Weed and pest control
Weeds
Weed control is especially important for the first six weeks, after which pumpkins are vigorous and will suppress weeds. Weeds can be controlled by cultivation, plastic mulches, hand weeding and herbicides.
Perennial weeds such as couch should be controlled the year before a crop is planted with a herbicide that contains glyphosate.
Control weeds by shallow cultivation (less than 8cm) between the rows until the vines start to run. Hand weed between the plants in the rows.
The use of polythene mulch (90cm wide) with trickle irrigation gives good control of weeds.
Pests
There should be a break of at least two years between cucurbit crops on the same ground. This will reduce pests such as nematodes and Fusarium fungi, which can cause the disease brown etch.
Caterpillars, mites, rats, snails, two-spotted mites and thrips may attack pumpkins but are usually not serious. Heliothis caterpillars may burrow into the fruit. Aphids should be controlled as they are a vector for many viruses, transferring the virus between plants within a crop.
The registration and availability of chemicals for pest, disease and weed control changes regularly. Consult a trained and experienced horticultural agronomist or the Australian Pesticides and Veterinary Medicines Authority (APVMA) website for chemicals which are currently registered or have a permit for use on this crop. The information on the label or permit for a chemical must be followed, including the directions for use, critical use comments, withholding period and maximum residue limit. Quality assurance (QA) schemes for horticultural crop production require producers to have current information on chemical registrations and permits readily accessible.
Cockatoos occasionally damage fruits severely in northern areas, up to one month before maturity.
Mice may eat the seeds, especially when planted on polythene mulch.
In the Kimberley, aphids, pumpkin beetle and 28-spotted ladybird beetle are the main insect pests.
Root knot nematode (Meloidogyne sp.) is damaging to pumpkins. Roots appear with small lumps. The pest is worst on sandy soils and irrigated areas that are cropped repeatedly.
The major leaf disease is powdery mildew which shows first as whitish to greyish areas on older leaves, mainly after flowering. It will also affect the stems. Bad infections result in small fruits. If the leaves wither, this can also result in sunburnt fruit. The disease must be controlled with fungicides every 7 to 14 days, as soon as it is seen on the leaves. Black spot (Alternaria cucumerina) is seen as small brown spots on the leaves and caused by a fungus.
Fusarium wilt causes plants to become yellow, stunted and wilted but is not often seen in well drained soils or where a rotation is practised.
Cucumber mosaic virus and zucchini yellow mosaic virus often cause severe damage to the fruit and plants at Carnarvon and Kununurra, and sometimes in the Perth area. Infected fruit has large knobby outgrowths and the leaves are mottled. There is no treatment for infected plants. However, planting on reflective mulch (to repel the aphid vector) and watering by trickle irrigation will help to reduce infection.
Fruit rots and brown etch of butternuts can be severe on the rind of the fruit in contact with the soil, especially after wet weather. They may be caused by several soil-borne fungi. Brown etch consists of concentric marks on the rind of the fruit and often with small cracks. It is reduced by restricting water in the last month of growth, followed by harvesting as soon as fruits mature.
Too much rain may cause rotting of young pumpkin fruits and corky outgrowths in butternuts. Scarring on the fruit may be caused by too much wind.
Woodiness or ‘boning’ in the flesh of the fruit may be caused by high temperatures and poor watering.
Pollination
Pumpkins have separate male and female flowers on the same plant. The male flower is large, yellow and has a long thin stalk and a spike in the middle of the flower. The female flowers are large and have a small swelling at the base.
There are normally sufficient wild bees for pollination in a commercial planting. If pollination is poor, especially in Kununurra, introduce one to four hives per hectare. An indication of poor pollination is small, deformed fruits with a small number of seeds or fruits that turn yellow and do not develop.
Pesticides should be sprayed in late afternoon when bee pollinators are less active.