and natural resources. While in later developmental stages, pumpkins can effectively suppress and outcompete weeds, during the first 6-8 weeks from planting, it is essential to take weed control measures. In general, 3 weedings in 10 days intervals may be needed, depending on the spoil seed bank (of weeds) and the environmental conditions. Most pumpkin farmers apply hand weeding and/or shallow cultivation (maximum at 8 cm before sowing and between plant rows) and plastic (or straw) mulch. In a conventional farm, growers may also apply herbicides (always after consulting a local licensed agronomist). The most common weeds observed in a pumpkin field are the following:

Annual, warm-season weeds: field bindweed or morning glory (Convonvulus arvensis), Bermudagrass (Cynodon dactylon), Common purslane (Portulaca oleraceae), Kochia (Bassia (Bassia scoparia), Puncturevine (Tribulus terrestris), Redroot pigweed (Amaranthus tetroflexus)
Cool season annual and biennials: Common mallow (Malva neglecta)
Cool season perennials: Foxtail barley (Hordeum jubatum), Quackgrass (Elymus repens).

For the grasses, most applications of herbicides are performed in the 2-6 leaf stage, while most perennials should be controlled before planting the crop. Crop rotation or/and the use of cover crops like rye or hairy vetch can be used to reduce the weed population in no-till systems.

References

Read more

15 Interesting Facts about Pumpkins

Pumpkin Nutritional Value and Health Benefits

Growing Pumpkins in Your Backyard

Plant Information and Variety Selection of Pumpkins

Soil Requirements, Soil Preparation and Planting of Pumpkin

Growing Pumpkins Outdoors for Profit – Complete Growing Guide from Start to Finish

Pumpkin Yield, Harvest and Storage

Common Pumpkin Pests, Diseases, and Weed control

Pumpkin Fertilizer Requirements

Pumpkin Water Requirements and Irrigation Systems

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